Self-Reinforced Composite Polyethylene (SRC-PE): A Novel Material for Orthopedic Applications

An approach to fabricating high fiber volume fraction UHMWPE composites where the reinforcing phase and the matrix phase are of identical composition, and the matrix derives directly from the fiber is characterized. The processing method utilizes a hot compaction technique. During hot compaction, UHMWPE fibers are heated in a constrained mold under pressure to allow diffusion bonding of adjacent fibers. Thus, a composite results where the matrix comes from the fibers; however, the fibers themselves retain much of their original mechanical properties. This material is referred to as self-reinforced composite polyethylene (SCR-PE). Preliminary processing methods are described, and the morphology of the unidirectional SRC-PE composites are examined along with their thermal and mechanical properties. SEM micrographs of etched cross-sections of the composites exhibit fully consolidated specimens in which the fibers are still easily distinguishable and areas of fiber-fiber bonding are revealed. DSC plots show that the composites have very similar thermal properties to the original fibers. The composites also exhibit substantial unidirectional strength in the fiber direction with an approximately ten fold increase in modulus (9.99 ± 1.06 GPa) and strength (506 ± 139 MPa) in tension as compared to reference UHMWPE. However, wide variations in mechanical properties with the type of loading (tension, compression, or bending) were observed. For instance, when compression tests were performed in the fiber direction, the unidirectional specimens exhibited low modulus (1.74 ± 0.46 GPa) and strength (33.8 ± 4.8 MPa), relative to tension and bending, which may be beneficial in orthopedic load bearing applications by allowing for more deformation during contact resulting in a lowering of contact stresses. However, the high tensile and bending strengths in the fiber direction can be advantageous in providing resistance to microfracture events associated with debris generation.