1. Durability of a starch-based biodegradable polymer 指導教授 : 王振乾 學生 : 陳雅貞 日期： 2010.09.20

2. Abstract The photo-oxidation and the photo-stabilization of a commercial biodegradable polymer have been investigated in order to establish the possibility of using this polymer as raw material for films for agriculture. The bioplastic film must possess specific mechanical and optical performance similar to those of the traditional films for agriculture, like polyethylene and poly[ethylene-co- (vinyl acetate)].

3. Materials The biodegradable polymer, MB non-genetically modified maize starch synthetic biodegradable polyester

4. Materials UV stabilizers benzotriazole benzophenone triazine HAS Tinuvin 327 Tinuvin 234 Tinuvin 1577 Lowilite 22 Sanduvor PR-31

5. Before processing The biodegradable polymer was carefully dried for 24 h in a ventilated oven at 60 ℃ followed by 24 h at 60 ℃ in a vacuum oven.

6. Processing Stabilized polymer: The thermal profile was 90-110-135-180 ℃ and the screw speed was set at 50 rpm. Unstabilized polymer: two different thermal profiles: 90-110-135-150 ℃ and 95-140-165-210 ℃, with the same screw speed.  The estimated residence time is about 100-150 s.  The final thickness of the films was in the range 250- 280 μ m.

7. Photo-oxidation Photo-oxidation was carried out using 8 UVB fluorescent lamps up to approximately 200 h. The adopted cycle consists of 8 h of ultraviolet irradiation at T =50 ℃ and 4 h without irradiation at T =35 ℃.

8. Conclusions The photo-oxidation seems to lead to some cross-linking and chain scission of the synthetic polyester. The better performance of benzophenone has been interpreted in terms of larger absorbance of UV radiations in the UV wavelength region where the biodegradable polymer absorbs.