Biodegradable Waste Frying Oil-Based Ethoxylated Esters as Highly Efficient Plasticizers for Poly(lactic acid)

Poly(lactic acid) (PLA) is a green but brittle thermoplastic, and its flexibility must be improved to meet the requirements of application. In this work, a series of waste frying oil-derived esters including ethoxylated esters and methyl esters were developed and then used as plasticizers for PLA. The influences of ester groups on the miscibility, mechanical properties, volatility resistance, and biodegradation of plasticized PLA were systematically studied and contrasted with that of PLA blended with dioctyl terephthalate. Glass transition temperature and tensile properties indicated that the plasticizing efficiencies of waste frying oil-based ethoxylated esters were better than that of dioctyl terephthalate or waste frying oil-based methyl ester, and its plasticizing efficiencies were increased with increasing the ethyoxyl units. Biodegradability test results indicated that the biodegradation rate of waste frying oil-based ethoxylated ester was accelerated by ethyoxyl units. In particular, waste frying oil polyacid (2-(2-(2-methoxyethoxy)ethoxy)ethanol) esters (WFOPA-3) owning maximum ethyoxyl units exhibited remarkable plasticization and biodegradable properties than those of other plasticizers. These results suggest that WOFOPA-3 can be used as a highly efficient and biodegradable plasticizer to replace petro-based dioctyl terephthalate.