Applications of the acetal polymers and copolymers

There has been a steady increase in demand for polyacetals over the years, with global nameplate capacity increasing from about 2 000t.p.a. at the beginning of the 1980s to about 6(X) 000 t.p.a. at the end of the century. In the same period consumption has risen from about 140000t.p.a. to about 480 000 t.p.a. In terms of nameplate capacity the acetal copolymers dominate the homopolymers by a ratio of the order of 3 1. 

About 95% of the polymers are processed by injection moulding. Virtually all the remainder is extruded into sheet and rods for subsequent machining into finished parts. 

The acetal resins may best be considered as engineering materials. They therefore become competitive with a number of plastics materials, nylon in particular, and with metals. 

Because of their light weight, ability to be moulded into intricate shapes in one piece, low coefficients of friction and absence of slip-stick behaviour, acetal resins find use as bearings. 

These figures are somewhat higher than those obtained with the nylons. 

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In pharmacy, HES is one of the most frequently employed volume expanders used to prevent shock following severe blood loss caused by trauma, surgery, or other problems. In industrial applications, HES and HPS are useful as protective colloid forming substances in aqueous vinyl acetate polymer and copolymer emulsions. In the food... 

The synthesis of poly(vinyl acetals) (252) represents another example of generating a heterocycle, in this case the 1,3-dioxane nucleus, by application of a polymer modification reaction. Generally, the polymer modified is poly(vinyl alcohol) (180) or one of its copolymers. The 1,3-dioxane ring is generated (Scheme 122) by an acid-catalyzed acetalization reaction with an aldehyde, although ketones have also been reacted. A review (71MI11102) is available covering synthesis, properties and applications of the two most common and industrially important poly(vinyl acetals), poly(vinyl butyral) and poly(vinyl formal), as well as many other functional aldehydes that have been attached. 

Vinyl lacquers are used mainly where a high degree of chemical resistance is required these lacquers are based on vinyl chlorides and vinyl acetates. Acrylic lacquers are based on methyl methacrylate and methyl acrylate polymers and copolymers. Other esters of acrylic and methacrylic acid also may be used to make nonconvertible film formers. Judicious selection of these acrylic acid or methacrylic acid esters allows one to produce film formers with specifically designed properties such as hardness, flexibility, gloss, durability, heat, and chemical resistance. Acrylic lacquers, however, are not noted for their water resistance. The principal uses of acrylic-type lacquers are fluorescent and metallic paints, car refinish applications, clear lacquers and sealers for metals, and protective coatings for aircraft components and for vacuum-deposited metals, as well as uses in pigmented coatings for cabinets and appliances. 

In a broad sense, polymer dispersions include both synthetic polymer dispersions and natural rubber (Table 6.1 ).The yearly production of synthetic polymer dispersions is about 10% of the overall polymer consumption [1]. Synthetic polymer dispersions are produced by emulsion polymerization. About half of these polymers are commercialized as waterborne dispersions. Carboxylated styrene-butadiene copolymers, acrylic and styrene-acrylic latexes and vinyl acetate homopolymer and copolymers are the main polymer classes (Table 6.2). The main markets for these dispersions are paints and coatings (26%), paper coating (23%), adhesives (22%) and carpet backing (11%) [2]. Polymer dispersions have also found an interesting market niche in biomedical applications (diagnosis, drug delivery and treatment [3]). 

Some specific recent applications of the chromatography-mass spectrometry technique to various types of polymers include the following PE [130, 131], poly(l-octene), poly(l-decene), poly(l-dodecene) and 1-octene-l-decene-l-dodecene terpolymer [132], chlorinated polyethylene [133], polyolefins [134,135], acrylic acid, methacrylic acid copolymers [136, 137], polyacrylate [138], styrene-butadiene and other rubbers [139-141], nitrile rubber [142], natural rubbers [143,144], chlorinated natural rubber [145,146], polychloroprene [147], PVC [148-150], silicones [151,152], polycarbonates (PC) [153], styrene-isoprene copolymers [154], substituted PS [155], polypropylene carbonate [156], ethylene-vinyl acetate copolymer [157], Nylon 6,6 [158], polyisopropenyl cyclohexane-a-methylstyrene copolymers [195], cresol-novolac epoxy resins [160], polymeric flame retardants [161], poly(4-N-alkylstyrenes) [162], pol)winyl pyrrolidone [31,163], vinyl pyrrolidone-methacryloxysilicone copolymers [164], polybutylcyanoacrylate [165], polysulfide copolymers [1669], poly(diethyl-2-methacryloxy) ethyl phosphate [167, 168], ethane-carbon monoxide copolymers [169], polyetherimide [170], and bisphenol-A [171]. 

Alkyd paints dominated the architectural coating market for a long period until the appearance of polymer dispersions or the so-called latex paints. Specifically for wall application waterborne paints based on poly(vinyl acetate) homo- and copolymers, styrene-acrylics and pure acrylic latexes almost completely took over the market from the alkyd resins for both interior and exterior application. However, for... 

The determination of the experimental variables for apphcation of this approach is based on analysis of FTIR data on the blends and is covered in the references noted above. The application of the association model to determine or predict the phase behavior of interacting polymer systems include poly(2,6-dialkyl-4-vinyl phenol) blends with poly(n-alkyl methacrylates) and ethylene-vinyl acetate copolymers [217], poly(4-vinyl phenol)/poly(hydroxybutyrate) blends [218] and poly(4-vinyl phenol) in ternary blends with PEMA and PMMA [219] as weU as a number of examples in [92]. The determination of the equihbrium constants Ka and Kb) from FTIR data has been reported for ethylene-methacryhc add copolymers with polyethers [118] and ethylene-methacrylic add copolymers with poly(2-vinyl pyridine) [220]. 

These materials are based on polymer latexes made by emulsion polymerization. They flow easily while the continuous water phase is present and dry by evaporation of the water, leaving behind a layer of polymer. In order that the polymer particles coalesce to form a continuous joint and be able to flow to contact the adherend surfaces, the polymers used must be above their glass transition temperature at use temperature. These requirements are similar to those for latex paints, so it is not surprising that some of the same polymers are used in both applications, for example, styrene-butadiene copolymers and poly(vinyl acetate). Nitrile and neoprene mbbers are used for increased polarity. A familiar example of a latex adhesive is white glue, basically a plasticized poly(vinyl acetate) latex. Latex adhesives have displaced solvent-based adhesives in many applications because of their reduced pollution and fire hazards. They are used extensively for bonding pile and backing in carpets. 

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