Method of producing biodegradable reference material and its biodegradability based on international standard evaluation method (ISO 14855-2)

Returnable cups made of poly(lactic acid) (PLA) are employed as an example of products made of biodegradable plastics. Two kinds of PLA samples plates and powders with different shapes were prepared from PLA cups. The plates were cut from a cup using nippers. Powders were prepared using a rotation mechanical mixer for 45 min. PLA powders were separated by sieves with 60 meshes (250 mu m) into a size ranging from 0 to 250 mu m. An average diameter of powders separated by a sieve is 169 mu m. Biodegradation tests of PLA plates, PLA powders and cellulose powders in controlled compost at 58 degrees C were performed using a Microbial Oxidative Degradation Analyzer (MODA) instrument according to ISO 14855-2. PLA powders showed almost the same biodegradation curve as that of cellulose powders. PLA plates biodegraded at a slower rate than PLA powders.