Hydrothermal aging behaviors of CMR/PLA biocomposites

Abstract

By melt blending method, the Chinese medicine residue (CMR) and polylactide (PLA) were mixed together using dioctyl phthalate (DOP) as plasticizer. The extrusion and injection-molding processes were used to prepare all the specimens of CMR/PLA composites. Hydrothermal aging was implemented through immersing samples in distilled water at 60, 90°C, and room temperature in different aging cycles. The properties of the CMR/PLA composites were characterized by mechanical property testing and the analyses of thermogravimetric (TG), Fourier-transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). The result showed that the temperature has a significant effect on the hydrothermal aging behavior of the composites. After 60°C hydrothermal aging of 8 days, the bending strength and the tensile strength have reduced to 7.04 and 4.32 MPa, respectively, while the bending strength and the tensile strength became to 1.32 and 2.48 MPa after 90°C hydrothermal aging of 15 h and then the mechanical properties completely lost after 20 h. When hydrothermal aged, the CMR/PLA composites continually undergo degradation, generating bare fibers and broken into small molecular chain structure from macromolecular. Through hydrolysis of ester group, fragmentation of macromolecule chain and the molecular weight decreased, and the interfacial adhesion between the CMR and the PLA is weakened.