Yeoh Cheow Keat
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Preferred name
Yeoh Cheow Keat
Official Name
Cheow Keat, Yeoh
Alternative Name
Yeoh, C. K.
Yeoh, Cheow Keat
Yeoh, Cheow-Keat
Main Affiliation
Scopus Author ID
16231574200
Researcher ID
EGP-0633-2022

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Mechanical and electrical performances of different silicone rubber content in polyurethane elastomer/silicone rubber/graphene nano-platelets conductive material

2021-07-21 , Heng C.W. , Teh Pei Leng , Nor Azura Abdul Rahim , Yeoh Cheow Keat

Immiscible polyurethane elastomer (PUE)/silicone rubber/graphene nano-platelets blend composites filled with different PUE/silicone rubber blend ratio were synthesised by using solution casting technique. In this work, two different types of silicone rubber: liquid silicone rubber (LSR) and powdered silicone rubber (PSR) were used as secondary matrix based on double percolation concept to construct an immiscible blend that has a balance electrical conductivity and mechanical properties. The electrical conductivity has increased gradually, but the mechanical properties of the composites shows a remarkable decline when silicone rubber loading increases up to 20 vol% for both blend systems. The well balance of electrical conductivity and performance is achieved at 15 vol.% of silicone rubber loading. Overall, PUE/PSR/GnPs at 15 vol. % of silicone rubber content has higher electrical conductivity and mechanical strength as compared to PUE/LSR/GnPs blend system.

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Microwave welding of thermoplastic using silicon carbide nanowhiskers as susceptor effect of heating duration

2024-06 , Phey Yee Foong , Voon Chun Hong , Lim Bee Ying , Teh Pei Leng , Yeoh Cheow Keat , Mohd Afendi Rojan , Nor Azizah Parmin , Subash Chandra Bose Gopinath , Foo Wah Low , Muhammad Kashif , Nor Azura Abdul Rahman , Sam Sung Ting , Veeradasan Perumal

Microwave welding is becoming more popular than conventional joining methods due to its advantages such as rapid and localised heating as well as applicable to components with complicated geometry. Previously reported susceptor, such as carbonaceous materials and conductive polymers, are toxic and the welding process involving these susceptors is time-consuming. Because of its exceptional microwave absorption and biocompatibility, silicon carbide nanowhiskers (SiCNWs) was employed as the microwave susceptor for microwave welding. Microwave welding in this study comprises of only three simple steps: SiCNWs suspension preparation, SiCNWs application and microwave heating. The weld strength of welded joint was then characterised using tensile test and energy dispersive x-ray spectroscopy equipped scanning electron microscopy (EDS-SEM) to study its mechanical properties and cross-section microstructure. The influence of microwave irradiation time was studied in this study, and it is found that the weld strength rose with the extension of microwave irradiation time, until a maximum weld strength of 1.61 MPa was achieved by 17 s welded joint. The development of SiCNWs reinforced PP nanocomposite welded joint layer is responsible for the enhanced weld strength. Prolonged heating duration may also result in flaws such as void formation at the welded joint, which subsequently lowered the weld strength to 0.60 MPa when the heating duration was extended to 20 s. In sum, a strengthen welded joint can be formed with rapid microwave heating under the proper control of heating duration.

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Investigation of blend ratios on physical, mechanical, and electrical properties of stretchable conductive ternary blend NRLVSR materials unfilled and filled system

2025-01 , Wern-Ming Che , Teh Pei Leng , Jalilah Abd Jalil , Yeoh Cheow Keat , Mohamad Nur Fuadi Bin Pargi

Stretchable conductive material has garnered significant attention in recent years since it offers both electrical conductivity and the ability to undergo significant deformation without losing its conductivity. Herein, NRL/VSR blend materials were prepared with varying blend ratios, both with and without GNP-SDS, using a simple mechanical stirring method. The main objective was to investigate the influence of blend ratios on the physical, mechanical, and electrical properties of the unfilled and filled blend systems. The findings revealed that the addition of VSR had a detrimental effect on the crosslink density of the resulting materials, leading to a negative impact on their mechanical properties. However, a contrasting observation was made regarding the electrical properties. The introduction of VSR induced the formation of a double percolation structure in the immiscible NRL/VSR blend. This double percolation structure facilitated the creation of a conductive network within the blend, which significantly improved its electrical properties by approximately 263.85 folds.

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Dielectric and mechanical properties of PLA-carbon composites

2024-04 , Mathanesh Thangarajan , Yeoh Cheow Keat , Teh Pei Leng , Wee Chun Wong , Chong Hui Yew , Kang Zheng Khor , Nor Azura Abdul Rahim , Voon Chun Hong

This study focuses on the development and characterization of Carbon-based Polylactide (PLA) composites for 3D printer filaments. The aim is to enhance the electrical and mechanical properties of PLA by incorporating recovered carbon black (RCB) in different mesh sizes (500, 1000, 1500, and 2000 mesh). Electrical impedance spectroscopy and dielectric constant measurements were performed to investigate the electrical properties of the composites. Results showed that the addition of RCB increased the dielectric constant, with values ranging from 2.5 to 7.1, indicating improved electrical performance. Scanning electron microscopy (SEM) analysis revealed the dispersion of carbon particles within the composites, enhancing their electrical conductivity. The effect of RCB particle size on electrical properties was also explored, with smaller particle sizes (2000 mesh) resulting in the highest conductivity of 6.2 S/m. Tensile testing demonstrated that the addition of RCB increases the tensile strength of PLA, with values ranging from 28.6 MPa to 47.2 MPa, and the elastic modulus, ranging from 832 MPa to 1.56 GPa, depending on the mesh size. The optimal combination of RCB content and mesh size resulted in a composite with a tensile strength of 43.8 MPa. Overall, this research provides insights into the development of Carbon-based PLA composites with improved electrical and mechanical properties.

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Properties of epoxy/LNR foam using sodium bicarbonate as a gas generator

2022-05-18 , Hussein M.S. , Teh Pei Leng , Zainuddin F. , Rahmat A.R. , Yeoh Cheow Keat

A series of porous epoxy foams toughened by liquid natural rubber (LNR) were fabricated by sodium bicarbonate (SB) as chemical foaming agent and finding the optimal composition ensuring both high porosity and mechanical strength. In this research, we studied the properties of epoxy foam by adding LNR as toughening agent in contents of (5 to 25 vol%) with adding 15 phr of SB as an optimal content foaming agent. The flexural, fracture toughness, compression, cross-link density, morphology and thermal stability properties of epoxy foam was characterized. Cellular plastics keep mechanical strength loss and plastic weight to a minimum through cells inside the foam. Increasing the content of LNR retarded the crosslinking reaction by increasing the expansion and affected the mechanical strength. A suitable expansion and mechanical strength were observed for epoxy-foam containing 10 to 15 vol% LNR. Densities of the foams can be tuned in a range of up to 0.760 g/cm3 by changing the content of LNR from 5 to 25vol%. The compressive strength was decreased from 8.62 and 4.15 MPa.

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Effect of silicone rubber on the properties of epoxy/recovered carbon black (rCB) conductive materials

2024-04 , Pei Chee Leow , Teh Pei Leng , Yeoh Cheow Keat , Wee Chun Wong , Chong Hooi Yew , Xue Yi Lim , Kai Kheng Yeoh , Nor Azura Abdul Rahim , Voon Chun Hong

The primary focus of this study is to investigate the effect of silicone rubber (SR) content on the mechanical, thermal, electrical conductivity, and morphological properties of epoxy/recovered carbon black (rCB) conductive material. The conductive material is used to produce the electrostatic discharge (ESD) tray for the electronic packaging industry. This study investigated the effect of silicone rubber content (0, 5, 10, 15, and 20 vol.%) on the properties of epoxy/SR/rCB conductive materials, with the rCB content fixed at 15 vol.% for its optimum electrical conductivity. The silicone rubber acts as a toughening agent for epoxy. Through the fracture toughness result, it can be identified that silicone rubber plays a role in improving the toughness properties of the epoxy/SR/rCB conductive material. The optimum results for mechanical properties were recorded at 5 vol.% SR. The addition of SR to the epoxy matrix enhances the electrical properties of the epoxy/SR/rCB conductive material. The effect of thermal aging on epoxy/SR/rCB conductive materials was also studied to determine the properties of the conductive material materials at high temperatures for a long period of time. After thermal aging, the mechanical, thermal, electrical conductivity, and morphological properties of the epoxy/SR/rCB conductive material were slightly reduced.

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A comparative study of microwave welding using multiwalled carbon nanotubes and silicon carbide nanowhiskers as microwave susceptors

2024-10 , Phey Yee Foong , Voon Chun Hong , Lim Bee Ying , Teh Pei Leng , Yeoh Cheow Keat , Mohd Afendi Rojan , Nor Azizah Parmin , Subash Chandra Bose Gopinath , Foo Wah Low , Muhammad Kashif , Nor Azura Abdul Rahman , Sam Sung Ting , Veeradasan Perumal

Recently, microwave welding has arisen as an advanced joining method due to its versatility and rapid heating capabilities. Among others, microwave susceptors play a crucial role in microwave welding, as different classes of microwave susceptors have distinct microwave heating mechanisms. In this work, polypropylene (PP) was utilized as a thermoplastic substrate and two types of microwaves susceptors, namely multiwalled carbon nanotubes (MWCNTs) and silicon carbide nanowhiskers (SiC NWs), were studied for microwave welding. The susceptor was first dispersed in acetone to form susceptor suspension. Next, the susceptor suspension was deposited onto the targeted area on substrate and paired with another bare PP substrate. The paired sample was then exposed to 800 W microwave radiation in a microwave oven. Afterward, the welded joint was evaluated using a tensile test and scanning electron microscopy to determine its joint strength and cross-section microstructure. The results showed that the joint strength increased as the heating duration increased. The welded joint formed using MWCNTs achieved a maximum strength of 2.26 MPa when 10 s was used, while the SiC NWs-formed welded joint achieved a maximum strength of 2.25 MPa at 15 s. This difference in duration in forming a complete welded joint can be attributed to the higher microwave heating rates and thermal conductivity of MWCNTs. However, increasing the heating duration to 20 s caused severe deformation at the welded joint and resulted in low joint strength. Overall, this study highlights the significance of understanding the microwave heating mechanism of different susceptors and provides essential insight into the selection of a microwave susceptor for microwave welding.

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Effect of printing parameters on tensile, dynamic mechanical, and thermoelectric properties of FDM 3D printed CABS/ZnO composites

2018-03-22 , Yah Yun Aw , Yeoh Cheow Keat , Mohd Asri Idris , Teh Pei Leng , Khairul Amali Hamzah , Shulizawati Aqzna Sazali

Fused deposition modelling (FDM) has been widely used in medical appliances, automobile, aircraft and aerospace, household appliances, toys, and many other fields. The ease of processing, low cost and high flexibility of FDM technique are strong advantages compared to other techniques for thermoelectric polymer composite fabrication. This research work focuses on the effect of two crucial printing parameters (infill density and printing pattern) on the tensile, dynamic mechanical, and thermoelectric properties of conductive acrylonitrile butadiene styrene/zinc oxide (CABS/ZnO composites fabricated by FDM technique. Results revealed significant improvement in tensile strength and Young's modulus, with a decrease in elongation at break with infill density. Improvement in dynamic storage modulus was observed when infill density changed from 50% to 100%. However, the loss modulus and damping factor reduced gradually. The increase of thermal conductivity was relatively smaller compared to the improvement of electrical conductivity and Seebeck coefficient, therefore, the calculated figure of merit (ZT) value increased with infill density. Line pattern performed better than rectilinear, especially in tensile properties and electrical conductivity. From the results obtained, FDM-fabricated CABS/ZnO showed much potential as a promising candidate for thermoelectric application.

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The effect of the GNP-SDS loadings on the properties of the NRL/GNP-SDS composites

2020-07-09 , Che W.M. , Teh Pei Leng , Jalilah Abd Jalil , Yeoh Cheow Keat

Stretchable conductive polymer composites (CPC) are fabricated by incorporating the conductive particles into the polymer matrix. In this paper, CPC was fabricated by incorporating the sodium dodecyl sulfate (SDS) modified graphene nanoplatelet (GNP) into natural rubber latex (NRL) by varying loading from 0phr to 9phr using a simple mechanical stirring method. The effect of the GNP-SDS loadings on the properties of the composites were study by investigated the crosslink density, tensile properties, morphology of the tensile fracture surface and electrical conductivity. The crosslink density of the composites shows a decreased trend. Then, due to the well dispersed GNP-SDS, the tensile strength increased but decreased at high filler loading caused by the agglomeration issue. The tensile modulus also increased with increasing filler loading due to the intrinsic high modulus of GNP and the reduction of chain mobility. However, the electrical properties of the composites improved as GNP-SDS loading increased and achieved a percolation threshold at 7phr.

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Comparison study: The effect of unmodified and modified graphene nano-platelets (GNP) on the mechanical, thermal, and electrical performance of different types of GNP-filled materials

2021-09-01 , Ka Wei K. , Teh Pei Leng , Yeoh Cheow Keat , Hakimah Osman , Sullivan M. , Voon Chun Hong , Lim Bee Ying , Mohamad Syahmie Mohamad Rasidi

Graphene nano-platelet (GNP) nano-fillers were successfully covalently functionalized with carboxylic and epoxide groups as proven by Fourier-transform infrared spectroscopy. This paper reports the effect of unmodified and modified GNP nano-fillers on the mechanical, thermal, and electrical performance of GNP-filled materials. The results show that the mechanical properties of GNP-filled materials were enhanced with a modified GNP nano-filler. Among the GNP-filled materials, the modified epoxy/NR/GNP compatibilized material shows higher flexural and toughness properties. The modified GNP nano-filler has reduced the thermal stability of the modified compatibilized material. This is because the oxygen-containing groups (C–O–C and –COOH) on the surfaces of modified GNP nano-fillers have lower thermal stability; which accelerates the thermal decomposition of the modified material. Modified compatibilized material shows higher electrical conductivity than the unmodified compatibilized material. X-ray diffraction results proved that d-spacing of modified GNP nano-fillers in modified compatibilized material was shortest when compared to unmodified GNP nano-fillers in unmodified compatibilized material, thus, allowing more electrons to travel at a faster rate through the conductive pathways.

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