Complex study of the physical properties of a poly(lactic acid)/poly(3-hydroxybutyrate) blend and its carbon black composite during various outdoor and laboratory ageing conditions

Abstract

Ageing of foils made from poly(lactic acid)/poly(3-hydroxybutyrate) PLA/PHB blends, unfilled or filled with 1 wt% of carbon black is presented. The foils were either buried in the soil or exposed to the sunlight for 4 months to imitate the behavior of the material when applied as mulching foils. In addition, UV-vis irradiation and hydrolysis over water vapor were studied under laboratory conditions. Finally, the effect of the ageing under the mentioned conditions on mineralization of the foils at room temperature was investigated in order to simulate plowing the material after its application. The degradation was studied by gel permeation chromatography and structural changes were investigated using differential scanning calorimetry. The changes in mechanical properties were investigated by dynamic-mechanical thermal analysis and a tensile test. Addition of carbon black to PLA/PHB resulted in improved photochemical stabilization of the foils, preventing supplemental crystallization during ageing and provided longer retention of the mechanical properties during ageing.