Azemi Samsuri

Puncture resistance of natural rubber latex unidirectional coated fabrics

A study was conducted on the puncture resistance of high-strength nonwoven natural rubber latex (NRL)-coated fabrics. High strength unidirectional (UD) polyethylene fabrics were coated using single dipping (SD), double dipping (DD), and triple dipping (TD) methods. The puncture resistance of the uncoated and coated fabrics was determined by measuring the force needed to penetrate the fabrics using a blunt probe. The mechanisms and modes of deformation involved during penetration were observed as well. In comparison with the uncoated fabrics, the SD, DD, and TD NRL coated fabrics gave higher puncture resistance of 39%, 47%, and 62%, respectively. The increments of the penetration force were proportional with the increase in the NRL-coated fabric thickness. For the uncoated fabric, the force given by the probe resulted in yarns stretching and yarn slippage upon penetration. However, the NRL-coated fabrics were not severely damaged but resulted in a curvature formed at the frontface of the fabric with minimal backface deformation. From the observations, the modes of failure were similar among the NRL-coated fabrics, that is, fiber stretching, delamination of NRL layer, and stretch marks on the fabric surface. The NRL layer acted as a protective sheath and increases the energy absorption and elasticity characteristics of the UD fabric.

Quasi-static puncture resistance of unidirectional coated fabric

High strength nonwoven fabric in the form of unidirectional structure are being used in ballistic protection applications due to their light weight and flexibility. In this study, natural rubber latex (NRL) was used as a coating material on unidirectional fabrics. It was found that the mechanical properties of the NRL coated unidirectional fabrics can be improved by adding fillers in the NRL compounding. Multiwall carbon nanotubes (MWCNTs) dispersion in several concentrations of 3 wt%, 5 wt% and 7 wt% were added into the NRL. The effects of filler loading of the MWCNTs in NRL were investigated under quasi-static penetration resistance test. In general, it was shown that the forces needed to penetrate the NRL coated fabric increases with higher content of filler loading and were higher in comparison with uncoated fabric. The NRL coated unidirectional fabrics with 7 wt% MWCNTs gave about 44% higher penetration resistance in comparisons with uncoated fabric. Several modes of fabric failure were observed after the quasi-static penetration resistance such as yarn stretching, yarn breakages as well as peeling off of NRL layer.

A new material for flexible antennas

This paper reports for the first time, the use of natural rubber as a substrate in the design of flexible antennas. Three inset feed patch antennas with different dimensions were simulated to resonate for 8 and 10 GHz. The rubber samples were prepared using two different amounts of carbon at 20 and 25 % to alter the dielectric properties. Investigations were done to understand the effects of natural rubber properties with the aim to facilitate efforts in flexible antenna design so that practical system requirements are met. The rest of this paper focuses on the effect of rubber properties on the antenna bandwidth, return loss and radiation patterns. From the results, it was observed that increasing the filler content and frequency would increase the antenna losses, but enhances the bandwidth, gain and directivity. This implies that the performance of rubber-based antennas can be controlled by the dielectric properties of rubber.

A theoretical investigation on the effects of rubber filler content on flexible antenna performance

Fillers are used in natural rubber to improve their mechanical and electronic properties. This paper presents a study on the effects of filler on flexible antenna performance utilizing natural rubber as their substrate. CST Microwave Studio was used to simulate three antennas resonating at 2.45 GHz with different permittivity and loss tangent (tan δ). The dielectric properties of rubber were varied through its filler content and the type of filler used in this project was carbon black. Microwave characterization of rubber and a preliminary study on its use as the substrate of a flexible antenna have been reported recently by our group. Understanding the effects of filler content on rubber properties will facilitate efforts in flexible antenna design so that practical system requirements are met. In this paper we report new advancements found in this study with respect to the effect of filler content on antenna quality factor (Q) and its consequences on bandwidth and gain. From the simulation, the bandwidths for the antennas increased with filler content while the resonant frequency can be tuned in the same manner. Therefore, we have demonstrated the possibility of controlling antenna performance by adjusting filler content.

Synthesis and characterization of non-isocyanate polyurethane from epoxidized linoleic acid - A preliminary study

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.

Physical and mechanical properties of compounded hydroxylated natural rubber

In this study, oil resistance properties, tensile strength and hardness properties of compounded hydroxylated Natural rubber (OONR) were evaluated. Oil and oxidation natural rubber (OONR) exhibited shorter cure time compared to the SMR-L and EPDM and recorded better crosslinks density. The performance of OONR clearly dominated the unmodified NR in terms of swelling to hydrocarbon oils and non-polar solvents. The OONR also depicted an increasing trend in hardness compared to the unmodified NR. However, the tensile strength of OONR vulcanizate was drastically decreased compared to SMR-L and EPDM compounded rubber.

Cure characteristics and mechanical properties of different accelerator systems for thick rubber article

Curing thick rubber article may create temperature gradient across the thickness of the article. Therefore, this may cause in the difference of properties between the inner and outer region. Thus, the thick rubber article was divided into several regions with different type of accelerators in each layer in order to produce uniform cured thick rubber article. In this study, the effect of different accelerators on cure characteristics and mechanical properties of natural rubber vulcanizates for the thick rubber article was investigated. The types of accelerators that were selected are N-cyclohexylbenzothiazole-2-sulphenamide (CBS), zinc diethyldithiocarbamate (ZDC) and diphenylguanidine (DPG). The cure characteristics, such as scorch time and cure time were studied at temperature range of 100-140 °C. The scorch time for control vulcanizate (NR140) showed the highest value (4.5 minutes) as the sulphanamide-type of accelerators was used. The combination of different accelerators produced almost similar scorch time at lower curing temperature for other vulcanizates (NR130, NR120, NR110 and NR100). The tensile strength and hardness values of all vulcanizates were also found to have similarity as compare to control vulcanizate (NR140), regardless of the different in type of accelerators and curing temperature that was applied for each vulcanizate. These indicate that the thick rubber article is able to be cured uniformly with less variation in the mechanical properties.Curing thick rubber article may create temperature gradient across the thickness of the article. Therefore, this may cause in the difference of properties between the inner and outer region. Thus, the thick rubber article was divided into several regions with different type of accelerators in each layer in order to produce uniform cured thick rubber article. In this study, the effect of different accelerators on cure characteristics and mechanical properties of natural rubber vulcanizates for the thick rubber article was investigated. The types of accelerators that were selected are N-cyclohexylbenzothiazole-2-sulphenamide (CBS), zinc diethyldithiocarbamate (ZDC) and diphenylguanidine (DPG). The cure characteristics, such as scorch time and cure time were studied at temperature range of 100-140 °C. The scorch time for control vulcanizate (NR140) showed the highest value (4.5 minutes) as the sulphanamide-type of accelerators was used. The combination of different accelerators produced almost similar scorch...

Thermal properties of hydroxylated natural rubber from in-situ hydroxylation process

A thermal property of hydroxylation of natural latex has been studied in this research. The effect of the hydroxylation conversion of the double bond to hydroxyl functionality of natural rubber in one pot solution using in-situ method. It was studied at different duration; 10, 20, 30, 40 and 50 hours of reaction. A mechanism for the hydroxylation of the natural rubber was also proposed. The result shows the optimum conversions of double bond to hydroxyl functionality was recorded highest at 40 hours and remain constant although the reaction was continued until 50hrs. Fourier Transform (FT) Raman spectroscopy was used to analyze the conversion. −1HNMR was used to confirm the formation of hydroxyl to support the peak from FT Raman spectra. Differential Scanning Calorimetric analysis was used to analyze the glass transition temperature (Tg) of modified and unmodified natural rubber. The result showed lower Tg in modified natural rubber compared to the unmodified natural rubber. On the other hand, the onset o...

Tensile properties of carbon black-filled natural rubber latex films using two different approaches of film preparation

A study was structured to investigate the effects of two different approaches of black-filled NRL films preparation on tensile strengths and tensile stress at 100% strain (M100). In the “First Approach”, carbon black dispersion was added into the NRL and mixed using mechanical stirrer. Then the black-filled NRL was coagulated with acetic acid and dried to form NR black-filled masterbatch. This black-filled NR masterbatch was then masticated and mixed with other compounding ingredients on the 2-roll mill. In the “Second Approach”, carbon black dispersion was mixed with NRL plus all other compounding ingredients using a mechanical stirrer at high mechanical stirring speed (200 rpm) for 3 hrs. Tensile test-pieces from these two rubber specimens were tested according to ISO37. It was observed that the tensile strengths are affected by both methods. In the case of masticated latex masterbatch, the black-filled NRL films gave higher tensile strength (25-27 MPa) as compared to un-masticated black-filled NRL film...

Blending of polyvulcanize natural rubber

Natural rubber (NR) latex is widely used in the manufacture of thin film barrier products such as gloves and condom. However, due to its low Tg, film casted from NR latex is soft and tacky, and needed to be strengthened to produced high performance products. Films of prevulcanized natural rubber latex (PVNR) blended with nanosized copolymer of n-butyl acrylate/butyl methacrylate (BA/BMA) were prepared at three different ratios of acrylate copolymer: PVNR. The tensile strength and elongation at break of films prepared decreased with increasing ratios of acrylate copolymer:PVNR. FESEM images showed the occurrence of agglomeration of the acrylate copolymers with PVNR molecules. The degree of agglomeration of the blended molecules increased with percentages of copolymer added. The decrease in the tensile strength and elongation at break may due to the agglomeration of the blended molecules suggesting poor dispersion and/or destabilization of PVNR molecules.