Study on Photodegradable Property of Low-density Polyethylene

　　Study on Photodegradable Property of Low-density Polyethylene
　　Plastics with photosensitizer show photodegradable property by adding different kinds of photosensitizers, which can be decomposed under the ultraviolet radiation when being discarded. They are a kind of energy-saving and environmental protection plastics which are mostly applied to agriculture films and packaging materials. Polyethylene (PE) is one of the important plastics used in these area, which, however, with poor photodegradability. So the study on the photodegradable PE becomes a hot topic these years.Based on the others’ study, the photodegradable Neodymium Magnets property of the low-density Polyethylene (LDPE) with different photosensitizer systems was studied in this paper. FeSt3, CeSt4, ReSt3 and their mixed systems of various components were added to LDPE. LDPE and photosensitizers were mixed well by the torque rheometer, and then the mixture was pressed to film samples with thickness of about 0.15mm by. the compression molding machine. The film samples were weathered by the ultraviolet in the home-maded irradiation box.
　　The photodegradable behavior of different photosensitizer systems were studied and the efficient photosensitizer systems were founded out by measuring the mechanical property, the carbonyl index, molecular weight, crystallinity and the surface appearance of the LDPE samples. The method of preparing controllable photodegradable plastics was brought out by analysing the influence factors of the photodegradation of LDPE.The experimental results showed that the photosensitized efficiency of FeSt3 was the best of the single photosensitizer systems. LDPE containing this photosensitizer turned into ageing period after being irradiated 24h and went on to frangibility period after being irradiated 130h. The photosensitized efficiency of FeSt3 and CeSt4 http://www.999magnet.com mixed system was the best of the two-component systems. LDPE containing this photosensitizer system(0.2%FeSt3 and 0.2%CeSt4) turned into ageing period after being irradiated 16h and went on to frangibility period after being irradiated 78h. 0.1%FeSt3+0.1%CeSt4+0.1%ReSt3 possessed the best photosensitized efficiency of the three-component system. LDPE containing this photosensitizer system turned into ageing period after being irradiated 20h and went on to frangibility period after being irradiated 168h. And ReSt3 could accelerate the photodegradation with FeSt3 and CeSt4 when the content was low. But it could restrain the photodegradation as a light stabilizer when the content was above 0.3%. With the lasting illumination, the mechanical property and the molecular weight of LDPE decreased, the carbonyl index and the crystallinity increased, and the surface of the sample appeared flaw and holes. In addition, the photodegradation process of the LDPE could be influenced by the circumstance temperature, the sample thickness, the level of the antioxidant and the content of CaCO3. The controllable photodegradable plastics could be prepared by controlling these factors.