Teh Pei Leng
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Preferred name
Teh Pei Leng
Official Name
Teh. Pei Leng
Alternative Name
Leng, T. Pei
Leng, T. P.
Teh, P. L.
Leng, Teh Pei
Main Affiliation
Scopus Author ID
6701800182

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Thermal Degradation of Photoluminescence Poly(9,9-dioctylfluorene) Solvent-Tuned Aggregate Films

2022-04-01 , Chew K.W. , Nor Azura Abdul Rahim , Teh Pei Leng , Abdul Hisam N.S. , Alias S.S.

The progression of the green emission spectrum during the decomposition of polyfluorenes (PFs) has impeded the development and commercialization of the materials. Herein, we constructed a solvent-tuned aggregated PFO film with the aim of retarding the material’s thermal degradation behavior which causes a significant decline in optical properties as a result of phase transformation. The tuning of the aggregate amount and distribution was executed by applying a poor alcohol-based solvent in chloroform. It emerges that at a lower boiling point methanol evaporates quickly, limiting the aggregate propagation in the film which gives rise to a more transparent film. Furthermore, because of the modulated β-phase conformation, the absorption spectra of PFO films were red-shifted and broadened. The increase in methanol percentage also led to a rise in β-phase percentage. As for the thermal degradation reactions, both pristine and aggregated PFO films exhibited apparent changes in the UV-Vis spectra and PL spectra. In addition, a 97:3 (chloroform:methanol) aggregated PFO film showed a more defined emission spectrum, which demonstrates that the existence of β-phase is able to suppress the unwanted green emission.

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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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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 Solvents on the Preparation of Poly(9,9-Dioctylfluorene) Thin Films

2022-01-01 , Chew K.W. , Nor Azura Abdul Rahim , Teh Pei Leng , Abdul Hisam N.S.

The optoelectronic properties of Poly(9,9-dioctylfluorene) (PFO) are highly influenced by the existence of a well-defined chain extended “β-phase” conformational isomer. This study aims to evaluate the produced PFO films optical properties. Pristine PFO films and aggregated PFO films were fabricated by the solvent casting method. PFO was first dissolved in chloroform and toluene separately. Meanwhile, for aggregated film, different percentage of methanol (poor solvent) was added to the PFO solution to induce β-phase formation. UV-vis measurement and scanning electron microscopy were used to characterize the films. The results reveal that PFO was fully soluble in chloroform while moderately soluble in toluene. This result was further confirmed by micrograph; the PFO film prepared from chloroform exhibited glassy conformation. While for the aggregation system, the absorption spectra of β-phase becoming more intense as methanol content increase.

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The effect of cuznfe2o4 on mechanical properties and thermal conductivity of abs manufactured using 3d printer

2020-01-01 , Hamzah K.A. , Yeoh C.K. , Mazlee Mohd Noor , Teh Pei Leng , Sazali S.A. , Wan Mohd Arif W Ibrahim

The aim of this study is the development of the ABS-CuZnFe2O4 composites using 3D printer. In this study, the effect of filler loading on the mechanical properties and thermal conductivity is examined. The result shows that at highest filler loading (14 wt%) the tensile strength was improved approximately 98% while the Young’s modulus increased about 23% compared to unfilled specimen. Meanwhile, the percentage of elongation decrease approximately about 49% when filled with 14 wt% of filler. The CuZnFe2O4 filler shows a greater effect on hardness value of the composites around 498% at maximum filler content. The thermal conductivity of the ABS increased up to 60% at full capacity of filler.

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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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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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Effect of solvent on mechanical and physical properties of PMMA/Sic composite films

2024-12 , Auni Fakhira Che Baharudin , Lim Bee Ying , Voon Chun Hong , Teh Pei Leng , Tan Soo Jin

The selection of solvent in solution casting is crucial as it may affect the morphology and properties of the resulting composite films. In this study, the effect of solvent on the properties of poly(methyl methacrylate)/silicon carbide (PMMA/SiC) composite films was investigated. By using acetone, the solution casting was carried out at various solvent-to-solid (S/S) ratio, from 4:1 to 10:1 at room temperature. It was found that the increasing S/S ratio enhanced the tensile strength and modulus of elasticity of pristine PMMA films but deteriorated its elongation at break, up to 8:1 ratio. The crystallinity of the PMMA films was found to increase with S/S ratio, as confirmed by the higher peak intensity in X-Ray Diffraction (XRD) patterns and the SEM micrographs. In the second part of the study, by using S/S ratio of 8:1, the nano sized SiC (0.25 wt%) was added as a filler into PMMA and toluene with different ratio was added as a secondary solvent. The addition of SiC has increased the tensile strength and modulus of elasticity of PMMA/SiC but decreased its elongation at break. However, the presence of toluene reduced the tensile strength of the PMMA/SiC composite films and resulting in rougher tensile fracture surfaces as shown in SEM micrographs. The toluene with nonpolar nature had affected the distribution of SiC in PMMA. It can be concluded that the properties of the PMMA composites films can be tailored according to the needs of applications.

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Functionalized carbon black in epoxy composites: effect of single- and dual-matrix systems

2022-07-01 , Phua J.L. , Teh Pei Leng , Yeoh C.K. , Voon Chun Hong

Functionalized carbon black (CB) using three different surface modification methods: wet oxidation, epoxy monomer impregnation, and air oxidation, in single-epoxy composites and dual-matrix epoxy/poly(methyl methacrylate) PMMA composites at 15 vol% of CB content was studied in this research. The characterization on the surface modification CB was done via Fourier transform infrared spectroscopy, Brunauer–Emmett–Teller (BET), and thermal gravimetric analysis. The phenol or ether, carboxylic acid, and epoxide functional groups were found on CB after surface modifications, along with a change in structure and BET surface area. Thermal degradation of CB was different after surface modification. This study further investigated the effect of the addition of surface-modified CB into epoxy resin, where the state of dispersion and distribution was observed under scanning electron microscopy. After surface modification, the mechanical testing via flexural and fracture toughness was done, where improvement was observed. A minor decrease in the electrical bulk conductivity of the composites was measured, which was due to a reduction in the degree of agglomeration. Both the thermal stability and CTE of surface-modified CB-filled epoxy composites show a decrement. Graphic abstract: Chemical modification of CB using air oxidation, wet oxidation, and epoxy monomer impregnation methods.[Figure not available: see fulltext.]

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Preparation and Characterization of Tensile Properties of PMMA/SiC Nanowhiskers Nanocomposite Films: Effect of Filler Loading and Silane Treatment

2023-10-01 , Lim Bee Ying , Voon Chun Hong , Lee L.Y. , Teh Pei Leng , Foong P.Y.

The preparation of nanocomposites through melt mixing was challenging as the nanofillers tend to form agglomeration. The silicon carbide nanowhiskers (SiCNWs) filled poly (methyl methacrylate) (PMMA) thin film in this study was prepared by means of solution casting. Acetone with low toxicity was used as solvent to dissolve the PMMA pellets. A coupling agent, silane was used to enhance the properties of composite films. Besides, the untreated and treated SiCNWs were filled into PMMA matrix, respectively with the filler loading varied from 0.2 to 0.8 wt%. The universal testing machine was used to investigate the tensile properties of composites. It was found out that the tensile strength of the PMMA was reduced in the presence of SiCNWs. However, the tensile strength had increased with the rise of filler loading. At 0.8 wt% of SiCNWs, the composites’ tensile strength was comparable to virgin PMMA. Meanwhile, the SiCNWs had reduced the elongation at break but increased the elastic modulus of PMMA/SiCNWs nanocomposite films. In addition, silane surface treatment on SiCNWs had improved the tensile strength and ductility but lowered the elastic modulus of the nanocomposites. The improvement was due to the enhancement of interfacial adhesion between SiCNWs and PMMA.

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