Development of thin elastomeric composite membranes for biomedical applications

A breakthrough has been made in blending of two immiscible biocompatible po lymers to form thin transparent interpenetrating network composite membrane s (CM) with exceptional improvement in properties. Two immiscible polymers, namely the biaxially drawn ultra high molecular weight polyethylene (UHMWP E) 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 interpenetra tion of PU in UHMWPE film. The intimate interaction of PU with UHMWPE fiber s was viewed through the transparency of CM. Differential scanning calorime try (DSC) data showed the melting temperature (T-m) 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 str ucture while HCM was a dense material without obvious void inclusions. The ultimate tensile strength and relative Young's modulus of CM are about 62 M Pa and 460 MPa, respectively. They are about four times greater in strength and 150 times greater in modulus compared with those of PU. Heat compactio n 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 a bout 26%, 8% more than that of the porous UHMWPE film while about 70% of HC M, which is a 50% increase achieved through heat compaction. The tensile fr acture toughness is about 93 mJ for CM and 211 mJ for HCM, two and five tim es that for the porous UHMWPE film, respectively. The significant modificat ion on the properties of the heat-compacted composite may raise broad inter est in using the CM to develop membrane-related devices and organ covers in biomedical applications. (C) 1999 Kluwer Academic Publishers.