Modification of poly (lactic acid) through the incorporation of gum rosin and gum rosin derivative: Mechanical performance and hydrophobicity

The modification of PLA by melt compound with gum rosin (GR) and pentaerythritol ester of GR (PEGR) was investigated by studying the mechanical and thermal performance, blends morphology, wettability, and water absorption. Standard testing specimens for characterization were made at a variate resin content of 5, 10, and 15 part per hundred resin (phr) and manufactured by injection molding. It was found that GR and PEGR had a lubricating effect in PLA polymeric chains, resulting in a remarkable increase of 790 and 193% in melt flow index with only 5 phr GR and PEGR contents, respectively. A significant change in more than 10° of increasing water contact angle was observed for PLA with 15 phr PEGR. Thermogravimetric analysis reveals that PEGR led to delayed PLA degradation/decomposition process to higher temperature, increasing the onset temperature (T5%) in more than 7°C for PLA with 15 phr PEGR.