Mechanical Properties of UV-Irradiated Low-Density Polyethylene Films Formulated With Carbon Black and Titanium Dioxide

This study reports on the effect of UV-rays on the mechanical
properties of low-density polyethylene (LDPE) films pigmented with carbon
black and titanium dioxide (TiO2) in different formulations. The film samples
were submitted to UV-soaking with fluorescent lamps for differ ent exposure
times and 40 oC. An untreated LDPE film is used for the purpose of
comparison. The physico-chemical structural changes in the irradiated films
were monitored by retained elongation- and stress-at-break and by Fouriertransform
infrared spectrophoto- metric methods. The changes in both film
tensile properties at break and in carbonyl groups under UV exposures are
discussed. Retained elongation-at-break is found to decrease with exposure
time for most studied formulations, except for formulation of TiO2 / carbon
black = 0.75, it increases with exposure time. The results show that the use of
both pigments, carbon black and TiO2 in appropriate concentration ratios gives
a reliable improvement in the mechanical and physico-chemical properties of
LDPE films exposed to UV-radiation.