Vinyl acetate-containing polymers

Hand building finishes that retain their stiffening and fullness effects after repeated launderings are considered to be durable. These products are usually aqueous emulsions of polymers that form water-insoluble films on the fibre surface when dried. The three main types of products are vinyl acetate-containing polymers, acrylic copolymers and thermosetting polymers. 

Chemical Properties. The chemical-resistance properties of methacrylic ester polymers are even higher than those of the acrylic esters. Methacrylic esters imdergo a lower degree of hydrolysis in either acidic or alkaline media than acrylics. Both acrylics and methacrylics easily outperform vinyl acetate-containing polymers which are well known to be susceptible to hydrolysis of the side-chain ester. There are marked differences in the chemical-resistance properties of different forms of PMMA. The syndiotactic (alternating) form of PMMA is the most chemically inert. The rate of hydrolysis for syndiotactic PMMA is lower than that for isotactic (26) radical polymerizations generate large portions of syndiotactic PMMA and benefit in terms of stability. 

The tensile modulus for the EVA blends with 5 wt.% loading of the organomontmorillonite decreased steadily from approximately 1800 kg/cm for the EVA with 3 wt.% vinyl acetate content to approximately 250 kg/cm for the EVA that contained 26 wt.% of vinyl acetate. The addition of 10 wt. % of the PEMA with 1 % content of maleic anhydride consistently resulted in a significant increase in tensile modulus. Approximately a 500 kg/cm increase was measured for the 3% vinyl acetate containing polymer to a doubling of the tensile modulus value for the 26% vinyl acetate containing copolymer. 

Block copolymers of vinyl acetate with methyl methacrylate, acryflc acid, acrylonitrile, and vinyl pyrrohdinone have been prepared by copolymeriza tion in viscous conditions, with solvents that are poor solvents for the vinyl acetate macroradical (123). Similarly, the copolymeriza tion of vinyl acetate with methyl methacrylate is enhanced by the solvents acetonitrile and acetone and is decreased by propanol (124). Copolymers of vinyl acetate containing cycHc functional groups in the polymer chain have been prepared by copolymeriza tion of vinyl acetate with A/,A/-diaIlylcyanamide and W,W-diaIl5lamine (125,126). 

Laoutid F, Gaudon P, Taulemesse JM, Lopez Cuesta JM, Velasco JI, Piechaczyk A. Study of hydromagnesite and magnesium hydroxide based fire retardant systems for ethylene-vinyl acetate containing organo-modified montmorillonite. Polym. Degrad. Stab. 2006 91 3074-3082. 

Hot-melt adhesives are applied in molten form and a bond forms between the substrates on cooling. These adhesives are used mainly for high-speed operations such as container formation and for some pressure-sensitive labels. The archetypal hot-melt adhesive is sealing wax, but nowadays they are mainly synthetic products such as high molecular weight ethylene-vinyl acetate co-polymers. 

The validity of this dynamic model can be justified by the fact that in polystyrene and other carbon-chain polymers of the type (—CH2—CHR—) (poly(p-chlorostyrene), poly(methyl acrylate) or poly(vinyl acetate)), containing no methyl groups bonded directly to the main chain, rotational isomerization with 17 5—6 Kcal/mol (in the time interval of r 10 — 10 s in solvents with ij 0.01 P) can occur ... 

Nitroparaffins are effective vinyl solvents. The solubility characteristics of 2-nitropropane are shown in Figures 20 and 21. Toluene and xylene are true solvents for only the most soluble copolymers and terpolymers. These polymers are represented by the carboxyl containing terpolymer (Figure 12), the high solubility copolymers (VC-TFCE copolymer) (Figure 14), and a non-vinyl acetate containing copolymer (Figure 13). Heat had to be applied to the last polymer to obtain complete solution. 

A third case arises when both Mi and Mt react more readily with Mi than with Mt. In such a mixture very little copolymer is formed at first, and the analysis of the polymer shows almost 100 per cent Mi homopolymer. After Ml is mostly consumed, some copolymer is fonned. Eventually, Ml homopolymer will be synthesized, but only after all Mi is gone. This is true of vinyl acetate-styrene copolymerization, where the styrene monomer is much more reactive than vinyl acetate. As a result, a copolymer of styrene and vinyl acetate containing appreciable amounts of the latter can be made only if the polymerization mixture contains a large excess of vinyl acetate. 

In equipment similar to that indicated in Procedure 4-2, into 500 ml of a 2% solution of poly(vinyl alcohol) (viscosity and degree of hydrolysis not specified in the original patent) is added a solution of 500 gm of vinyl acetate containing 0.25 gm of dibenzoyl peroxide along with 5 ml of a 1.0% aqueous solution of hydrogen peroxide. With agitation, the mixture is heated for 6 hr at 70 C. The reaction mixture is then cooled to 4°C, filtered, and washed repeatedly with water at 5°C. The polymer is dried under reduced pressure at moderate temperatures (yield, 85% of theory). 

Partially hydrolyzed poly(vinyl acetate) contains both hydroxyl and acetate groups. When the OH groups in partially hydrolyzed poly(vinyl acetate) are condensed with aldehydes, acetal units are formed. The resulting polymer contains acetal, hydroxyl, and acetate groups and is known as the poly(vinylac-etals) (Equation 5.9). 

Ethylene-vinyl acetate (EVA) polymers (containing 65%-70% by weight of vinyl acetate) are of industrial interest as high-molecular weight plasticizers for PVC, mainly because of their low cost. A polymeric plasticizer PB-3041 available from Du Pont allows the preparation of a highly permanent plasticized PVC formulation. It is believed to be a terpolymer of ethylene, vinyl, acetate, and carbon monoxide. Also, butylene terephthalate-tetrahydrofuran block copolymers, with the trade name of Hytrel (Du Pont), are used as excellent permanent plasticizers of PVC. 

Not all hydroxyl groups participate in formations of acetals and some become isolated. Atypical poly(vinyl acetal) contains acetal groups, residual hydroxyl groups, and residual acetate groups from incomplete transesterification of the parent polymer. 

In order to enhance the adsorption of a molecule on the surface, one may incorporate specific groups on a random basis on the chain. These groups will enhance the adsorption of the polymer and hence may provide effective stabilization. A good example is partially hydrolysed poly(vinyl acetate). The polymer chain contains random segments of vinyl acetate (which are hydrophobic in nature) and these will enhance the adsorption of the molecule on a hydrophobic surface such as polystyrene. The conformation of such molecule is shown in Figure 16.1(b). Clearly if all of the segments are made hydrophobic, the molecule will lie flat on the surface, as represented in Figure 16.1(c). Such molecules will not offer any steric stabilization. 

Triblock polymers such as PPPPPP-QQQQQ-TT RRRRRR are sometimes used too, but they are not necessarily more effective than diblock types. Core-shell copolymers such as glycidyl methacrylate-ethylene-vinyl acetate, containing both polar and nonpolar units, have been used to compatibilise and toughen blends of two brittle polymers. 

Journal of Applied Polymer Science 83, No.4, 24th Jan.2002, p.923-8 POSTPOLYMERISATION OF VINYL ACETATE-CONTAINING LATEXES... 

Certain properties may best be explained by examining the molecular structure of polyvinyl acetate and some of its copolymers. Fig. 5 compares polyethylene and polyvinyl acetate homopolymers. Polyethylene is, of course, a flexible polymer, whereas polyvinyl acetate homopolymer is hard and brittle because steric hindrance between alternate acetate groups restricts movement of the molecules. A copolymer of vinyl acetate containing 25 weight... 

The release coating, applied as a very thin film to the reverse side of the backing (see Fig. 1), can be a silicone or an alkyd or copolymer containing long aliphatic hydrocarbon constituents. Thus, ethylene w-stearamide, for example, can be added to a paint vehicle or, less commonly, used alone. The copolymers are crosslinkable emulsions of an acrylate or vinyl acetate containing a monomer like stearyt acrylate. Other polymers or materials that provide a low energy hydrocarbon moiety, which tends to concentrate in the surface, are used to a lesser extent. 

Vinyl acetate (VA)/crotonates copolymer became available in the late 1950s. It was the first polymer used in fixatives to contain carboxyHc acid groups which, depending on neutralization percent, could produce variations in film properties eg, stiffness, humidity resistance, resiUency, tack, and removabihty by shampoo. It has largely been replaced in hair sprays by newer polymers. 

The principal chemical markets for acetylene at present are its uses in the preparation of vinyl chloride, vinyl acetate, and 1,4-butanediol. Polymers from these monomers reach the consumer in the form of surface coatings (paints, films, sheets, or textiles), containers, pipe, electrical wire insulation, adhesives, and many other products which total biUions of kg. The acetylene routes to these monomers were once dominant but have been largely displaced by newer processes based on olefinic starting materials. 

Almost all synthetic binders are prepared by an emulsion polymerization process and are suppHed as latexes which consist of 48—52 wt % polymer dispersed in water (101). The largest-volume binder is styrene—butadiene copolymer [9003-55-8] (SBR) latex. Most SBRlatexes are carboxylated, ie, they contain copolymerized acidic monomers. Other latex binders are based on poly(vinyl acetate) [9003-20-7] and on polymers of acrylate esters. Poly(vinyl alcohol) is a water-soluble, synthetic biader which is prepared by the hydrolysis of poly(viayl acetate) (see Latex technology Vinyl polymers). 

Poly(vinyl alcohol) used to manufacture the poly(vinyl acetal)s is made from poly(vinyl acetate) homopolymer (see Vinyl polymers, vinyl alcohol polymers Vinyl POLYMERS, vinyl acetate polymers). Hydrolysis of poly(vinyl acetate) homopolymer produces a polyol with predominandy 1,3-glycol units. The polyol also contains up to 2 wt % 1,2-glycol units that come from head-to-head bonding during the polymeri2ation of vinyl acetate monomer. Poly(vinyl acetate) hydrolysis is seldom complete, and for some appHcations, not desired. For example, commercial PVF resins may contain up to 13 wt % unhydroly2ed poly(vinyl acetate). Residual vinyl acetate units on the polymer help improve resin solubiHty and processibiHty (15). On the other hand, the poly(vinyl alcohol) preferred for commercial PVB resins has less than 3 wt % residual poly(vinyl acetate) units on the polymer chain. 

Copolymers wet and adhere well to nonporous surfaces, such as plastics and metals. They form soft, flexible films, in contrast to the tough, horny films formed by homopolymers, and are more water-resistant. As the ratio of comonomer to vinyl acetate increases, the variety of plastics to which the copolymer adheres also increases. Comonomers containing functional groups often adhere to specific surfaces for example, carboxyl containing polymers adhere well to metals. 

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