Poly (L-lactic acid) (PLA)/starch blends with starch content of 30 wt% were
made by injection molding. The blends were exposed to the field in differe
nt three terms (from May, September, and December) and the effects of field
temperature and number of microorganisms on the degradation rate were inve
stigated. The tensile strength of the blend decreased to zero in a month wi
thout any influence of the exposure terms. On the other hand, the degradati
on of PLA in the blend was faster at higher temperatures and at larger numb
er of microorganisms. The PLA/starch blends coated with pure PLA and poly (
epsilon -caprolactone) (PCL) were also made by a conventional coating metho
d to control the degradation rate. The degradations of the coated blends we
re depressed for 2 similar to 4 weeks; after that they degraded immediately
. For the 2 similar to 4 week period, multiplication of microorganisms in t
he blends were suppressed by the coating.