Radiation grafting of vinyl monomers onto poly(tetrafluoroethylene) powderproduced by gamma irradiation and properties of grafted poly(tetrafluoroethylene) filled low density polyethylene

Scrap poly(tetrafluoroethylene) (PTFE) was gamma irradiated under an ambien t atmosphere in order to produce extensive chain scission and oxidative deg radation. After irradiation the PTFE was ground into a fine powder (2 degre es -PTFE) and graft;ed with styrene (St), vinyl acetate (VAc), and 4-vinylp yridine (4-VP) by using the direct irradiation technique. The grafted PTFE were then blended with low density polyethylene (LDPE). The study covered t he characterization of irradiated PTFE and grafted 2 degrees -PTFE powder w ith various methods. Mechanical grinding was found to reduce trapped radica ls formed during the irradiation process faster than the annealing process. Grafting on 2 degrees -PTFE was followed by gravimetric analysis, TGA, and the change in the particle size of the samples. Although we reached almost 20% grafting by weight in the St and 4-VP monomers, VAc grafting was found to be maximum at around 8% by weight at the maximum absorbed dose. The add ition of VAc grafted 2 degrees -PTFE into LDPE produced better final mechan ical properties with a fine dispersion. However, as may be expected, the in corporation of the other two 2 degrees -PTFEs into LDPE showed low film qua lity and poor mechanical properties. (C) 2000 John Wiley & Sons, Inc.