Photo-oxidation of polyethylene nanocomposites

Increasing environmental concerns about plastic wastes in the community has led to the development of environmental friendly polymeric packaging materials. Polyethylene, one of the widely used packaging materials, can be made biodegradable by blending it with biopolymers such as starch and/or pro-oxidants which are metal complexes (e.g. cobalt stearate, cerium stearate). However recent studies on polyethylene degradation have found that addition of nanoclay, which is used as filler in polymer composites mainly to enhance their barrier, thermal and mechanical properties, increases the photo-oxidative degradation of polymer nanocomposites. However the influence of pro-oxidants on the photo-oxidation of polymer nanocomposites is not yet known in detail. The present study aims to investigate the effects of pro-oxidants and nanoclay, and their concentrations on the photo-oxidation of polyethylene composites. Photo-oxidation of polyethylene film samples was conducted in an accelerated QUV weathering tester which reproduces the damage caused by sunlight, rain and dew at various temperatures to mimic large scale composting. Oxidation rate of the film was determined by measuring the carbonyl absorbance using FT-IR spectroscopy and molecular weight changes were determined using Gel Permeation Chromotography. Changes in mechanical properties were measured using universal testing machine (Instron). Preliminary results show that the rate of photo-oxidative degradation of polyethylene nanocomposites with or without pro-oxidants is much faster than that for polyethylene. It is also found that the pro-oxidant has relatively greater influence on the rate of photo-oxidation of the polymer as compared to nanoclay.