Study of Ethylene/Vinyl Acetate Transformation to Ethylene/Vinyl Alcohol Copolymer by NMR and DSC
Hydrolysis of ethylene-vinyl acetate copolymer in alkaline conditions using two systems of NaOH/methanol and KOH/isopropanol has been studied and the formation of ethylene-vinyl alcohol copolymer was systematically examined using NMR spectroscopy and DSC measurements. Vinyl acetate weight percentage and the degree of hydrolysis were calculated from NMR spectroscopy and it is shown that hydrolysis by NaOH/methanol system has higher rate and reaches a maximum of nearly 100 percent compared with KOH/isopropanol system. DSC was used to follow melting temperature and ΔH of the hydrolysis products. The results have shown that the obtained copolymers have higher melting temperature and ΔH indicating that ethylene-vinyl acetate copolymer is converted to ethylene-vinyl alcohol. Moreover, DSC confirms the results of NMR in which higher degree of hydrolysis is reached using NaOH/methanol system. Based on the experimental results and system used, the hydrolysis is reached its maximum between 10 and 30 min in this study.