MISCIBILITY BEHAVIOR OF ETHYLENE-VINYL ACETATE NOVOLAC BLENDS

Blends of ethylene vinyl acetate (EVA) resin, containing different amo unts of vinyl acetate, and phenolic resin (Novolac type) were characte rized by i.r. spectroscopy and differential scanning calorimetry (d.s. c.). The blends were prepared in the melt state at 130 degrees C in a batch mixer. The compositions ranged from 20 to 80 wt% Novolac. Miscib ility behaviour was investigated through i.r. spectroscopy which was f ocused on the region of the spectra corresponding to the stretching fr equency of carbonyl groups of vinyl acetate. The addition of Novolac t o EVA resins was found to result in strong molecular interactions betw een their functional groups, resulting in a splitting of the i.r. spec trum corresponding to the carbonyl group of EVA into two bands. Moreov er, the absorption band of the carbonyl groups of EVA is shifted in th e blends to lower wavenumber values by approximately 30 cm(-1). D.s.c. analysis has shown a total miscibility of the components for the whol e range of composition, with a positive deviation from the Fox equatio n. However, for certain compositions, Kwei's equation was found to fit well with the experimental data. The results showed an improved compa tibility between Novolac and EVA resin, an outcome of the specific int eractions between the hydroxyl groups of Novolac and the carbonyl grou ps of EVA. It was also shown that no chemical reaction occurred betwee n blend components, even at high temperature (180 degrees C).