Polyurethane segmented polymers are well known for their biocompatibility, strength and resilience, and abrasion-resistant properties. Polyurethane formulations directed at biomaterials applications have traditionally involved making compromises in either mechanical properties or biostability performance. For example, today’s soft, flexible formulations possess excellent stability, but suffer from poor compressive strength and creep resistance. This project was aimed at investigating the incorporation of organoclay fillers in biomedical polyurethanes and the resulting effect on the morphology and properties of the material.
Layered silicate-polymer nanocomposites were chosen due to recent findings that these materials offer improvements in mechanical, thermal and gas barrier properties. The silicate clays are made up of layers. These self organize to form stacks of cations between negatively charged platelets. Upon addition of clay to the polyurethane the polymer diffuses between the layers to separate them. This has been found to provide strengthening while maintaining high elongation to break. Three structures can be obtained: exfoliated (total loss of clay stacking structure), intercalated (distance between clay platelets expanded by polymer but registry retained) and phase separated (no intercalation of polymer between platelets of clay). It has been found that modifying the clays through cation ion exchange has the potential to further improve these properties.