Development of thin elastomeric composite membranes for biomedical applications.

A breakthrough has been made in blending of two immiscible biocompatible polymers to form thin transparent interpenetrating network composite membranes (CM) with exceptional improvement in properties. Two immiscible polymers, namely the biaxially drawn ultra high molecular weight polyethylene (UHMWPE) film and polyether polyurethane (PU) were used. The fabrication included solution casting and heat compaction. During the fabrication, the CM still preserved the orientation of UHMWPE fibers but introduced the interpenetration of PU in UHMWPE film. The intimate interaction of PU with UHMWPE fibers was viewed through the transparency of CM. Differential scanning calorimetry (DSC) data showed the melting temperature (Tm) of UHMWPE increased by about 10 degrees C in CM and about 5 degrees C in heat-compacted membranes (HCM). Morphological observations indicated that CM presented a layered structure while HCM was a dense material without obvious void inclusions. The ultimate tensile strength and relative Young's modulus of CM are about 62 MPa and 460 MPa, respectively. They are about four times greater in strength and 150 times greater in modulus compared with those of PU. Heat compaction resulted in a membrane with nearly five times the tensile strength and 50 times the Young's modulus of PU. The engineered ultimate strain of CM is about 26%, 8% more than that of the porous UHMWPE film while about 70% of HCM, which is a 50% increase achieved through heat compaction. The tensile fracture toughness is about 93 mJ for CM and 211 mJ for HCM, two and five times that for the porous UHMWPE film, respectively. The significant modification on the properties of the heat-compacted composite may raise broad interest in using the CM to develop membrane-related devices and organ covers in biomedical applications. Copyright 1999 Kluwer Academic Publishers