Influence of hydrolysis on the crystallization of ethylene-vinyl acetate copolymers

The effect that side-chain groups exerts on the crystallization of a series of random ethylene-vinyl acetate (EVAL) copolymers and some of their hydro lyzed derivatives was analyzed by X-ray diffraction and differential scanni ng calorimetry (DSC). The variation of the polyethylene (PE) crystalline la ttice due to the substitution of bulky acetate groups by hydroxyl ones whil e maintaining constant the rest of structural variables of the polymers (mo lecular weight, molecular weight distribution, side group distribution, etc .) is discussed in the light of the expansion of the a and b- unit cell par ameters and the variation of the crystallite width. It has been confirmed, in accordance with earlier results, that acetate groups are rejected from t he crystalline lattice, while hydroxyl groups are able to enter on an equil ibrium basis. Finally, crystallinity and melting temperatures of the terpol ymers are shown to be independent of the hydroxyl group content.