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Abstract

The effect of varying processing temperatures (200, 220 and 240°C) on the thermal and mechanical properties of uncoated and epoxy-coated chrome-tanned leather wastes-ABS composites has been studied. The results obtained showed that the mechanical properties of the composites decreased as the processing temperature increased. Epoxy-coated leather wastes fibre-ABS (CLWABS) composite yielded better mechanical properties compared to the uncoated leather wastes-ABS composite (LWABS). These results were obtained at an optimized processing temperature of 200°C. Furthermore, the results were confirmed by the field emission scanning electron microscopy (FESEM) studies. The differential scanning calorimetry (DSC) studies revealed that the epoxy-coated leather wastes fibres (CLW) showed higher onset and melting temperatures of 131.8 and 179.35°C than the uncoated leather wastes fibres (LW) with glass transition (Tg) and melting (Tm) temperatures of 128.2 and 169.4°C, respectively. When the LW and CLW fibres were mixed with Acrylonitrile butadiene styrene (ABS), the Tg and Tm of CLWABS composite were found to be 94.9 and 269.8°C, respectively, higher than the LWABS composite with Tg and Tm of 89.1 and 261.6°C, respectively. Thus, this study has demonstrated that utilization of epoxy-coated chrome-tanned leather wastes fibres as fillers in the design of ABS-based composites will help a great deal in addressing the problem of solid waste pollutants in our environment.

Keywords

Acrylonitrile butadiene styrene epoxy coating leather wastes polymer composites solid waste pollutants

Introduction

Before now, there was massive interest in the use of plant fibres in polymer composites because of their attendant benefits. Among the findings reported so far on natural fibre reinforced high temperature engineering plastics such as date palm leaf fibre/recycled poly(ethylene terephthalate), PET/Hemp, Jute fabric/polyamide and empty fruit bunch fibre/recycled poly(ethylene terephthalate), it was observed that the processing temperature of the natural fibre reinforced thermoplastics is highly dependent on the thermal degradation temperature of the natural fibres since the maximum processing temperature for natural cellulose-based fibres occurs at around 200°C.^1-4 Above this temperature, there is usually thermal degradation of natural fibres and consequently the decrease in mechanical properties of the resultant composite.^5-7 As a result, other natural fibre/fabric such as leather is being considered. Hence, leather is a natural fabric obtained when animal skin or hide is tanned. Tanning of leather is done to render them imputrescible and increase chemical and physical durability over time.⁸ Tanned leather is chemically composed of proteins, water plus other mineral matters. Additionally, other chemical processes are also being experimented to improve the thermal stability of leather, particularly leather wastes from industrial operations.

The conversion of leather wastes generated from leather industries into valuable products is a growing interest among researchers because of the large amount of wastes generated from the leather and footwear industry which constitute environmental pollution.⁹ Polymer composites of leather wastes based fillers have been reported to be useful for many applications such as in construction materials, automobile interior mouldings, heat and sound insulating boards, shoe soles and flooring materials.¹⁰ Waste leather buff filled polycaprolactone (PCL) biocomposites were also developed, and they could be used to produce low cost materials suitable for applications in footwear, bags and suitcase industries.¹¹ Similarly, eco-friendly biocomposites were developed using waste leather buff (WLB) as filler in polylactic acid (PLA) matrix, and the aim was to reduce the environmental issues and provide sustainable solution.¹² The physical and mechanical properties of chrome-tanned cow leather was improved via treatment with different aldehyde and ketone sodium bisulphite adducts and grafting with 1-Vinyl-2-pyrrolidinone.¹³ In the same vein, a novel composite material from natural rubber and leather waste was developed for use in the textile and footwear industries.¹⁴

The processing parameters for the manufacturing of thermoplastic composites are very important as these parameters such as processing temperature, pressure and time have a direct influence on the mechanical properties and performance of the final composite product depending on the individual machine and materials.^15,16 The development of composites of high temperature polymers with leather fibres via melt-mixing technique requires proper settings of processing parameters for ultimate performance of the composites. These parameters, especially temperature is critical in the processing of high temperature thermoplastic composites as low processing temperature will lead to non-homogeneous distribution of fibres and on the other hand, higher processing temperature might result to thermal degradation of the fibres as well as the matrix.¹⁷

Several authors have reported the effect of processing parameters on natural fibre/polymer composites. For instance, Thitithanasarn et al.⁴ studied the effect of moulding time with processing temperatures of 270 and 290°C on the mechanical properties of Jute fabric-reinforced sandwich composites fabricated with engineering thermoplastics. They also concluded in their study that it was feasible to process jute fibre filled engineering polymer composites at high temperature provided the exposure time during processing is within the safe limit and should not exceed 3 min. El-Shekeil et al.¹⁷ studied the effect of different processing parameters such as temperature, time and speed on the tensile properties of thermoplastic polyurethane (TPU) reinforced short kenaf fibre composites and found that optimum values of 190°C, 11 min, and 40 r/min, of temperature, time and speed, respectively, gave the best tensile properties. Vogt et al.¹⁶ also obtained vast improved results with considerably reduction in processing times to only 3 min as a function of temperature. When processing engineering thermoplastic polymers, it is necessary that the processing temperature is high enough to be able to melt the thermoplastic material and to enable a relatively quick heat transfer throughout the whole structure for homogeneous mixing. The processing temperature should also be sufficiently high to reduce the viscosity of the molten thermoplastic polymer, so as to facilitate the incorporation process. However, the temperature should not be too high, to prevent the matrix from becoming too fluid, which would make a controlled matrix flow more difficult and further extend drying time.

The processing temperature of the natural fibre-reinforced thermoplastics is limited due to the potential of fibre degradation at high temperatures. Therefore, polymer matrices that have been processed with natural fibres are limited to low melting temperature (commodity) thermoplastics such as polypropylene (PP), polyethylene (PE), poly vinyl chloride (PVC), polystyrene (PS) and poly (lactic acid) with melting points that are lower than the degradation temperature of the natural fibres.⁸ Kim and Park¹⁸ also reported that the thermal degradation is dependent on both temperature and time. They emphasized that the acceptable processing temperature should be that which is applied for only a short period of time. In another study, it was recommended that the time parameter needs to be well coordinated with the other values and preferably the processing time should be kept as short as possible, to reduce the cycle times and increase the efficiency of a production process.¹⁹

The use of epoxy coatings in improving thermal and mechanical properties has been successfully reported. These include natural kenaf fibres/high temperature engineering polyethylene terephthalate (PET) who pre-coated the fibres used in the preparation of their composites to improve the thermal resistance.^20,21 Furthermore, Saliu et al.²² incorporated epoxy coated-sodium hydroxide treated kenaf fibres into thermoplastics Acrylonitrile butadiene styrene (ABS) at processing temperature of 230°C and dynamically cured epoxy at high temperature (80°C) in order to prevent degradation. However, the researchers found that an optimum level of mechanical properties were obtained with epoxy coated fillers and concluded that epoxy coated bast kenaf fibre can be incorporated into higher temperature engineering thermoplastic ABS without degradation of the fibres.

Despite these breakthroughs in leather waste composites, and epoxy coating technology, epoxy-coating of leather wastes for composite preparation with high temperature polymers has not yet been reported, to the best of our knowledge. However, to solve the problem of leather fibre degradation at high processing temperature and further expand the scope of processing natural protein fibres for high temperature polymer composite applications, innovative techniques are required to reduce the gap between the processing temperatures of engineering polymers and the decomposition temperatures of leather fibres. Thus, this study seeks to study the effect of processing temperatures on the mechanical properties of developed novel epoxy-coated chrome tanned leather-based ABS composites.

Experimental

Materials

The waste chrome-tanned leather shavings and trimmings (LW) selected for use as filler in the investigation was obtained from a footwear and leather manufacturing industry in Malaysia. A commercial grade ABS polymer chips used as the matrix was obtained from Toray Plastics Malaysia Sdn. Bnd. Epoxy resin (diglycidyl ether bisphenol A, DGEBA)/hardener (polyamide) and Acetone (C₃H₆O) that were used for surface-coating of the leather were supplied by Oriental Option Sdn. Bhd and SYSTERM, respectively.

Methods

Epoxy surface-coating of leather fibres

The epoxy coating solution was prepared by mixing 50 g epoxy resin with 250 g acetone as diluent at an optimised weight ratio of 1:5 to give a viscosity of 6.6 cps. Thereafter, the hardener was incorporated into the coating solution at the ratio of 10:1 (epoxy coating solution: hardener). Subsequently, 30 g leather wastes were chopped into 5 cm length, washed with water, drained, neutralized and finally dried at 80°C for 1 h in an air oven. After cooling to ambient temperature, 27.08 g leather fibres were recovered, and soaked in the already prepared epoxy coating solution for 5 min. This activity was conducted in a controlled atmosphere to check the evaporation of acetone. At the end of the soaking process, the leather fibres were retrieved, re-weighed (38.25 g) and allowed to cure at a temperature of 80°C for 24 h in an air-circulated oven. Meanwhile, during the soaking of the leather fibres in the epoxy coating solution, there was absorption as well as adsorption of the coating solution by the leather fibres, and this is expressed as coating solution uptake as given in equation (1)²³

Coating solution uptake, % = (\frac{W_{a}}{W_{b}} - 1) X 100

(1)

where W_a and W_b are weight of the fibres after and before coating process, respectively.

Thereafter, the coated leather wastes (CLW) were further chopped into short fibres (5 mm) using a Fritsch Power Cutting Mill Pulverisette 15 pulverizing machine (product of Germany) and oven-dried at 40°C for 48 h. Later, the epoxy-coated leather wastes were stored in a desiccator prior to use as fillers for composites fabrication.

Composite compounding and fabrication

Compounding of epoxy-coated leather wastes (CLW) and uncoated leather wastes (LW) with ABS was done at an optimized constant fibre loading of 10 wt. % followed by melt-mixing and moulding in a twin-screw extruder (PRISM TSE SYSTEMS 2094, UK) and compression moulding machine (Hung Ta Instrument, Taiwan) at a varied extrusion and moulding temperatures of 200, 220 and 240°C, respectively. The extruder speed and dwelling time of 50 r/min and 5 min, respectively, were used throughout the extrusion process. The compression moulding pressure and time of 65 kg/m² and 5 min were also maintained constant, respectively. The extrudates were pelletized, dried at 80°C before compression moulding. Pre-heating and hot pressing times were 2 and 3 min, respectively. The sample sheet was then placed between two plates of a cold press to cool at 25°C for 5 min. The composites boards were cut for mechanical tests such as tensile and flexural tests.

Characterization

To establish the suitability of the developed chrome-tanned leather wastes-ABS composites for high strength and temperature applications, the thermal, mechanical and microstructural properties were assessed.

Thermal property assessment

The thermal property (glass transition, crystallization and melting temperatures) of the developed leather wastes-ABS composites was investigated by differential scanning calorimetry (DSC). This test was carried out using a NETZSCH DSC 200 F3 Maia model to study the glass transition, crystallization and melting temperatures behaviours of the uncoated (LW) and coated leather waste (CLW) fibres samples before melt mixing (extrusion) and their constituent composites with ABS (LWABS and CLWABS). This was done in accordance with ASTM D3418-82 standard on a heating run of 30–300°C and crystallisation step from 300°C down to 30°C at 10 °C/min.

Microstructural property investigation

The microstructural investigation which reveals the morphologies of LWABS and CLWABS composites samples were carried out using field emission scanning electron microscopy (FESEM) (ZEISS FE-SEM SUPRA 40VP Model, product of Germany) at a magnification of between 500 and 1000. Before examination, the samples were sputter-coated with a thin layer of platinum using a Quorum Sputter-Coater machine (Quorum model Q150RS, UK) in order to improve the surface conductivity and to prevent weak resolution from electrostatic charging.

Mechanical properties (Tensile and Flexural) testing

Mechanical properties of the developed leather wastes-ABS composites were measured according to ASTM D 638 and ASTM D 624 for tensile and three point bending flexural properties, respectively. Tensile testing was conducted using a Computer controlled Shimadzu autograph precision Universal Tester (Model AG-X Series, Japan). Five specimens were cut out using a band saw with dimension of 150 × 13 × 3 mm³ and were tested at a cross-head speed of 500 mm/min in a standard laboratory atmosphere of 23°C and 50% relative humidity. Flexural (three point bending) test was carried out using the same Universal Tester. Five specimens were cut out using a band saw with dimension of 150 × 13 × 3 mm³ and were tested with crosshead speed of 2 mm/min.

Results and discussion

Coating solution uptake

From the assay, the total weight of the coating solution was summed up to 330.00 g. It was also observed that after uptake of the coating solution by the leather fibres, 11.17 g of the coating solution was taken up by the fibres after 5 min. However, the uptake of epoxy coating solution by the leather wastes was estimated using equation (1). Thus, the uptake of epoxy coating solution by the leather fibres was estimated to be 41.25%. General observation of the uptake process shows that diffusion of coating solution into the fibre substance, and coating film formation on the fibre surface followed the mechanism suggested by Ghazter et al.²³

DSC thermal analysis

Differential Scanning Calorimetry (DSC) analysis of coated-leather waste fibres (CLW) and uncoated leather waste fibres (LW) is given in Figure 1, whereas the DSC results of coated-leather waste-ABS (CLWABS) and uncoated-leather waste-ABS (LWABS) are given in Figure 2. From Figure 1, it could be observed that the glass transition temperature (Tg) of LW which is defined by the onset temperature was found to be 128.2°C whereas 131.8 ^oC was observed as the Tg for CLW. Furthermore, the endothermic melting peak (melting temperature, Tm) for LW was observed to be 169.4°C.

Figure 1.

Differential scanning calorimetry thermograms of uncoated (LW) and epoxy-coated leather waste (CLW) fibres.

Figure 2.

Differential scanning calorimetry thermograms of coated (CLW-ABS) and uncoated (LW-ABS) leather waste short fibre filled ABS composites. ABS: Acrylonitrile butadiene styrene.

The endothermic melting peak temperature for CLW fibre was found to be 179.3°C. When compared to the LW fibres, it could be observed that the Tg and Tm of the epoxy-coated leather (CLW) fibres are higher. The reason could be due to effect of the epoxy coating on the leather wastes fibres. Furthermore, the reason for the observed lower thermal behaviour in LW is traceable to the fact that the protein content of leather has low melting temperature. Thus, the observed peak indicates the temperature point at which melting of leather fibres was maximum. For the CLW, it is important to note that epoxy resin contains hydroxyl groups throughout the backbone, and this may undergo crosslinking reactions.²⁴ Thus, epoxy-coating process could affect the interfacial properties of the leather fibres, stiffen the proteinous peptide chains as well as create a barrier that may require higher energy to disrupt.²⁵ Consequently, the thermal response of the CLW fibres became higher than the LW fibres.

Generally, from the DSC results obtained, it is observed that the epoxy-coated leather wastes (CLW) fibres have higher Tg and Tm compared to the uncoated LW fibres. This indicates that epoxy coating improved the thermal stability of LW fibres.²⁶

Figure 2 shows the DSC results of ABS, coated leather wastes-ABS (CLWABS) composite and uncoated leather wastes-ABS (LWABS) composites. In the Figure 2, the temperature responses of ABS, CLWABS and LWABS composites were given. ABS polymer has Tg of 101.2°C. The mixture of uncoated leather wastes fibres with ABS (LWABS) gave Tg of 89.1°C. However, when the epoxy-coated leather waste fibres were mixed with ABS (CLWABS), two interphases were formed (fibre-epoxy coating, and epoxy coating-ABS interphases). DSC thermal response of the CLWABS composite revealed a Tg of 94.9°C, showing a marginal increase when compared to the Tg for LWABS (89.1°C). The fact that ABS showed highest Tg could be due to effect of acrylonitrile and styrenic phenyl molecules present in ABS which might have caused steric hindrance, requiring higher thermal energy to effect molecular mobility.

When leather wastes were mixed with ABS (LWABS), the observed Tg could be due to the fact that during the mixture which involved shearing, it was possible that the shearing action disoriented the composition of ABS, and thus reduced the ab initio steric hindrance, resulting to the observed Tg. In addition, the fact that CLWABS showed a marginal increase could be attributed to effect of epoxy coating.²⁶ With increase in temperature, CLWABS and LWABS composites showed crystallization behaviours at 211.2°C and 220.1°C, respectively, after glass transition, indicating that the two composites contained both amorphous (from both ABS and leather fibres) and crystalline (from leather fibres) domains. It could be recalled that ABS does not exhibit true melting due to its amorphous nature. However, further observation of Figure 2 shows presence of exothermic peak at 232.7°C, which indicates enthalpy relaxation and curing.^27,28

The endothermic melting peak (Tg) for CLWABS was observed at 269.8°C, while 261.6°C was found to be the Tg for LWABS composite. The reason for the CLWABS composite having higher melting temperature than LWABS composite could be attributed to effect of epoxy-coating of the leather fibres as explained earlier. Considering the observed results, it could be concluded that CLWABS composite was more thermally stable compared to neat ABS and LWABS composite. The improved thermal stability of CLWABS composites is as a result of epoxy coating effects.

Tensile Properties

The tensile strength of neat ABS, epoxy-coated and uncoated leather fibres filled ABS composites are given in Figure 3. The tensile strengths of neat ABS, CLWABS and LWABS composites at a processing temperature of 200°C was found out to be 40.6 MPa, 36.5 MPa and 34 MPa, respectively. This shows that at 200 ^oC, the tensile strength of uncoated leather waste fibres filled ABS was quite lower than that of the ABS. But when the leather waste fibres were epoxy-coated, the resulting CLWABS composites showed an increase in the tensile strength. At higher processing temperature of 220 ^oC, the tensile strengths of coated CLWABS and uncoated LWABS composites were found to be 35.8 MPa and 34.4 MPa, respectively. When the processing temperature was increased to 240 ^oC, the tensile strengths were observed to be 34.3 MPa and 32.3 MPa, respectively, for CLWABS and LWABS composites. Generally, it could be seen in Figure 3 that the tensile strength of both coated and uncoated leather wastes fibres composites gradually decreased with increasing processing temperature from 200 to 240°C. The fact that ABS exhibited tensile strength values higher than those of CLWABS and LWABS composites confirms the amorphous nature of ABS.

Figure 3.

Effect of processing temperature on the tensile strength of ABS, coated and uncoated leather waste short fibres filled ABS composites. ABS: Acrylonitrile butadiene styrene.

However, coated CLWABS composites showed higher tensile strength when compared to the uncoated leather wastes fibres-ABS composites, LWABS. This was due to effect of the epoxy coating on leather wastes fibres which impregnated the fibre substance, and thus made them more compact and impervious to solvents, resulting in increased stiffness, hardness and rigidity which translated to higher tensile strength than the uncoated leather wastes fibres. Due to this improvement on the leather waste fibres, when they were mixed with ABS, there was increase in interfacial bonding between the coated leather waste fibres and ABS matrix. Again, the epoxy coating of leather waste fibres helped to distribute applied load or stress on the fibres, unlike when the same load or stress is applied on the uncoated fibres, there would be stress concentration due to uneven distribution of load.²⁹

The plot of tensile modulus against processing temperatures given in Figure 4 shows behaviour similar to that of tensile strength versus processing temperature. From the Figure 4, the neat ABS had a tensile modulus of 2752.2 MPa. With respect to the leather waste fibres-ABS composites, the CLWABS composites gave highest modulus of 2584.7 MPa at 200°C, and decreased to 2444.8 MPa and 2117.7 MPa with increase in temperature of 220°C and 240°C, respectively. Generally, the observed results have shown that tensile properties of both coated CLWABS and uncoated LWABS composites are optimum at 200 ^oC, and thereafter decreased with increase in processing temperature.

Figure 4.

Effect of processing temperature on the tensile modulus of ABS, coated and uncoated leather waste short fibres filled ABS composites. ABS: Acrylonitrile butadiene styrene.

Flexural properties

The results of flexural strength (Figure 5) and flexural modulus (Figure 6) of neat ABS, epoxy-coated and uncoated leather fibre filled ABS composites are shown. In Figure 5, the flexural strength of neat ABS, coated (CLWABS) and uncoated (LWABS) composites at a processing temperature of 200°C were found to be 61.3 MPa, 50.3 MPa and 48.4 MPa, respectively. It was observed that these flexural strength values decreased gradually as the temperature increased up to 240°C. This result showed similar decreasing trend with that obtained for tensile strength in Figure 3. When compared to the coated leather waste fibres-ABS (CLWABS), the flexural strength of neat ABS (61.3 MPa) showed a slight reduction by 17%, but displayed a 21% reduction when compared with uncoated (LWABS) composite, at 200°C. Similarly, the flexural modulus of the CLWABS and LWABS composites were observed to decrease with increase in processing temperature (see Figure 6). The results are validated by our previous finding where there was a slight decrease in impact strength upon addition of fillers at a constant processing temperature of 200°C.²⁰ Similar observation was reported by Talib et al. with composites of short leather fibre reinforced unsaturated polyester composites.³⁰

Figure 5.

Effect of processing temperature on the flexural strength of ABS, coated and uncoated leather waste short fibres filled ABS composites. ABS: Acrylonitrile butadiene styrene.

Figure 6.

Effect of processing temperature on the flexural modulus of ABS, coated and uncoated leather waste short fibres filled ABS composites. ABS: Acrylonitrile butadiene styrene.

Nonetheless, it was observed that the flexural strength and modulus of coated fibre composites (CLWABS) were superior to the uncoated composites (LWABS). Maximum flexural strength and modulus of 50.3 MPa and 2365.0 MPa, respectively, were obtained at 200°C for coated fibre CLWABS composites, which indicates that 200°C is considered as the optimized processing temperature at which the composites performed better. However, the strength and modulus of all the constituent composites generally decreased with increase in processing temperature from 200°C to 240°C. Flexural strength values obtained at 240°C were generally low as compared to those obtained at processing temperature of 200°C. Interestingly, El-Shekeil et al.¹⁷ reported similar observation on the effect of processing temperature on tensile properties of TPU/Kenaf composites using three different temperatures of 180, 190, and 200°C. They found that processing temperatures lower than 180°C were lower than the melting temperature, and thus, inadequate for homogeneous mixing of fibres and polymer matrix. Further, in their report, processing temperature of 190 ^oC was considered adequate and optimum, and therefore ensured better interfacial bonding.

It is worth noting that, from the flexural properties analyses results obtained, surface coating of leather fibres with thermoset epoxy resin prior to incorporation with engineering thermoplastic polymer improved the flexural properties of the composites. The uncoated LWABS composites showed inferior flexural properties as a result of fibre degradation at high processing temperature. Other researchers have reported various significant improvements in mechanical properties with epoxy coated fibre filled engineering composites.^4,20,21,23 They concluded that flexible or diluted epoxy resin is considered useful for surface modification in enhancing the mechanical properties of natural fibre filled engineering thermoplastic polymer composites.

Microstructural property

In order to understand the cohesive interaction between the leather waste fibres and the ABS matrix after tensile properties analysis, microstructural analysis was performed by scanning electron microscopy (SEM) on the coated leather wastes-ABS (CLWABS) and uncoated leather waste-ABS (LWABS) composites at processing temperatures of 200, 220 and 240°C. The results are given in Figure 7.

Figure 7.

SEM micrographs of epoxy-coated leather waste fibres-ABS (CLWABS) and uncoated leather waste fibres-ABS (LWABS) composites at processing temperature of 200, 220 and 240°C. ABS: Acrylonitrile butadiene styrene.

The CLWABS composites processed at 200 ^oC shows the coated leather waste (CLW) fibres were well wetted by the ABS matrix. As the processing temperature increased to 220 ^oC, the wettability of the fibres by the matrix decreased as revealed by protrusion of the fibres. Further increase in processing temperature up to 240 ^oC shows corresponding decrease in wettability of the fibres by the ABS matrix. This is due to the fact that viscosity of polymer matrix decreases with increase in temperature.

As for the uncoated leather waste fibre (LWABS) composites, the poor wettability of the fibres and the associated lack of cohesion can be visibly observed in Figure 7. The lack of cohesion was observed to increase with increase in processing temperature. The interfacial bonding between the uncoated fibre and ABS matrix was observed to be weak, and this was adjudged to be the reason for the low mechanical properties depicted by the LWABS composites. The SEM results also revealed evidence of fibre pullout from the matrix due to the weak fibre/matrix interface. The observed good interfacial adhesion between the coated leather fibres and the ABS matrix was ascribed to be responsible for the better mechanical properties they have over the uncoated leather waste fibres-ABS composites.

Conclusion

The effect of processing temperatures on the thermal and mechanical properties of epoxy-coated and uncoated chrome-tanned leather waste short fibre filled ABS composites at different extrusion processing temperatures was studied. The epoxy-coated leather waste short fibres filled ABS (CLWABS) and uncoated leather waste fibres (CLWABS) composites were processed at varying temperatures of 200, 220 and 240°C. The results obtained showed that the mechanical properties of the polymer composites decreased as the processing temperature increased. Epoxy-coated leather fibre filled ABS composites CLWABS yielded superior thermal and mechanical properties compared to the uncoated LWABS composites. The Differential Scanning Calorimetry (DSC) studies revealed that the epoxy-coated leather waste (CLWABS) composite showed higher Tg and Tm of 94.9 and 269.8°C, respectively, than the uncoated leather wastes (LWABS) composite with Tg and Tm of 89.1 and 261.6°C, respectively. An optimized processing temperature of 200°C was established. The field emission scanning electron microscopy (FESEM) studies revealed strong fibre/matrix interfacial bonding between coated leather fibres and ABS matrix while the uncoated LWABS composites revealed evidence of poor interfacial adhesion. The obtained results have demonstrated that epoxy-coated chrome-tanned leather waste fibres could be utilized to develop high strength and thermally stable polymer composites that could be utilized for load-bearing engineering applications. In addition, this study is so important because it can help in addressing the problem of environmental pollution caused by leather wastes.

Footnotes

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) disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: This work was supported by the authors are grateful for the research support from Centre of Polymer Composites Research and Technology (PoCresT), Institute of Science (IOS), Universiti Teknologi MARA (UiTM). Shah Alam Malaysia.

ORCID iD

Innocent O Arukalam

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Effect of processing temperatures on the thermal and mechanical properties of leather waste-ABS composites

Abstract

Keywords

Introduction

Experimental

Materials

Methods

Epoxy surface-coating of leather fibres

Composite compounding and fabrication

Characterization

Thermal property assessment

Microstructural property investigation

Mechanical properties (Tensile and Flexural) testing

Results and discussion

Coating solution uptake

DSC thermal analysis

Tensile Properties

Flexural properties

Microstructural property

Conclusion

Footnotes

Declaration of conflicting interests

Funding

ORCID iD

References