A novel thermoplastic polyurethane scaffold fabrication method based on injection foaming with water and supercritical carbon dioxide as coblowing agents

Injection foaming is an method for mass producing lightweight, foamed plastic components with excellent dimensional stability while using less material and energy. In this study, a novel injection foaming method employing supercritical C[O.sub.2] (scC[O.sub.2]) and water as coblowing agents was developed to produce thermoplastic polyurethane (TPU) components with a uniform porous structure and no solid skin. Various characterization techniques were employed to investigate the cell morphology, crystallization behavior, and static and dynamic mechanical properties of solid injection molded samples, foamed samples using C[O.sub.2] or water as a single blowing agent, and foamed samples using both C[O.sub.2] and water as coblowing agents. When compared with C[O.sub.2] foamed samples, samples produced by the coblowing method exhibited much more uniform cell morphologies without a noticeable reduction in mechanical properties. Moreover, these TPU samples had almost no skin layer, which permitted the free transport of nutrients and waste throughout the samples. Such a mass-produced, skin-free structure is desirable in tissue engineering. In this study, the biocompatibility of the scaffolds was confirmed and the effect of these blowing agents on the TPU foaming behavior was studied.
INTRODUCTION Synthetic and natural polymers have been used in tissue engineering to prepare temporary scaffolds for transplanted cells for tissue recovery and organ replacement. A wide variety of fabrication methods [...]