Microstructural evaluation of an elastomeric composite membrane from two immiscible polymers (UHMWPE and polyurethane) for soft tissue replacement

Abstract

The incorporation of ultrahigh molecular weight polyethylene (UHMWPE) fibers with polyurethane (PU) elastomers is of practical importance in improving the physical properties of the individual polymers for biomedical applications. In this study, the microstructure of the polyurethane composite made of a porous biaxially drawn UHMWPE fibrous membrane and a polyether PU in a solution casting process, was evaluated by means of scanning electron microscopy (SEM), polarised light transmission, and visible light transmission. This composite membrane (CM) has shown remarkable enhanced mechanical and thermal properties over that of UHMWPE and PU, and can be made into thin membranes of ≈30 μm in thickness. The SEM morphological observations showed that PU infiltrated into the fibrous UHMWPE films, forming an inter-woven connection between PU and UHMWPE fibers. Polarised light transmission morphological observations over a temperature range of 25–150°C, revealed an intimate interaction between PU and UHMWPE fibers, which preserved well UHMWPE fiber formation and orientation even at a temperature higher than the melting point of UHMWPE fibers. Visible transmission light data provided further evidence for both infiltration and interaction of PU in the fibrous UHMWPE membrane. The increase in light transmission after the heat compaction process indicated that microvoids could be effectively removed, and it explained further the increase in mechanical properties as reported earlier. A model was proposed to explain the interaction of the two immiscible polymers to form an elastomeric CM.