Abstract
Bulk oriented films based on ultrahigh molecular weight polyethylene (UHMWPE) with a drawing ratio of 35 were prepared by using a low solvent concentration. Bulk oriented films were filled with fluorinated multi-walled carbon nanotubes (FMWCNTs). The structure of bulk oriented films on UHMWPE, which were manufactured at different stages of orientation, was investigated by scanning electron microscope (SEM) and differential scanning calorimetry (DSC). The addition of FMWCNTs at a concentration of 0.05 wt % in bulk oriented UHMWPE films led to an increase in the tensile strength by 10% (up to 1020 ± 23 MPa) compared to unfilled oriented films. However, the addition of FMWCNTs at a concentration of more than 0.5 wt % led to a decrease in tensile strength due to excessive accumulation of nanotubes and hindering of self-diffusion of UHMWPE macromolecules. The multiple increase in tensile strength, doubling the hardness, the formation of fibrillar structure, and the presence of carbon nanotubes led to a significant increase in tribological properties in bulk oriented films. Bulk oriented UHMWPE/1% FMWCNT films can be operated at a maximum contact pressure that is 18 times higher and exhibit a specific wear rate more than an order of magnitude and less than the traditional UHMWPE of isotropic structure. Bulk oriented UHMWPE/1% FMWCNT films have an extremely low dry coefficient of friction (COF) of 0.075 at a contact pressure of 31 MPa. The developed bulk oriented films can be used for manufacturing frictional surfaces for sliding bearings, or for acetabular cups for knee and hip endoprostheses.
Highlights
Ultrahigh molecular weight polyethylene (UHMWPE) is a unique material that is widely used in a variety of fields: medicine, ballistic protections, sports, and industrial tribology
Nanotubes accumulated on the surface of UHMWPE particles prevent the penetration of the solvent into the inside of the particle, and non-regular macrovoids in xerogels with a fluorinated multi-walled carbon nanotubes (FMWCNTs) content of 0.5 and 1 wt % form as a result
The accumulation of FMWCNTs on the surface of UHMWPE particles is associated with the method of their introduction into the UHMWPE
Summary
Ultrahigh molecular weight polyethylene (UHMWPE) is a unique material that is widely used in a variety of fields: medicine (acetabular cups for knee and hip endoprostheses [1], bone scaffolds [2], medical grade UHMWPE fiber, etc.), ballistic protections (protective garment, armor vests, helmets), sports, and industrial tribology. The most significant properties of UHMWPE are high biocompatibility, unique mechanical properties of highly oriented fibers and films, and antifriction, which includes the ability to work under dry sliding conditions, as it exhibits a low friction coefficient and a high wear resistance. Polyethylene chains have a covalent C–C bond with a very high energy of 335 kJ/mol. Extended polyethylene chains are potentially very stiff and strong. There is a special main interest in obtaining materials based on UHMWPE with an oriented supramolecular structure. The ultimate strength and elastic modulus of composites based on UHMWPE with isotropic structure do not exceed
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