Biodegradation Behavior of Three - Layer Sheets Based on Gelatin and Poly (lactic acid) Buried under Indoor Soil Conditions

J. F. MARTUCCI; R. A. RUSECKAITE

POLYMER DEGRADATION AND STABILITY

ELSEVIER SCI LTD

Lugar: Amsterdam; Año: 2015

0141-3910

The biodegradation of three-layer sheets composed by glycerol ? plasticized bovine gelatin film as inner layer coated by two outer layers of poly(lactic acid) (PLA) was examined under indoor soil burial conditions during 120 days, using the natural soil microflora as degrading medium. The residual degraded samples of the multilayer and individual components were taken regularly from the soil to determine the water uptake, weight loss, variations in thermal properties and morphologies. Multilayer sheet exhibited reduced water uptake compared to gelatin counterpart associated with the protecting the middle gelatin layer against water by the hydrophobic PLA layer at both sides. Gelatin layer almost disappeared over 25 days while pure PLA layer suffered marginal weight loss upon 120 days in soil. Contrary, multilayer sheet was degraded at much higher extent, leading to an overall mass reduction of approximately 20 % at the end of the experiment. The presence of gelatin in the multilayer seems to enhance the water availability around the three-layer sheet soil micro-environment, inducing gelatin hydrolysis (chemical and enzymatic) and favoring the abiotic hydrolysis of PLA which in turn possibly stimulates the action of more active soil microorganisms against PLA. This was experimentally confirmed by the presence of filamentous (actinomycete and fungi) microbes on the surface of the multilayer. The glass transition temperature of the degraded multilayer samples slightly increased while the degree of crystallinity augmented significantly up to 78 % at day 120th, evidencing the crystallization of the amorphous PLA induced by bio/degradation in soil.