RELEVANCE OF POLYURETHANE CONFIGURATION ON ADHESION PROPERTIES

Five one-component solvent-based adhesives (series C) prepared from ep silon-polycaprolactone polyurethane (PU) polymers were used to join un chlorinated and chlorinated synthetic vulcanized styrene-butadiene rub ber. PU films were characterized by infra-red (i.r.) spectroscopy, dif ferential scanning calorimetry (d.s.c.), wide angle X-ray diffraction (WAXD), gel permeation chromatography (g.p.c.) and advancing contact a ngle measurements. T-peel tests in styrene-butadiene rubber/PU/styrene -butadiene rubber joints were carried out. The experimental results ob tained allowed a distinction of PU films of series C according to thei r different configuration, i.e. the relative fraction and distribution of hard to soft segments: (i) PU with a relatively low hard/soft segm ent ratio (C1, C2, C4); and (ii) PU with a relatively high hard/soft s egment ratio (C3, C5). A correlation, which was different for unchlori nated and chlorinated rubber, between advancing contact angle measurem ents, hard/soft segment ratio and T-peel strength of rubber/PU joints was found. For chlorinated rubber/PU adhesive/chlorinated rubber joint s, the PU films with the highest surface energy produced the highest T -peel strength. Furthermore, an interaction between the carboxylic and chlorinated groups on the chlorinated rubber surface and the polyeste r and/or urethane groups of PU was probably produced, in such a way th at the highest T-peel strength corresponds to the polyurethane with th e highest relative amount of soft segments.