Heat shrinkability of electron-beam-modified thermoplastic elastomeric films from blends of ethylene-vinylacetate copolymer and polyethylene

The heat shrink ability of electron-beam-irradiated thermoplastic elastomer ic films from blends of ethylenevinylacetate copolymer (EVA) and low-densit y polyethylene (LDPE) has been investigated in this paper. The effects of t emperature, time and extent of stretching and shrinkage temperature and tim e have been reported. Based on the above data, the optimized conditions in terms of high heat shrinkage and low amnesia rating have been evaluated. In fluence of radiation doses (0-500 kGy), multifunctional sensitizer levels ( ditrimethylol propane tetraacrylate, DTMPTA), and blend proportions on heat shrinkability has been explained with the help of gel fraction and X-ray d ata. With the increase in radiation dose, gel fraction increases, which in turn gives rise to low values of heat shrinkage and amnesia rating. At a co nstant radiation dose and blend ratio, percent heat shrinkage is found to d ecrease with increase in DTMPTA level. Gel content increases with the incre ase in EVA content of the blend at a constant radiation dose and monomer Le vel, giving rise to decrease in heat shrinkability. Heat shrinkage increase s with the increase in percent crystallinity, although the amnesia rating f ollows the reverse trend. (C) 2000 Elsevier Science Ltd. All rights reserve d.