Synthesis, analysis, and application of lactide-based polyester as coating with improved mechanical and rheological behavior

Abstract

Lactide-based polyester resin was synthesized from diethylene glycol and phthalic anhydride with 20, 30, and 40% lactide compositions. The lactide was prepared from lactic acid and the polyester resin was functionalized with carbon–carbon crosslinking by polycondensation reaction. The purpose of this investigation was to enhance the properties such as thermal, mechanical, and rheological behavior of polyester resin synthesized using lactide. The resin was also characterized for acid values, hydroxyl values, and bio-based content. The bio-based content varied from 76 to 92% for variable composition of lactide in the resin. Acid value confirmed the formation of polyester resin and the hydroxyl value indicated the occurrence of crosslinking. The flow viscosity is an important characteristic of resins that are intended to be used as matrix in composite applications, and it was measured at different stress levels at varied temperatures. The performance of a mild steel specimen coated with the synthesized polyester was evaluated for mechanical properties such as tensile strength, impact resistance, flexibility, scratch resistance, and adhesion test. It revealed that lactide-based polyester resin had better mechanical, rheological, and anticorrosive properties than simple polyester resins.