Friction and wear behavior of ultrahigh molecular weight polyethylene as a function of crystallinity in the presence of the phospholipid dipalmitoyl phosphatidylcholine

Abstract

In this study, the friction and wear behavior of ultrahigh molecular weight polyethylene (UHMWPE) were evaluated as a function of polymer crystallinity in the presence of the phospholipid dipalmitoyl phosphatidylcholine (DPPC) dissolved in ethanol. Samples of UHMWPE were separately heat treated to get high and low crystallinity samples. Degree of crystallinity was evaluated using differential scanning calorimetry. Quantitative friction and wear experiments were conducted using a custom-made microtribometer with commercially available spherical Si(3)N(4) probes in controlled and phospholipid-dissolved lubricants. The higher crystallinity sample exhibited slightly lower friction than the lower crystallinity in the control and decreased significantly when phospholipids were present. The higher crystallinity sample showed a higher wear resistance than the lower crystallinity sample during all reciprocating wear tests. DPPC acting as a lubricant had a marginal effect on the wear resistance of high crystallinity UHMWPE, whereas the low crystallinity sample became more prone to wear. Atomic force microscopy topography images and contact angle measurements of both samples before and after phospholipid exposure indicate that the higher crystallinity sample absorbed a greater density of DPPC. Increasing crystallinity is a way of escalating adsorption of surface active phospholipids onto UHMWPE to make it a more wear-resistant load-bearing material for total joint replacements.

Ultra-High-Molecular-Weight-Polyethylene (UHMWPE) as a Promising Polymer Material for Biomedical Applications: A Concise Review

“…[14][15][16][17]. Many methods such as improving cross-linking [18][19][20][21], or crystallinity percentage [22][23][24][25] through irradiation [26], surface modification through plasma treatment [27,28], or introducing effective textures [29,30], and reinforcements with particles or fibers [31][32][33] have been used for enhancing properties of UHMWPE.…”

Conventional and Highly Crosslinked Polyethylene in Total Knee Arthroplasty—A Design-Independent Wear Investigation

“…As the crosslink density is commonly measured by the means of a swell-ratio [15,22], increased crosslinking might also result in an increasing difficulty for the diffusion molecules of the lubricant to pass the molecular structure of UHMWPE on their way into the bulk of the polymer substance which is linked closer, if there are more crosslinks. In addition, diffusion is expected to also depend on the morphologic structure of the amorphous regions of UHMWPE [32]. It can be hypothesized that this effect could, to a very low amount, result in higher dynamically induced fluid uptake, linked to the morphology of UHMWPE and hence dependent on crosslinks.…”

Friction Measurements on Contact Lenses in a Physiologically Relevant Environment: Effect of Testing Conditions on Friction

“…In addition, lipids also have been shown to act as boundary lubricants, which may provide another explanation for the lower CoF observed in TLF. 47,48 Thus, the higher lipid content of TLF compared to TMS-PS could influence the nature and the quantity of deposition of the contact lenses, generally leading to a lower CoF. A lubricant that closely mimics the composition of tear liquid is required to simulate the effects that the interplay between lipid and protein adsorption (expected in vivo) has on the CoF of SCL materials.…”