Polyvinyl alcohol crystallises readily but not polyvinyl acetate. Why?
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Answer:
Polyvinyl acetate and polyvinyl alcohol
Polyvinyl acetate (PVA) and polyvinyl alcohol (PVOH) are further examples of ethylene copolymers. PVA is used as an emulsion adhesive for bag, sack and carton making. PVOH is produced by hydrolysis of PVA and the strong hydrogen bonding imparted by the –OH groups means that pure PVOH is water soluble. The degree of water solubility is controlled by the amount of hydrolysis. Specific packaging uses for PVOH are in unit doses of detergents, where the entire pack is placed in the washing machine, and for agrochemicals, where the pack is placed into a tank of water and mixed. In both of these examples the advantages are that a measured dose of product is used, with no spillage on decanting and, in the latter case, limited exposure of personnel to what may be a toxic product.
Explanation: