淀粉/聚乙烯薄膜中聚乙烯的降解特性研究

Degradation Behavior of Polyethylene in the Starch-Polyethylene Film

对含 30 %淀粉的淀粉 /聚乙烯薄膜进行环境降解、环境生物降解和环境曝晒试验 ,发现淀粉 /聚乙烯薄膜在环境中曝晒降解的速度远远大于生物降解的速度。在应用环境中经过 4周的降解 ,薄膜中聚乙烯的分子量损失达 6 2 .5 % ;经 5周的曝晒降解后 ,薄膜中聚乙烯的分子量损失达 87.5 % ;薄膜降解后 ,平板流变粘度降低 2个数量级以上。而在生物降解试验中 ,同样的试样经 4周降解后 ,尽管样品失重达 2 8%以上 ,但薄膜中的聚乙烯分子量损失不到 10 % ,平板流变粘度无明显变化。说明 ,淀粉对聚乙烯的光降解具有较强的促进作用。电镜结果发现生物降解 1周 ,薄膜表面微突消失 ;2周 ,薄膜出现明显孔洞 ;3周 ,薄膜布满 5 mm～ 10 mm大小的孔洞。但未能肯定这种孔洞是由微生物攻击薄膜中的淀粉引起。

The degradation behavior of polyethylene in the starch polyethylene films was studied.The samples containing 30% starch were evaluated for their degradability by exposing them to the normal applied environment,biologic environment and sunlight.The polyethylene in the experimental samples was degraded much more rapid under sunlight than that in the biologic environment.The polyethylene molecule weight in the sample of which degraded in the normal applied environment after 4 weeks reduced 62 5% compared with the original sample.Exposed under the sunlight after 5 weeks,its polyethylene molecular weight reduced 87 5% compared with the original sample and its viscosity reduced to the centi grades compared with the original samples.Although the sample weight reduced up to 28% in biologic environment after 4 weeks,however,its polyethylene molecule weight reduced less than 10% compared with the original sample and its viscosity had little change.It is obvious that starch can accelerate the photochemistry degradation of the polyethylene.The SEM showed that the surface of the sample was flatting after a week in the biologic environment.Some visualize holes were found after 2 weeks and the holes sized 5 mm to 10 mm were found after 3 weeks degraded in the biologic environment but that they are caused by microorganism or not is not confirmed until now.