ASSESSMENT OF BIODEGRADABILITY OF POLYCAPROLACTONE BY MITI TEST METHOD

The biodegradation of polycaprolactone (PCL) and PCL-diol was studied by MITI test method varying the particle size and molecular weight of the test substance and the activated sludge concentration. The biodegr adation began after an induction period. The induction period for the biodegradation of PCL was longer with the larger particle size of the test substance and it was dependent on the molecular weight. The biode gradation rate was faster and consequently the biodegradability after 28 days was higher with (i) smaller particle size of the test substanc e, (ii) lower molecular weight and (iii) higher activated sludge conce ntration. Especially the particle size of the test substance strongly affected the rate of the biodegradation of PCL. These results were dif ferent to those of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHB/P HV), the biodegradation of which was not dependent on the particle siz e and the activated sludge concentration. The cause of the difference between both plastics and the mechanism of the biodegradation are disc ussed. From this study, it was concluded that the particle size of the test substance is one of the factors affecting the biodegradability o f plastics and that it should be taken into account when the biodegrad ability of different kinds of plastics is compared.