Photocrosslinking of functionalized rubbers IX. Thiol-ene polymerization of styrene-butadiene-block-copolymers

A thermoplastic elastomer, polystyrene-block-polybutadiene-block-polystyren e (SBS) with a high vinyl content (59%), was crosslinked within a fraction of a second by UV-irradiation in the presence of a trifunctional thiol and an acylphosphine oxide photoinitiator. The curing process was followed by L R spectroscopy, insolubilization and hardness measurements. Both the thiol and the photoinitiator concentrations were shown to affect the kinetics of the thiol-ene polymerization. Insolubilization was found to occur even at v ery low concentrations in thiol (less than or equal to 1 wt%) and in photoi nitiator (0.1 wt%). The heat resistance of the photosensitive formulation i s high enough at 150 degrees C to allow this system to be used for hot-melt adhesive applications. (C) 2000 Elsevier Science Ltd. All rights reserved.