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Enhancement of tribological properties and characteristic of polymer matrix composite (UHMWPE reinforced with short fibres of polyester) for Total Disc Replacement (TDR)

Obaid M. N., Radhi S. H.

Journal of Achievements in Materials and Manufacturing Engineering

2020

Vol. 102, nr 2

55--65

Purpose: The number of people suffering from Degenerative Disc Disease (DDD) is increasing. The disease causes heavy pain and restrict a number of day-to-day life activities. In extreme cases, the degraded disc is removed under total disc replacement which is usually made up of Ultra-High Molecular Weight Polyethylene (UHMWPE). The material has astounding biocompatible characteristics mechanical properties and wear resistance. However, these characteristics are insufficient in arthroplasty application. Therefore, research investigations are ongoing to improve tribological properties through reinforcement that may result in a composite material of UHMWPE. Thus the current study is aimed at reinforcing UHMWPE with short fibres of polyesters to enhance the tribological properties and surface characteristic so as to improve wear resistance and nourish the fibroblast cells on synthetic disc. Design/methodology/approach: The researcher prepared UHMWPE composite material, reinforced with different weight fractions of short polyester fibres (2, 4, 6, 8 and 10% following hot press method. Further pin-on-disc device was used to study the tribological properties (coefficient of friction and volume of wear). The study tested surface roughness and surface characteristics by atomic force microscopy (AFM) device, hardness by shore D device, contact angle to study the effect of polyester short fibres on wettability of UHMWPE surface and tested the thermal properties and crystalline degree using Differential Scanning Calorimetry measurement (DSC) device. Findings: The results infer that the wear resistance got improved when using 2% w.t polyester though it got decreased initially. However, the value was still more than neat UHMWPE. There was a decrease observed in coefficient of friction, but after 4 w.t% polyester, the coefficient of friction got increased due to increasing percentage of fibres which make it harder and stiff compared to UHMWPE. There was a decline observed in surface roughness due to alignment of the fibres with smooth surface. The contact angle got increased in a moderate range while the roughness enhanced the growth of fibroblast cell. The hardness of composite material got increased, because the fibres turned stiffer and harder than the matrix. DSC results infer the improvements in thermal stability due to high thermal properties of polyester fibres compared to UHMWPE. The degree of crystallinity got increased which in turn enhanced wear resistance, especially at 6 w.t % polyester fibres. There was a mild increase observed in density since the density of polyester is higher than polymer. Research limitations/implications: The major challenge was the dispersion of fibres. Uniform distribution of fibres within the matrix (UHMWPE) was achieved through two steps of mixing processes such as mechanical mixture and twin extruder. In future studies, fatigue tests must be conducted to study the behaviour of prepared composite materials under fatigue cycle. Practical implications: A significant objective is how to connect among different properties to obtain good improvement in tribological and surface properties so as to enhance wear resistance and growth of fibrolase cells. Originality/value: In this study, polymeric short fibres were used as reinforcement with polymeric matrix to enhance the wettability of fibres with matrix. In this way, the bonding among them got increased which supports the tribological, surface, and crystalline behaviour.

Effect of selective laser melting technology on the tribological properties of the prototype of intervertebral disc endoprothesis

Mróz A., Wiśniewski T., Skalski K.

Inżynieria Powierzchni

2016

nr 2

24--30

Podjęto pracę nad zaprojektowaniem nowej konstrukcji endoprotezy krążka międzykręgowego odcinka lędźwiowego kręgosłupa, której komponenty metalowe wykonano ze stopu CoCrMo przy zastosowaniu technologii selektywnego topienia laserowego (SLM). Do badań porównawczych zostały wytworzone endoprotezy metodą obróbki skrawaniem z zastosowaniem obrabiarek sterowanych numerycznie (CNC). Wykonane prototypy poddano testom tribologicznym z wykorzystaniem symulatora kręgosłupa SBT-03.1. Celem pracy było określenie potencjału technologii SLM w procesie wytwarzania elementów endoprotez krążka międzykręgowego oraz określenie wpływu tej technologii na opory tarcia oraz ilość generowanych produktów zużycia.

Work on the design of a new construction of intervertebral disc prosthesis of the lumbar spine has been started; the metal components of this endoprosthesis have been manufactured of CoCrMo alloy using the technology of selective laser melting (SLM). For comparative studies, the endoprostheses have been manufactured by machining with the use of numerically controlled machine tools (CNC). The fabricated prototypes have undergone the tribological tests using the SBT-03.1 spine simulator. The aim of the study was to determine the potential of SLM technology in the fabrication process of the elements of intervertebral disc endoprosthesis and to determine the impact of this technology on friction resistance and the amount of generated wear debris.