Biodegradable plastics, LDPE, L-LDPE, HDPE, PP, added starch and other additives (imperfect degradation type) were pretreated in some kind of soil which was examined as clear as possible and tested the effect of microorganism to the polymer degradation. The results gave the fact that the polymer degradation enlarged with increasing abundance of microorganism.
On the base of this consequence, after the lay-in-soil test used compost which has more abundance of microorganism than other soil was carried out for eight months, mainly observing the interface of polymer and starch by using SEM, we confirmed the presense of several passing void (about 200μmφ) regarded as lost of polymer, and also confirmed tat the number of void and the degree of polymer damage were inversely proportional to the crystallinity of polymer. And in the vicinity of the void edge, the degradation was enlarged as closer to void, so it was assumed that the reason of polymer lost was the progress of polymer degradation and decay occuring consumption of starch at the same time, and never eaten by insects.
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