Study of the acetoxy‐hydroxide transformation in ethylene‐vinyl acetate copolymers

Ethylene‐vinyl alcohol (EVAL) copolymers and ethylene‐vinyl alcohol‐vinyl acetate (EVALVA) terpolymers with different VA content were achieved by hydrolysis of ethylene‐vinyl acetate (EVA) copolymers of low vinyl acetate content. Several experimental techniques (elemental analysis, thermogravimetry, NMR and IR spectroscopy) were used for the analysis of the composition of copolymers and terpolymers. The results have been critically discussed. Kinetic aspects of the acetoxy‐hydroxide transformation of the EVA copolymers have been analysed, such as the influence of steric and neighbouring group effects on the rate of this transformation. The kinetics can be expressed by a second order kinetic equation and the acetoxy groups joined to hydroxy groups are rapidly transformed. The reaction rate depends on the vinyl acetate content; the higher the vinyl acetate content of the EVA copolymer, the higher is the rate of the transformation process. Another important conclusion is related with the dependence of the rate constant on the concentration of the EVA copolymer in the reaction, on the base of equivalent ester group concentration.