Impact resistance and fractography in ultra high molecular weight polyethylenes

• Published in: Journal of the mechanical behavior of biomedical materials Vol. 30; pp. 111 - 122
• Main Authors: Puértolas, J.A., Pascual, F.J., Martínez-Morlanes, M.J.
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier Ltd 01.02.2014
• Subjects: Biocompatible Materials; Ductile brittle transition; Fractography; Gamma Rays; Impact energy; Instrumented impact test; Izod; Materials Testing; Mechanical Phenomena; Melting; Polyethylenes; Polymers; Remelting; Resins; Surface Properties; Surgical implants; Toughness; UHMWPE; Vitamin E; Impact energy; Toughness; UHMWPE; Izod; Fractography; Instrumented impact test
• ISSN: 1751-6161; 1878-0180
• DOI: 10.1016/j.jmbbm.2013.10.028

Highly crosslinked ultra high molecular weight polyethylenes (UHMWPE) stabilized by a remelting process or by the addition of an antioxidant are highly wear resistant and chemically stable. However, these polyethylenes currently used in total joint replacements suffer a loss of mechanical properties, especially in terms of fracture toughness. In this study we analyze the impact behavior of different polyethylenes using an instrumented double notch Izod test. The materials studied are three resins: GUR1050, GUR1020 with 0.1wt% of vitamin E, and MG003 with 0.1wt% of vitamin E. These resins were gamma irradiated at 90kGy, and pre and post-irradiation remelting processes were applied to GUR1050 for two different time periods. Microstructural data were determined by means of differential scanning calorimetry and transmission electron microscopy. Fractography carried out on the impact fracture surfaces and images obtained by scanning electron microscopy after etching indicated the existence of a fringe structure formed by consecutive ductile–brittle and brittle–ductile transitions, which is related to the appearance of discontinuities in the load–deflection curves. A correlation has been made of the macroscopic impact strength results and the molecular chain and microstructural characteristics of these aforementioned materials, with a view to designing future resins with improved impact resistance. The use of UHMWPE resins with low molecular weight or the application of a remelting treatment could contribute to obtain a better impact strength behavior. [Display omitted] •Impact strength of polyethylenes was obtained by instrumented double notch Izod test.•Raw UHMWPE resins, gamma irradiated and remelted samples were dealt with.•Discontinuities in the load–deflection curves have been related to SEM fractography.•A correlation between microstructural parameters and energy has been established.