Synthesis, characterization and performance evaluation of a nontoxic functional plasticizer for poly(vinyl chloride) derived from sustainable lactic acid

Abstract

The use of plasticizers is crucial in enhancing the flexibility of engineering plastics. Currently, the primary plasticizers employed in poly(vinyl chloride) materials are nonrenewable phthalates. These exhibit a detrimental impact on the environment and human health owing to their toxic benzene ring structure. Consequently, the development of easily synthesizable, green plasticizers with excellent properties using biobased resources has been a long-standing objective in the field of resin plasticizing. Herein, we synthesized a branched lactic acid ester (BLAE) plasticizer using esterification and acid anhydride end-capping methods. Further, we investigated its application performance and oral toxicity. The abundance of polar ester groups in the oligolactic acid structure enables them to form secondary bonds with polymer chains. This results in a glass transition temperature is 59% less than that of pure poly(vinyl chloride), thereby improving the mechanical properties of the material. The addition of the BLAE plasticizer not only improved the thermal stability of the compound film but also effectively reduced the self-catalytic dehydrochlorination reaction of poly(vinyl chloride). This overcomes the limitations of unmodified poly(vinyl chloride), such as performance deterioration and color variation due to light exposure. Furthermore, the hydrophobicity of the compound film was substantially enhanced, resulting in outstanding antifouling and self-cleaning properties. These findings suggest that lactic acid-based plasticizer exhibits comparable or even superior overall performance when compared to commercially available plasticizers such as dioctyl phthalate and acetyl tributyl citrate. This work not only addresses the gap in the toxicity assessment of lactic acid plasticizers but also demonstrates their nontoxic characteristics in acute oral toxicity tests. This research offers novel insights into the green synthesis and functional development of biobased plasticizers, showcasing considerable potential for the substituting of dioctyl phthalate.