Enhancement of tribological properties
and characteristic of polymer matrix
composite (UHMWPE reinforced with
short fibres of polyester) for Total Disc
Replacement (TDR)
Authors: Obaid M.N. , Radhi S.H. 
Published: January 2021

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.