Thermomechanical Properties of Polylactide/Oligomerized Castor Oil Blends

Polylactide, a commercially available bio-based, compostable polymer, is a renewable, environmentally friendly alternative to petroleum based polymers. A drawback of PLA is its brittleness, but this can be improved through compatibilized blending. PLA can be toughened by the incorporation of vegetable oils, but due to the large differences in viscosity and molecular weight, they are not very compatible. Oligomerized vegetable oils can potentially be more compatible. Blends of PLA with oligomerized castor oil (oligoCO) were produced via melt mixing using a Haake batch mixer. The oligoCO was synthesized via free radical polymerization in a supercritical carbon dioxide (scCO₂) medium to varying molecular weights. The effectiveness of the oligoCO as a toughening agent for PLA is investigated. The thermal properties of the blends were determined using thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). Scanning electron microscopy was used to analyze the morphology of the blends. The mechanical properties of blended samples are determined and assessed by tensile and impact testing as well as dynamic mechanical analysis.