Photoinitiated modifications of polymers: photocrosslinking, surface photografting and photolamination

Abstract

Based on extensive studies of photoinitiated reactions of synthetic polymers, processes for modification of sheets, films, filaments and yarn have been invented and developed. Using ultra violet irradiation, photocrosslinking of polyethylene melts as a continuous process on line with an extruder has been invented. Effective photocrosslinking has also been obtained for ethylene-propylene-diene (EPDM) elastomers and ultra high strength fibers of high density polyethylene (HDPE). A continuous process for surface modification of polymers by surface photografting has been invented and applied to strips of film, filaments and yarns. The inert surface of polyolefins, polyesters and polyamids, grafted with functional vinyl monomers, show decreased contact angle with water, increased adsorption of dyes and increased adhesion to other polymers. Photoinitiated lamination of polymer films and sheets has been invented and developed as a ”bulk surface photografting process”. Two or more films and sheets are interdispersed with reactive layers of monomer and initiator and then bonded together by photoinitiated grafting with ultraviolet irradiation. The crosslinked network formed is grafted to two adjacent polymer surfaces. This gives laminates of high lamination strength, high barrier properties, and promising commercial applications.