Miscibility behaviour of ethylene vinyl acetate/Novolac blends

Abstract

Blends of ethylene vinyl acetate (EVA) resin, containing different amounts of vinyl acetate, and phenolic resin (Novolac type) were characterized by i.r. spectroscopy and differential scanning calorimetry (d.s.c.). The blends were prepared in the melt state at 130°C in a batch mixer. The compositions ranged from 20 to 80 wt% Novolac. Miscibility behaviour was investigated through i.r. spectroscopy which was focused on the region of the spectra corresponding to the stretching frequency of carbonyl groups of vinyl acetate. The addition of Novolac to EVA resins was found to result in strong molecular interactions between their functional groups, resulting in a splitting of the i.r. spectrum corresponding to the carbonyl group of EVA into two bands. Moreover, the absorption band of the carbonyl groups of EVA is shifted in the blends to lower wavenumber values by approximately 30 cm −1. D.s.c. analysis has shown a total miscibility of the components for the whole range of composition, with a positive deviation from the Fox equation. However, for certain compositions. Kwei's equation was found to fit well with the experimental data. The results showed an improved compatibility between Novolac and EVA resin, an outcome of the specific interactions between the hydroxyl groups of Novolac and the carbonyl groups of EVA. It was also shown that no chemical reaction occured between blend components, even at high temperature (180°C).