Papers by Author: Azemi Samsuri

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Authors: Ummu Qani’ah Yasin, Dzaraini Kamarun, Che Mohd Som Said, Azemi Samsuri
Abstract: Blooming is a diffusion process whereby compounding ingredients dispersed in rubber matrix migrate to the rubber surface and appears as a layer of white crystalline material. Blooming is a typical phenomenon observed in rubber compounds which could lead to problems such as discoloration and poor appearance of products as well as loss of adhesion. Cause of blooming was still unclear and this research was carried out to identify the effect of compounding ingredients and crosslink concentration on blooming rate in natural rubber compounds. In this project 6 natural rubber formulations based on three different types of compounding ingredients at two different concentrations of crosslinker were compounded and tested for their blooming characteristics. Sulphur, wax and dithiocarbamate as the compounding ingredients were mixed with natural rubber in the presence of 1 and 6 phr of peroxide as the vulcanizing agents. The effect of crosslink concentration on blooming rate of the compounded rubber was then determined. The blooming rate was determined by the weight of the blooming material on the rubber surface as a function of time. The blooming rate was found to be affected by the types of compounding ingredients and crosslink density of rubber. Wax with 6 phr of peroxide showed the highest amount of bloom and the highest blooming rate while the dithiocarbamate accelerator with 1 phr peroxide showed the lowest amount of bloom and the lower blooming rate. As expected, all the compounding ingredients showed an increase of crosslink concentration as the loading of peroxide increases. The blooming rate was also found to be affected by the crosslink concentration of rubber. As the crosslink concentration increases, the rate of blooming increases as were shown by wax and dithiocarbamate accelerator. However, sulphur showed the opposite trend whereby the crosslink concentration increases but the blooming rate decrease. This could be due to the high peroxide level retarding the sulphur blooming process.
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Authors: Siti Aisyah Jarkasi, Dzaraini Kamarun, Azemi Samsuri, Amir Hashim Md Yatim
Abstract: Fillers play important roles in enhancing mechanical properties of NR latex films. The effect of filler dispersion and amount of dispersing agent to the tensile strength and tearing energy of NR latex films were investigated in this study. The studies were carried out by (i) varying the amount of dispersing agent (Anchoid) added which is an anionic surfactant; and (ii) varying the speed of stirring during mixing of latex with compounding ingredients. It was observed that tensile strength and tearing energy were affected by both factors listed. In the case of NR latex film filled with 10 pphr of carbon black (Super Abrasion Furnace, SAF), the optimum stirring speed was 400 rpm and the optimum amount of surfactant was in the range of 5 to 10 % by weight. High tensile strength ranging from 29 - 31 MPa and high tearing energies ranging from 90.6 - 111.0 kJ/m2 were achieved from optimization of these two factors; rendering their importance.
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Authors: Siti Zulaikha Ibrahim, Che Mohd Som Said, Mohamad Asri Ahmad, Azemi Samsuri
Abstract: In this study, several batches of natural rubber (SMR L) were compounded with three different types of accelerators, which were N-cyclohexylbenzothiazole-2-sulphenamide (CBS), diphenylguanidine (DPG) and zinc diethyldithiocarbamate (ZDEC). ZDEC is known as an ultrafast accelerator. The rubber compounds were cured at 140°C, 130°C, 120°C, 110°C and 100°C in accordance with the temperature gradients observed within the thick rubber block. The main aim of this study is to cure the rubber at each temperature region to the same cure time as that of the outermost region (20 minutes at 140°C). The amount of sulfur and accelerator were adjusted accordingly at each curing temperature to match the state of cure at 140°C. The state of cure of of the vulcanized rubbers were measured using hardness and tensile strength. The same state of cure is achieved if the hardness and tensile strength value are within ±2 IRHD and ±3 MPa, respectively with that of the control vulcanized rubber (hardness and tensile strength cured at 140°C). The results shows that the hardness and tensile strength of the vulcanized rubber at each temperature region are within the expected margins. The results clearly indicated that the type and amount of accelerators, and the amount of sulfur were correctly chosen at each temperature.
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Authors: Hambali Raden Siti Amirah, Mohd Ahmad Faiza, Azemi Samsuri
Abstract: Non-isocyanate polyurethane (NIPU) was synthesized from epoxidized linoleic acid (ELA) from rubber seed oil. In this study, carboxylation method was used to synthesize a new monomer, carboxylated linoleic acid (CLA) to produce urethane inter-linkage polymer. ELA with tetrabutylammonium bromide (TBABr) as catalyst was purged with carbon dioxide as gas reactant. Pressure and temperature reactions were controlled at 10 psi and 150 °C. CLA was mixed with ethylenediamine (EDA) and the viscous mixture was cured in a covered mold in an oven at 100 °C and curing was performed after 12 hours. Tacky test was done to evaluate the curing. The initial epoxy value of ELA was 7.36 % and it was observed during synthesis to reduce via Oxygen Oxirane Content test, which illustrated the conversion of ELA to CLA. The formation of epoxy group in ELA to carboxylate functional group in CLA was characterized using Fourier Transform Infrared (FTIR) at absorption peak of 1803.69 cm-1 that represent cyclic carbonate group. H-NMR was used to support the characterization of ELA and CLA.
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