Properties of elastomeric polyurethanes obtained with epsilon-caprolactone macroglycol

Three elastomeric polyurethanes were obtained by reacting MDI (diphenylmethane-4,4'-diisocyanate) with epsilon-caprolactone macroglycols of different molecular weight (1000-3000 daltons); the chain extender used was 1,4-butane diol. The increase in the molecular weight of the macroglycol modified the degree of phase separation and the interactions between the hard and soft domains in the polyurethane structure. The properties of elastomeric polyurethanes were studied by using Gas Permeation Chromatography, FTIR spectroscopy, DSC, DMTA, rheology (stress-controlled rheometer), contact angle measurements, and T-peel strength tests. The use of low molecular weight macroglycol produced polyurethane with small crystallinity, relatively higher T-g and reduced softening enthalpy. Therefore a poor degree of phase separation was produced and reduced mechanical and viscoelastic properties were obtained. On the other hand, a high molecular weight macroglycol improved the degree of phase separation producing better mechanical, viscoelastic and thermal properties in the polyurethanes. Furthermore, the increase in molecular weight of macroglycol increased the adhesion of PVC/polyurethane adhesive joints and further changed the locus of failure. (C) 1997 Elsevier Science Ltd.