Glycerol Ester of Rosin

Glycerol Ester of Rosin as Bio-Based Additives to Improve the Properties of Polylactic Acid

de la Rosa-Ramírez, Harrison, et al. Journal of Polymers and the Environment, 2023, 31(12), 5446-5461.

This study examined the influence of two bio-based rosin esters-rosin-derived pentaerythritol (UTP) and glycerol (UTG) esters-as additives for enhancing the processability and thermal stability of polylactic acid (PLA).
Blend Preparation and Analysis
Amorphous PLA was blended with UTP or UTG at 1, 3, and 5 parts per hundred resin (phr) via melt extrusion. The resulting formulations were injection-molded and assessed for thermal degradation, microstructure, melt flow index (MFI), and processing behavior.
Key Results
· Processability Improvements: Adding just 1 phr of either rosin ester doubled the MFI compared to neat PLA, enhancing melt fluidity. This allowed a 20°C reduction in injection temperature and a >30% drop in injection pressure (from 110 Bar for pure PLA to 70 Bar for blends). Packing pressure also decreased by ~38%. These changes reduce energy consumption and equipment wear.
· Thermal and Mechanical Performance: The esters marginally improved PLA's thermal stability (degradation onset ~3°C higher) while maintaining tensile strength, consistent with their role as external lubricants.
· Morphological Insights: At ≤5 phr, both esters dispersed uniformly within PLA, with UTP exhibiting stronger interfacial adhesion. However, 5 phr blends showed minor agglomerations without voids, suggesting optimal loading below this threshold.
UTP and UTG demonstrate significant potential as sustainable lubricants to enhance PLA processing efficiency without compromising mechanical integrity.