Effect of nano-sized zinc citrate on the supercritical carbon dioxide-assisted extrusion foaming behavior of poly(lactic acid)

摘要

Poly(lactic acid) (PLA) foams containing various amounts of an epoxy as a chain extender (CE) and nano-sized zinc citrate as a nucleating agent are prepared by continuous extrusion using supercritical CO2 (sc-CO2) as a physical foaming agent. Processing parameters such as the CE content, sc-CO2 flow rate, and foaming temperature are optimized with regard to the apparent density and expansion ratio of the PLA foams. The nano-sized zinc citrate exhibits a high nucleation activity for the crystallization of the PLA. The addition of 0.5 wt nano-sized zinc citrate significantly increases the compressive strength and modulus of the PLA foams from 0.124 MPa and 3.1 MPa to 0.35 MPa and 19 MPa, respectively. The PLA/0.5 wt nano-sized zinc citrate foam shows a microcellular structure with an average cell diameter of 17.1 mu m.