Bio‐tribological characterisation of ultra‐high molecular weight polyethylene against different metal counterparts

Abstract

Excessive wear is a key issue affecting the performance of ultra‐high molecular weight polyethylene (UHMWPE)‐based artificial prosthesis. This work is focussed on the bio‐tribology behaviours of UHMWPE when mating with different metal counterparts (iron‐based 316L, Co‐based Stellite‐S21 and Stellite‐S22). According to the ASTM F732 standard, two million cycles comparative wear tests were carried out under bovine serum lubrication. When coupled with S21, S22, and 316L metal counterparts, the obtained average wear factors of UHMWPE were 1.333 ± 0.192, 1.360 ± 0.160, and 1.190 ± 0.177 × 10−6 mm3/N · m, respectively. Initial surface roughness of the metal counterpart has shown an important role in controlling the volume of UHMWPE wear, especially the first one million cycles. Compared with 316L, CoCrMo‐based counterparts possessed relative higher hardness and exhibited less rise in surface roughness caused by wear. For UHMWPE‐on‐metal bearings, random scratch, surface pit, and wear debris attachment were commonly seen, which suggested the coexistence of abrasion, third‐body abrasion, and adhesion‐based wear. In contrast, the metal counterpart was slightly scratched with no polymer transfer film formation. The work conducted in the present study gives useful knowledge regarding the UHMWPE‐on‐metal bearing design. With an intention to minimise wear, surface roughness of metal counterpart should be carefully controlled.

Tribological and morphological properties of bentonite nano‐clay/CaCO3 reinforced high‐density polyethylene nanocomposites

“…The amount of wear debris noted was less as compared to samples such as BC‐5/10, BC‐5/15, and BC‐10/15. However, the wear debris collected was all identical in shape indicating a repetition of the same kind of flakes and wear process 32 . Moreover, a lower weight percent of oxygen and lower Ca/Si (1.22) indicates lower oxidation and higher compressive force‐bearing ability 20 …”

“…Similar results can also be found in research work conducted recently. 31,32,35 We speculate that this composite abrasive wear is the result of higher incompatibility of CaCO 3 with HDPE. The imperfectly bonded CaCO 3 particles were pulled out by the pin, resulting in excessive wear.…”

“…As a result of the identical wear process identical flakes were generated and then broken due to identical surface roughness as appearing in the SEM image included (Figure 11A). 31,32 The existence of Mg, Al, Ti, and Si, can be viewed as part of bentonite nano clay. The presence of C and Ca can be seen at both higher and low energy peaks the as a residue of CaCO 3 (Figure 10B).…”

“…However, the wear debris collected was all identical in shape indicating a repetition of the same kind of flakes and wear process. 32 Moreover, a lower weight percent of oxygen and lower Ca/Si (1.22) indicates lower oxidation and higher compressive forcebearing ability. 20 On the other hand, particulate wear debris of the samples BC-0/10 and BC-0/15 can be seen in Figure 11.…”

“…The flakes appeared to be identical due to an identical wear process resulting under the same type of dry sliding wear process. As a result of the identical wear process identical flakes were generated and then broken due to identical surface roughness as appearing in the SEM image included (Figure11A) 31,32. The existence of Mg, Al, Ti, and Si, can be viewed as part…”