PHOTO-CROSS-LINKING OF FUNCTIONALIZED RUB BER .6. CATIONIC POLYMERIZATION OF EPOXIDIZED RUBBER

Epoxidised natural rubber has been crosslinked quasi-instantly by UV-i rradiation in the presence of a sulfonium salt. The ring-opening catio nic polymerisation has been studied quantitatively by infrared spectro scopy and shown to proceed by long kinetic chains. A tridimensional du al polymer network has been produced by photocrosslinking of a rubber having both epoxy and pendent acrylate functions in its chain. The add ition to the epoxidised rubber of a multifunctional monomer, such as v inyl ether, acrylate or cycloepoxide, leads to a substantial increase of the polymerisation rate, as well as of the degree of crosslinking. Interpenetrating polymer networks have thus been produced within a few tenths of a second under intense illumination, or within a few minute s by simple exposure to sunlight. The addition of a radical photoiniti ator was shown to enhance the crosslinking polymerisation of the acryl ate monomer, and at the same time to slow down that of the oxirane rin g, because of mobility restrictions brought upon by the fast build up of the acrylate polymer network. Copyright (C) 1996 Elsevier Science L td