The Research On UV-irradiation And Biodegradation Of Low Density Polyethylene (LDPE) Film

At present, most waste plastics are burned for disposal, set on fire or heating degradation. Some plastics are recycled for utilization. Unfortunately, the effect is not satisfied. After the research on the development of degradable plastics and the research on degradation of plastics, the study on the biodegradation of the ordinary plastics becomes the leading topic. Particularly, the biodegradation of polyethylene becomes the principal problem, which can solve the white pollution ultimately.Plastics degradation is the combination of photo-degradation and biodegradation, beginning with the photo-degradation and metabolized by biodegradation and turning into humic substance, H₂O and CO₂. The addition of different kinds of photo sensitizer shows the different degree of photo-degradation of LDPE films. The photosensitive activity of the FeSt₃ is the best, followed by CeSt₄ and MnSt₂. The research also shows that the life-span of the LDPE films can be controlled by the content of the photo sensitizer and the illumination time. After 60h UV-irradiation, the LDPE films which contain 0.4% FeSt₃ can not be used and the viscosity average molecular weight reduces to 9000, which can be used as carbon source by P.simplicissimum.In order to enhance the utilization of LDPE films as carbon source and accelerate the biodegradation, the addition of different surfactants to the culture medium shows that the mineral oil improved the growth of Penicillium simplicissimum on the surface of LDPE, but Tween 80 and Triton X-100 had no effect on the growth. After 120h UV-irradiation, the FTIR spectrum showes the typical carbonyl peak at 1715 cm-1 and double-bond at 910 cm-1 and then reduce after incubation with Penicillium simplicissimum for 28 days due to their utilization by the fungus. With the increase of concentration of the mineral oil, there is denser biofilm formed on the LDPE and the weight loss of the PE also increases. But when the concentration of the mineral oil is too high, it restrains the biodegradation The viscosity average molecular of LDPE films decreases 11.25% in addition of mineral oil while only 2.5% in free of mineral oil. The addition of mineral oil had an active effect on the biodegradation of LDPE, enhancing the degradation of LDPE by Penicillium simplicissimum.