MOBILITY OF A TACKIFYING RESIN IN A PRESSURE-SENSITIVE ADHESIVE

A detailed study of the mobility of a tackifying resin in a pressure-s ensitive adhesive (PSA) has been done for the first time. The objectiv e of this work is to relate changes in adhesive performance with tacki fier loading to tackifier mobility. Tackifiers are low-molecular weigh t resins that improve the overall performance of PSAs. They increase t he adhesive tack or the ability to form a bond of measurable strength after brief contact under slight applied pressure. In this study the d iffusion of n-butyl ester of abietic acid (n-BEAA) in either polyisopr ene (PI) (M-w = 195,000 M-w/M-n similar to 1.05) or poly( ethylene-pro pylene) (PEP) (M-w = 40,000 M-w/M-n similar to 2.30) was measured by P ulsed Gradient Spin Echo-Nuclear Magnetic Resonance (PGSE-NMR) as a fu nction of both tackifier concentration and temperature. The concentrat ion dependence of the tackifier's diffusion coefficient was weak for b oth systems. The weak variation in mobility with composition for the P I/n-BEAA system was consistent with that system's weak variation in ta ck with composition. On the other hand, blends of PEP/n-BEAA showed on ly modest variation in mobility, even though these adhesive systems sh owed appreciable enhancement of tack at intermediate compositions. (C) 1998 John Wiley & Sons, Inc.