Weather ageing characterization of the mechanical properties of the low density polyethylene

Tensile samples of low density polyethylene (LDPE) films with different thickness and disc samples for ultrasonic measurements were outdoor exposed to weather for different ageing times before being tested. The strength parameters of the material (yield strength and sonic modulus) decrease with increasing ageing time up to 7 days, then they start to recover, whereas ductility decreases continuously with ageing time. The results are discussed in terms of oxidation and cross-linking. Below 7 days of ageing the oxidation process dominates the degradation whereas above this period the cross-linking overrides the former one. (C) 1998 Elsevier Science Limited. All rights reserved.