Aerobic and anaerobic biodegradability of polymer films and physico-chemical characterization

Aerobic and anaerobic biodegradation of four different kinds of polymers, polylactic acid, polycaprolactone, a starch/polycaprolactone blend (Mater-bi^®) and poly(butadiene adipate-co-terephthalate) (Eastar bio^®) has been studied in the solid state under aerobic conditions and in the liquid phase under both aerobic and anaerobic conditions.Several standard test methods (ISO 14851, ISO 14853, ASTM G 21-90 and ASTM G 22-76 and NF X 41-514) were used to determine the biodegradability. To determine the efficiency of the biodegradation of polymers, quantitative (mass variations, oxygen uptake, pressure variations, biogas generation and composition, biodegradation percentages) and qualitative (variation of T_g and T_f, variation of molar mass by SEC, characterization by FTIR and NMR spectroscopy) analyses were made and materials were characterized before and after 28 days of degradation.After 28 days, the degradation of materials depends on the material and on the test conditions used. The degradation is better under aerobic conditions, in particular for Mater-bi and polycaprolactone. Nevertheless, we can notice that it is the amorphous part of the polymer which is more attacked by the micro-organisms but, after 28 days, they do not seem to cleave macromolecules inside the material: bacteria attack the surface of the polymer and seem to consume the macromolecules one after another (there is no significant variation in the molar mass and no difference between FTIR and NMR spectra before degradation and after 28 days of degradation).