Effect of Carboxylated Carbon Nanotubes on the Structure and Properties of PLA/PVDF/ADR Blends

Poly(lactide) (PLA)/polyvinylidene difluoride (PVDF)/chain extender containing epoxy functional groups (ADR)/carboxylate multiwall carbon nanotubes (MWCNTs-COOH) composites were prepared by combining solution blending and melt blending techniques. The dispersion state of MWCNTs-COOH in the composites was controlled by the in situ reaction between carboxyl groups in MWCNTs-COOH and epoxy groups in ADR, and the effects of MWCNTs-COOH on the structure and properties of the blends were systematically studied. The torque data demonstrated that the introduction of MWCNTs-COOH could enhance the melt strength of the blends. DSC data showed that the MWCNTs-COOH could act as a nucleating agent to improve the crystallization ability of PLA. DMA data and rheological behavior revealed that MWCNTs-COOH could reinforce the interaction between PLA and PVDF interface. The mechanical data indicated that the introduction of the MWCNTs-COOH enhanced the tensile strength of the composites, but significantly reduced the elongation at break. With the increase of MWCNTs-COOH content, the heat deflection temperature (HDT) of the material was obviously increased, and the dielectric constant of the composites showed an upward trend.