Vinyl acetate groups copolymers

Highly purified diallyl maleate and fumarate in an inert atmosphere, are said to polymerize very rapidly [118], However, trace impurities and atmospheric oxygen substantially reduce the polymerization rate under ordinary circumstances. Naturally with the double bond between the two carboxylate groups and the two allylic double bonds, crosslinking takes place at very low conversion. Even so, in copolymer systems such as in poly(vinyl acetate) emulsion copolymers, the cross-linking of a fumarate or maleate within the latex particles appears not to interfere significantly with film formation properties. As a matter of fact these monomers are incorporated in poly(vinyl acetate) latices used in adhesives and in water-based paints. 

To obtain a higher effidency of photocrossiinking and to improve technological properties of prepared films (smoothness of the surface, transparoic ), 3 to 5% of ethylene-vinyl acetate copolymer having about 12% of vinyl acetate groups ate added [90], Increase of the molecular mass of the added copolymer leads to the increase of insoluble gel which indicates that this copolymer incorporates into the polyethylene network. The decrease or increase of vinyl acetate content in the cx>polymer below/ above an optimum value always reduces the effidency of photoo-osdinldng. 

Multifunctionality can be introduced not only through copolymerization but also by polymer analogous reactions in a postpolymerization modification step, often in combination with the introduction of additional comonomers during the polymerization process. Well-known technical examples are copolymers of polyvinyl alcohol and polyvinyl acetate with different amounts of vinyl acetate (see Section 3.1.3), which all derive from homopoly(vinyl acetate) and are the result of acetate hydrolysis to a different extent. The content of remaining vinyl acetate groups defines the hydrophilicity/hydrophobicity of the copolymer and thus the amphiphilic and stabilizing character of the material. 

Photolabile groups on polymers can serve as sites for photoinitiated graft copolymerizations. For instance, when polymers and copolymers of vinyl ketone decompose in ultraviolet Imht in the presence of acrylonitrile, methyl methacrylate, or vinyl acetate, graft copolymers form ... 

The efficiency of the AB group of coalescents towards almost all polymer types has already been mentioned. For styrene-acrylics and vinyl acetate - Veova copolymers, the diesters have a significant edge in performance compared with other members of that group. This advantage is shown in the reduction in amount required to attain a particular MFFT or the actual MFFT for a given addition level. 

Ethylene-vinyl acetate (EVA) copolymers. EVA copolymers are given by the structure shown in Fig. 1.27 and find commercial importance in the coating, laminating, and film industries. EVA copolymers typically contain between 10 and 15 mol % vinyl acetate, which provides a bulky, polar pendant group to the ethylene and provides an opportunity to tailor the end properties by optimizing the vinyl acetate content. Very low vinyl-acetate content (approximately 3 mol %) results in a copolymer which is essentially a modified low-density polyethylene, " with an even further reduced regular structure. The resultant copolymer is used as a film due to its flexibility and surface gloss. Vinyl acetate is a... 

Determination of Free and Combined Vinyl Acetate Groups in Vinyl Chloride-Vinyl Acetate Copolymers... 

Fig. 5.11 Melting temperature of rapidly crystallized fractions of copolymers of ethylene as determined by differential scanning calorimetry hydrogenated poly(butadiene) (A), ethylene-vinyl acetate ( ), diazoalkane copolymer with propyl side groups (A), ethylene-butene copolymer ( ), ethylene-octene copolymer ( , a).(74)...

Copolymers of ethylene and vinyl acetate are significant commercial materials and are generally prepared by high pressure processes similar to those previously described. The introduction of random vinyl acetate groups into the polymer leads to a progressive reduction in crystallinity and stifftiess which is directly... 

This new model is more simple and accurate than the previous one. However, the fitting parameters are interaction parameters as they don t reflect a simple dependence. Parameter Ci multiplies the complex viscosity of the resin, but depends on the oil concentration. This dependence could be due to the influence of the oil-resin fraction, which determines the cohesion of the synthetic binder. Parameter C2 multiplies the complex viscosity of the oil-polymer blend, but depends on the resin-polymer ratio, perhaps due to the interaction between the resin and the vinyl-acetate groups present in the EVA copolymer [20]. And finally, parameter C3 is independent of complex viscosity, but depends on the polymer concentration, probably due to the strong influence of the polymer on the fluidity of the samples, which is clearly present in a rheological test such as the temperature sweep test. 

Poly (vinyl acetate) (PVAc) is an inexpensive, high-tormage bulk commodity polymer which, unlike most vinyl polymers, is moderately biodegradable [73]. It is an amorphous material with a 3 of about 30 °C. In contrast, poly(vinyl alcohol) (PVA) is a synthetic, hydrophilic, biodegradable, biocompatible and highly flexible polymer, in spite of its highly crystalline structure. The Tg and of PVA are about 80 °C and 230 °C, respectively. PVA is obtained by the hydrolysis of PVAc, and usually contains a small amount of residual vinyl acetate groups. Partial hydrolysis of PVAc is a simple route to obtain poly(vinyl acetate-co-vinyl alcohol) [P(VAc-co-VA)] copolymers. 

Ester groups occur in a wide range of polymers (e.g., polyethylene terephthalate) and in copolymers such as, for example, ethylene vinyl acetate. The classical chemical method for the determination of ester groups, namely, saponification, can be applied to some types of polymer. For example, copolymers of vinyl esters and esters of vinyl esters and esters of acrylic acid, can be saponified in a sealed tube with 2 M sodium hydroxide. The free acids from the vinyl esters were determined by potentiometric titration or gas chromatography. The alcohols formed by the hydrolysis of the acrylate esters were determined by gas chromatography. Vinyl acetate ethylene copolymers can be determined by saponification with 1 N ethanolic potassium hydroxide at 80 C for 3 hours and back titration with standard acid or by saponification with p-toluene sulfonic acid and back titration with standard acetic acid [49, 50]. 

NMR has also been used to determine ethyl acrylate in ediyl acrylate-ethylene and vinyl acetate-ethylene copolymers. Measurements were made on 10% solutions in diphenyl ether at an elevated temperature. Resolution improved with increasing temperature and lower polymer concentration in the solvent. This technique has also been used to identify ester groups in acrylic copolymers and copolymers. 

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. 

Gross-Linking. A variety of PE resins, after their synthesis, can be modified by cross-linking with peroxides, hydrolysis of silane-grafted polymers, ionic bonding of chain carboxyl groups (ionomers), chlorination, graft copolymerization, hydrolysis of vinyl acetate copolymers, and other reactions. 

Vinyl resins ie, copolymers of vinyl chloride and vinyl acetate which contain hydroxyl groups from the partial hydrolysis of vinyl acetate and/or carboxyl groups, eg, from copolymerized maleic anhydride, may be formulated with alkyd resins to improve their appHcation properties and adhesion. The blends are primarily used in making marine top-coat paints. 

The nmr spectmm of PVAc iu carbon tetrachloride solution at 110°C shows absorptions at 4.86 5 (pentad) of the methine proton 1.78 5 (triad) of the methylene group and 1.98 5, 1.96 5, and 1.94 5, which are the resonances of the acetate methyls iu isotactic, heterotactic, and syndiotactic triads, respectively. Poly(vinyl acetate) produced by normal free-radical polymerization is completely atactic and noncrystalline. The nmr spectra of ethylene vinyl acetate copolymers have also been obtained (33). The ir spectra of the copolymers of vinyl acetate differ from that of the homopolymer depending on the identity of the comonomers and their proportion. 

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