Vinyl acetate radiation effect

In addition to, or instead of, polystyrene and oils, polymers such as polypropylene, polyethylene, or ethylene-vinyl acetate copolymer can be blended with these block copolymers. Blends with S-B-S or (S-B) -X block polymers usually show greatly improved ozone resistance (S-EB-S already has excellent ozone resistance). In addition, these blends have some solvent resistance. In certain cases, some oils that are stable to UV radiation reduce the stability of the blends however, the effects can be minimized by the use of UV stabilizers and absorptive or reflective pigments (e.g., carbon black or titanium dioxide). 

By a technique which interposed a rotating sector between a source of UV radiation and a dilatometer bearing a monomer, variations in the rotational speed of the sector and size of the opening, controlled bursts of radiation strike the monomer and induce polymerization. From the frequency of exposure and the effect on the polymerization many of the kinetic constants were evaluated. In this connection it should be noted that vinyl acetate exhibits virtually no absorption of UV radiation at 290-300 nm. On the other hand, acetaldehyde has an extinction coefficient of 14 at 290 nm and an extinction coefficient of 15 at 300 nm. Therefore acetaldehyde can act as a photo-sensitizer for the polymerization of vinyl acetate at wavelengths above 299.8 nm [23]. At 366 nm, 2,2 -azo-bisisobutyronitrile has been used as a sensitizer [29,180]. Azobicyclohexane carbonitrile is a UV sensitizer suitable for use with a 124 watt mercury arc at 25°C which does not produce a dark reaction in rotating-sector experiments. Its absorption peak is at 350 mn with an extinction coefficient of 16 [181]. 

Wang, B., Wang, X., Shi, Y. et al. 2012. Effect of vinyl acetate content and electron beam irradiation on the flame retardancy, mechanical and thermal properties of intumescent flame retardant ethylene-vinyl acetate copolymer. Radiation Physics and Chemistry 81 308-315. 

Dalai, S., Wenxiu, G., Radiation effects on poly(propylene) (PP)/ethylene-vinyl acetate copolymer (EVA) blends. Journal of Applied Polymer Science 2002, 86, 3420-3424. 

Wang, B.B., Song, L., Hong, N.N., Tai, Q.L., Lu, H.D., Hu, Y. Effect of election beam irradiation on the mechanical and thermal properties of intumiscent flame retarded ethylene-vinyl acetate copolymer/orcanically modified montmorillonite compositions. Radiat. Phys. Chem. 80, 1275-1281 (2011)... 

Figure 19 Effects of monomer and grafting method on morphological structures of cotton-cellulose copolymers, as shown by electron microphotographs of fibrous copolymer cross-sections (a) immersion of cellulose in solution of styrene in methanol then high-energy IR radiation (b) immersion of cellulose in solution of vinyl acetate in 70% aqueous ZnClj then high-energy irradiation (c) immersion of cellulose in aqueous solution of butyl methacrylate then high-energy irradiation.

Armstrong et al. have extensively studied the effect of this radiation on grafting butadiene, styrene, vinyl chloride, vinyl esters, acrylic, and methacrylic esters, acrylonitrile and other less common monomers on Nylon 66 fibers. They observed the influence of oxygen, water, methanol, acetic acid, dose of irradiation as well as temperature (160-163). 

Shin, J., Kim, Y., Lee, K., Lim, Y. M., and Nho, Y. C. 2008. Significant effects of sodium acetate, an impurity present in polyf vinyl alcohol) solution on the radiolytic formation of silver nanoparticle. Radiat. Phys. Chem. 77(7) 871-876. 

An extensive study has been made of the graft polymerization of vinyl monomers (e.g. methyl methacrylate, sodium vinyl sulphonate, 4-vinylpyridine, acrylamide, and acrylic acid) onto dissolving pulp and groundwood initiated by acetic acid and hydrogen peroxide. It is possible to predict accurately the extent of grafting and the properties of the graft copolymers. The effects of solvents on the radiation-induced grafting of vinylpyridines onto cellulose have been examined. ... 

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