53 -4 Coatings Technology Handbook, Third Edition gloss. 12 Parasubstituted phenolic novolak resins that have been modified with rosin make excellent ink additives. Rosin modification of the phenolic resin raises the melting point and gives the phenolic excellent oil solubility. The formulations consist of a phenolic resin, oils, pigments or dyes, driers, and lubricants or plasticizers. 13 The proper balance of ingredients gives the desired combination of hardness, viscosity, penetration, and drying rate. 53.4 Epoxy Hardeners Phenolic resins may be combined with epoxy resins for use in protective coatings. Phenolic–epoxy products are also used in laminates, prepreg manufacturing, molding materials, and electrical insulation coatings. The phenolic resin is used as a coreactant to produce thermoset systems with improved heat and chemical resistance. Non-heat-reactive (novolak) resins are used to cross-link the epoxies. The epoxy resins are typically epoxy–phenolics or bisphenol A-based resins. 14 The reaction mechanism is different from the resole–epoxy reactions. The coating is heat-activated and uses a base catalyst such as an amine, dicyandiamide, or an imidazole. 15 The phenolic hydroxyl group reacts with the epoxy group to form a polyether structure, which has an advantage, because no volatiles are released during cure. This allows for thick films to be produced with low shrinkage and no voids from volatile emission. The phe- nolic–epoxy reaction using a base catalyst can be demonstrated as follows: For critical electrical applications, “high purity” resins are used. These products are made according to stringent specifications limiting the amount of water, ions, and free monomers present in the resin. 53.5 Summary Phenolic resins were one of the first synthetic polymers to have widespread commercial importance. Their outstanding performance properties have given them a permanent role in the coatings industry. They are used in applications ranging from railroad tank cars to carbonless copy paper. Phenolic resins are also used on a wide variety of substrates including metal, wood, paper, and ceramics. There are so many types of phenolic resin available to the marketplace that a particular resin can be selected for virtually any application. Phenolic resins should not be overlooked when choosing a high performance polymer. Phenolics currently do not receive the same attention as some of the more recently developed polymers, but for many applications, there is simply no substitute for phenolic resins. Phenolics will continue to have an important role in the coating industry because of their versatility, coatings properties, and reasonable price. OH OH CH 2 CH 2 CH 2 CH 2 CH 2 CH 2 H 2 C CH . CH 2 O-R OCH 2 -CH CH 2 n n n + O O Base ∆ OCH 2 CH(OH)CH 2 O-R OCH 2 -CH(OH)CH 2 O OCH 2 CH(OH)CH 2 O-R OCH 2 -CH(OH)CH 2 O DK4036_book.fm Page 4 Monday, April 25, 2005 12:18 PM © 2006 by Taylor & Francis Group, LLC Phenolic Resins 53 -5 References 1. J. S. Fry, C. N. Merriam, and W. H. Boyd, Chemistry and Technology of Phenolic Resins and Coatings , in ACS Symposium Series. Applied Polymer Science. Washington, DC: American Chemical Society, 1985, p. 1147. 2. R. T. Morrison, and R. N. Boyd, Organic Chemistry , 3rd ed. Boston: Allyn and Bacon, 1973, p. 1147. 3. J. S. Fry, C. S. Merriam, and W. H. Boyd, Chemistry and Technology of Phenolic Resins and Coatings , ACS Symposium Series, Applied Polymer Science. Washington, DC: American Chemical Society, 1985, p. 1149. 4. Union Carbide Corp., Formulation Suggestions — Durable Phenolic Baking Coatings for Rigid Metal Substrates (F-60675), 1988. 5. A Knop, and L. Pilato, Phenolic Resins. Berlin: Springer-Verlag, 1985, p. 247. 6. Union Carbide Corp., Ucar Phenolic Resin BKS-7570 (F-60689), 1988. 7. R. W. Martin, The Chemistry of Phenolic Resins. New York: Wiley, 1956, p. 203. 8. R. R Myers and J. S. Long, Film Forming Compositions. New York: Dekker, 1972, p. 155. 9. R. W. Martin, The Chemistry of Phenolic Resins. New York: Wiley, 1956, p. 205. 10. R. G. Middlemiss, J. Water Borne Coat. , November (1985). 11. S. H. Richardson, Paint Varnish Prod., August (1955). 12. A. Knop, and W. Scheib, Chemistry and Application of Phenolic Resins. Berlin: Springer-Verlag, 1979, p. 192. 13. National Association of Printing Ink Manufacturers, Pattern Printing Ink Formulae. NAPIM, 1974. 14. J. S. Fry, Ucar Phenolic Resins for Epoxy Hardeners. Union Carbide Corp. (P-)-3(57). 15. U. S. Patent 3,493,630, Union Carbide Corp. DK4036_book.fm Page 5 Monday, April 25, 2005 12:18 PM © 2006 by Taylor & Francis Group, LLC 54 -1 54 Coal Tar and Asphalt Coatings 54.1 Coal Tar Types 54- 1 54.2 Asphaltic Types 54- 3 Bibliography 54- 4 Coal tar coatings have been used for many centuries because of their resistance to water and biological organisms. Coatings based on asphalt have been developed for over a century. This is a brief review of the materials. 54.1 Coal Tar Types Bituminous coal, a very complex chemical mixture, decomposes into simpler components when heated in retorts without air above 700 ° C (1292 ° F). Gas, aqueous vapor, and coal tar are driven off, leaving coke as residue. The coat tar is dehydrated and heated in stills to yield oil and coal tar pitch. Depending on the source of the coal tar and the amount of heat applied, pitches of different characteristics are obtained. When used as bases for superior coatings, coal tar pitches are reprocessed, and any corrosion-accelerating substances are removed. Various types of coal tar pitches are then blended together. The outstanding quality of coal tar paints is their extremely low permeability, their high electrolytic resistance, and their remarkable resistance to the disintegrating action of water. There are hardly any materials, old or new, that are as water resistant as properly compounded coal tar coatings. They will not be affected by mineral oil but may be dissolved by vegetable and animal oil, grease, and detergents, if they are in direct contact with them. Their resistance to weak mineral acids, alkalis, salts, brine solutions, and other aggressive chemicals is good. Furthermore, coal tar paints give more value per dollar than any other protective coating. This fact should not be overlooked when selecting paint for a certain job. Coal tar paints are made by dissolving the processed pitch or blend of pitches in suitable solvents. Skill and experience are essential in compounding coal tar paints because similar physical characteristics of raw materials do not necessarily mean similar behavior of the finished product under exposure. The raw materials selected for the blending, the degree of refining, and the addition of other modifiers, often in small quantities, decide the final merit of the coating. There are five main types of coal tar coatings: 1. Thin coal tar pitch solutions without any filler 2. Heavy coal tar pitch solutions with inert fillers added 3. Very heavy coal tar pitch coatings containing inert fillers possessing a thixotropic gel structure but only medium inherent viscosity 4. Heavy coal tar emulsions containing inert fillers and having low inherent viscosity 5. Hot applied coal tar coatings Henry R. Stoner Henry R. Stoner Associates DK4036_book.fm Page 1 Monday, April 25, 2005 12:18 PM © 2006 by Taylor & Francis Group, LLC 54 -2 Coatings Technology Handbook, Third Edition The first three types are solutions and have about the same chemical and water resistance. They vary mainly in the thickness of the film that can be laid down in a single coat. The fourth type, coal tar emulsions, consists of dispersions of coal tar pitch in water and are inferior in corrosion resistance to the solution type. This is not a fault of the pitch itself but is caused by the higher permeability of the applied film. Pitch particles dispersed in water are relatively large and do not coalesce as completely after drying as the much smaller dissolved pitch particles do. But coal tar emulsions have other very good features that will be mentioned later. The fifth type, coal tar pitch reinforced with inert filler and applied in a molten state over a primer, is called in the trade, coal tar enamel. These enamels have all the good qualities of coal tar paints, but in a higher degree, because the coating is very thick and does not depend on the evaporation of solvent to set. Type 1 is a thin coal tar solution of low viscosity with a solids content of 60 to 70% and a spreading rate of 300 to 400 square feet per gallon, and it gives an approximate thickness of 1 to 2 mils per coat. This thickness cannot be increased because the thin solution cannot be applied at a lower rate without sagging. Type 2 is designed to achieve a heavier coat; a filler coal tar solution must be used, which, in addition to its higher solids content, can be applied at approximately 180 square feet per gallon without sagging. This produces an approximate dry film thickness of 6 mils. To apply even heavier coatings by brush, a gel must be selected that can be applied at the low rate of 75 square feet per gallon without sagging. This will produce a dry film thickness of approximately 16 mils in one coat. Coal tar emulsions will not sag at a coverage of 75 square feet per gallon and will give approximately a 12 mil dry film thickness in one coat. Coal tar paints afford protection by the mechanical exclusion of moisture and air. If they are applied as a continuous film without holidays, they give almost perfect protection. As it is impossible to avoid pinholes and flaws in a one-coat application, more than one coat will be necessary. They dry by solvent evaporation only. Concrete, as a rule, can be protected with thin coal tar solutions, but steel requires heavier coatings that will form an almost impervious barrier against severe corrosive influences. All coal tar paints “alligator,” more or less, in the sun. The paint will look like an alligator skin, and hence, the name alligatoring. This alligatoring is a surface defect. It is brought about by the hardening of the upper layer of the film, stimulated by the sun’s rays. This causes the upper layer to contract, crack, and slip over the lower stratum which is still soft. If not enough coats are applied, these alligator marks can go right down to metal, opening the path for atmospheric corrosion. Alligatoring does not (or only to a limited degree) occur under water, where the coating is protected from the rays of the sun. Coal tar emulsions do not produce this phenomenon, probably because the pitch particles are not fused as tightly as in solution types; therefore, coal tar emulsions can be used as topcoats over badly alligatoring heavy coal tar paints. Bear in mind that these emulsions have less protection capabilities in immersion service and are not recommended for such use. There are several popular methods to prevent alligatoring of heavy coal tar coatings, which are temporarily exposed to sun and air before submersion. The older method uses a whitewash. Add slowly and simultaneously 150 lb of processed quicklime and 1 gal of boiled linseed oil to 50 gal of water, containing 10 lb of salt dissolved therein. While being mixed and for 15 min thereafter, the mixture shall be stirred continuously and allowed to cool. It shall be free from lumps and foreign matter. The whitewash shall be aged for at least 3 days before application (NAVDOCKS Specification 34 Yc). A more current approach is to use an acrylic latex paint, or a similar emulsion paint applied to the surface of the coal tar coating. However, note that discoloration of this paint’s film by the oils in the coal tar coating is not deemed as a cause for failure. The solvents used in coal tar pitches are strong in odor, and adequate ventilation is necessary during applications and drying. Coal tar emulsions, which use water as a volatile thinner, are in this respect superior and should be used where proper ventilation is not possible. Coal tar paints give excellent protection at low cost in dam and flood control installations, penstocks, piers, marine work, etc. DK4036_book.fm Page 2 Monday, April 25, 2005 12:18 PM © 2006 by Taylor & Francis Group, LLC 55 -1 55 Vulcanizate Thermoplastic Elastomers 55.1 Introduction 55- 1 55.2 Properties 55- 1 55.3 Processing 55- 2 55.4 Uses of TPV 55- 2 55.1 Introduction A thermoplastic elastomer (TPE) is a material that is processed in the same manner as a conventional thermoplastic but gives a finished article with properties and performance similar to those of a thermoset rubber. Thermoplastic vulcanizates (TPVs, referred to as elastomeric alloys in some earlier literature) are a generic class of TPEs with a chemically cross-linked rubber phase in a continuous matrix of thermo- plastic. TPVs thus have properties significantly better than those of the same rubber/thermoplastic composition with little or no cross-linking of the rubber phase (i.e., and olefinic blend). performance, moderate cost TPEs. They have performance and cost higher than those of the styrenic and olefinic blend TPEs and lower than those of the polyurethanes, copolyesters, and polyamides. 55.2 Properties The cross-linking of a TPV rubber phase gives improvement to a number of properties of a specific rubber/thermoplastic composition, such as EPDM rubber/polypropylene (PP). These property improve- ments include tensile strength, tensile and compression set resistance, stress relaxation, fluid resistance, and retention of properties at elevated temperature. These improvements qualify TPVs for many uses where a simple rubber/polyolefin blend would be inadequate. Key parameters for the premium performance of a TPV are (1) the degree of cross-linking of the rubber phase, (2) the degree of dispersion of the rubber phase in the thermoplastic phase, and (3) the thermody- namic compatibility of the polymers present. TPV performance is known to be improved by greater cross- linking, dispersion, and polymer compatibility. TPVs with high polymer compatibility have no need for a compatibilizer; those with low compatibility (e.g., NBR rubber/PP) will need one to stabilize the intermin- gling of the rubber and thermoplastic chains. The mutual compatibility of the rubber and thermoplastic polymers will increase as the difference in their solubility parameters (i.e., cohesive energy density) decreases. The hardness of TPVs ranges from 35 Shore A up to 50 Shore D. EPDM/PP TPVs are generally suitable for use in air from –60 ° C to 135 ° C, and those from nitrile rubber/PP have a range in air from –40 ° C to Charles P. Rader Advanced Elastomer Systems, L.P. DK4036_book.fm Page 1 Monday, April 25, 2005 12:18 PM © 2006 by Taylor & Francis Group, LLC Figure 55.1 compares the generic classes of TPEs by performance and cost. The TPVs are medium Vulcanizate Thermoplastic Elastomers 55 -3 of 100,000 MT should have been reached between 2000 and 2003 . Why has this growth been so great? Perhaps the principal reasons are (1) TPVs are the closest approach of any TPE to the properties and performance of a conventional thermoset rubber, and (2) TPVs permit close-to-optimum exploitation of the economic advantages inherent in the processing of a TPE. To day’s applications of TPVs number well into the thousands, penetrating virtually all major uses of rubber — but with one massive exception, that of penumatic tires, which consume slightly more than one-half of the rubber produced in the world. In other rubber application areas, TPVs have been eminently successful. A leader in this success has been the automotive segment, where these materials enjoy uses in convoluted protective boots, seals, jacketing, hose, grommets, weather stripping, and numerous other specific parts. TPVs function well in under-the-hood uses where other TPEs are inad- equate for the service temperature, which continues to progress upward. Architectural uses also provide a ready market for TPEs. Hundreds of large buildings around the world now employ window glazing and/or chemical expansion joints extruded from an EPDM/PP TPV. Mechanical rubber goods embrace those uses in which a molded or extruded rubber article is a component part of a useful assembly. Major TPV uses in this area include household appliances, office equipment, toys, and other items requiring the use of boots, bushings, seals, tubing, and other rubber articles. EPDM/PP TPVs have excellent electrical insulating properties — dielectric constant, resistivity, dielec- tric strength, power factor — that render them quite suitable for use as primary insulators or as jacketing materials. Electrically conducting wire can readily be coated by crosshead extrusion of a TPV for use in automotive, construction, industrial, appliance, and many other applications. EPDM/PP TPVs have unusually low toxicity for a rubber. This explains their broad utility for direct contact with foods and potable water. TPVs have also found use in health care applications in hospitals and physician’s offices and in pharmaceutical applications involving direct contact with preparations to be taken orally or injected into the bloodstream. DK4036_book.fm Page 3 Monday, April 25, 2005 12:18 PM © 2006 by Taylor & Francis Group, LLC 56 -1 56 Olefinic Thermoplastic Elastomers 56.1 Introduction 56- 1 56.2 Properties 56- 2 Limitations of TPOE Compounds 56.3 Usage 56- 2 56.1 Introduction Olefinic elastomers based upon ethylene-propylene and/or ethylene-propylene-diene monomer rubbers (EPR or EPDM) are thermoplastic by virtue of their alloying with isostatic crystalline polypropylene and/or high-density polyethylene (HDPE). These products are produced by high intensity mixing in Banburies continuous mixers, and extruders. The olefin plastics are either pellets or reactor beads, while the rubber can be in bale form for mixing in a Banbury. For mixing in an extruder or continuous mixer, the rubber must be converted to a pellet or granular particle. The high intensity mixing results in a simultaneous comminution of the polymers, with the olefin as the continuous phase and the rubber the dispersed phase. Thus the blend is thermo- plastic: the blend viscosity is largely controlled by the choice of polyolefin, and the elasticity is controlled by the rubber segment of the blend. Thermoplastic olefinic elastomers (TPOEs) can be manufactured by blending alone, which limits the elevated temperature properties of the mix, or by blending and cross-linking in situ during the com- pounding operation. When the compounds are cross-linked, the elevated temperature properties are enhanced. The processing “nerve” of the blend is reduced, and thinner, more complex extruded products are possible. The polymer compound is made broadly versatile by the inclusion of a great variety of additives. In addition to the initial choice of polymers, the ratio of plastic to rubber (hard to soft segment) controls the hardness of the compound to some degree. The use of high permanence petroleum oils that function as permanent plasticizers assists in the control of hardness. Flexural modulus or toughness is more readily controlled by the rubber polymer. The combined use of these ingredients results in a wide variety of physical properties. Fillers, such as fine particle calcium carbonates, clays, talc, and silicas are all usable. TPOE compounds cannot be made to be clear; but very pale, pastel colors are possible. Translucent colors are possible in thin sections. For outdoor use, protection against ultraviolet radiation is needed. The general-purpose compounds are not flame retardant inherently and require a package of halogen donor additives to pass any necessary specifications. Jesse Edenbaum Consultant DK4036_book.fm Page 1 Monday, April 25, 2005 12:18 PM © 2006 by Taylor & Francis Group, LLC Coating Applications • Primer Systems 57 -1 57 Ethylene Vinyl Alcohol Copolymer (EVOH) Resins 57.1 Polymer 57- 1 57.2 Barrier Properties 57- 1 57.3 Regulatory Approval 57- 4 57.4 Fabrication Methods 57- 4 57.1 Polymer Ethylene vinyl alcohol (EVOH) resins are hydrolyzed copolymers of vinyl acetate and ethylene. The vinyl alcohol base has exceptionally high gas barrier properties, but it is water soluble and difficult to process. By copolymerizing ethylene with vinyl alcohol, the high gas barrier properties are retained and significant improvements are achieved in moisture resistance and processibility. A typical reaction for producing EVOH resins is shown on page 57-3 . Under proper conditions, this reaction yields a copolymer that is more than 99% hydrolyzed. 57.2 Barrier Properties EVOH copolymers are highly crystalline, and their properties are highly dependent on the relative concentration of the comonomers. Generally speaking, as the ethylene content increases, the gas barrier properties decreases, the moisture barrier properties improve, and the resins are processed more easily The presence of a hydroxyl group in the molecular chain renders the gas barrier properties of the properties decrease. However, by proper use of companion materials in a multilayer structure, this effect can be minimized. content of the EVOH and maintain superior gas barrier properties. In this article, any aqueous-based food is considered to be 100% relative humidity; the storage environment is shown at relative humidities of 65 and 85%. R. H. Foster Eval Company of America DK4036_book.fm Page 1 Monday, April 25, 2005 12:18 PM © 2006 by Taylor & Francis Group, LLC Ta ble 57.1 lists the range of EVOH resins presently available. (see Table 57.2). EVOH resins sensitive to moisture. As the moisture content of the resin increases, the gas barrier Ta ble 57.3 shows how the combination of different materials can be used to minimize the moisture Ethylene Vinyl Alcohol Copolymer (EVOH) Resins 57 -3 In addition to being outstanding as barrier properties, EVOH resins offer excellent barriers to a variety of flavors, aromas, and solvents (see Table 57.4 and Table 57.5). TA BLE 57.4 Flavor Barrier Data (Citrus and Tropical Flavors) a Film b Thickness ( µ m) Duration 1 h 2 h 15 h 1 Day 4 Days 35 Days EVOH-32 15 A A A A A A EVOH-44 15 A A A A A A BO EVHO 15 A A A A A A BO Nylon 15AABBB B OPP 20 B B C C C C PVDC 25 A A B B B B LDPE 50 D D D D D D a Key: A, no detection; B, faint flavor; C, partial flavor; D, flavor clearly distinguished. b BO EVOH, biaxially oriented EVOH; BO Nylon, biaxially oriented nylon; OPP, ori- ented polypropylene; PVDC, polyvinylidene chloride; LDPE, low density polyethylene. TA BLE 57.5 Flavor, Aroma, and Solvent Barrier Properties a Resin b Allyl Sulfide: Garlic-Food Type (Croutons, Snacks, Salad Dressins) Acetic Acid Vinegar-Food Type (Cheddar Cheese, Snacks, Condiments) Ethylene Acetate: Laminating Adhesive Solvent Residual To l u ene: Printing Ink Solvent Residual Methyl Ethyl Ketone Printing Ink Solvent Residual HDPE-Nylon-EVa 0.00008 0.92 0.03 0.02 0.005 HDPE-EVOH-EVA 0.00075 0.035 0.0043 0.007 0.035 PVDC-PP-PVDC 0.0068 1.98 0.34 0.22 3.09 OPP-HDPE-EVOH-EVA 0.00076 1.40 0.15 0.00003 0.09 EVA-Glassine-PVDC 0.50 4.18 6.47 3.15 15.1 a g/24 h, m 2 , 100 pm at 70 ° F. b HDPE, high-density polyethylene; EVA, ethylene vinyl acetate; PVDC, polyvinylidene chloride; OPP, oriented polypro- pylene. + + CxC — — — — HH HH CyC — — — — HH HO —(CH 2 —CH 2 ) x —(CH 2 —CH) y — —— O O C — CH 3 Ethylene Vinyl Acetate CopolymerVinyl Acetate Monomer Ethylene Monomer (CH 2 —CH 2 ) x —(CH 2 —CH) y (CH 2 —CH 2 ) x —(CH 2 —CH) y —— O C C — CH 3 Ethylene Vinyl Acetate Copolymer Ethylene Vinyl Alcohol Copolymer (EVOH) Heat Catalyst DK4036_book.fm Page 3 Monday, April 25, 2005 12:18 PM © 2006 by Taylor & Francis Group, LLC [...]... (Soarnol resins) in Japan and Solvay (Clarene resins) in Europe © 20 06 by Taylor & Francis Group, LLC DK4036_book.fm Page 1 Monday, April 25 , 20 05 12: 18 PM 58 Elastomeric Alloy Thermoplastic Elastomers Charles P Rader Advanced Elastomer Systems, L.P 58 .1 Properties 58 -1 58 .2 Processing 58 -2 58 .3 Uses of Elastomeric Alloys 58 -2 A thermoplastic elastomer (TPE) is a material with the functional... injected into the bloodstream © 20 06 by Taylor & Francis Group, LLC DK4036_book.fm Page 1 Monday, April 25 , 20 05 12: 18 PM 59 Polyvinyl Chloride and Its Copolymers in Plastisol Coatings 59 .1 Introduction 59 -1 59 .2 Formulation .59 -1 Resins • Plasticizers • Solvents • Other Additives Jesse Edenbaum Consultant 59 .3 Plastisol Manufacturing Procedures 59 -4 Equipment • Quality Control... comonomer content will normally vary from 3 to 10% Other comonomers are sometimes used 59 -1 © 20 06 by Taylor & Francis Group, LLC DK4036_book.fm Page 1 Monday, April 25 , 20 05 12: 18 PM 60 Polyvinyl Acetal Resins 60.1 Chemistry and Manufacture 60-1 60 .2 Availability, Economics .60-1 60.3 Properties 60 -2 Reactivity and Compatibility • Physical and Chemical Properties • Solution Viscosity...DK4036_book.fm Page 5 Monday, April 25 , 20 05 12: 18 PM Ethylene Vinyl Alcohol Copolymer (EVOH) Resins 57 -5 • Using EVOH films that are laminated to other substrates or coated with other materials • Coating various substrates or monolayer containers with EVOH resins... competitive with those of a thermoset rubber, the ultimate tensile strength is generally significantly lower relative to a thermoset 58 -1 © 20 06 by Taylor & Francis Group, LLC DK4036_book.fm Page 3 Monday, April 25 , 20 05 12: 18 PM Elastomeric Alloy Thermoplastic Elastomers 58 -3 These materials have been especially well received by the automotive industry, with typical uses being hoses, jacketing, grommets,... Two-phase EAs range in hardness from 55 Shore A to 50 Shore D EAs derived from ethylene propylene diene monomer (EPDM) rubber and polypropylene have a service temperature range from –60°C to 1 35 C in air Two-phase EAs from nitrile rubber and polypropylene have a service temperature ranging from 40°C to 1 25 °C in air The specific gravity of single-phase EAs ranges from 1 .2 to 1.3, and that of two-phase EAs... polyvinyl alcohol The chemistry of preparation is outlined in Equation 60.1, where R can be H or any of a wide variety of organic radicals OH H+ CH2 — CH— CH2 — CH — — OH + RCHO — — CH2 — CH— CH2 — CH O + H2O O — CH R While many polyvinyl acetals have been prepared,1 ,2 the only commercially important polymers are the formal (R = H) and the butyral (R = n – C3H7), derived from the acetalization of polyvinyl... during processing, and in the finished state A typical plastisol formulation is shown in Table 59 .1 59 .2. 1 Resins PVC dispersion resins are very fine particle size products made by emulsion polymerization and finished by the spray drying technique These paste resins are characterized by their molecular weight, particle size, and shape They are predominantly homopolymers, but there are also a wide variety... n-butyraldehyde, respectively The generalized structure of the polyvinyl acetal molecule is shown in Figure 60.1 Molecular weights, weight average molecular weight (Mw), range from about 25 ,000 to 150 ,000 for the formal and from 40,000 to 25 0,000 K for the butyral, depending on grade The three chemical moieties are randomly distributed along the polymer chain While simple in concept, the actual commercial preparation... Continuous Thin Film Applications 59 .1 Introduction PVC plastisols are liquid dispersion systems of polyvinyl chloride and/or PVC copolymer resins in compatible plasticizers The liquids vary in viscosity from thin milklike fluids to heavy pastes that have the consistency of molasses The lowest viscosity products are generally used for spray coatings and some paper and fabric coatings, while the higher viscosity . 2 Monday, April 25 , 20 05 12: 18 PM © 20 06 by Taylor & Francis Group, LLC 55 -1 55 Vulcanizate Thermoplastic Elastomers 55 .1 Introduction 55 - 1 55 .2 Properties 55 - 1 55 .3. versatility, coatings properties, and reasonable price. OH OH CH 2 CH 2 CH 2 CH 2 CH 2 CH 2 H 2 C CH . CH 2 O-R OCH 2 -CH CH 2 n n n + O O Base ∆ OCH 2 CH(OH)CH 2 O-R OCH 2 -CH(OH)CH 2 O OCH 2 CH(OH)CH 2 O-R OCH 2 -CH(OH)CH 2 O . Monday, April 25 , 20 05 12: 18 PM © 20 06 by Taylor & Francis Group, LLC 56 -1 56 Olefinic Thermoplastic Elastomers 56 .1 Introduction 56 - 1 56 .2 Properties 56 - 2 Limitations