Near-Surface Reconfiguration of Biopolymer Blends by Mechanical Embossment: Creation of Friction-Reduced Foils

Biopolymer blends of polylactic acid (PLA) and polybutylene adipate-co-terephthalate (PBAT) are extruded into flexible monolayer films. These blends are excellent candidates for the realization of environmentally friendly packaging applications. A necessary pre-requisite for that are appropriate tribological properties under mechanical contact. Reasonable wear resistance allows good protection of packed goods, and low friction forces reduce difficulties in stacking. In this research, mechanical embossment under high loads at room temperature was used for the modification of polymer surfaces to exhibit a significant friction reduction under dry conditions. The results particularly show a systematic decrease in the coefficient of friction for biopolymer blends containing 30 wt% and 40 wt% PBAT. FTIR was used to analyze the change in surface composition after mechanical embossing. A sophisticated FTIR calibration method revealed that the blend with 30 wt% PBAT shows a modified distribution of PBAT and PLA at the surface due to mechanical embossment. This leads to a controlled and long-lasting modification of the surface properties without a substantial change in the chemical composition of the polymer in bulk. Without the use of additional coatings, biodegradable packaging foils with improved characteristics are accessible.