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Abstract

Ultrahigh molecular weight polyethylene (UHMWPE) are widely used as a biomaterial for manufacturing of prostheses, implants and other biomedical components with complex geometry and shapes. Continuous loading of these components subject to heavy stress and deformation resistance should have enhanced mechanical and chemical properties. This paper aims to improve the mechanical and thermal aspects of the conventional UHMWPE by supplementing reduced Graphene oxide (rGO) in varying weight percentages to develop polymer bio nanocomposite samples. The effect of green synthesized GO nanoparticles in the UHMWPE polymer was investigated for biomedical application. The rGO was distributed in a UHMWPE matrix using a unique and optimized technique to create high-performance nanocomposites. The proposed UHMWPE filled with different loading (0, 0.5, 1.0,1.5, 2.0, and 3.0 wt.%) of rGO was produced by Ultrasonication in an acetone medium. The findings suggest that evenly distributed rGO layers were present throughout the polymer matrix. This, in turn, indicates a good connection between the fillers and matrix by Scanning electron microscopy (SEM) and Energy Dispersive X-Ray Analysis (EDAX), resulting in better composite capabilities. The layers of rGO-aided lamellar arrangements and microfibers between the crystals were observed in the results. The Microhardness of the bio nanocomposite (1 Wt.% rGO/UHMWPE) with 1wt.% rGO in the UHMWPE matrix increased by 2.8% compared to an unfilled polymer. At the same rGO concentration, the bio nanocomposite had a crystallization degree of 46.96%. To achieve optimal performance, rGO content of 1wt.% was added to the sample, which is ideal in many situations where good mechanical and thermal qualities are required during operation. The outcomes reveal that the rGO supplement primarily boosts the thermo-mechanical performances of the modified bio-nano composites for orthopedic products.

Graphical Abstract

Keywords

UHMWPE Graphene oxide Implants Mechanical Bio-nanocomposites Microhardness SEM EDAX

Introduction

Biomaterial research has been one of the fastest growing and most active fields in recent years due to its usefulness and societal interest. Polymeric biomaterial has emerged at the tip of developing new tailored-made bio-nano composites. Polymer matrix composites have become an alternative to metal/metal matrix composites due to their high biocompatibility, mechanically strong chemically stabilized structure adaptability, and durability concerns.^1,2 It can be used for drug delivery, tissue engineering, cancer therapy, biosensors, artificial joints, and many other things.^3–5 The hybrid and supramolecular approaches are recently used in polymeric biomaterial research, resulting in the significant contemporary development of polymer science and engineering. Polymer morphologies and structural features can be fine-tuned to fulfill various medical application needs. The natural and inorganic nanoparticles application for polymeric biomaterials may be mixed to obtain new and improved properties that can enhance the performance and efficiency of the developed materials. Bioinspired and adaptive polymer systems were also created to improve the required material design. It has been remarked that numerous studies have been published on the improvement of the bio nanocomposites properties needed for mechanical and tribological applications. For biomedical applications, such as Bearings, Pins, Coatings, Wires, and Artificial joints, polymer matrix composite materials have emerged as a viable alternative to metals. Also, their alloys consist of enhanced benefits of low density, simplicity of manufacturing, significant shock absorption capacity, wear resistance and high vibration self-lubrication.^6–8 Many studies have been conducted to enhance the polymer characteristics of UHMWPE since its debut in the 1960s as a preferred material for implant-bearing components. Because of its clinical performance over the past few decades, UHMWPE is commonly used for artificial joints.^9,10 Firdous et al.¹¹ studied the Polarimetric characterization of UHMWPE for bone substitute biomaterials. The findings show that UHMWPE is a robust and compact compatible material. This research aims to establish an optical evaluation approach for bone graft substitute biomaterials within the medical business.

In contrast, UHMWPE seems to have a weak load-bearing capability, a low Young's modulus, and an anti-fatigue capability.¹² As a result, attempts have been devoted to enhancing UHMWPE tribological properties. In contrast, UHMWPE's thermo-mechanical properties are little affected by Vitamin E incorporation.^13,14 Another common technique is the addition of fillers material to recover mechanical, tribological, and biocompatibility properties.^15–17 Inorganic fillers such as kaolin,¹⁸ zirconium,^9,19,20 and nano zinc oxide²¹ were utilized for this purpose.

In order to improve the processability of UHMWPE, Wu et al.²² used differential scanning calorimetry to study the crystallization and melting behaviour of UHMWPE and its composites filled with CaCO₃, acrylic acid-modified CaCO₃(AA-CaCO₃), and PE wax coated CaCO₃(PEW@ CaCO₃). Adding CaCO₃, AA- CaCO₃, and PEW@ CaCO₃ raises the crystallization temperatures (T_cs) and crystallinity of UHMWPE owing to the heterogeneous nucleation of fillers. The PEW@ CaCO₃ demonstrates better improvement in processability of UHMWPE than AA-CaCO₃. This is because the PEW macromolecular chain of PEW@ CaCO₃ is more compatible with the UHMWPE than the AA-CaCO₃. Khasraghi and Rezaei²³ explored the effect of MWCNTs (1wt.%) in UHMWPE and HDPE blends. The two variants of HDPE were used, HDPE 5218 and HDPE 3840 for this study. It was found that the mechanical characteristics of the blend samples made with HDPE 5218 were somewhat enhanced due to the incorporation of MWCNT. The composites crystallization was improved by adding MWCNT to 20 wt.% of the UHMWPE blend but slowed at higher UHMWPE contents. UHMWPE/HDPE/MWCNT nanocomposites were found to be less elastic than their blends. In the study of Dubey et al.,²⁴ the effect of Graphene nanoplatelets (GNPs)/hydroxyapatite (HA) in PMMA bone cement is used to produce a biopolymer composite. The amount of each nanofiller applied is between 0 and 0.5 wt.%. The results reveal that a sample containing 1.5 wt.% of GNP/HA/PMMA led to an increase in flexural strength of 49.28% and an increase in flexural modulus by 30.80%. Furthermore, it has a compression modulus of 57.41% and a compression strength of 31.7%. Thus, finds suitable to be used in various biomedical industries. Liang et al.²⁵ explored the growth of organic montmorillonite (OMMT) clay-filled UHMWPE nanocomposite by Ultrasound-assisted melt mixing. It showed that melt mixing with ultrasonic and extensional deformation was beneficial in silicate layer exfoliation, filler distribution, and dispersion. The material's thermal stability, tensile strength, storage modulus, and complicated viscosity were all observed to improve with the addition of the right amount of OMMT but worsened with the addition of ultrasound treatment by ultrasound-assisted vane mixer (UAVM).

In addition to this, Hussain.et al.²⁶ studied the new material developed from nano Al₂O₃/Vitamin-C filled UHMWPE Polymer matrix bio nanocomposite as a biomaterial for artificial cartilage in three variations (0.5,1 and 2 wt.%) of nano Al₂O₃ was analyzed with 2 wt.% Vitamin C in UHMWPE. A higher wear resistance against Ti6Al4V alloy has been noted with 2wt.% Al₂O₃ under Human serum environment due to film formation on the developed bio nanocomposite surface. Suner. et al.²⁷ explored UHMWPE/GO biomaterial for joint application using a hot press moulding technique (185^°C under 15 Mpa). The addition of GO improved the oxidative resistance, thermal stability, wettability, and mechanical properties of the polymer matrix. 0.5 wt.% of GO showed the optimal physical and mechanical properties for the developed biomaterial concerning unfilled one. Chen et al.²⁸ also developed the GO (0-1wt.%) based UHMWPE biomaterial having porous structure by utilizing NaCl which gets evaporated under higher temperature forming porous surface in UHMWPE/GO composite by Hot-press molding. The combination of GO and NaCl improves wear resistance and reduces friction in the UHMWPE polymer matrix. The effect of Alumina Toughened Zirconia (ATZ) was examined by Duraccio et al.²⁹ comprising ATZ 20–80 wt.% within the UHMWPE matrix using several blending methods followed by compression molding and found good cells interaction with improved mechanical properties. Additionally, the composite with the least quantity of ATZ (2.5 wt.%) exhibits significant yield stress improvement. The supplement of 2.5 wt.% ATZ in the UHMWPE matrix enhances hydrophobicity and cell interaction compared to a pristine one, expanding UHMWPE's use for biomedical applications. Bhusari et al.¹⁷ described a novel method for covalently grafting polyethylene chains with GO nanosheets. Processability was enhanced by employing melt-extrusion and injection moulding methods with appropriate loading of modified GO. A Dual hybrid technique was utilized to blend HDPE-UHMWPE for composite development with a small amount of surface-modified GO. A 60/40 ratio of the polymer matrix having 1 wt.% content of GO (surface modified) resulted in mechanical properties. As a result of this research, tensile strength and elastic modulus increased by 65 MPa and 908 MPa, respectively. Suresha et al.³⁰ explored the behavior of copper nanoparticles (n-Cu) and CNTs mixed with UHMWPE. The improvement in sliding wear behavior has been reported by use of nano-fillers in very limited quantity i.e. (0.1–0.5 wt.%). In addition, the CNTs (1-D filler) decrease the interface surface area., increases UHMWPE interchange, and inhibit interlocking with a furrowing of developed composite with respect to steel counterpart, lowering both, the coefficient of friction (µ) and explicit wear rate (Ks). UHMWPE with 0.5 wt.% CNTs beat the other combinations in terms of tribological performance. A decline in the Ks value has been reported with the increase of abrading distance as well as the coarseness of the emery paper. Also, UHMWPE/CNTs beats both pristine and nano Cu-reinforced UHMWPE in terms of abrasion resistance.

Due to the high melting point of UHMWPE, production techniques for final products intended for industrial applications are limited and complex. As long as the polymer chains of UHMWPE are mobile enough to bend in a specific direction, different shapes can be formed from the same polymer chain.³¹ Because of this, long-range lamellar crystalline structures are created surrounded by an amorphous region. They are also associated with “microfibrils" that behave as bridges seen between crystalline lamellae. The relative quantities and shape of the amorphous and crystal structures directly impact UHMWPE's mechanical, thermal, and surface characteristics.^32,33 It's also possible to change the design of the polymer by inserting two-dimensional carbon nanomaterials into a UHMWPE matrix. This can help to improve the polymer's characteristics and make it much easier to work with. Various Carbon materials such as carbon black, carbon nanodots (C-dots), Graphene nanoparticles (GNPs), and carbon nanotubes (CNTs, SWCNTs, and MWCNTs) have been utilized as fillers in UHMWPE. Economic consideration of the fillers added to improve UHMWPE properties is the prime perspective of researchers from the beginning. The cost and processing of these fillers are much more, making them less efficient for general biomedical and industrial use. These variables considerably influence the manufacturing of low-cost and high-performance UHMWPE composites as implants. Table 1 Depicts a summary of previously published studies in the area of nanomaterial supplements in the polymer matrix and their end-use with remarks.

Table 1.

Prior work summary for the supplement of nanomaterials in polymer composite.

Reinforcement (nanomaterials)	Matrix (polymer)	Fabrication process	Mechanical property enhanced (↑), decline (↓)	Applications	Ref
Polyethyleneimine (PEI) modified GO (0.5,1,3 wt.%) (optimal 1 wt.%)	UHMWPE/HDPE blend (60/40)	Melt-extrusion	Increasing adequate interfacial adhesion and matrix compatibility ultimate tensile strength (↑) @120% improvementelastic modulus (↑) @40% improvement	Bone tissue engineering applications	[17]
GO (1,2,3 wt.%) and nHA (15 wt.%) optimal (15 wt. % nHA and 1 wt. % GO)	Polylactic acid (PLA)	Electrospinning	Tensile strength (↑) Modulus (↑) Water uptake (↑)	Scaffolds for bone tissue	[34]
Bioactive glass (BAG) (5, 10, and 20 wt.%) optimal (20Wt.%)	HDPE	Melt compounding and fused filament fabrication (FFF) technique	Tensile strength (↑) (16.25 MPa. —20wt.% BAG) tensile modulus (↑) (1.41 times better than HDPE-pristine, 1.82 times higher than printed HDPE) porosity (↑) @12.23% flexural modulus and strength (↑) (1.44 and 1.20 times higher than printed HDPE) Compressive modulus and strength (↑)	Orthopedic implants and scaffolds	[35]
GNPs (graphene nano platelets) (0.1, 0.3, 0.5, 1, 3 or 5 wt.%) using ball milling (0.5, 1.4, 2.3 or 4.6 wt.%) using blade mixture. No optimal content for all the properties	UHMWPE	Mechanical mixing (ball mill and blade mixer)- thermo-compression at (195, 220 and 240⁰C.) The powder blend is deposited on a pre-formed virgin UHMWPE disk (dia. 90 mm)	Better adhesion to the substrate and higher ductility @blade mixture. Wear resistance (↑) @ 20 and 15%, with ball mill and blade mixing technique. (The wear rate of the blade mixer was almost double that of the ball milling results.) coefficient of friction (COF) (↓) @∼25%, below 3 wt.% content hardness (↑) 24% (for both mixing techniques)	For coating purposes, joint replacements	[36]
Functionalized single-walled carbon nanotubes (f-SWCNTs) (0.01 and 0.1 wt.%) Optimal (0.1 wt.%)	UHMWPE	Ultrasonication and hydraulic pressing method-single-point incremental forming process (SPIF) for knee implant development	Ultimate tensile strength (↑) @ 65%, Young’s modulus (↑) @12%	Hip, cranial and knee artificial implants	[37]
GO; MoS₂ (molybdenum disulfide) Optimal (0.7 wt.% GO and 15 wt.% MoS₂)	PEEK	Hot isostatic pressing	Friction coefficient and wear rate (↓), hardness (↑), tensile strength (↑) and thermal stability (↑)	Tribological application	[38]
GNPs (2%, 5%, 7.5%, and 10% wt.%) Optimal (10% wt.%)	Poly (ethylene terephthalate) (PET)	Micro compounding and micro-injection molding	Elastic modulus (↑) @58%, crystallinity (↑) @ 50%	Packaging, automotive, and aerospace	[39]
GO (0.25,2.25Wt.%) Optimal (2.25Wt.%)	Chitosan	Ultrasonication-casting on teflon plate-peeling	Tensile strength (↑) by 2.5 times, Young’s modulus (↑) by 4.6 times, glass transition temperature (↑) from118°C to 158°C, hardness (↑) @60%	Drug delivery food packaging and biosensors, and	[40]
Nanodiamond (ND) (0.1,0.3and 0.5 wt.%) with 5Wt.%ZrO filler as the positive control	PMMA (poly-methyl methacrylate)	In situ polymerization	Flexural strength (↑) @20% FOE 1Wt.%, elastic modulus (↑) surface hardness (↑)	Lubricants, tissue engineering, coatings, bone cement and implants	[41]

Incorporating different nanomaterials has observed a tremendous improvement in property enhancement in various types of the polymer matrix. This work targets the supplement of Graphene and its derivatives because of its enormous success in today's areas of study and the ease with which it may be modified without causing significant difficulty. The Graphene was successfully isolated using graphite in 2004, and much work has been devoted to obtaining its massive amounts.^10,42 Both GO and rGO are by-products of the oxidation of graphite. It implies that GO possesses several oxygen-containing functional groups on its basal and layer edges. Both distribution and dispersion of Graphene sheets must be tailored throughout the nanocomposite manufacturing process. It is mainly performed to enhance the surface and mechanical characteristics of the nanocomposites. Researchers nowadays are concentrating on investigating the achievements of Graphene and Graphene derivatives in a diverse range of industrial and biomedical products. Several recent research studies have been published exploring the adaptation of Graphene in solar devices, food industries, drug delivery, biomedical fields, automobile industries, and many more. These investigations have shown that adding carbon nanoparticles to the UHMWPE matrix enhanced its hardness as well as tribological properties.^43–46 More research needs to be done to better understand the influence of Graphene/Graphene-derived fillers on the properties of the polymer matrix. Research on Graphene and its derivatives for biomedical applications has proven the range of its potential as a biomaterial throughout the last decade. Chemical or physical reduction processes transform GO into other Graphene derivatives, such as rGO. Much research has been done on biomedical nanocomposites based on nanofillers. Reinforcement materials such as graphite, Graphene oxide (GO), Graphene nanoparticles (GNPs), carbon nanotubes (CNTs), nanodiamonds (NDs) and other forms of Carbon-based nanomaterials (CBNs) have been extensively investigated in polymers such as PMMA, PEEK, PLA, UHMWPE, HDPE, and LDPE, and others, for mechanical, thermal, and tribological applications. The harmless chemical reaction of hydrothermal reduction was used to produce rGO, and Ultrasonication was used to achieve a surfactant-free dispersal of the rGO. Optimization of ultrasonic settings was utilized to create a stable rGO dispersion that could be used to deliver the anti-cancer drug Paclitaxel with more efficiency than previously possible.⁴⁷ Apart from this, very little research has been done on how rGO affects polymer matrixes. Kang et al., Priyadarsini et al., and Lee et al. have identified the increased Osteogenesis impact rGO most desired property for bioimplant development.^48–50 As a result, further research is required to explore its relevance to implant development. Bhattacharyya et al.⁵¹ developed a reduced GO-based UHMWPE composite using the in-situ reduction method in the presence of phenylhydrazine, a toxic substance, but the composites show high strength and creep resistance. Mindivan and Çolak also evaluated the different loading of rGO (0.1, 0.3, 1.0, and 2.0 wt.%) synthesized from the green route and found good results.⁵²Generally, the rGO is synthesized by using phenyl hydrazine as a reduction agent. Hydrazine derivatives are strong and most used reducing agents but highly toxic and instability. These limit its large-scale application. With the growing concern of the biomedical sector, the green route has been used in various applications in biomedical. Especially in biomaterial industries, to develop more compatible and long-lasting implants. Therefore, recently greener materials (amino acid, plant extracts, microorganisms, proteins, hormones etc.) were used to substitute toxic hydrazine used in GO reduction and their yields.^53–55 The procedure of green synthesis of rGO (Figure 1) consists of the following set of procedures:

Figure 1.

Green synthesis of rGO.

According to the above state of the art, there is very little work on supplementing reduced Graphene oxide (rGO) in UHMWPE. The incorporation of rGO has shown better results as desired by different kinds of biomaterials, biomedical devices (sensors), tissue engineering, coating, bone implants, etc. The inquiry into the influence of greenly derived rGO on mechanical qualities is still in its early stages. It demands more focus from the scientific community, biomedical society, and industrial sectors. Few of them have investigated the incorporation of carbon-based materials with Hap nanoparticles in UHMWPE. This research aims to improve the physio-mechanical properties of UHMWPE by using biocompatible nanofillers (rGO). As indicated in the literature review, most work exists to supplement Graphene, GO, GNPs, Hap, CNT's, MWCNT's, SWCNT's, ND's nanofiller materials in the matrix phase. By incorporating rGO (green) into the UHMWPE polymer matrix, the author attempts to overcome the mechanical performance limitation of the UHMWPE articulating material (Hip, Knee, Shoulder, finger, etc.). The present paper evaluated an extensive range of wt.% (0, 0.5,1,1.5,2, and 3) to better understand the synthesized bio-nano composites. Furthermore, mechanical properties (tensile, flexural, and hardness) are assessed and elaborated along with structural, morphological, and thermal investigation. Through FESEM, Fracture surface analysis of tensile samples, Fourier transform infrared spectroscopy (FTIR), X-ray powder diffraction (XRD), and Differential scanning calorimetry (DSC), respectively. The current research aims to develop a cost-effective green bio nanocomposite with minimal loading and enhanced characteristics. It could be a forward step to aid the healthcare industry in fabricating economic and durable implants and regular minimization surgery. This form of rGO-incorporated implants opens up new possibilities in the biomedical sector to develop liner implant materials with high strength, biocompatibility, wear resistance, and drug-delivery capacity, primarily for knee, shoulder, fingers, and hip joint assemblies.

Materials and Methodology

The materials and fabrication techniques used in developing nanocomposite materials are described in the following section. The first section describes the specifications and properties of various materials that have been used in the development of nanocomposite materials. The second section describes the two-step procedure, which includes nano powder development and hot compaction of nano powders.

Materials

The essential polymer matrix was procured via Merck (Sigma-Aldrich) in the form of UHMWPE powder (white colour) with an average molecular weight of 3 x 10⁶–6 x 10⁶ g/mol and a density of 0.94 g/mL at ambient temperature. In this, a melting temperature of 198–201^°C and reduced Graphene oxide (rGO) nanoparticles synthesized from the green route with vitamin C and having CAS number 7782425 having average numbers of layers 2–6 along with 0.48 g/mL density at 25°C having the purity of about 98–99% was purchased from Nano_researchlab, Jharkhand India. Acetone having CAS number 67641 along with 58.08 g/mol Molecular weight and 784 kg/m³ density (Purity % > 99%) was purchased from Rankem (LR Lab Reagent).

Methodology

The developed bio nanocomposite was prepared by adopting a two-step process. The first step involves preparing nanocomposite powders using Ultrasonication and stirring inside a liquid media. The whole fabrication process is represented most simply in Figure 2. The reinforcing phase and UHMWPE powder were formerly weighed on a digital weight indicator, according to Table 2, which depicts the sample formulation. To assess rGO incorporation, (0.5, 1, 1.5, 2, and 3) wt.% rGO was introduced to the polymer matrix.

Figure 2.

Schematic view of the sample fabrication procedure.

Table 2.

Formulation and composition of the prepared samples.

Samples Nomenclature	Composition (weight fraction)
Samples Nomenclature	UHMWPE (%) rGO(%)
UHMWPE	100	0.0
0.5 wt.% rGO/UHMWPE	99.5	0.5
1 wt.% rGO/UHMWPE	99	1.0
1.5 wt.% rGO/UHMWPE	98.5	1.5
2 wt.% rGO/UHMWPE	98	2
3 wt.% rGO/UHMWPE	97	3

A suspension of rGO nanoparticles was prepared by Ultrasonication for 60 min at 50 W in 30 mL of acetone. A UHMWPE-50 mL acetone combination was then added to the resultant mixture, ultrasonicated for another hour to get the final version. The mixture was then stirred for another 60 min at 75 C to remove its solvent media, whereas the stirring operation avoided any deposition. To achieve effective solvent extraction, the resultant powder was heated in a hot air oven for 50 h at 80°C. Finally, the obtained powder mixture is ball milled for around 2 h to blend and prevent any particle deformation, if any, properly.

The second step involved transferring the final dry powders to the Mild steel die, which were hot-pressed at 210°C with 100 bars of pressure for 1 h. They were then cool to room temperatures to deliver the nanocomposite with desired shape (10x10 cm square blocks of 4 mm thickness). In the whole process, silicon oil is used as a lubricating medium to remove the composite from the die surface easily. At last, the different ASTM Standard samples were cut according to the standard specification. A pristine UHMWPE sample is fabricated using the same two-step process described above to compare with the newly produced nanocomposites.

Characterization of rGO/UHMWPE bio nanocomposite

Mechanical characterization

The developed samples of bio nanocomposite's tensile, flexural, and Shore D hardness tests were determined using ASTM standards. The following sections describe in-depth info about mechanical performances.

Tensile testing

Each batch is made and tested using three Dumbbell form specimens (ASTM D638) with a (t = 3.2 + 0.4 mm, g = 7.62 mm), where (t) represents thickness in mm and (g) stands for gauge length in mm. In order to perform the experiments, we used a Universal Testing Machine (UTM) of the INSTRON® brand (Model 3365) at a 10 mm/min crosshead speed in a uniaxial direction using a load cell of 5-KN. Also, to increase the accuracy of the test conducted, the mean value of results was recorded.

Flexural testing

For each batch, three 80x10x4 mm³ cuboidal shape samples are created and tested in accordance with ASTM D790 standards. At a 2 mm/min speed, a three-point bending method is employed in UTM. In accordance with the aforementioned specification, the span length is adjusted to 16x4 mm, which dictates that the span length must be 16 times the thickness of the sample, i.e. (4 mm). The tensile and flexural testing process can be understood in Figure 3 and Figure 4.

Figure 3.

Tensile testing of developed bio nanocomposite samples.

Figure 4.

Flexural testing of developed bio nanocomposite samples.

Shore D hardness

Composite samples were tested for hardness using a hardness tester (DUROMETER Shore D- ASTM D2240, MILHARD) with Shore hardness type-D. The given hardness value is an average of nine measurements taken across samples of each kind. In this test, the intender is brought in contact with each piece, and the readings indicated on the dial were recorded.

FESEM analysis

At an accelerating voltage of 5–10 kV, a high vacuum field emission scanning electron microscope (MIRA3 TESCAN, USA) was utilized to analyze the UHMWPE/rGO Bio nanocomposite microstructure. Before the FESEM investigation, all test specimens and the pristine UHMWPE were placed in the machine tray. The polymer surface was conductive and coated with gold-coated using automated sputter coater equipment (Quorum Mini Sputter Coater, SC7620, UK). The samples were then magnified under an electron microscope to evaluate their structure and morphology.

Thermal characterization

Using a Differential Scanning Calorimetry (DSC2-00754) instrument, the melting temperature (Tm), the temperature at which melting begins (T_mi), and the temperature at which melting ends were all determined (T_mf). Also, after sintering/consolidation, the degree of crystallization (X_c) of UHMWPE/rGO Bio nanocomposites was also investigated. Heating each sample to 200°C for 5 min wiped off the thermal history of the produced nanocomposites. The test samples were then heated at 10°C/min from ambient temperature to 200°C. For DSC analysis, a test sample weight of 3.04 mg is employed. The aluminum pan was used during a DSC scan to hold the sample.

FTIR spectroscopy

The chemical and structural changes in the Bio nanocomposite were investigated using Fourier transform infrared spectroscopy (FTIR). The FTIR spectra of UHMWPE/rGO were collected at a wavenumber of 4000 to 400 cm^-1 at a resolution of 4 cm^-1 with two scans on every sample using a PerkinElmer FTIR Spectrum, which was manufactured in the United States of America. Before analysis, every powder sample was placed in the oven for about 24 h to eliminate any moisture content from the powder. The findings were recorded once the tests were completed.

X-Ray diffraction analysis

The UHMWPE/rGO Bio nanocomposite crystalline structure was determined using X-ray diffraction analysis. In this experiment, an X-ray diffractometer (Rigaku Ultima IV model, Japan) was used, which operated at 40 mA and 40 kV voltage and emitted (Cu K-alpha) radiation with a wavelength of =0.154 nm was used to perform the measurements. The dried samples were placed on a quartz substrate before being placed into the sample holder. The XRD spectra were collected at a 2θ range of 5–80° at a speed of 4°/min, with a step length of 0.02.

Results and discussions

The present work illustrates the mechanical performances such as tensile, flexural and hardness, thermal analysis (DSC) and morphological investigation of developed bio-nano composite, including the fractography study of tensile samples. These properties are highly desired for biomaterials application, specifically in the development of orthopedic components. The findings of mechanical testing of rGO modified UHMWPE are described in this section. Figure 5(a) demonstrates tensile stress-strain curves of the developed samples. Elastic modulus, yield strength, tensile strength, and the elongation at break calculated from the plots are also compared.

Figure 5.

Mechanical characteristics: (a) Tensile; (b) Flexural properties.

The results of the mechanical tests are shown quantitatively in Table 3. As shown in Figure 5(a)., the elastic modulus, yield strength, and tensile strength increase with the addition of fillers, while the values decrease for higher rGO content, i.e., for 1.5, 2, and 3 wt. %, while elongation at break declines with fillers and is minimum for 1 wt. % of filler content. Elastic modulus, yield strength, and elongation to break will be the primary parameters we use to assess the mechanical properties of the newly developed materials. In arthroplasty, implants are not allowed to yield, and any plastic deformation beyond the yield point is considered a failure. A particle that may reinforce polymer material mechanism may be used to explain the mechanical features of UHMWPE/rGO composites, owing to the intense contact between rGO and the UHMWPE matrix.^56,57 Because of rGO's ultrahigh surface area, portions of the polymer chains were adsorbed onto the surface. rGO sheets were randomly dispersed in those composites with a low rGO concentration and served mainly to increase yield strength. This was true for the composite with 0.5wt.% rGO. Its layered structure made it easier for the load from the polymer matrix to be transferred into and out of the rGO. Furthermore, the layers were a little loose, so they could absorb some of the energy from the outside. Furthermore, when the rGO content of the composites increases, the UHMWPE chains may be damaged, and the composites' plastic deformation would decrease.⁵⁸ The elastic modulus and yield strength of composite containing 1 wt% rGO were found to be enhanced by around 107% and 46%, respectively, when contrasted to the pristine sample, which is in line with previous investigations.⁵⁹ It is worth noting that this level of increase in UHMWPE mechanical characteristics has previously been reported with HAp loading of 40wt.%.⁶⁰ It's acceptable to assume that integrating rGO from the green route simultaneously is a better option for improving the mechanical characteristics of UHMWPE than using other expensive nanomaterials alone since less filler is needed. According to the elongation at the break graph in above Figure 5(a), the addition of rGO fillers exhibits diminishing trends, with the lowest value being around 74% lower with 1 wt.% rGO in comparison to pristine UHMWPE. Even though rGO fillers have a detrimental impact on the ductility of the polymer matrix, all of the bio nanocomposite samples that have been developed meet the tensile requirements meant for a complete hip replacement.^56,61 Studies show that the yield strength of UHMWPE sockets utilized in total hip joint replacements should be around 19 MPa.⁶¹ These samples' elastic modulus and tensile strength are superior to those of pure UHMWPE, even though all samples have appropriate yield strength. Moreover, the tensile characteristics obtained in this research are greatly improved above those obtained before when carbon-based fillers were included.^59,62 Bio nanocomposites made with rGO, and UHMWPE have strong flexural strength, as shown in Figure 5(b). In general, the flexural strength of UHMWPE climbed up to 70% when 1 Wt. % of rGO was added to it. There is a massive drop in the flexural strength of UHMWPE/rGO blends if they have more than 1wt.% rGO. The exciting thing is that when 1 Wt. % of rGO is added to the composites, and their flexural strength exhibits a considerable rise. Flexural strength may increase because reduced entanglement between polymer chains may boost flexural strength. The study conducted by Weir wt.al; investigated the conformations of polymer chains in nanocomposites composed of polymer and Graphene oxide. The chains are found to have a decreased radius of gyration, which is compatible with their confinement at a solid interface inside the melt. They discovered that confining the polymer chains led to a comparable decrease in interchain entanglements. Using a simple scaling argument, they also computed a contribution to the plateau modulus from the deformed polymer network and remarked that both the findings are significant. Their findings represent a substantial advance in how two-dimensional nanoparticles alter the global characteristics of materials when they are present in low loadings.⁶³ Li et al. conducted a study to see the effect on the rheological and mechanical properties of ultrahigh molecular weight polyethylene by incorporating high-density polyethylene/polyethylene glycol. However, when the PEG percentage increases, UHMWPE/PEG blends' mechanical characteristics decline. Adding HDPE may enhance the processability of UHMWPE/PEG blends by lowering their apparent shear viscosity, storage modulus, loss modulus, and complex viscosity. PEG may increase UHMWPE's processability by lowering its molecular chains' entanglement density, but it also introduces a lot of defects into the UHMWPE blend. Consequently, the mechanical characteristics of UHMWPE will be compromised by incorporating PEG.⁶⁴ Using neutron spin echo spectroscopy, Fabiani et al.; examined the melt chain dynamics of ultrahigh molecular weight polyethylene (UHMWPE) and its composites with Graphene oxide (GO) nanosheets. When compared to the pristine UHMWPE, they notice hindered chain dynamics. They suggest a paradigm in which the polymer is partially immobilized on GO sheets' upper and lower surfaces. This model allows them to measure the thickness of the adsorbed and free polymer fractions and the adsorbed layer. Their results provide nanoscopic evidence of GO preventing entanglement development in a polymer melt, a phenomena that had been observed at the macroscale before via rheological measurements.⁶⁵ As a consequence, the restriction on chain movement was loosened, and a more significant amount of force was needed to allow polymer chain slippage before breaking. Higher stress requirements indicate the positive interaction of filler with the polymer matrix. The findings of Mohanty and Nando agree with such findings.⁶⁶ They suggested that a synergistic effect may be achieved if the blend components interact well with one other. These factors may also be responsible for the observed mechanical behavior. The establishment of an accumulation in the UHMWPE matrix indicates an increase in rGO concentration.^67,68 The reduced strength found in blends with a greater rGO content may be due to inadequate adhesion between the matrix and rGO at enhanced filler content. For 1 Wt.% content, a similar trend can be seen in Flexural Modulus, which exhibits the highest modules compared to various developed nanocomposites.

Table 3.

The results of mechanical testing of the developed samples.

Sample	Tensile properties			flexural properties
	Elastic modulus (MPa) ± standard error (n = 3)	Yield strength (MPa) ± standard error (n = 3)	Tensile strength (MPa) ± standard error (n = 3)	Elongation at break (100%) ± standard error (n = 3)	Flexural strength (MPa) ± standard error (n = 3)	Flexural modulus (MPa) ± standard error (n = 3)
UHMWPE	424 ± 36	14.07 ± 0.6	14.99 ± 1.1	445 ± 7.5	44.22 ± 7.0	2835.76 ± 176
0.5 wt.% rGO/UHMWPE	816 ± 34	22.98 ± 0.6	23.97 ± 0.8	153 ± 4.6	53.66 ± 0.3	3313.95 ± 66
1 wt.% rGO/UHMWPE	879 ± 62	20.55 ± 0.5	20.30 ± 0.3	113 ± 6.3	75.05 ± 10.3	4935.92 ± 417
1.5 wt.% rGO/UHMWPE	811 ± 67	20.84 ± 0.6	21.39 ± 0.6	136 ± 8.0	55.76 ± 12.5	3503.52 ± 479
2 wt.% rGO/UHMWPE	747 ± 70	19.75 ± 0.8	21.13 ± 0.4	127 ± 4.9	42.36 ± 5.4	2397.03 ± 176
3 wt.% rGO/UHMWPE	333 ± 61	19.76 ± 0.7	23.07 ± 0.7	141 ± 2.9	47.01 ± 7.5	2682.99 ± 214

Shore D hardness

The fluctuation of hardness values with increasing rGO content into the UHMWPE polymer matrix can be seen in Figure 6 and Table 4.

Figure 6.

Variations of hardness as a function of rGO addition.

Table 4.

ShoreD hardness variations as a function of rGO addition.

Sr.no	Samples	Shore D hardness ± standard error (n = 3)
1	UHMWPE	62	61.3 ± 0.6
		61
		61
2	0.5 wt.% rGO/UHMWPE	63	62.7 ± 1.5
		61
		64
3	1 wt.% rGO/UHMWPE	63	63.0 ± 1.0
		64
		62
4	1.5 wt.% rGO/UHMWPE	61	61.3 ± 0.6
		62
		61
5	2 wt.% rGO/UHMWPE	60	60.0 ± 1.0
		59
		61
6	3 wt.% rGO/UHMWPE	58	57.7 ± 0.6
		58
		57

For lower wt. % values of filler incorporation, the hardness of the rGO-filled nanocomposites grew gradually with increasing rGO content. With 1.0 wt.% of rGO content in UHMWPE, the microhardness value of the material raised by around 2.8%, from 61.3 to 63.0. Thus, it could be claimed that small amounts of rGO might significantly increase the hardness of UHMWPE. This was attributed to rGO's outstanding mechanical qualities, which allowed it to sustain partial loads Archard's prediction and were critical for transferring load. According to,⁵⁹ increasing the hardness of UHMWPE or its composite would minimize the plastic contact regions between the plastic and the metal. As a result, we expect that UHMWPE-rGO composites containing coordination metal material will have superior friction performance when compared to unfilled UHMWPE. At last, EDS and XRD results show that rGO dispersion within the polymer matrix might improve indentation resistance.⁵³

There was a drop in hardness as the graphite concentration increased (>1 to 3 wt. %) owing to the decrease in the UHMWPE matrix used as the binding phase. A similar pattern was observed when graphite incorporated UHMWPE composite was tested from 0 to 30 wt. %.⁶⁹

The effect of rGO on polymeric structure

The processing parameters and rGO wt. %. presents directly impact the structure and morphology of the polymer matrix. The dispersion of rGO particles inside the polymer matrix is shown by correlating SEM Micrographs of rGO with various produced bio nanocomposites. Figure 7 and Figure 8 showed the SEM images of multi-layered reduced graphite oxide and the surfaces of rGO/UHMWPE bio nanocomposites with different content of rGO. Also, it has been observed that no voids and the wavy surface are observed with unfilled UHMWPE (Figure 9). It can be noted that the surface of rGO-0.5 wt. % and rGO- 1 wt.% nanocomposite was primarily flat, but it also had areas that appeared like wavy riverbed patterns. The bio nanocomposite micrographs further demonstrate that rGO was fully submerged in the UHMWPE matrix, showing that rGO and the matrix exhibit robust interfacial contact.⁷⁰

Figure 7.

SEM images of reduced Graphene oxide nanoparticles.

Figure 8.

Scanning electron microscopy image of bio nanocomposites: (a) Nodule area with 0.5 wt. % rGO content; (b) (c) The lamellae and fibrillar junctions for rGO levels of 1 and 1.5 wt. %; (d) (e) for 2&3 wt. % rGO content with agglomeration zone.

Figure 9.

Scanning electron microscopy image of UHMWPE (pristine): illustrate basic pristine UHMWPE structure, i.e., lamellae and fibrillar junctions.

In the UHMWPE matrix, the rGO nanofillers are well distributed due to the absence of rGO clusters. The nanofillers are well distributed, as shown by the polymer matrix's rise in the nanofiller percentage. Furthermore, the surface morphology changes dramatically as the quantity of rGO grows above 1 wt.%. The morphology of the developed bio-nano composite appeared visibly rough and distorted in appearance. Consequently, the elevated amount of rGO has hampered polymer rearrangement and chain folding. The clusters get more prominent as the rGO concentration rises from 1.5, 2, and 3 wt. %. As a result, the approach used to create the UHMWPE nanocomposite is a practical methodology for achieving an appropriate dispersion of rGO. After the Ultrasonication of rGO, the reduced Graphene oxide is instantly incorporated with the UHMWPE powder using high-speed stirring. This phase is critical because it encourages the rGO layers on UHMWPE particles to be covered. The rGO layers may be dispersed by Ultrasonication; however, when the solvent is evaporated, the layers (rGO) which were not adequately deposited on the polymer surface prefers to become aggregated at different sites forming agglomeration. As a result, the powder blend was pulverized effectively for 120 min using a ball milling method to blend the nanocomposite powder well.

The fracture morphology of the tensile samples was examined using a scanning electron microscope with a 5 kV accelerating voltage (Figure 10 and Figure 11). The green colour marks represent an improvement in ductility (rGO filled) compared to the pristine sample (indicated by red marks). The dog-bone pieces were sliced parallel to the fracture surface 1–3 mm underneath it. Before SEM examination, each sample was gold plated to make it conductive. Observations during the tensile test revealed significant elongation before fracture development, a typical example of ductile failure. Before the specimen broke, it developed a fracture on its surface. The fracture surface micrographs exhibit ductile failure characteristics such as plastic deformation and fibrils on the surface caused by particle separation during the tensile test.^71–73 Crack initiation is often followed by crack propagation, in which more fibrils experience severe plastic deformation until they burst. Figure 10 shows fewer fibrils than 1wt%. rGO content bio nanocomposite demonstrating lesser ductility. Also, no voids in the fracture surface reveal excellent interaction between filler and matrix components. An acute sharp fracture is seen with UHMWPE (pristine) in comparison to 1Wt.% rGO/UHMWPE nanocomposites.

Figure 10.

SEM Micrographs of UHMWPE bio nanocomposites: fractured (pristine UHMWPE) tensile dog bone sample.

Figure 11.

SEM Micrographs of UHMWPE bio nanocomposites: Fibril’s pull out in a fractured tensile dog bone sample with 1wt. % rGO concentration. 1 Wt.% rGO/UHMWPE fracture surfaces indicate excellent rGO-UHMWPE matrix bonding.

EDS analysis's elemental mapping of bio nanocomposites demonstrates that oxygen was evenly distributed throughout the bio-nano composites (Figure 12(a) and (b)). The oxygen dispersion is vital since the filler, i.e., rGO, contains namely rGO, comprises functional groups that contain oxygen. Results from the EDS were compared to those from the pristine composite and the Element overlay for 1wt. % rGO Content bio nanocomposite reveals the homogeneous distribution of rGO in UHMWPE. As shown in eZAF Smart Quant Results and Sum Spectrum of EDAX analysis, the increase in oxygen suggests that rGO is well dispersed within the developed composite. The oxygen level also increases due to the presence of an oxygen-containing group rGO.

Figure 12.

EDX spectrum of (a) Pristine UHMWPE and (b) Developed bio nanocomposite with 1wt.% rGO content.

DSC analysis

DSC analysis was used to determine microstructural changes after adding reinforcements to the matrix, and the melting temperature (T_m) and degree of crystallization (X_c) were measured. DSC endotherm graph (Figure 13) was used to compute the melting temperature (peak temperature in the DSC), and crystallinity was estimated using equation (1)

X_{c} = \frac{Δ H}{{Δ H}_{o}}

(1)

Figure 13.

Graphs showing endothermic DSC plots of samples for pristine UHMWPE and UHMWPE/rGO series composites.

The apparent enthalpy of fusion per grams of composite is denoted by ΔH, while the heat of fusion of a pure 100% crystalline polyethylene is denoted by ΔH_o, which is 289 J/g.⁷⁴ Table 5 summarizes the findings. As seen in this Table 5, the addition of rGO enhanced X_c, indicating that rGO nanoparticles had a nucleating influence on the crystallization and microstructural characteristics of the matrix. As demonstrated, the crystallinity of the composites increased sharply from 40.61% to 45.44% when the introduction of rGO reached 0.5 wt. % and continued to grow up to 1.5 wt.% of rGO and undulated moderately with the addition of rGO. Crystallinity decreased to 36.29% and 34.74% with the addition of 2 wt.% and 3 wt.% rGO, respectively, but it remained more remarkable than that of pristine UHMWPE. Figures 8 and 9 illustrate the SEM images to examine the crystal structure of UHMWPE (pristine) and UHMWPE/rGO composites. The crystalline state can easily be correlated from these micrographs. rGO enhanced the crystalline structure in the UHMWPE matrix. rGO layers enclosed the molecular chain in the crystal structure. Higher polymer adsorbed on rGO's surface may explain the enhanced crystallinity, and rGO may operate as a heterogeneous nucleating site for crystallization, thereby boosting crystallinity in UHMWPE.^75,76 However, when the rGO content increased, a significant proportion of rGO diffused into the UHMWPE matrix. Due to the high contact force among fillers and polymer matrix, crystallinity tends to be stable within a range.¹⁷ UHMWPE exhibits enhanced mechanical capabilities as the number, concentration, or thickness of crystalline regions increases, increasing the degree of crystallinity.⁵⁶ Crystallinity is one of the polymeric properties that might impact wear resistance. Mechanical characteristics, such as crystallinity, are directly linked to polymer wear resistance, and mechanical attributes are directly linked to polymer structures.⁷⁷ Furthermore, when polymers are exposed to a wet environment, liquids may permeate into the amorphous areas of the polymer, altering mechanical qualities such as hardness and strength. The crystallinity of a semi-crystalline polymer is inversely related to the number of amorphous zones in the polymer matrix. As a result, more excellent crystallinity might possibly lower a polymer's sensitivity to water absorption and enhance wear resistance. Aside from enhanced crystallization and nucleating effects of reinforcement, this may be another reason for improving the mechanical characteristics of the developed composite.²³ Also, a decrease of melting temp has been seen with the rise of rGO fillers, which is slightly higher than the pristine sample for 1.5 wt. % filler content shows the possibility of work of a larger temperature range in which such material can be processed. The starting of melting range is marked with T_mi, and the end of the melting process unto which whole of the amorphous and crystalline part of the bio nanocomposite is melted is shown by T_mf in Table 5. Thus, giving a possibility for mass production at the biomedical industries level.

Table 5.

Crystallization degree (X_c) and Melting temperature (T_m) calculated using DSC plots.

Sr.no	Samples	Crystallization degree X_c (wt.%)	Melting temperature (T_m)	Start of melting (T_mi)	End of melting (T_mf)
1	UHMWPE	40.61	134.02	108.64	149.65
2	0.5 wt.% rGO/UHMWPE	45.44	126.71	70.56	143.81
3	1 wt.% rGO/UHMWPE	46.96	128.52	76.99	142.82
4	1.5 wt.% rGO/UHMWPE	47.16	134.44	84.68	143.33
5	2 wt.% rGO/UHMWPE	36.29	118.61	70.04	136.41
6	3 wt.% rGO/UHMWPE	34.74	124.09	68.46	148.81

Fourier-transform infrared spectroscopy

UHMWPE/rGO bio nanocomposite FTIR spectra were shown in Figure 14 and Table 6 for various groups, respectively. When applied to the unfilled UHMWPE, the CH asymmetric vibration, the CH symmetric vibration, the CH₂ bending vibration, and the CH₂ rocking vibration all have peaks of 2915.96 cm⁻¹, 2847.38 cm⁻¹, 1467.03 cm⁻¹, 720.10 cm⁻¹ respectively.⁷⁸ Since the infrared absorption peak position of rGO/UHMWPE composites does not shift with increasing rGO content. This indicates that rGO did not significantly affect the molecular structure of UHMWPE during the ultrasonic dispersion and hot-pressing process and that UHMWPE did not degrade during either step. Apart from that, the impact of CH₂ twisting vibration (1264.29 cm⁻¹) as well as the effect of (C-O-C) vibration 1054.89 cm⁻¹ were statistically significant when rGO was present in a polymer matrix.⁷⁹ Because of the presence of rGO, the intensity of the peaks at 22915.96 cm⁻¹, 2847.38 cm⁻¹, 1467.03 cm⁻¹, 720.10 cm⁻¹,1260.15 cm⁻¹, and 1054.79 cm⁻¹ increased, perhaps indicating stronger interaction between filler and the Polymeric matrix.

Figure 14.

FTIR spectral analysis of UHMWPE (pristine) and UHMWPE/rGO bio-Nanocomposites.

Table 6.

Data obtained from FTIR spectra of rGO filled UHMWPE and pristine UHMWPE.

Functional group present	UHMWPE (wavenumber Cm⁻¹)	UHMWPE/rGO (wavenumber Cm⁻¹)
CH2 symmetric stretching vibrations	2847.38	2847.71
CH2 asymmetric stretching vibrations	2915.96	2914.94
CH2 bending vibrations	1467.03	1463.83
CH2 twisting vibration	-	1264.29
(C-O-C) vibration	-	1054.89
CH2 rocking vibration	720.10	719.98

XRD analysis

Unfilled and rGO filled bio nanocomposites XRD diffraction patterns are depicted in Figure 15. Diffractograms of the orthorhombic crystal show two peaks at 2θ° = 21.46 and 23.84, which correspond to the (110) and (200) planes, respectively.⁸⁰ From XRD analysis it is clear that with the increase of rGO content up to 1.5wt.% the crystallinity shows increasing trends and then declines with further increase of rGO content. This result is similar to the study conducted by Li.et al. They utilized solution mixing to develop different carbon materials (Graphite particle (GP), Graphite nanoplatelets (GNP), and flaky Graphene oxide (GO) as filler, based nanocomposites. According to the results, heterogeneous nucleation and the effect of carbon materials that restrict crystal development are present throughout the UHMWPE crystallization process. Both of these factors work together to prevent crystal growth. The macromolecular chain motion of UHMWPE is slowed down because of the heterogeneous nucleation of carbon materials. This is the reason why crystallinity increases at lower wt.% of filler than at higher wt.% i.e. above 1.5 to 3wt.%.⁸¹ Another study by Çolak.et al. also shows the same trend. The results of XRD analysis show an increase in crystallinity at lower content of reduced Graphene oxide (rGO), which further shows a decline at higher wt.% of rGO filler. Since, the low RGO content was able to operate as nucleation sites rather than causing disruptive rearrangement and chain folding throughout the crystallization process.⁸² The nanoconfinement impact of Graphene nanoplatelets on the characteristics of matrix-grafted Graphene/polysulfide polymer nanocomposites is explored in the study conducted by Amangah et al., the results of DSC and XRD demonstrated that the addition of modified Graphene (mGO) up to 0.7 wt.% boosts the crystallinity of nanocomposites, but that the crystallinity diminishes beyond that. This shows that the crystallinity of the sample grows with the amount of mGO added, since mGO functions as a nucleating agent during the crystallization process. With the increase in filler loading, nanoconfinement effect of Graphene nanoplatelets came into play, resulting in a decrease of crystallinity.⁸³ With the incorporation of 3wt.%, a decline in intensities of both peaks as in the UHMWPE XRD diffraction pattern, was observed. It can be correlated with crystallinity alteration in the polymer matrix.⁷⁵ There will be less crystallinity and more disruption during the crystallization process due to the fillers' high rGO content (3 wt. %), making them ineffective as nucleation centers and causing chain folding and rearrangement disruptions. UHMWPE/rGO bio nanocomposite crystallite size data for 2θ = 23.84° is shown in Figure 15. Increasing the size of the crystalline structure in the UHMWPE/rGO bio nanocomposite will change the wear behaviour of the developed composite.⁸⁴ The XRD patterns of nanocomposites also did not show any unique diffraction peak, with the exception of orthorhombic crystal peaks of empty polymer, which were detected in the patterns of pristine polymeric material. That rGO had been exfoliated in the UHMWPE matrix was evident from this finding.²³

Figure 15.

XRD plot for developed nanocomposites.

Conclusion

This paper presents an effort to apply rGO reinforced polymeric biomaterials to different types of contacting surfaces and joints in the human body. Due to various factors, including obesity, medical issues, accidents, sports activities, an unhealthy diet, and the natural deterioration of joints over time, surfaces and joints are subjected to a variety of loading conditions during the course of daily activities. These loading conditions change throughout an individual's life due to various factors, including age, gender, and physical condition. Green-produced reduced Graphene oxide was employed as reinforcement in UHMWPE. The bio nanocomposites were created using liquid-phase Ultrasonication, ball mill pulverization, and hot pressing in a hydraulic system. The study illustrates the effect of rGO-modified UHMWPE and obtained promising results. Based on the acquired findings, the following conclusions were drawn:

• A series of Ultrasonication processes evenly disseminate the rGO sheets in the polymer matrix. Compared to other fillers cited in the literature, such as CNTs, MWCNTs, and more expensive nanofillers, rGO could improve UHMWPE's mechanical and thermal properties with only a small amount of filler content.

• Increasing rGO concentration improved UHMWPE crystallinity. rGO improved UHMWPE/rGO bio nanocomposite's thermal performance. High-rGO content greater than 1wt.% shows a decline in crystallinity.

• It was found that the rGO concentration of 0.5 wt.% and 1 wt.% gave the best tensile strength results. A good flexural response is also seen with 1wt.% of rGO Content. Furthermore, even small Wt.% of rGO can significantly boost the micro-hardness. There was a significant interaction response between the rGO lamellar structure and the UHMWPE matrix, resulting in better load transfer performance.

• SEM and EDAX analysis show the good dispersion of rGO nanofillers for 1Wt.% sample. Well-coated nanofillers with polymer matrix are observed in the SEM image. Also, the EDAX shows the uniform distribution of rGO throughout the polymer matrix. Investigating the fractography of tensile (Dog-Bone) test specimens of rGO/UHMWPE Nanocomposite shows ductile fracture properties. It could be possible due to the lubricating effect of rGO.

• The XRD diffraction pattern and FTIR demonstrate the excellent interaction between the polymer (UHMWPE) and the nanofiller (rGO).

• The two most important factors affecting the success of UHMWPE/rGO composites were the free-space effect and the interaction-force effect. In thermal characteristics, these two elements are mutually offsite. In terms of mechanical capabilities, these two features mutually reinforce one other. As a result of these mechanical and thermal qualities, it could be inferred that rGO mixed UHMWPE is a potential material for the future of biomaterial implants due to its low cost and excellent thermal and mechanical properties.

This research demonstrates the effectiveness of rGO-reinforced nanocomposites and their potential for use in developing orthopedic components. It may be utilized as a linear acetabular material; however, it can also be used in knee, shoulder, and finger implants, biomedical sensors, thermal barriers, and various medical devices. This investigation was confined to mechanical tests such as tensile, flexural and Shore D hardness and some advanced characterization that yielded positive results as a preliminary screening on rGO-filled bio-nanocomposites. On the other hand, the shape and distribution of wear particles may have a considerable influence on the in-vivo performance of the material. Recent nanocomposite research has suggested that using smaller filler particles might provide more impressive results with lower filler concentrations and increased capabilities. This may be accomplished by dispersing the nano-fillers with other ceramic nano-fillers to offer high strength and lubricating effect while maintaining the requisite optimal qualities. Further research is needed to study the composite's viscoelastic behaviors, tribological characteristics, and toughness. These qualities might be investigated in the future to better understand the suggested nanocomposites.

Footnotes

Acknowledgment

The authors would like to acknowledge the kind support of the laboratories facilities available at Central Institute of Petrochemicals Engineering & Technology (CIPET), Lucknow and Indian Institute of Technology (IIT), Roorkee (Saharanpur Campus), India.

Declaration of conflicting interests

The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Funding

The author(s) received no financial support for the research, authorship, and/or publication of this article.

ORCID iD

Rajesh Kumar Verma

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Development of reduced Graphene oxide modified Ultrahigh molecular weight polyethylene (rGO/UHMWPE) based Nanocomposites for Biomedical Applications

Abstract

Keywords

Introduction

Materials and Methodology

Materials

Methodology

Characterization of rGO/UHMWPE bio nanocomposite

Mechanical characterization

Tensile testing

Flexural testing

Shore D hardness

FESEM analysis

Thermal characterization

FTIR spectroscopy

X-Ray diffraction analysis

Results and discussions

Shore D hardness

The effect of rGO on polymeric structure

DSC analysis

Fourier-transform infrared spectroscopy

XRD analysis

Conclusion

Footnotes

Acknowledgment

Declaration of conflicting interests

Funding

ORCID iD

References