Effects of the composition of hot-melt adhesives on their bulk and interfacial properties

Abstract
Specific interactions in binary blends, models of hot-melt adhesives, of ethylene-vinylacetate copolymer (EVA) with different terpene-phenol low molecular weight tackifying resins (TPR) are first investigated by means of Fourier transform infrared spectroscopy (FTIR) as a function of the composition of the blend. Molecular electron donor-acceptor (or "acid-base" according to Lewis' concept) complexes are clearly evidenced between TPR hydroxyl and EVA carbonyl groups. Quantitative data on the fraction of acid-base bonded carbonyl groups and the enthalpy of pair formation are then obtained. Secondly, the analysis of the interface between the blends and basic (aluminium) or acidic (glass) substrates by FTIR allows us to show the establishment and to quantify the strength of acid-base interfacial interactions in both cases. Finally, the comparison between the interfacial and bulk properties data and adhesive strength measurements (peel energy) leads to the estimation of fundamental parameters of adhesion science, in particular the acid-base component of the energy of adhesion and the number of acid-base interactions per unit interfacial area.