FOURIER-TRANSFORM IR STUDY OF ACID-BASE INTERACTIONS - BLENDS OF ETHYLENE-VINYLACETATE COPOLYMER AND TERPENE-PHENOL RESINS

Specific interactions in binary blends of ethylene-vinylacetate copoly mer (EVA) with various low molecular weight terpene-phenol tackifying resins (TPR) were systematically investigated, as a function of the co mposition of the blend and of the electron-acceptor ability of the res in, using attenuated total reflection Fourier transform IR (ATR-FTi.r. ) spectroscopy. Molecular acid-base complexes (according to Lewis' ele ctron acceptor-donor concepts) were evidenced between TPR hydroxyl gro ups and EVA carbonyl groups. Quantitative information on the fraction of acid-base bonded entities, the enthalpy and the equilibrium constan t of pair formation were obtained. It appears that the amorphous phase s of such polymer blends remain thermodynamically miscible whatever th e composition of the blend and the resin acidity. On the contrary, a c rystalline transition of the EVA copolymer is observed, depending on t he blend composition and resin acidity. This transition is discussed i n terms of enthalpy and entropy considerations based on FTi.r. and dif ferential scanning calorimetry (DSC) investigations. Fundamental resul ts are then summarized in order to predict the melting enthalpy of a p olymer blend. (C) 1998 Elsevier Science Ltd. All rights reserved.