Kinetic evaluation of the size-dependent decomposition performance of solvent-free microcellular polylactic acid foams

Abstract

A thermal gravimetric method is described for evaluating the kinetics of cell size-dependent decomposition and lifetime estimation for microcellular tissue engineering scaffolds made of biodegradable polylactic acid (PLA) foams. PLA foam cell sizes from 550 to 20 μm were fabricated experimentally using a solvent-free solid-state foaming technique under saturation pressures from 1 to 5 MPa. The thermal properties of the PLA foams with respect to the cell sizes were measured using thermal gravimetric analysis in a nitrogen atmosphere and the activation energy and pre-exponential factor were derived to evaluate the decomposition kinetics and estimate lifetime. It was found that small cell sizes can be achieved under high saturation pressures and that the thermal stability of PLA decreases after the fabrication process. The cell size-dependent thermal stability and degradation rate indicate that a PLA foam of larger cell sizes has a shorter degradation time, a few tenths that of the PLA raw material, at a temperature of 37°C. The results suggest that it is feasible to optimize fabrication parameters to obtain appropriate cell sizes and lifetimes that satisfy the application requirements for various organs. This study provides the basis for precise scaffold design and quantitative analysis of PLA foams in tissue engineering applications.