Mechanical and transport properties of irradiated linear low density polyethylene (LLDPE)

Films of a new linear low density polyethylene (LLDPE) were exposed to acce lerated weathering in a UV chamber at 60 degreesC for increasing times. The changes in the mechanical properties, due to the degradation were followed by determining the elastic modulus (E), the stress at the yield point (sig ma (y)), the post yield stress drop (PYSD), the stress at the breaking poin t (sigma (b)), the strain at the breaking point (epsilon (b)). and the toug hness (t). They were correlated to the exposure time and to the carbonyl in dex, previously determined on the same samples. All the mechanical paramete rs were found to be very sensitive to the chemical degradation and to the m orphological changes. Furthermore the curves of the mechanical parameters a s a function of the exposure time allowed the determination of the point be yond which the material becomes useless. This point corresponds to 150 h of irradiation and to a carbonyl index of 0.3. The transport properties, diff usion and sorption, of a non polar molecule, n-pentane and a more polar mol ecule, dichloromethane were also correlated to the changes in the molecular structure. (C) 2001 Elsevier Science Ltd. All nights reserved.