Vinyl acetate groups

Ethylenevinylacetate (EVA) is the most used type (approximately 80%) it can be varied in viscosity (melt index) and content of acetate in broad ranges. It is semicrystalline. The vinyl acetate groups provide improved adherability towards many materials. The low heat stability, however, limits the areas of application. 

Sorokin, A., Influence of the Intramolecular distribution of vinyl acetate groups in polyvinyl alcohols on their physiochemical and biological properties, Polymeric Materials Science and Engineering of the American Chemical Society Meeting, Vol. 78, Spring, Dallas TX 1998. 

Figure 6.11 shows the adsorption isotherms of PVA with various molecular weights on PS latex (at 25 °C) [38]. The polymers were obtained fractionating a commercial sample of PVA with an average molecular weight of 45 000 Da (the polymer also contained 12% vinyl acetate groups). As with PEO, the amount of adsorption was increased with increases in M, and the isotherms were also of the high-affinity type. F at the plateau was increased linearly with... 

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. 

Density of EVA is higher due to bulky vinyl acetate group. Hence, EVA density can not be compared to other polyethylenes. 

Another carrier polymer is polymer-plasticized poly(vinyl chloride) (PVC/EVACO), which was developed for medical application. Hydroxyl groups as functional groups were created through saponification of the vinyl acetate groups of the EVACO component. 

The grafted polymer poly[(ethylene-co-vinyl acetate-co-carbon monoxide)-graft-vinyl chloride] (PVC/EVACO) known in medical applications as plasticized poly(vinyl chloride) was apphed as a carrier polymer for the covalent immobilization of fibronectin. The surface modifications were carried out on foils both with closed surface structure and with microporous surfaces produced by a phase-inversion technique. The vinyl acetate groups of the carrier polymer were saponified and then reacted with hexamethylene diisocyanate (HDI) as a spacer. Fibronectin is immobilized upon reaction of the free isocyanate group with an amino group of the protein (Fig. 33). The saponification of the carrier polymer was verified by IR-ATR and XPS [149]. The presence of hydroxyhc groups after hydrophihzation is demonstrated by a contact angle of 61° while that of the basic polymer is 110°. 

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

Bondesen and Oksman (2007) studied the feasibility of using PVA as compat-ibilizer to improve the dispersion of cellulose whiskers in PLA matrix. The hydroxyl groups on partial hydrolyzed PVA are expected to interact with the hydrophilic surfaces of the cellulose and the residual vinyl acetate groups with the hydrophobic PLA. Two feeding methods were used and evaluated dry mixing with PLA prior to extrusion or pumping as suspension directly into the extrader. Due to immiscibility of the polymers, phase separation occurred with a continuous PLA phase and a discontinuous PVA phase. The whiskers were primarily located in flie PVA phase and only a small amount was located in the PLA phase. This inadequate dispersion of whiskers in the PLA phase was probably the reason why no improvements in thermal properties were observed for the nanocomposites. The relatively small improvements in tensile properties of the nanocomposites also indicated that it was principally the PVA phase that was reinforced with whiskers rather than the PLA phase. 

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. 

To assess the possibility of ehemical interaction of fillers with polyrmers, we used the method of IR spectroscopy. The following IR bands were foimd to be characteristic of SEVA 1,740 cm (vibrations of the aldehyde group) 1,380 cm (vibrations of the vinyl acetate group) 1,240 cm 1,050 cm 797 cm and 607 cm [3],... 

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. 

Finer details can be resolved by TEM either on stained samples (Fig. 11.18) or on replicas of etched samples. The classical osmium tetroxide treatment has proven very useful. Apart from staining of unsaturated rubber polymers, it effectively stains structures containing vicinal hydroxyl groups. Thus the vinyl-acetate groups of EVA-45 could be stained... 

EAM radiation resistance depends on its content of vinyl-acetate groups The higher the content, the more free radicals and hydrogen peroxides are formed, and the lower the resistance [746]. 

Poly(vinyl alcohol) (PVOH) is generally obtained from the hydrolysis of poly(vinyl acetate) and thus often water soluble versions contain up to 25 mole% vinyl acetate groups. FuUy hydrolyzed PVOH is highly crystalline and has limited water solubihty, imless higher temperatures are utilized. PVOH, with repeating secondary hydroxyls, offers the abihty to be either a proton donor or proton acceptor for hydrogen bonding interactions with other polymers. Miscibility of PVOH has been observed with water soluble polymers, such as poly(N-vinyl... 

Table I shows the measured vinyl acetate content of each of the samples based on the stoichiometry of every vinyl acetate group decomposing to acetic acid and a polyolefin in the initial weight loss. The DY values are those measured as the changes in weight of the sample by TGA. With the exception of the 12% nominal vinyl acetate sample, relatively close agreement was found between the nominal values and the TGA data.

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