PHOTOINITIATED MODIFICATIONS OF POLYMERS - PHOTO-CROSS-LINKING, SURFACE PHOTOGRAFTING AND PHOTOLAMINATION

Based on extensive studies of photoinitiated reactions of synthetic po lymers, processes for modification of sheets, films, filaments and yam have been invented and developed. Using ultra violet irradiation, pho tocrosslinking of polyethylene melts as a continuous process on line w ith an extruder has been invented. Effective photocrosslinking has als o been obtained for ethylene-propylene-diene (EPDM) elastomers and ult ra high strength fibers of high density polyethylene (HDPE). A continu ous process for surface modification of polymers by surface photograft ing has been invented and applied to strips of film, filaments and yar ns. The inert surface of polyolefins, polyesters and polyamids, grafte d with functional vinyl monomers, show decreased contact angle with wa ter, increased adsorption of dyes and increased adhesion to other poly mers. Photoinitiated lamination of polymer films and sheets has been i nvented and developed as a ''bulk surface photografting process''. Two or more films and sheets are interdispersed with reactive layers of m onomer and initiator and then bonded together by photoinitiated grafti ng with ultraviolet irradiation. The crosslinked network formed is gra fted to two adjacent polymer surfaces. This gives laminates of high la mination strength, high barrier properties, and promising commercial a pplications.