Foaming and thermal characteristics of bio-based polylactic acid–thermoplastic polyurethane blends

Abstract

This paper reports a research work on characterization of foamed biocompatible polylactic acid–thermoplastic polyurethane blends in terms of microstructural, thermal, and physical properties. The brittleness of the polylactic acid is compensated via blending with an elastoplastic phase of thermoplastic polyurethane. A range of low bulk density foam with a high cell density was produced in a solid state foaming process. Addition of thermoplastic polyurethane phase acted against the cell growth and thus foam expansion, apparently due to its inherent lower storage modulus, which weakens the polymer matrix and leads to gas escape phenomenon. Evaluation of thermal properties showed a tangible effect of blending and foaming process on crystallization of the specimens, which confirmed that the sensitivity of polylactic acid’s crystallinity to CO2 gas saturation was reduced as a result of thermoplastic polyurethane addition. Measurement of cell diameters and cell densities of the foamed samples demonstrated formation of the fine closed cells structure as a result of suitable foaming parameters that were able to deal with stiffness and strength of the polymeric matrix.