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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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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Effect of infill pattern on mechanical properties of 3D printed PLA and cPLA

2020-11-24 , Yeoh C.K. , Cheah C.S. , Pushpanathan R. , Song C.C. , Tan M.A. , Teh Pei Leng

PLA are the most sustainable alternatives and can fit in a wide-range of applications of electronics, nonwoven fabrics and food packaging. With these PLA's adaptability and suitability in many techniques of production such as injection moulding, extrusion, and blow moulding, PLA has become high interest in the production process. Besides, PLA as a thermoplastic polyester that mostly obtained from renewable materials [1]. Infill patterns can affect the mechanical properties of 3D printed PLA and cPLA. PLA with zig zag infill pattern has higher tensile strength of 23.409 MPa compared to PLA with grid and concentric infill pattern. Meanwhile, cPLA with grid infill pattern has higher tensile strength of 30.5638 MPa compared to cPLA with concentric and zig zag infill pattern. By using the suitable infill pattern parameter, the 3D printed PLA and cPLA can have good mechanical properties and can be applied in packaging, pharmaceuticals, textiles, automotive, biomedical and tissue engineering. It has been widely investigated for biomedical applications due to its biodegradability and biocompatibility.

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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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The effect of coated calcium carbonate using stearic acid on the recovered carbon black masterbatch in low-density polyethylene composites

2023-01-01 , Leow V.J. , Teh Pei Leng , Yeoh C.K. , Nor Azura Abdul Rahim , Wong W.C. , Voon Chun Hong , Mohamed Rasidi M.S. , Lim Bee Ying

This research focuses on recycling rubber tire waste through pyrolysis to produce recovered carbon black (rCB). The rCB is combined with recycled low-density polyethylene (rLDPE), calcium carbonate (CaCO3), fatty acid, metallic stearate, and polyethylene (PE) wax to create an rCB masterbatch for household packaging. Surface modification of CaCO3 particles using stearic acid improves the compatibility with LDPE. The study investigates mechanical properties, morphology, melt flow index (MFI), X-ray diffraction, and thermogravimetric analysis in three systems: uncoated, coated, and a hybrid combination of coated and uncoated CaCO3 in LDPE/rCB masterbatch composites. The coated system demonstrates higher mechanical properties and improved compatibility between CaCO3 and LDPE. All three systems exhibit enhanced thermal stability and MFI compared to virgin LDPE, with the coated system showing the most significant improvement. The study showcases the potential of LDPE/rCB masterbatch composites for household packaging, with the coated system displaying the optimum performance across various characteristics.

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The influence of liquid silicone rubber on the properties of polyurethane elastomer/liquid silicone rubber/graphene nanoplatelets stretchable conductive materials

2022-11-01 , Heng C.W. , Teh Pei Leng , Nor Azura Abdul Rahim , Yeoh C.K.

This work reports the influence of liquid silicone rubber (LSR) as a secondary matrix in the polyurethane elastomer (PUE)/LSR/graphene nanoplatelets (GnPs) stretchable conductive materials. PUE was prepared by mixing with diphenylmethane-4,4-diisocyanate (MDI) and 1,4 butanediol (BDO). The content of LSR varied from 0 to 50 vol.% at fixed 1.0 vol.% of graphene nanoplatelets (GnPs) as a conductive filler. Liquid silicone rubber was used as the secondary immiscible phase to localize GnPs into a path in the primary phase in order to obtain higher electrical conductivity value. The tensile strength of the PUE/LSR/GnPs decreased with increasing LSR content, while the tear strength shows the optimum value at 10 vol.% of LSR. The incorporation of 20 vol.% of silicone rubber has proven to enhance the thermal stability of the blends.

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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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Mechanical properties and thermal and electrical conductivity of 3D printed ABS-copper ferrite composites via 3D printing technique

2022-01-01 , Hamzah K.A. , Yeoh C.K. , Mazlee Mohd Noor , Teh Pei Leng , Aw Y.Y. , Sazali S.A. , Wan Mohd Arif W Ibrahim

This study examines the effect of particulate reinforcement on the mechanical properties of 3D printed acrylonitrile–butadiene–styrene (ABS). Copper ferrite (CuFe2O4) as a reinforcer with various loadings was used to print ABS composite specimen, namely, 8, 11 and 14 wt%. Mechanical testing such as tensile test and hardness test was performed on the printed samples. Specimens with 14 wt% of CuFe2O4 showed a 135% increase in tensile strength compared to the pure ABS specimens. Specimens printed with 14 wt% of CuFe2O4 are 14% harder compared to the pure ABS specimens. Thermal conductivity increased 93% for specimen loaded with 14 wt% reinforcer. Electrical conductivity shows a one-order increase for composite specimen compared to control specimen.

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UV Modified Epoxy for LED Encapsulant

2020-06-16 , Cheah L.B. , Heng C.W. , Ng S.Y. , Teh Pei Leng , Prabakaran A/L Poopalan

Light Emitting Diode (LED) packaging is important for the protection and enhancement of light extraction efficiency in LED. The most commonly used encapsulant is epoxy resin, which is the annealing cured. Multilayer time delayed aging of the epoxy resin causes delamination during packaging process. Ultraviolet (UV) modification is introduced in the curing process of epoxy resin to enhance the curing process of the epoxy. In this paper, the samples tested are either modified with UV or vice versa. Differential Scanning Calorimeter (DSC) is used for the analysis of the sample. Six samples are tested. Data analysis is based on the heat of reactions between the mixed materials; either the process is exothermic or endothermic when the temperature changes. The reaction between the materials determines its ability to crosslink, viscosity and temperature control for the whole reaction.

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