sábado, 15 de febrero de 2020

SOLUCIONES QUIMICAS Y FORMULACIONES

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martes, 18 de abril de 2017

The Chemistry factor : What is Chemistry all about, by Idrani Mukharji





 
Cover Stories: A chemist’s chemist

Tobin J. Marks: What is chemistry all about?

The 2017 Priestley Medalist recounts a life intertwined with chemistry
Department: Science & Technology
Keywords: Priestley, Tobin J. Marks
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The Priestley Address of 2017 Priestley Medalist Tobin J. Marks, given at the 253rd ACS National Meeting, San Francisco, April 4, 2017.
Image of the Priestley Medal.
 
The Priestley Address of 2017 Priestley Medalist Tobin J. Marks, given at the 253rd ACS National Meeting, San Francisco, April 4, 2017.
Let me begin by saying how honored I am to be selected as this year’s Priestley Medalist and to join the distinguished cohort of previous medalists. I also wish to salute this year’s ACS national award winners, an impressive group of chemists and accomplishments. Congratulations! In this address I would like to share a story with you, part biographical, part scientific, and part philosophical, relating something of my career, how that is intertwined with the science I have done and am currently doing, where it is going, and lastly, how it relates to the question of what chemistry is all about.
My grandparents on both sides emigrated from Czarist Russia and came to America for freedom and a better life. I was fortunate to grow up in the Washington, D.C., area (in Arlington, Va., and Bethesda, Md.) in a family having a deep respect for learning, hard work, and service. Like many of my generation, dynamic science teachers, highly motivated classmates, and Sputnik kindled my fascination with science. I owned a Gilbert Chemistry Set and tinkered with explosives and rockets, which I’m sure horrified my normally tolerant parents. I was fascinated with what things are made of and how that affects their properties.
On graduating from high school in Bethesda, I entered the University of Maryland, which always has had excellent science and engineering programs. I chose chemistry as a major partly because of my fascination with what things are made of and how to make them. I also took excellent physics and math courses, and like all chemistry majors then, German language courses.
There was great camaraderie among the “Terp” [University of Maryland]chemistry majors, and it seemed that the more noxious the odors emanating from a lab experiment, the more we relished it, possibly because students majoring in other subjects were repelled! We realized how much we were learning and how much we enjoyed laboratory work, and we were thrilled. I vividly remember one of my classmates pronouncing, “chemistry is my religion,” which captures some of that slightly wacky sentiment.
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Marks with his research group in the late 1970s.
Credit: Courtesy of Tobin Marks
A picture of Tobin Marks and his research group from the 1970s posing outside on grass.
 
Marks with his research group in the late 1970s.
Credit: Courtesy of Tobin Marks
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Marks with his current research group.
Credit: Mitch Jacoby/C&EN
A photo of Tobin Marks and his current research group at Northwestern University.
 
Marks with his current research group.
Credit: Mitch Jacoby/C&EN
There was a generally good-natured rapport between professors and students in that era, and I learned that each professor has a different lecturing and teaching style, and that in itself was good for me. I vividly remember that a physics professor’s humorous request that the chemistry majors in the lecture hall erase the large blackboards was met with good-natured hisses and boos from the chemistry majors, after which we came to the front and dutifully erased the blackboards. Of course, we eventually got to know all of the Maryland chemistry faculty and felt unique as “chem majors.” With determination and diligence, most of us traversed the great divide between physical-chemistry-oriented freshman chemistry and phenomenology-, structure-, and mechanism-oriented organic chemistry. Chemistry majors had laboratory courses most weekday afternoons and sometimes on Saturdays, so we felt comfortable in the laboratory.
A transformative experience at Maryland was the National Science Foundation-funded summer undergraduate research program, which allowed us to work in a professor’s laboratory with a modest stipend. Most exhilarating for me was working with a young inorganic chemistry professor, Samuel Grim, synthesizing organophosphorus compounds and measuring their NMR parameters. I learned to work and think independently and to appreciate the power of “just-in-time learning,” meaning that when a puzzling result stares you in the face, the urgency of trying to understand it and planning what to do next greatly accelerates the learning process.
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Undergraduate research at the University of Maryland (goggles lifted for the photographer).
Credit: Courtesy of Tobin Marks
A photo of Tobin as an undergraduate student at the University of Maryland in a lab.
 
Undergraduate research at the University of Maryland (goggles lifted for the photographer).
Credit: Courtesy of Tobin Marks
To me, the graduate students in the Grim group were stimulating, fun people, and although I didn’t quite understand who postdocs were, they were also impressive. From this experience I yearned for more research! Inorganic chemistry was taught by James Huheey, and his crystal-clear lectures kindled new interests, leading me to borrow Sam Grim’s copy of the landmark Cotton and Wilkinson inorganic textbook. I was entranced by the chemistry the vast periodic table offered, and attending graduate school was my ambition.
The honors chemistry program at Maryland required a written senior thesis and original research proposal, both to be defended before a faculty committee. The former task was straightforward because I had coauthored several publications by then, and the latter sent me exploring new literature. What captivated me was Rowland Pettit’s report that the elusive cyclobutadiene molecule could be stabilized by coordination to an iron carbonyl fragment. The ramifications of that chemistry formed the basis of my proposal, which emerged from the oral defense unscathed and stoked my interest in the organic-inorganic chemistry interface. Indeed, unusual interfaces between dissimilar substances continue to intrigue me.
Every time I climb the steps at the Massachusetts Ave. entrance to MIT, the adrenaline pumps as it did the first time when I entered graduate school as an NSF Predoctoral Fellow. The world-class MIT inorganic group consisted of Al Cotton, Alan Davison, Dick Holm, and Dietmar Seyferth, with George Whitesides closely associated. It had great intellectual power and breadth. I joined Al Cotton’s group because of his infectious enthusiasm and interesting projects on stereochemically nonrigid organometallic molecules.
MIT housed essentially all science and engineering in one giant complex of interconnected buildings, so in addition to chemistry coursework, I attended lectures and seminars in other departments and cross-registered at Harvard University for William Lipscomb’s famous chemical bonding course. MIT provided an extremely stimulating environment, filled with scientific leaders and a warm Cotton group camaraderie; Al gave me the freedom to sample this environment broadly, for which I will be forever grateful. After initial research speed bumps where difficultly synthesized new molecules turned out to be completely rigid, my persistence, bolstered by Al’s and George’s good advice, paid off. I enjoyed mentoring our research group’s junior members and vowed to create such an environment when I had my own research group. At Maryland I was an ACS student affiliate, at MIT I became a full ACS member, and I recently celebrated my 50th anniversary.
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Figure 1

Structure of new families of alkyls, aryls, acyls, tetrahydroborates, alkane activation products, and hydrides.
 

Figure 1

My quest for an academic position took me to U.S. regions I had never visited before, including Northwestern University, which, on the day I visited, was 0 °F with a 40 mile-per-hour wind. All science and engineering was housed in one large building, and I found the chemistry department to be research-intense, collegial, and well-equipped. The inorganic group and associated faculty, Fred Basolo (2001 Priestley Medalist; 1983 ACS president), Jim Ibers, Ralph Pearson, Duward Shriver, and Brian Hoffman, were world-class, and I happily joined as an assistant professor. I soon had my laboratory in place with enthusiastic graduate and undergraduate students, but what research to do? An empty canvas awaited my brush! Although I could not forget my organometallic roots, I was inspired by George Whitesides’ advice to strike boldly into new fields, to push the frontiers.
To my thinking, the f elements (lanthanides and actinides) offered untapped possibilities in that their properties differed radically from transition metals (for example, larger ionic radii, different bonding), and we set off to explore the chemistry of unknown metal-alkyl and metal-hydride bonds. My first NSF proposal was successful, although similar to what Bob Langer told us in his 2012 Priestley Address, one reviewer was critical to the point of irrationality. Undeterred, we forged ahead and soon could tell the world about remarkable new families of alkyls, aryls, acyls, tetrahydroborates, alkane activation products, and hydrides, as well as evidence for fleeting formyl, π-olefin, π-alkyne, π-arene, and H2 complexes (figure 1). One striking characteristic of these complexes was their extraordinarily high reactivity and catalytic activity versus that of their closest transition-metal analogs. We next extended this work to organolanthanides and again struck gold.
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Figure 2

Credit: Courtesy of Tobin Marks/C&EN
An expanded uranyl-encapsulated metallomacrocycle.
 

Figure 2

Credit: Courtesy of Tobin Marks/C&EN
Invaluable collaborations to more deeply understand molecular and electronic structure with Roald Hoffmann of Cornell University; Andrew Streitwieser, Ken Raymond, and Dick Andersen of the University of California, Berkeley; Victor Day of the University of Nebraska; Ignazio Fragalá of the University of Catania; Herbert Schumann of the Technical University of Berlin; Geoffrey Cloke of Sussex University; and Jack Williams and Lester Morse of Argonne National Laboratory greatly enriched this field. We wondered what other unusual transformations could take place around large actinide centers, and, for example, found that in the presence of the uranyl ion (UO22+), condensation reactions that normally produce porphyrin-like metal phthalocyanine complexes—robust pigments used in blue jeans and auto paints (we’ll return to them later)—instead yield unusual expanded uranyl-encapsulated metallomacrocycles (figure 2). Analogous porphyrinic complexes now play a major role in photodynamic cancer therapy.
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Northwestern University’s Ipatieff professors of catalytic chemistry.
Credit: Courtesy of Tobin Marks
A group of photos depicts Northwestern’s Ipatieff professors of catalytic chemistry, beginning with Vladimir N. Ipatieff, then Herman Pines, Robert Burwell, Wolfgang Sachtler, and finally Tobin Marks.
 
Northwestern University’s Ipatieff professors of catalytic chemistry.
Credit: Courtesy of Tobin Marks
As we explored f-element catalytic chemistry, the enormous reaction rates intrigued us. If kinetics were not limiting, but only thermodynamics were, could we discover new catalytic transformations using bond energy information? Fortunately, stimulated by the work of Jack Halpern (and later John Bercaw, Bob Bergman, Carl Hoff, and others), we had already constructed sophisticated calorimetry equipment and were in a position to address these questions. Our bond enthalpy data provided new perspectives on the relative energetics of various metal-ligand bonds as a function of location in the periodic table (differences can be dramatic) but also clues to designing new catalytic transformations.
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Figure 3

Hydroelementation processes involving heteroatom-H addition to carbon-carbon unsaturation mediated by organolanthanides.
 

Figure 3

Combining exploratory chemistry with reaction mechanism analysis, we showed that hydroelementation processes involving heteroatom-H addition to carbon-carbon unsaturation are mediated by organolanthanides, and later other metal centers, to effect rapid hydroamination, hydrophosphination, hydroalkoxylation, hydrosilation, and hydrothiolation reactions of significant scope (figure 3). Moreover, many of these processes could be coupled to polymerizations to create heteroatom-functionalized polyolefins. In recent work, we coupled the microscopic reverse of homogeneous olefin hydroalkoxylation with tandem heterogeneous hydrogenation to hydrogenolyze C–O functionalities of the type found in biomass feedstocks.
During these times, I was also fascinated by the multifaceted role of metal ions “in biology and, with Jim Ibers, launched a synthetic, spectroscopic, and X-ray diffraction study to understand the molecular and electronic structures of the then-mysterious “blue” copper proteins. Using pyrazolylborate ligands to simulate the proposed multi-imidazole metal binding sites in the actual proteins, our students prepared very thermally labile facsimile complexes with most of the correct protein spectroscopic signatures—a significant advance at that time.
Later and of a more organometallic flavor, I was intrigued by reports that metallocene complexes of the type (C5H5)2MX2, where M = Ti, Zr, V, Mo, and X = halide, were potent antitumor agents in mice. Our question was whether the carcinostatic activity mechanism was similar to that established by Steve Lippard for cisplatin, involving key binding to specific DNA sequences. We launched detailed spectroscopic and X-ray crystallographic studies of (C5H5)2MX2(aqueous) interactions with oligonucleotides and whether (C5H5)2MX2(aqueous) inhibited the cleavage of small circular double-stranded DNAs by restriction endonucleases, in the manner of cisplatin. Our search for nonlabile DNA-metallocene coordination chemistry was inconclusive; however, we found that these metallocenes do inhibit certain important DNA processing enzymes, implicating a different anticancer mechanism.
When I arrived, Northwestern had a world-renowned heterogeneous catalysis group, founded when the distinguished Russian chemist, Vladimir Ipatieff fled the Soviet Union in 1931 to be jointly professor of chemistry at Northwestern and director of research at nearby Universal Oil Products. Ipatieff received many international recognitions (among them the 1939 ACS Willard Gibbs Medal) and, with faculty member Herman Pines, developed a catalytic process for high-octane aviation fuel, helping the U.K.’s Royal Air Force win the 1940 Battle of Britain. I am honored to now occupy Ipatieff’s chair.
In the late 1970s, I became intrigued with reports that chemisorption of simple and catalytically marginal early-transition-metal organometallic complexes on relatively mundane oxide surfaces such as dehydroxylated alumina (DA) yielded mysterious surface species that were highly active olefin hydrogenation and polymerization catalysts. In collaboration with Bob Burwell, who had the necessary catalytic equipment, we established that when adsorbed on DA, [(CH3)5C5]2M(CH3)2 (M = Th, U) and related Zr-methyl complexes hydrogenated simple olefins at rates comparable to supported platinum metals, and rapidly polymerized ethylene. Kinetic poisoning experiments established that only about 5% of these surface complexes were catalytically significant, not uncommon in heterogeneous catalysis. Furthermore, high-resolution cross-polarization/magic-angle spinning (CP-MAS) solid-state NMR argued that the active species were formed when Lewis acid sites on the DA surface abstracted a methide anion from the metal center, yielding for Zr, a formal 14-electron d0 cation. When I proposed this structure at an ACS meeting, it was met with skepticism. But what else could cause such enormous enhancements in catalytic activity?
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Figure 4

Credit: Courtesy of Tobin Marks/C&EN
An example of Lewis acidic, hydrocarbon-soluble, and “Teflon-coated” perfluoroarylboranes explored as methide abstractors, in this case, B(C6F5)3.
 

Figure 4

Credit: Courtesy of Tobin Marks/C&EN
At this time I was collaborating with Jim Stevens of Dow Chemical. The industrial and academic communities were ablaze with excitement when Walter Kaminsky of Hamburg University reported that ill-defined, partially hydrolyzed trimethylaluminum species (MAO) somehow activated organozirconium complexes to form potent and equally ill-defined homogenous olefin polymerization catalysts. What chemistry gave rise to such species? We quickly established that the CP-MAS NMR spectra of evaporated MAO-zirconacene solutions were virtually identical to the same zirconacenes on DA. For unambiguous characterization and well-defined, isolable catalysts, we explored Lewis acidic, hydrocarbon-soluble, and Teflon-coated perfluoroarylboranes as methide abstractors, starting with B(C6F5)3. (figure 4)
What followed was amazing: new families of isolable, highly active “single-site” polymerization catalysts, additional perfluoroaryl-borane/alane cocatalysts and weakly coordinating anions, numerous X-ray structures, and precision analysis of molecular dynamics, thermodynamics, and polymerization mechanisms. We showed how the electrostatic catalyst+···cocatalystˉ ion pairing can direct olefin insertion stereochemistry and polymer architecture. Partnering with Dow, our chemistry to date has enabled production of about 30 billion kg of stronger, more processable, more recyclable polyolefins, including those produced from sustainable sugarcane ethanol. Strong, lightweight, inexpensive, chemically inert polyolefins find use in products as diverse as automotive parts, food packaging, agriculture, clothing, solar cell coatings, and medical prosthetics.
In recent work, we have been creating binuclear complexes with mechanistically dissimilar metal catalytic sites and demonstrating enzyme-like cooperative interactions, scaling with M···M’ distance and affording new polymers. We are revisiting the original surface-bound catalysts and find that very strong Brønsted acidic surfaces create species with virtually 100% of the sites catalytically active for olefin polymerization, and even more intriguing, arene hydrogenation. The combination of EXAFS (with Jeff Miller of Argonne National Lab), two-dimensional solid state NMR (with Marek Pruski of Ames National Lab), DFT computation (with Alessandro Motta of Rome University), and detailed mechanistic analysis has illuminated the catalyst structures and explained why H2 delivery is selective for a single arene π-face. For mixtures of aromatics, these catalysts exhibit significant selectivity for carcinogenic benzene hydrogenation, modeling possible processes for detoxifying gasoline.
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Figure 5

A “shish kebab” in which phthalocyanine polymers are connected via central Si-O-Si, Ge-O-Ge, or Sn-O-Sn linkages.
 

Figure 5

Soon after I arrived at Northwestern, I was intrigued by the work of Stanford University’s Jim Collman on metal complexes that crystallize in stacks like coins to provide a pathway for one-dimesional electrical conduction. Brian Hoffman, Jim Ibers, Mark Ratner, and I collaborated on synthetic, spectroscopic, structural, and theoretical studies of these systems and showed that metal or ligand “partial oxidation,” for example, by I2, creates empty bandlike states and, in cases such as metallophthalocyanines, “metallike” 1-D conductivity. However, for molecular systems, the challenge remained of ensuring that face-to-face stacking was preserved, ideally with controllable π-π distances. We addressed this issue with a “shish kebab” strategy in which phthalocyanine polymers were connected via central Si–O–Si, Ge–O–Ge, or Sn–O–Sn linkages (figure 5). We could then “dial in” the levels of oxidation while preserving the stacking, and analyze the results with a variety of incisive structural, spectroscopic, magnetic, electrical, and theoretical tools.
My fascination with charge transport phenomena in solids has continued, and today involves both “soft” (organic molecules and assemblies; polymers) and “hard” (oxides, chalcogenides) materials. The former studies focus on transistors, solar cells, and organic light-emitting diodes (OLEDs) using tunable, Earth-abundant organic materials. We seek to print these as “inks” in high-throughput production. The key materials in a transistor, the basic building block for all modern electronics, are the semiconductor, gate dielectric, and the source, drain, and gate electrodes. Our first target was relatively unexplored electron-transporting (n-type), versus established hole-transporting (p-type), organic semiconductors—necessary components of complementary circuits for high-speed, low-power operation. Collaborations with colleague Tony Facchetti, and later with Mike Wasielewski, yielded environmentally stable, high-mobility n-type semiconductors, and ultimately, devices with inkjet-printed complementary circuits. Theoretical studies with Mark Ratner convincingly defined the electronic structural and molecular architectural requirements for n-type semiconductors.
Gate dielectrics positioned between the transistor gate electrode and the semiconductor modulate the flow of current through the semiconducting channel and are critical to real world performance. Collaborating with Tony Facchetti and Mark Ratner, we invented self-assembled nanodielectrics (SANDs) that are compatible with organic electronics and deliver high dielectric constants, charge-trap-free interfaces, and nanoscale thicknesses. SANDs significantly enhance the performance of diverse organic and inorganic transistors, are radiation-hard, and are compatible with many substrate types; they stimulated fruitful device collaborations with Mark Hersam and Lincoln Lauhon of Northwestern; John Rogers, now of Northwestern; David Janes of Purdue University; and many companies. This also led to the cofounding of two Northwestern spinoffs with Tony Facchetti, Polyera and Flexterra, to transform these laboratory discoveries into printed products.
My interest in hard materials began with metal oxides. The late 1980s advent of cuprates with astounding superconducting properties caused me to ask whether such films could be grown using chemical processes. Therefore we designed, synthesized, and refined volatile metal-organic Y, Ba, Cu, Tl, Bi, and Ca precursors that enabled the controlled growth of excellent quality superconducting cuprate films by a scalable metal-organic chemical vapor deposition (MOCVD) process in collaboration with Northwestern engineers Bruce Wessels, Carl Kannewurf, and Bob Chang. These films and our ability to vary stoichiometry provided samples for studies aimed at understanding the intrinsic current-carrying capacity of these materials.
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Figure 6

Credit: Courtesy of Tobin Marks/C&EN
Two images depict how inorganic and organic materials are combined to create a high-performance transistor with high optical transparency.
 

Figure 6

Credit: Courtesy of Tobin Marks/C&EN
We next turned to other oxides, especially those combining optical transparency and electrical conductivity, which while seemingly contradictory, is realized in materials such as tin-doped indium oxide (ITO), used in flat-panel displays, solar cells, touch screens, and numerous other products as transparent electrodes. We reasoned that alternative growth techniques, doping, and oxide matrices might enhance conductivity at comparable transparencies, and allow growth on flexible plastics. Soon, MOCVD growth of cubic, optically transparent ­Cd1-xInxO films demonstrated record conductivity and benefited from theoretical collaboration with physicists Arthur Freeman of Northwestern and Julia Medvedeva, now of the University of Missouri). We also employed another low-temperature technique to grow In2O3 films on SAND, yielding transparent transistors with exceptional performance.
We next sought the solution-phase growth of electronically functional, ideally flexible semiconducting, dielectric, and conducting oxide films from solution at temperatures compatible with polymeric substrates. This was achieved via combustion synthesis, affording amorphous oxide films and flexible transparent transistors of electronic quality comparable to those grown by industrial sputtering processes (figure 6). Similar strategies afforded transparent flexible electrodes for rollable plastic solar cells, and unusual “antiambipolar” heterojunctions with carbon nanotubes and 2-D metal chalcogenides, in collaboration with Mark Hersam and Lincoln Lauhon. Such devices have potential in Wi-Fi and Bluetooth circuitry. Similar concepts were employed in our very successful design of polymer solar cells.
This concludes a brief summary of my research at Northwestern, crossing many disciplinary boundaries. These accomplishments would not have been possible without collaborators around the globe and the dedicated enthusiasm of my students and postdocs who contributed immensely to this enterprise. I dedicate this address to them.
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Miriam E. Marks
Credit: Tobin Marks
A photo of Tobin Marks’s daughter, Miriam.
 
Miriam E. Marks
Credit: Tobin Marks
As Jackie Barton noted in her 2015 Priestley address, many of life’s pathways are the products of accidents and opportunities. In that way I met and married my lifetime partner and fellow chemist, Indrani Mukharji. Coming from an academic family of two scientists, she understands the life we lead and amazingly puts up with me. Indrani’s father was Gilbert Stork’s first postdoc, moving with him from Harvard to Columbia University in the 1950s. We still keep in touch with Gilbert.
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Indrani Mukharji, and Marks.
Credit: Courtesy of Tobin Marks
A photo of Tobin and his wife, Indrani Mukharji.
 
Indrani Mukharji, and Marks.
Credit: Courtesy of Tobin Marks
After spending a decade as a corporate scientist, Indrani has been a senior administrator at Northwestern for the past 22 years. Our daughter, Miriam Marks, wanted a different life. After studying public policy and economics at Stanford, she is now a student at New York University Law School. I will be forever indebted to them for their love, moral support, and endless patience.
And what of chemistry? Why is it unique? Steve Lippard argued in his 2014 Priestley address that the term “central science” might imply a mere service role. And I suspect that all scientists feel that their discipline is central. Lord Rutherford once said that “all science is either physics or stamp collecting.” So we might instead regard chemistry as the “all-pervasive science,” or the “interfacing science,” or the “indispensable science.” However, I feel that we should ask what we chemists do that is truly unique and that will be forever unique. I would argue that first and foremost, chemists make things, that with deep knowledge and skill we create “the stuff that dreams are made of.”
As you ponder these issues, you may feel the need for a libation. So I will close with a toast to our ACS award winners, to chemists in every walk of life, and to chemistry as an enduring, indispensable, and dynamic science! Good night and safe travels!

More on this story:

miércoles, 15 de febrero de 2017

Epoxies: easy to apply one component grip enhancers

Dura-Grip™ SLIP RESISTANT EPOXY WITH GRIT PRODUCT DATA SHEET

_




CHARACTERISTICS
Dura-Grip is a Water Based Epoxy Ester
coating specifically designed to provide skid resistant durable textured coating for foot traffic
on steel, fiber
glass, treated aluminum, concrete and properly primed wood substrates. Dura-Grip is ideal on boats,
trailers, laundry rooms, on steps and ramps, and a variety of Light Industrial, Commercial and
Residential areas.
Color: ........................................... 12 Colors Available Coverage: .................
................. .................400 ft2/gal Recommended:
......................................... 400 ft2/gal
@ 4 mils wet .............................................. 1.5 mils dry
Drying Time @ 77°F (25°C), 50% Relative Humidity
Temperature and humidity dependent
Touch: ...................................... 30 - 40 min. Tack Free Recoat or Topcoat:
.................................. 1 – 2 hours Dry Hard:
....................................................... 72 hours Full Cure:
...................................................... 5-7 days
Flash Point:................................................... > 212° F Finish: ......... S/G
Textured (50-60 units @ 60° Gloss) Cleanup:
............................................................ Water Vehicle Type:
........................................... Epoxy Ester
VOC (less exempt solvent):160 - 180 g/L.,1.3 – 1.55 lb/gal
Volume Solids: ................................................. 36.7%
Weight Solids: .................................................. 46.1%
Weight/Gallon: ............................................ 8.5 – 10.1
Measured Static Friction of Coating Surfaces: ASTM C 4518-91 Steel-0.158 Rubber –0.742
A.I.M. category: Non-flat Interior/Exterior Coatings




Mildew - Remove from exposed wood or other surfac before painting by washing with a solution of
1-part liq household bleach and 3 parts of water. Apply the solut and scrub the mildewed area.
Allow the solution to remain on the surface for 10 minutes. Rinse thoroughl with water and allow
the surface to dry before painting Wear protective eyewear, waterproof gloves and protective
clothing. Quickly wash off any of the mixtur that comes in contact with your skin or eyes. Do not a
detergents or ammonia to the bleach/water solution. APPLICATON
Mix Dura-Grip thoroughly before and during each application! Apply with brush, roller or squeegee.
Avoi painting late in the day when dew or condensation is likely to form or when rain is
threatening. Apply when the temperature is 50° F (10° C) min., 90° F (32°C) m (air, surface and
material), at least 5° F above dew poi The relative humidity should be 85% maximum. Do no apply to
porous substrates new wood, plywood, exteri drywall, etc. if the substrates have a moisture content
greater than 15%. In most cases, use at mixed consistency. Do not expose subject surfaces to foot
traffic in less than 72 hrs. More time may be necessar depending upon atmospheric conditions.
Brush - No reduction is necessary. Use a nylon/polyester brush.
Roller - No reduction is necessary. Use a 3/8” woven nap with a phenolic core.
Squeegee - Flat Rubber
GENERAL SURFACE PREP
Surfaces must be clean, dry and free from contaminants such as, oil, waxes, grease, dirt, mildew or
other foreign contaminants. Shiny surfaces should be de-glossed by lightly sanding or using a
chemical de-glosser before using Dura-Grip. For wood surfaces, one coat of exterior oil base primer
recommended over clean dry
wood substrates. For concrete, clean with tri-sodium phosphate (TSP) and a firm bristle brush.
Rinse area thoroughly with water. New and smooth dense concrete will require an acid etch before
any application of Firm Foot. Aluminum and other non-ferrous metals should be treated with an
aluminum acid etch preparation available at most paint / hardware stores. Over ferrous metals a
solvent based primer, will provide additional rust prevention. Fiberglass should be lightly sanded
or wiped with acetone before application.
Supersedes previous data sheets for this product.
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Note: Epoxies and Epoxy Esters may need to be recoated every 1-2 yr. on Exterior exposures due to
the damaging affects of UV degradation.
CLEANUP INFORMATION
Clean hands and tools immediately with soap and warm water.
CAUTIONS
Protect from freezing. This product contains solvents and/or other chemical ingredients. Adequate
health and safety precautions should be observed during storage, handling, use and drying periods.
READ MATERIAL SAFETY DATA SHEETS BEFORE USING THIS PRODUCT
LIMITATIONS
The technical data and suggestions for use in this product data sheet are currently correct to the
best of our knowledge, but are subject to change without notice. Because application and conditions
vary, and are beyond our control, we are not responsible for results obtained in using this
product, even when used as suggested. The user should conduct tests to determine the suitability of
the product for the intended use (including liability for breach of warranty, strict liability in
tort, negligence or otherwise) is limited exclusively to replacement of the product or refund of
its price. Under no circumstance are
we liable for incidental and consequential damages.

miércoles, 7 de diciembre de 2016

Eliminate Fragrances.......


 

fragranceimageMELBOURNE, AUSTRALIA—A University of Melbourne researcher has found that over one-third of Americans report health problems—from asthma attacks to migraine headaches—when exposed to common fragranced consumer products such as air fresheners, cleaning supplies, laundry products, scented candles, cologne, and personal care products.

The study also found that fragranced products may affect profits, with more than 20 percent of respondents entering a business, but leaving as quickly as possible if they smell air fresheners or some fragranced product. More than twice as many customers would choose hotels and airplanes without fragranced air than with fragranced air.

In the workplace, over 15 percent of the population lost workdays or a job due to fragranced product exposure. Over 50 percent of Americans surveyed would prefer fragrance-free workplaces. And over 50 percent would prefer that health care facilities and professionals were fragrance-free.

The research was conducted by Professor Anne Steinemann, from the University of Melbourne School of Engineering, who is a world expert on environmental pollutants, air quality, and health effects. Professor Steinemann conducted a nationally representative population survey in the United States, using a random sample of 1,136 adults from a large web-based panel held by Survey Sampling International (SSI). The results are published in the international journal Air Quality, Atmosphere & Health.

‘A Huge Problem’

When exposed to fragranced products, 34.7 percent of Americans suffer adverse health effects, such as breathing difficulties, headaches, dizziness, rashes, congestion, seizures, nausea, and a range of other physical problems. For half of these individuals, effects are potentially disabling, as defined by the Americans with Disabilities Act.

“This is a huge problem; it’s an epidemic,” says Professor Steinemann.

Fragranced products are pervasive in society, and over 99 percent of Americans are regularly exposed to fragranced products from their own use or others’ use. Reports of adverse health effects were as frequent and wide-ranging across all types of fragranced products.

“Basically, if it contained a fragrance, it posed problems for people,” Professor Steinemann said.

Professor Steinemann is especially concerned with involuntary exposure to fragranced products, or what she calls “secondhand scents.” She found over 20 percent of the population suffer health problems around air fresheners or deodorizers, and over 17 percent can’t use public restrooms that have air fresheners. In addition, over 14 percent of the population wouldn’t wash their hands with soap if it was fragranced.

Many React to Cleaning Products

Over 12 percent of the population experience health problems from the scent of laundry products vented outdoors, over 19 percent from being in a room cleaned with scented products, and over 23 percent from being near someone wearing a fragranced product.

More generally, over 22 percent of Americans surveyed can’t go somewhere because exposure to a fragranced product would make them sick.

“These findings have enormous implications for businesses, workplaces, care facilities, schools, homes, and other private and public places,” said Professor Steinemann. For instance, a growing number of lawsuits under the Americans with Disabilities Act concern involuntary and disabling exposure to fragranced products.

Professor Steinemann’s earlier research found that fragranced products—even those called green, natural, and organic—emitted hazardous air pollutants. However, fragranced consumer products sold in the United States (and other countries) are not required to list all ingredients on their labels or material safety data sheets. Nearly two-thirds of the population surveyed were not aware of this lack of disclosure, and would not continue to use a fragranced product if they knew it emitted hazardous air pollutants.

Recommends Fragrance-free Policies

Professor Steinemann’s research continues to investigate why fragranced product emissions are associated with such a range of adverse and serious health effects. In the meantime, for solutions, Professor Steinemann suggests using products that do not contain any fragrance (including masking fragrance, which unscented products may contain). She also recommends fragrance-free policies within buildings and other places.

“It’s a relatively simple and cost-effective way to reduce risks and improve air quality and health,” she explains.

Professor Steinemann has also completed a survey of the Australian population, with results expected to be published soon. “The numbers are similarly striking,” she said.

Professor Steinemann can be reached at anne.steinemann@unimelb.edu.au.

 

jueves, 17 de noviembre de 2016

11/11/2016

Protecting IAQ Through Cleaning And Maintenance




A report, recently posted on the US Environmental Protection Agency (EPA), finds that "climate change may worsen existing indoor environmental problems and indoor air quality (IAQ)."

One reason for this is the fact that we spend 90 percent of our time in an indoor environment such as a school, office, factory, or home. However, most of these buildings were built to meet environmental conditions at the time of construction, conditions that are changing rapidly due to climate change. 

Because of this, one of the most effective ways to protect IAQ and adjust to changing environmental conditions is "the operation and maintenance of buildings," according to the EPA.

The EPA report states that there are three broad approaches to help moderate indoor air pollution as climate changes advances.  These are:

1. Source control
2. Ventilation
3. Air cleaning systems.

"There is not a lot that the professional cleaning industry can do about improving ventilation or installing air cleaning systems," says Mike Sawchuk, Chief Business Development Officer for Avmor, a leading manufacturer and marketer of professional cleaning products in North America. 

"But there are many things we can do when it comes to source control and it all starts with the cleaning chemicals we select."

According to Sawchuk, green-certified cleaning chemicals introduced over the past decade have dramatically reduced the number of volatile organic compounds and other harmful chemical emissions released into the air.

However, times are changing and we cannot rest on past laurels, according to Sawchuk. 

"Of the major green-certification organizations, [at this time] only Green Guard has raised the bar, taking a very focused look at the impact of cleaning chemicals on IAQ.  With climate change advancing, this is something all of the major certification organizations should be doing." 

Until then, he recommends using green certified products that are "dual certified" with Green Guard.

Sawchuk adds that in the past few years, the leading green certification organizations have been moving in different directions, specializing on different products and industries.

"No matter what directions they take, IAQ is an issue they must always stay focused on...and this is going to be even more important in coming years."

martes, 15 de noviembre de 2016

The best Scientist

Does Chlorine
Get a Bad Rap?
When it comes to disinfection at treatment plants, chlorine has quite the reputation. To some, it’s
known as a reliable and trusted solution. To many others, especially among the public at large,
it’s looked at with skepticism and concern – but that may be simply a matter of not knowing the
facts. Either way, it’s one of the ubiquitous aspects of water and wastewater disinfection… and for
good reason.

To separate fact from fiction and clear up exactly how chlorine should be utilized at treatment
plants, we spoke with Evoqua Water Technologies’ Daryl Weatherup, director of marketing for the
company’s Wallace & Tiernan brand. He walked us through the different forms chlorine can take, its
reputation among the industry and ratepayers, and how to determine its best use at a given plant.

How is chlorine utilized at treatment plants?
Chlorine is used in many water and wastewater applications, not only in the U.S. but around the
world. It really has been the most predominant method of disinfection for the past century.

What’s different about chlorination, though, is that it’s not just available in one format. There
are several formats that it is available in: gaseous chlorine, liquid sodium hypochlorite (bleach
being the common household name), dry or solid form tablets or pellets of calcium hypochlorite, and
then the fourth main way to apply chlorine in water and wastewater systems is actually generated
onsite through the electrochlorination of brine or saltwater solutions.

Do you think that chlorine has the reputation that it deserves?
I think there are two sides to the reputation of chlorine and chlorination. On the one hand,
chlorine has a great reputation as being a widely used disinfectant that has really transformed
the water industry and improved human health, environmental water quality, and sanitation over the
last 100 years.
But there’s also a negative side to it. When chlorine’s applied in the right amount to the
controlled process, it is a good

disinfectant. But if it is released in a spill or leak in higher doses, it can be harmful. I think
that is where some of the negative connotation comes about and the reputation it has as being
potentially unsafe.

Do you think that reputation it has as a dangerous chemical is more prevalent among ratepayers or
with the professionals who are actually disinfecting water?


Water Online • www.wateronline.com
1


&A





I think it’s a little bit of both. At the consumer ratepayer level, they get a lot of their
information through the media, and the media doesn’t always report safety incidents in the right
way. Oftentimes there are accidents that happen that are not caused by chlorine but get reported as
involving chlorine. At least in the U.S., there are a higher number of safety incidents with other
liquid chemicals and other dangerous substances in treatment plants than there are with chlorine
gas.

On the professional level, there is competition with other methods of disinfection. Some
are chemical-free but provide no residual disinfectant, which is required in municipal water
distribution. Those that offer chemical-free solutions might add to the negative reputation that
chlorine can have.
What advances in process and technology are making chlorine safer today?
There are quite a few things that have changed over the last 100 years with the way chlorination is
done today. It started out in
1913 with the first commercial chlorinator, and the technology has improved quite a bit since.
The main things that have changed are the engineering methods available, the materials of
construction available — metal alloys, engineered plastics, and so forth — that have really
allowed us to improve the quality of the actual chlorine dosing systems themselves, the
chlorinators. We’ve engineered chlorinators to be more durable, have fewer moving parts, and be
inherently safe.
Aside from that, there are additional devices that help make the overall chlorination systems
safer, such as double- check valves and seals, safety shut-off valves, or emergency vapor
scrubbers — also manufactured by Evoqua — which can scrub all of the chlorine gas out of a room
even in the event of a full-scale release. We’ve manufactured this for our systems as a secondary
safety system. There are other ancillary items, like gas detection systems and fire safety doors,
that can go towards making the overall system very, very safe.

What alternatives to chlorination are out there?
There are no other alternative methods that provide the same cost-effective benefits as
chlorination or are as widely used
as chlorination. There are other methods that are called “alternate disinfectants,,,”
including UV and ozone, as well as various other types of disinfectants that are innovative but not
as widely used.

How should a treatment plant assess the different forms of chlorine that exist and make a selection
on which one is the best for them?
This is probably the question I receive the most. The best answer that I can give is that it’s
really a local decision that needs to take
into account several factors. It is not just about capital costs or operating costs alone.

We work with the water utility and ask them what their decision-making factors and drivers
are. Are there any environmental concerns? Is the facility in a rural area or an urban area? What’s
the distance away from the nearest chemical supplier?

Beyond that, we look at their water-quality

goals and disinfection targets, along with the capacity and treated flow rate. That will determine
what the total chlorine demand is. We also take into consideration, from that, how often they might
need to order chemicals.

As a manufacturer of all four types of chlorination systems, not to mention UV, we offer expertise
on which format of
chlorine is best for the given application. I think it’s important to have a well-balanced view of
what is available and not be pushed towards one method or another. Additionally, there are
consultants we work with who also specialize in this selection process. The U.S. EPA and AWWA
both offer information about selecting disinfectants and have published resource manuals on
those as well.
If someone tells you they believe using chlorine as a disinfectant is dangerous, how do you
respond?

Anything can be dangerous when it’s mishandled, and that chlorine is by far the safest, most
widely used, and most reliable form of disinfection. One of the things that works against switching
away from chlorination to other methods is typically the cost, the reliability, and the
availability to the general public. That’s why, after a century, it’s still the most widely used
form of disinfection in the world today.


Water Online • www.wateronline.com
2

The best Scientist

Does Chlorine
Get a Bad Rap?
When it comes to disinfection at treatment plants, chlorine has quite the reputation. To some, it’s
known as a reliable and trusted solution. To many others, especially among the public at large,
it’s looked at with skepticism and concern – but that may be simply a matter of not knowing the
facts. Either way, it’s one of the ubiquitous aspects of water and wastewater disinfection… and for
good reason.

To separate fact from fiction and clear up exactly how chlorine should be utilized at treatment
plants, we spoke with Evoqua Water Technologies’ Daryl Weatherup, director of marketing for the
company’s Wallace & Tiernan brand. He walked us through the different forms chlorine can take, its
reputation among the industry and ratepayers, and how to determine its best use at a given plant.

How is chlorine utilized at treatment plants?
Chlorine is used in many water and wastewater applications, not only in the U.S. but around the
world. It really has been the most predominant method of disinfection for the past century.

What’s different about chlorination, though, is that it’s not just available in one format. There
are several formats that it is available in: gaseous chlorine, liquid sodium hypochlorite (bleach
being the common household name), dry or solid form tablets or pellets of calcium hypochlorite, and
then the fourth main way to apply chlorine in water and wastewater systems is actually generated
onsite through the electrochlorination of brine or saltwater solutions.

Do you think that chlorine has the reputation that it deserves?
I think there are two sides to the reputation of chlorine and chlorination. On the one hand,
chlorine has a great reputation as being a widely used disinfectant that has really transformed
the water industry and improved human health, environmental water quality, and sanitation over the
last 100 years.
But there’s also a negative side to it. When chlorine’s applied in the right amount to the
controlled process, it is a good

disinfectant. But if it is released in a spill or leak in higher doses, it can be harmful. I think
that is where some of the negative connotation comes about and the reputation it has as being
potentially unsafe.

Do you think that reputation it has as a dangerous chemical is more prevalent among ratepayers or
with the professionals who are actually disinfecting water?


Water Online • www.wateronline.com
1


&A





I think it’s a little bit of both. At the consumer ratepayer level, they get a lot of their
information through the media, and the media doesn’t always report safety incidents in the right
way. Oftentimes there are accidents that happen that are not caused by chlorine but get reported as
involving chlorine. At least in the U.S., there are a higher number of safety incidents with other
liquid chemicals and other dangerous substances in treatment plants than there are with chlorine
gas.

On the professional level, there is competition with other methods of disinfection. Some
are chemical-free but provide no residual disinfectant, which is required in municipal water
distribution. Those that offer chemical-free solutions might add to the negative reputation that
chlorine can have.
What advances in process and technology are making chlorine safer today?
There are quite a few things that have changed over the last 100 years with the way chlorination is
done today. It started out in
1913 with the first commercial chlorinator, and the technology has improved quite a bit since.
The main things that have changed are the engineering methods available, the materials of
construction available — metal alloys, engineered plastics, and so forth — that have really
allowed us to improve the quality of the actual chlorine dosing systems themselves, the
chlorinators. We’ve engineered chlorinators to be more durable, have fewer moving parts, and be
inherently safe.
Aside from that, there are additional devices that help make the overall chlorination systems
safer, such as double- check valves and seals, safety shut-off valves, or emergency vapor
scrubbers — also manufactured by Evoqua — which can scrub all of the chlorine gas out of a room
even in the event of a full-scale release. We’ve manufactured this for our systems as a secondary
safety system. There are other ancillary items, like gas detection systems and fire safety doors,
that can go towards making the overall system very, very safe.

What alternatives to chlorination are out there?
There are no other alternative methods that provide the same cost-effective benefits as
chlorination or are as widely used
as chlorination. There are other methods that are called “alternate disinfectants,,,”
including UV and ozone, as well as various other types of disinfectants that are innovative but not
as widely used.

How should a treatment plant assess the different forms of chlorine that exist and make a selection
on which one is the best for them?
This is probably the question I receive the most. The best answer that I can give is that it’s
really a local decision that needs to take
into account several factors. It is not just about capital costs or operating costs alone.

We work with the water utility and ask them what their decision-making factors and drivers
are. Are there any environmental concerns? Is the facility in a rural area or an urban area? What’s
the distance away from the nearest chemical supplier?

Beyond that, we look at their water-quality

goals and disinfection targets, along with the capacity and treated flow rate. That will determine
what the total chlorine demand is. We also take into consideration, from that, how often they might
need to order chemicals.

As a manufacturer of all four types of chlorination systems, not to mention UV, we offer expertise
on which format of
chlorine is best for the given application. I think it’s important to have a well-balanced view of
what is available and not be pushed towards one method or another. Additionally, there are
consultants we work with who also specialize in this selection process. The U.S. EPA and AWWA
both offer information about selecting disinfectants and have published resource manuals on
those as well.
If someone tells you they believe using chlorine as a disinfectant is dangerous, how do you
respond?

Anything can be dangerous when it’s mishandled, and that chlorine is by far the safest, most
widely used, and most reliable form of disinfection. One of the things that works against switching
away from chlorination to other methods is typically the cost, the reliability, and the
availability to the general public. That’s why, after a century, it’s still the most widely used
form of disinfection in the world today.


Water Online • www.wateronline.com
2

Dura-Grip™ SLIP RESISTANT EPOXY WITH GRIT PRODUCT DATA SHEET

_




CHARACTERISTICS
Dura-Grip is a Water Based Epoxy Ester
coating specifically designed to provide skid resistant durable textured coating for foot traffic
on steel, fiber
glass, treated aluminum, concrete and properly primed wood substrates. Dura-Grip is ideal on boats,
trailers, laundry rooms, on steps and ramps, and a variety of Light Industrial, Commercial and
Residential areas.
Color: ........................................... 12 Colors Available Coverage: .................
................. .................400 ft2/gal Recommended:
......................................... 400 ft2/gal
@ 4 mils wet .............................................. 1.5 mils dry
Drying Time @ 77°F (25°C), 50% Relative Humidity
Temperature and humidity dependent
Touch: ...................................... 30 - 40 min. Tack Free Recoat or Topcoat:
.................................. 1 – 2 hours Dry Hard:
....................................................... 72 hours Full Cure:
...................................................... 5-7 days
Flash Point:................................................... > 212° F Finish: ......... S/G
Textured (50-60 units @ 60° Gloss) Cleanup:
............................................................ Water Vehicle Type:
........................................... Epoxy Ester
VOC (less exempt solvent):160 - 180 g/L.,1.3 – 1.55 lb/gal
Volume Solids: ................................................. 36.7%
Weight Solids: .................................................. 46.1%
Weight/Gallon: ............................................ 8.5 – 10.1
Measured Static Friction of Coating Surfaces: ASTM C 4518-91 Steel-0.158 Rubber –0.742
A.I.M. category: Non-flat Interior/Exterior Coatings




Mildew - Remove from exposed wood or other surfac before painting by washing with a solution of
1-part liq household bleach and 3 parts of water. Apply the solut and scrub the mildewed area.
Allow the solution to remain on the surface for 10 minutes. Rinse thoroughl with water and allow
the surface to dry before painting Wear protective eyewear, waterproof gloves and protective
clothing. Quickly wash off any of the mixtur that comes in contact with your skin or eyes. Do not a
detergents or ammonia to the bleach/water solution. APPLICATON
Mix Dura-Grip thoroughly before and during each application! Apply with brush, roller or squeegee.
Avoi painting late in the day when dew or condensation is likely to form or when rain is
threatening. Apply when the temperature is 50° F (10° C) min., 90° F (32°C) m (air, surface and
material), at least 5° F above dew poi The relative humidity should be 85% maximum. Do no apply to
porous substrates new wood, plywood, exteri drywall, etc. if the substrates have a moisture content
greater than 15%. In most cases, use at mixed consistency. Do not expose subject surfaces to foot
traffic in less than 72 hrs. More time may be necessar depending upon atmospheric conditions.
Brush - No reduction is necessary. Use a nylon/polyester brush.
Roller - No reduction is necessary. Use a 3/8” woven nap with a phenolic core.
Squeegee - Flat Rubber
GENERAL SURFACE PREP
Surfaces must be clean, dry and free from contaminants such as, oil, waxes, grease, dirt, mildew or
other foreign contaminants. Shiny surfaces should be de-glossed by lightly sanding or using a
chemical de-glosser before using Dura-Grip. For wood surfaces, one coat of exterior oil base primer
recommended over clean dry
wood substrates. For concrete, clean with tri-sodium phosphate (TSP) and a firm bristle brush.
Rinse area thoroughly with water. New and smooth dense concrete will require an acid etch before
any application of Firm Foot. Aluminum and other non-ferrous metals should be treated with an
aluminum acid etch preparation available at most paint / hardware stores. Over ferrous metals a
solvent based primer, will provide additional rust prevention. Fiberglass should be lightly sanded
or wiped with acetone before application.
Supersedes previous data sheets for this product.
es
uid ion

y
.

e
dd

d ax.
nt. t
or



y






Note: Epoxies and Epoxy Esters may need to be recoated every 1-2 yr. on Exterior exposures due to
the damaging affects of UV degradation.
CLEANUP INFORMATION
Clean hands and tools immediately with soap and warm water.
CAUTIONS
Protect from freezing. This product contains solvents and/or other chemical ingredients. Adequate
health and safety precautions should be observed during storage, handling, use and drying periods.
READ MATERIAL SAFETY DATA SHEETS BEFORE USING THIS PRODUCT
LIMITATIONS
The technical data and suggestions for use in this product data sheet are currently correct to the
best of our knowledge, but are subject to change without notice. Because application and conditions
vary, and are beyond our control, we are not responsible for results obtained in using this
product, even when used as suggested. The user should conduct tests to determine the suitability of
the product for the intended use (including liability for breach of warranty, strict liability in
tort, negligence or otherwise) is limited exclusively to replacement of the product or refund of
its price. Under no circumstance are
we liable for incidental and consequential damages.

Advanced Technologies for Guaranteed Performance
Industrial and municipal wastewater treatment generates odors that can be strong, persistent, and a
nuisance to employees, residents, businesses, and industries located near the
wastewater treatment plant.


SPECIAL BLEND MISTER CT‐417 AND MISTING ASSEMBLY TM‐0010 OFFER A GREAT SOLUTION
Example: An atomized “dome” of Odor Neutralizing products that can be used to control odors rising
from a primary equalization tank at a municipal
wastewater facility.
Odors are generated in varying degrees throughout the wastewater treatment
process with the main odor‐generating areas being pump stations, head works, clarifiers, digesters,
aeration basins, lagoons and sludge handling areas, sludge drying beds, manholes areas amongst
others.

Odors that are generally associated with this process include hydrogen sulfide, ammonia, sulfur
dioxide, aromatic hydrocarbons, mercaptans, amines and indoles.

Hydrogen sulfide is a serious problem in wastewater treatment plants. Fogging systems installed at
the bar screens and digesters, can solve the problem. In some cases the odor control products can
also be diluted with plant water for a combined action, synergistic operation.

Septage haulers need to take their loads somewhere and that is usually the local wastewater plant.
Raw septage is especially odorous and can present odor problems to plants that otherwise have their
industrial emissions under control. Simple fan or nozzle atomization systems positioned near the
unloading point and vented or open downstream locations will provide simple and effective temporary
odor control as needed.
CHEMTRON
3901 S.W. 47TH AVE. #400, DAVIE, FLORIDA 33314
Phone: (954)584-4530, Fax: (954)584-4531
email: sales@ChemTron.com
www.chemtron.com

lunes, 25 de abril de 2016

DPNP

Glycol Ether DPNP

CAS No: 29911­-27-­1


Glycol Ether DPNP is a slow-evaporating glycol ether that has a near mid-range balance of hydrophobic and hydrophilic characteristics, and it offers significant water solubility.

Glycol Ether DPNP is used in water and solvent-based coatings. It provides great coalescing and film and surface tension reducing properties. Applications include many products in the Paints, Coatings, Inks, and Adhesives industries as well as some agricultural and textile products.

We have helped multiple customers, from small end users to large Fortune 500 customers, with their Glycol Ether DPNP supply requirements and can ship bulk and various packaged products to meet such needs. Download more information below or call us! +1-866-282-3384

viernes, 1 de mayo de 2015

Chemistry of boiler's feedwater for different metals


Developing a feedwater chemistry program that will minimize corrosion across a variety of metallurgies doesn’t have to be difficult. This article reviews the requirements for three common metallurgies in condensate and feedwater piping and the chemistry options that operators have to minimize corrosion in this critical area of the plant. 

Alloys found in the condensate and feedwater systems of power plants include carbon steel for piping, pumps, and in some cases heat exchangers. Many systems still have some copper-based alloys from admiralty brass, and copper-nickel (Cu-Ni) alloys all the way to 400 Series Monel, primarily as feedwater heater tubes.

The major corrosion mechanisms affect the carbon steel and copper alloys. These include flow accelerated corrosion (FAC) and corrosion fatigue in carbon steel as well as ammonia-induced stress corrosion cracking, and ammonia grooving in copper alloys. FAC can have a variety of appearances (Figures 1 and 2).

PWR_030115_WaterChem_Fig1
1 Typical. Classic flow-accelerated corrosion (FAC) orange peel texture with no oxide coating. Courtesy: M&M Engineering Associates Inc.

 

PWR_030115_WaterChem_Fig2
2. Atypical. Compare the previous example with this one showing an unusual pattern of FAC in a deaerator. Courtesy: M&M Engineering Associates Inc.

Gradually, as aging feedwater heaters are replaced, plants often choose to go with a stainless steel alloy such as 304 or 316 for feedwater tubing. When the last copper feedwater heater is replaced, a change in feedwater chemistry is in order.

Stainless Steel

Stainless steel is protected by a tight adherent chromium oxide layer that forms on the surface. Stainless steels alloys are resistant to essentially all the corrosion mechanisms that commonly affect copper and carbon steel alloys in feedwater.

There is the tendency to think that stainless steel is the perfect alloy to replace copper-alloy feedwater heaters. However, stainless steel has its own Achilles heel: Chlorides can cause pitting, and chloride and caustic have, in some cases, led to stress corrosion cracking (SCC).

Typically, these chemicals are not present in sufficient concentration to cause corrosion on the tube side of feedwater heaters. However, there are cases where contamination of the steam that feeds the shell side of the stainless steel–tubed heat exchanger has resulted in SCC.

Remember, it is not the average concentration of the chloride or caustic that is of concern. Spikes in contamination can collect and concentrate in the desuperheating zone of the shell side of the feedwater heater and in crevices. These are the areas that can fail, even if the steam is pure most of the time. Where there is a potential for chloride or caustic contamination of the steam, stainless steels may not be the best fit or, at a minimum, alloys should be considered that have a higher resistance to chloride attack, such as 316 or 904L. In general however, it may be more productive to work on eliminating the potential for contamination than to alloy around the problem.

The most commonly quoted downside to the replacement of copper-alloy feedwater heater tubes with stainless steel is the difference in thermal conductivity. A quick look at the reference values will show that a 304 stainless steel has only one-seventh the thermal conductivity of admiralty brass and about one-third the conductivity of 90-10 Cu-Ni alloy. Numerous papers have been published discussing why these “textbook” values are unlikely to be experienced in the real world. This is certainly an important consideration with condenser tubes, where the potential for cooling water–side deposits and condenser cleanliness is likely to have a much more prominent effect on heat transfer than the textbook thermal conductivity of the tube metal. However, feedwater heater tubes should have little steam- or water-side fouling. Other factors, such as tube thickness may offset some of the thermal conductivity loss, and there are other design factors, such as susceptibility to vibration damage, to consider in selecting a material.

Carbon Steel

Carbon steel is passivated by the formation of a dual layer of magnetite (Fe3O4). The layer closest to the metal is dense but very thin, whereas the layer closest to the water is more porous and less stable. Hydroxide ions are necessary for the formation of magnetite. Due to the common utility practice of using feedwater to control the final temperature of superheat and reheat steam, the source of hydroxide in feedwater must be volatile, and ammonia or an amine is generally used for this purpose. A solid alkali such as sodium hydroxide must never be introduced ahead of where the takeoff to the attemporation is located.

Ammonia is very volatile, remaining in gaseous state during initial condensation. This may occur in the deaerator, condenser, or on the shell side of a feedwater heater. This lowers the effective pH of the first condensate and increases the solubility of the magnetite layer in that area. This can increase the rate of FAC in these areas.

For carbon steel, higher pH values are better for the production and stability of magnetite. Operating with low pH values in the feedwater and condensate destabilizes magnetite and increases the rate of FAC on carbon steel in the feedwater system. It also increases the iron in the feedwater, which generally winds up on the waterwall tubes. This iron deposition increases the risk of under-deposit corrosion mechanisms, inhibits heat transfer across the tube, and increases the frequency of chemical cleaning.

A case can be made for the use of carbon steel feedwater heater tubes, particularly alloys such as T-22, which contains 2.25% chromium (Cr) and 1% molybdenum (Mo). It has better thermal conductivity than stainless steel, is highly resistant to chloride SCC, and because it contains 2.25% Cr, is generally considered immune to FAC.

Copper Alloys

Copper alloy corrosion in the power industry has been studied in depth due to problems with copper deposits on the high-pressure (HP) turbine that reduced turbine efficiency and the maximum load that the unit could produce.

Zinc-containing brass alloys such as admiralty brass are particularly susceptible to attack from ammonia vapors. This can result in ammonia-induced SCC on the steam side of the condenser or feedwater heater. The same alloys are susceptible to a mechanism termed “ammonia grooving,” where steam and ammonia condense on the tube sheet and support plates of the feedwater heater and run over the tubes, creating a narrow group of corrosion directly adjacent to the tube sheet or support plate. Copper alloys containing nickel are far less susceptible to ammonia-induced SCC.

Admiralty brass alloys have the additional concern of corrosion of zinc in the alloy due to low-pH conditions in the feedwater or steam. Over time, the zinc can leach from the brass matrix, leaving only the copper sponge, which has little structural strength. This mechanism is called dezincification. Although not as common, copper-nickel alloys can also suffer from dealloying (Figure 3).

PWR_030115_WaterChem_Fig3
3. Weakened. Dealloying, dezincification in brass alloys, or removal of nickel from copper-nickel alloys will destroy the strength of the material. Courtesy: M&M Engineering Associates Inc.

There are three separate rates associated with the rate of corrosion of any copper alloy. These have been referred to as:

·         Rd—the rate at which corrosion products leave the surface as a dissolved species in the water (typically copper ammonium complexes).

·         Rf—the rate at which corrosion products (copper oxides in operating steam and condensate systems) form on the surface of the metal.

·         Rs—the rate at which copper corrosion products (typically oxides) leave the surface as suspended particles.

These rates are not necessarily correlated with each other and may not occur under the same chemical conditions. Copper oxide formation (Rf) can be protective, minimizing further corrosion of the alloy—as long as it remains intact. When chemical conditions change, such as moving from an oxidizing to a reducing condition, Rd and Rs may increase dramatically. Protective copper oxides are aggressively dissolved by the combination of ammonia, carbon dioxide, and oxygen. The most common place for all three of these to be present is in a copper-tubed condenser that has air in-leakage issues.

Once these corrosion products are dissolved or entrained, they are subject to downstream chemical conditions, where a change in the at-temperature pH or the oxidation reduction potential (ORP) in a specific location can cause the copper to “plate out” as copper metal on suction strainers, pump impellers, or on another feedwater heater tube surface in the form of a pure copper “snakeskin.” They may also continue on through the feedwater system and deposit on a boiler or superheater tube or on the HP turbine. Similar conditions (plating out) can occur in stainless steel sample lines, making the accurate measurement of copper corrosion products in a conventional sample line difficult.

Chemical Control of Feedwater

Proper alloy selection, either in the initial construction or as equipment is replaced, should be carefully considered. Once the decision is made, the water chemistry program must follow to minimize corrosion of the feedwater equipment and deposits in the boiler and turbine. The more metals there are in the mix, the more things need to be considered in the chemistry program. Copper alloys, in particular, force compromises, as the optimum chemistry requirements for copper and iron cannot be met simultaneously.

Feedwater pH Control. The pH limits recommended on all ferrous-alloy condensate and feedwater piping are now a minimum of 9.2 with an upper limit of 9.8 or even 10.0 in systems with an air-cooled condenser. If there are no copper alloys in the system, the biggest downside to having too much ammonia in the system is the frequent replacement of cation conductivity columns rather than corrosion in the carbon steel.

For those operating heat-recovery steam generators (HRSGs), there can be a significant drop in pH of the low-pressure (LP) drum water as ammonia (and some amines) leaves with the LP steam. It is important that the LP drum pH be monitored continuously and controlled certainly within the range of 9.2–9.8. Some suggest a minimum pH of 9.4 for water in the LP drum to protect downstream high-pressure and intermediate-pressure economizers.

The current recommended pH range for systems that have copper in either the main condenser or feedwater heaters is 9.0–9.3. (See the sidebar for an explanation of the necessity of accurate pH measurement.) Laboratory studies have shown that is actually the minimum range for avoiding copper corrosion in the copper alloys used in feedwater heaters and condensers. Lower feedwater and condensate pH values (for example, pH 7.0) have higher copper corrosion rates than pH 9, particularly under oxidizing conditions.

Measuring pHAccurate pH measurement in high-purity water is difficult. The very low specific conductivity of the water combined with the potential for ammonia to be lost and carbon dioxide to be simultaneously absorbed by the sample while it is being collected and measured can lead to confusing results. Inaccurate pH monitoring can result in over- or under-feeding of ammonia or amines.
Continuous online pH monitoring using pH probes specifically developed for high-purity water can improve the accuracy and reliability of the measurement.
The pH of high-purity waters can also be calculated from a combination of the specific conductivity and cation conductivity results. This can be done manually, or there are commercially available instruments that display a calculated and measured pH.
Due to these issues with pH, specific conductivity is often used to control the ammonia feed instead of controlling directly from a pH meter.

Ammonia or Amines. The addition of ammonia to condensate is the simplest and most direct way to raise the pH of the condensate and feedwater into the desired range to create and stabilize the magnetite layer. In all-ferrous systems, there should be a clear case or desired objective for using any other chemical for pH control. On the other hand, the use of neutralizing amines in the utility steam cycle has a long, successful history, particularly in units that have copper alloys in the feedwater heaters.

The decision to use neutralizing amine for iron corrosion should be based primarily on the need to provide more alkalinity (a higher pH) in an area of concern than can be achieved simply by increasing the ammonia levels. This may include areas where steam is first condensing into water, such as in an air-cooled condenser, or where water/steam mixtures are being released, such as in the deaerator.

Although amines are more common when copper alloys are found in the feedwater system or condenser, their presence does not necessarily require the use of a neutralizing amine. There are many mixed-metallurgy units that operate using ammonia and that carefully control air in-leakage with very low copper corrosion rates.

The choice of which neutralizing amine to use (and there are many) should be based on where and how it is to function. It is critical that both the basicity (amount of pH rise per ppm of amine) and volatility of the amine (the ratio of what goes into the steam versus what remains in the water) is matched to the application.

The criticism of the general use of amines in high-pressure utility cycles is centered on two issues: the degradation of these organic molecules in the steam cycle (particularly in the superheater and reheater) and the consequence of these degradation products—namely, an increase in the cation conductivity of the condensate and feedwater.

It has been long known that as neutralizing amines pass through the steam cycle, they break down into ammonia and organic acid byproducts such as acetic acid, formic acid, and carbon dioxide. The percentage of degradation is certainly specific to the particular amine and concentration in the steam, but it is also unit specific and depends, at a minimum, on the size and complexity of the superheater and reheater piping, where it appears most of the degradation occurs.

Those who advocate for the sole use of ammonia instead of amines point to the degradation of these products and see them as “single-use” chemicals—good for only one trip around the steam cycle. If all the amine degrades with one trip through the superheater and reheater, it cannot be available to minimize the corrosion of copper condenser tubes or affect the pH of a steam/water mixture in the feedwater, and so it would not be worth the trouble.

However, there are many different factors that affect amine degradation rates and, therefore, how beneficial an amine might be in the system. These include the operating pressure of the unit, where the copper alloys are located, and whether the unit even has a reheater. For example, in the standard triple-drum HRSG, a significant percentage of the amine may leave with the LP steam, where it recycles through the condenser and preheater sections of the HRSG and never sees the high-temperature areas. This would significantly increase its longevity and usefulness.

All these factors need be taken into account when considering whether an amine would be beneficial at a particular plant. It would behoove anyone who is considering trying an amine to set up to sample and test for the amine and degradation products around the cycle and also quantify improvements to iron and copper corrosion rates. That will help them determine, for their particular unit, if the benefits of amine use outweigh the costs.

The degradation products of any amine will add to the cation conductivity of the condensate and feedwater. The longevity and chemical structure of the amine will affect the cation conductivity “bump” that the plant will experience. Degassed cation conductivity can remove carbon dioxide but generally not all the other organic acids produced by amines. So if amines are used, the normal cation conductivity will need to be adjusted for the presence of these products.

Controlling Oxidation Reduction Potential

It can be generalized that the ability of an alloy to withstand corrosion is a function of the stability and tenacity of the oxide layer that forms on the metal surface. As discussed above, stainless steel has a very tight and tenacious layer of chromium oxide that prevents corrosion of the metal from oxygen and from the common pH ranges found in feedwater.

Establishing and maintaining a good oxide layer on carbon steel is critical to minimizing FAC. Copper oxides are also protective—as long as they remain in place.

Particularly in the case of copper alloys, the oxide layer can be easily disrupted. Research has shown that one of the most corrosive times for copper alloys is when they cycle between a reducing and oxidizing condition. Therefore, it is imperative that mixed-metallurgy feedwater systems contain sufficient reducing agent such as hydrazine or carbohydrazide to maintain a reducing condition at all times.

A reducing condition is not the same as the absence of dissolved oxygen. Regardless of how well the deaerator is functioning, if there are copper feedwater heaters in the system, the continuous addition of a reducing agent is required to achieve the negative ORP that is protective of copper alloys.

All volatile reducing agents used in utility cycles break down at temperatures typically associated with HP feedwater heaters or the economizer—and certainly by the time the water reaches the boiler. Therefore, regardless of which reducing agent is added to the condensate pump discharge, there is no protection for the copper alloy condenser tubes against the combined effect of dissolved oxygen, carbon dioxide, and ammonia. This is why it is so critical to minimize air in-leakage and control feedwater pH.

Many units have been replacing copper alloy feedwater heaters with carbon steel or stainless steel tubes over the years. When the last copper feedwater heater is replaced, the reducing agent can almost always be eliminated, regardless of whether the condenser contains copper alloys or not.

Carbon steel corrosion is inhibited by the presence of small amounts of dissolved oxygen. Research has shown that as little as 5 ppb to 10 ppb of dissolved oxygen significantly reduces the rate of FAC under feedwater conditions. This occurs because the dissolved oxygen present in the low-temperature feedwater (from the condenser to the deaerator) forms iron oxides that fill in the pores of the outer layer of the magnetite, dramatically improving its stability. Even in the absence of any measurable dissolved oxygen, after the deaerator, the ORP remains positive and increases the stability of the magnetite layer through the HP feedwater heaters and economizer.

The formation of these more resilient protective oxides is the basis of oxygenated treatment, which is successfully used on all supercritical plants in North America and many HP drum units. However, simply discontinuing the use of a reducing agent should never be confused with oxygenated treatment, where pure oxygen is purposefully injected, the deaerator vents are closed, and the dissolved oxygen levels in the feedwater are an order of magnitude higher than in a conventional feedwater system.

Stable feedwater chemistry in the absence of a reducing agent continues to strengthen the passive oxide layer throughout the feedwater piping over time. Therefore, although dissolved oxygen levels may temporarily spike during a startup, it is also unnecessary to add a reducing agent during layup or for the subsequent startup. ■

David Daniels is a POWER contributing editor and senior principal scientist at M&M Engineering Associates Inc.

 

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GREEN CHEMICALS

The Green Seal certification is granted by the organization with that name and has a great number of members contributing with the requirements to pass a raw material or a chemical product as "green". Generally for a material to be green, has to comply with a series of characteristics like: near neutral pH, low volatility, non combustible, non toxic to aquatic life, be biodegradable as measured by oxygen demand in accordance with the OECD definition.
Also the materials have to meet with toxicity and health requirements regarding inhalation, dermal and eye contact. There is also a specific list of materials that are prohibited or restricted from formulations, like ozone-depleting compounds and alkylphenol ethoxylates amongst others. Please go to http://www.greenseal.com/ for complete information on their requirements.
For information on current issues regarding green chemicals, see the blog from the Journalist Doris De Guzman, in the ICIS at: http://www.icis.com/blogs/green-chemicals/.
Certification is an important — and confusing — aspect of green cleaning. Third-party certification is available for products that meet standards set by Green Seal, EcoLogo, Energy Star, the Carpet & Rug Institute and others.
Manufacturers can also hire independent labs to determine whether a product is environmentally preferable and then place the manufacturer’s own eco-logo on the product; this is called self-certification. Finally, some manufacturers label a product with words like “sustainable,” “green,” or “earth friendly” without any third-party verification.
“The fact that there is not a single authoritative standard to go by adds to the confusion,” says Steven L. Mack M.Ed., director of buildings and grounds service for Ohio University, Athens, Ohio.
In www.happi.com of June 2008 edition, there is a report of Natural formulating markets that also emphasises the fact that registration of "green formulas" is very confused at present, due to lack of direction and unification of criteria and that some governmental instittion (in my opinion the EPA) should take part in this very important issue.