Performance of photo-degradation and thermo-degradation of polyethylene with photo-catalysts and thermo-oxidant additives.

Nano-TiO2 particles were used as photo-catalysts and ferric stearate (FeSt3) powders were used as the thermo-oxidant promoters for degradable low-density polyethylene films in order to increase the rate of abiotic degradation of waste PE in the natural environment. The TiO2–FeSt3–polyethylene (TFPE) composite film was synthesized through two stages: a melt-granulating process and a film-blowing process. The final TiO2 and FeSt3 in composite film were controlled at around 1 wt%. The film thickness was about 25 μm. The photo-degradation and thermo-degradation of the composite film were investigated by exposing to UV irradiation for 240 h and/or in an air oven maintained at 70 °C for 30 days. Their residues were assembled in a aquatic test systems, and the effective biodegradation was assessed by monitoring the amount of CO2 developed over time according to the international standards ISO 14852 (1999). After 30 days of thermo-oxidative degradation, TFPE film containing both TiO2 and FeSt3 exhibited the strong characteristic absorptions of the carbonyl group (> C=O) and the amorphous region in ATR-FTIR spectroscopy. The loss rate for tensile strength and elongation at break of TFPE film reached 60% and 97.7%. After 240-h UV irradiation, the weight loss of TFPE film was 14%, and also, the absorption peaks appeared for carbonyl (> C=O) group and hydroxyl group in FTIR spectroscopy. The results showed that the addition of TiO2 and FeSt3 into the PE film could promote the photo-degradation and thermo-oxidative degradation of PE film. A lot of oxygenated groups were inserted into PE matrix during photo- or thermo-aging treatments, which was helpful for further biodegradation of films. Residues of TFPE films could be degraded completely by microorganism after incubation in aqueous medium. [ABSTRACT FROM AUTHOR]