Polyvinyl alcohol glass transition temperature

Glassy polymers with much higher glass transition temperatures and more rigid polymer chains than rubbery polymers have been extensively used as the continuous polymer matrices in the zeolite/polymer mixed-matrix membranes. Typical glassy polymers in the mixed-matrix membranes include cellulose acetate, polysul-fone, polyethersulfone, polyimides, polyetherimides, polyvinyl alcohol, Nafion , poly(4-methyl-2-pentyne), etc. 

Polyvinyl alcohol (PVA) is a water-soluble polymer with a glass transition temperature, T, of 80 °C. Although its name implies a homopolymer stmcture, the structure of commercial PVA is a copolymer of vinyl alcohol and vinyl acetate as seen in Fig. 4.2. PVA is made by the incomplete hydrolysis of polyvinyl acetate... 

PVA is not suitable as the base of packaging materials since its physical and mechanical properties are impaired abruptly above the glass-transition temperature (28°C). It is used, nevertheless, along with polyvinyl butyral (PVB), polyvinyl alcohol (PVAL), alcohol-soluble polyamides and polyacrylates as a layer-carrier of Cl in multilayered films. The layer is formed via application of emulsions, suspensions or solutions of named polymers containing Cl onto the base film [23-26]. 

Murakami, H., Kushida, T., and Tashiro, H. 1998. Fast structural relaxation of polyvinyl alcohol below the glass-transition temperature. J. Chem. Phys. 108 10309-10318. 

As indicated in Table 6, the glass transition temperature (7 ) has notable effects on properties of adhesive emulsions. Varying the amount of ethylene incorporated into a copolymer has a direct relationship to the T the more ethylene, the lower the Tg. The glass transition temperature affects such properties as flexibility, water resistance, PVC adhesion, paper adhesion, and setting speed. The three emulsions in Table 6 are all protected with polyvinyl alcohol. The major difference among them is the ethylene content as illustrated by the Tg, It should be noted that water resistance and ease-of-cleanup are inversely related. 

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