Vinyl polymers, Poly

Vinyl Acetate—Ethylene Copolymers. In these random copolymers, the ratio of ethylene to vinyl acetate (EVA) is varied from 30—60%. As the vinyl acetate content increases, the oil and heat resistance increases. With higher ethylene content the physical strength, tensile, and tear increases. The polymers are cured with peroxide. The main properties of these elastomers include heat resistance, moderate oil and solvent resistance, low compression set, good weather resistance, high damping, exceUent o2one resistance, and they can be easily colored (see Vinyl polymers, poly(VINYL acetate)). 

The poly(vinyl acetal) prepared from acetaldehyde was developed in the early 1940s by Shawinigan Chemicals, Ltd., of Canada and sold under the trade name Alvar. Early uses included injection-molded articles, coatings for paper and textiles, and replacement for shellac. Production peaked in the early 1950s and then decreased as a result of competition from less expensive resins such as poly(vinyl chloride) (see Vinyl polymers, poly(vinyl chloride)). 

Plasticizers. Plasticizers are materials that soften and flexibilize inherently rigid, and even britde polymers. Organic esters are widely used as plasticizers in polymers (97,98). These esters include the benzoats, phthalates, terephthalates, and trimeUitates, and aUphatic dibasic acid esters. Eor example, triethylene glycol bis(2-ethylbutyrate) [95-08-9] is a plasticizer for poly(vinyl butyral) [63148-65-2] which is used in laminated safety glass (see Vinyl POLYMERS, poly(vinyl acetals)). Di(2-ethyUiexyl)phthalate [117-81-7] (DOP) is a preeminent plasticizer. Variation of acid and/or alcohol component(s) modifies the efficacy of the resultant ester as a plasticizer. In phthalate plasticizers, molecular sizes of the alcohol moiety can be varied from methyl to tridecyl to control permanence, compatibiUty, and efficiency branched (eg, 2-ethylhexyl, isodecyl) for rapid absorption and fusion linear (C6—Cll) for low temperature flexibiUty and low volatility and aromatic (benzyl) for solvating. Terephthalates are recognized for their migration resistance, and trimeUitates for their low volatility in plasticizer appHcations. 

Figure 14.4.5 Free-radical vinyl polymerization of the monomer methyl methacrylate to form the vinyl polymer poly(methyl methacrylate) (PMMA).

Poly(vinyl acetate), the precursor of poly (vinyl alcohol), hydrolyzed to less than 70%, is claimed to be nonbio degradable under conditions similar to those that biodegrade the fully hydrolyzed polymer (100) (see VINYL POLYMERS POLY (vinyl ACETATE POLYMERS). 

The second method is the most widely used to prepare optically active vinyl polymers (poly-a-olefins, poly-vinyl-ethers, polyacrylic esters and amides etc.. ... 

Substituted polyacetylenes usually show a softening point in the range of ca. 200 to 400 °C (Table 27). It should be noted that these softening points are higher than those of usual vinyl polymers. Poly(l-chloro-2-phenylacetylene) does not melt but only decomposes (dehydrochlorinate) at high temperature. It is known that polyacetylene isomerizes at 145 °C from cis to trans and undergoes an exothermic reaction at 325 °C, but does not melt below 400 °C during its differential thermal analysis 9S). 

Rhum, D., Vinyl polymers. Poly (vinyl acetate). Interscience New York, 1970 Vol. 21. 

Vinylic polymers Poly(alkyl cyanoacrylate)s Poly(vinyl alcohol)... 

Unlike other vinyl polymers, poly(vinyl alcohol) cannot be prepared by the addition polymerization of the corresponding monomer precursor, and must instead be derived from poly(vinyl acetate) by hydrolysis of acetate ester side chains to hydroxyls. Products of varying molecular weight are obtained by selecting poly(vinyl acetate) precursors of the desired molecular weight. Further the degree to which the hydrolysis is complete (quantitative) is also controlled to obtain copolymer products having the solubility and other properties wanted. The chemical composition of the precursor, and the hydrolyzed products is outlined below. 

D. L. Cincera, Vinyl polymers [poly(vinyl alcohol)], Kirk-Othmer Encyclopedia of Chemical Technology, 3rd ed., John Wiley Sons, New York, VoL 23, 1980, pp. 857858. 

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