Effect of colorant, thickness, and pro-oxidant loading on degradation of low-density polyethylene films during thermal aging

Abstract

This work investigated the effect of colorant, thickness and pro-oxidant loading on degradation behavior of low-density polyethylene films during thermal aging. Films were formulated according to Taguchi design of experiments. The following degradation responses were monitored with thermal aging time: tensile strength, oxygen uptake, and carbonyl index. This study showed that colorant and pro-oxidant loading exhibited significant effect on the tensile strength of thermally aged films. White colorant and increased loading of pro-oxidant from 2% to 4% w/w reduced the tensile strength of aged films by 15.9% and 16.9%, respectively. However, incorporating yellow colorant improved the tensile strength of aged films by 3.2% as compared to noncolored films. Meanwhile, all three factors significantly influenced the maximum oxygen uptake of exposed films. White and yellow colorants increased the maximum oxygen uptake of aged films by 90.6% and 56.2%, respectively, when compared to films without colorant. On the other hand, increased film thickness from 1 to 3 mil lowered the maximum oxygen uptake by 31.6%, while increased pro-oxidant loading from 2% to 4% w/w showed an uptake increase of aged films by 204.3%. For the carbonyl index response, the index significantly increased by 84.6% with increased loading of pro-oxidant from 2% to 4% w/w, showing accelerated degradation of exposed films during thermal aging. Enhanced degradation of white films is due to the oxidative reactivity of titanium dioxide present in white colorant. Aromatic amine stabilizer in yellow colorant acts as antioxidant that delays film degradation.