Papers by Keyword: Natural Rubber (NR)

Abstract: This study investigated the synthesis and characterization of poly(lactic acid)-grafted natural rubber (PLA-g-NR) in molten state. The grafting was carried out in an internal mixer without and with the presence of tin octoate catalyst (TO). The grafting of lactide onto NR was carried out by using maleic anhydride (MA) as a linker. The FTIR and ¹H-NMR spectra revealed new peaks for the MA-grafted NR (NR-g-MA) and PLA indicating that MA was grafted onto NR and that LA was successfully polymerized into PLA. It was also found that MA grafted onto NR could assist as a linker for connecting PLA with NR via esterification reaction between hydroxyl group (OH) at the end chain of PLA and carboxylic group (COOH) from ring opening reaction of MA. Moreover, the decrease of residual LA peak in FTIR spectra suggested that the presence of TO catalyst in the reactive blend promoted higher degree of polymerization of PLA from ring opening reaction of LA.

Abstract: The present research aimed to develop natural rubber (NR) hybrid composites reinforced with calcium carbonate/carbon black (CC/CB) and calcium carbonate/silica (CC/SC). The influence of CC/CB and CC/SC with various filler ratios (120/0, 90/5, 60/10, 30/15 and 0/20) on cure characteristics and mechanical properties of the vulcanizates was investigated and their reinforcing efficiency was compared. It has been found that incorporation of CB in the hybrid filler decreases the scorch time and cure time but increases crosslink density, whereas the incorporation of silica showed cure retardation. As CB or SC content increases, stiffness, tensile strength and tear strength increase, while elongation at break and compression set decrease. Scanning electron microscopy studies also reveal poor filler dispersion and poor adhesion between filler particles and matrix in the vulcanizates with increasing in CC content in a weight filler ratio which causes inferior mechanical properties. Incorporation of CB or SC content enhanced the mechanical properties of the vulcanizates, where CC/CB hybrid system exhibited higher reinforcing efficiency compared with CC/SC hybrid system.

Abstract: Curing characteristics and swelling behavior of natural rubber/styrene butadiene rubber/recycled nitrile glove (NR/SBR/rNBRg) blends were investigated. Eleven composition ratio; 50/50/0, 50/40/10, 50/30/20, 50/20/30, 50/10/40, 50/0/50, 40/50/10, 30/50/20, 20/50/30, 10/50/40, and 0/50/50 of SMRL/SBR/rNBRg with the size of rNBRg ; 2.5 3.0 cm² were prepared by using two roll mill at room temperature. Cure characteristics such as scorch time,t₂, cure time,t₉₀, minimum torque, M_L, maximum torque, M_H, and swelling behavior of SMRL/SBR/rNBRg ternary blends were examined. Results indicated that the scorch time and maximum torque of the NR/SBR/rNBRg blends decreased with increasing rNBRg content. The minimum torque of the blends increased as rNBRg content increased. The cure time of NR/SBR/rNBRg blends show a unique trend, which are depending on the domain rubber content. The increment in rNBRg content decreased the crosslink density of NR/SBR/rNBRg blends.

Abstract: Wollastonite filled natural rubber (NR) compounds were prepared using a laboratory two-roll mill. The filler was loaded into NR at different loading, i.e., 0, 10, 20, 30 and 40 part per hundred of rubber (phr). The effect of wollastonite on curing characteristic, tensile and morphology properties has been studied. Results indicated that the cure time (t₉₀), scorch time (t₂), tensile strength and elongation at break of the NR compounds decrease with increasing wollastonite loading but the maximum torque, tensile modulus M100 (stress at 100% elongation), M300 (stress at 100% elongation) increase with increasing wollastonite loading. The fracture surface morphology of the NR compounds was investigated with a scanning electron microscope (SEM). More filler detachment from NR surface was observed with increasing wollastonite loading.

Abstract: Study the effect of kaolin clay as a synergistic agent on flame retardancy and thermal degradation in natural rubber based on intumescent flame retardant (IFR); consisting of ammonium polyphosphate (APP) as acid source, pentaerythritol (PER) as a carbonization agent and melamine (ME) as a blowing agent was undertaken. The intumescent was examined at different loading (60, 80 and 100 phr). Kaolin clay was incorporated into flame retardant at four different concentrations (0.5, 1.0, 1.5 and 2.0 wt% of flame retardant) to investigate the synergism between the flame retardant materials. The flammability and thermal degradation of composites were characterized by UL-94 rating (vertical burning) test, cone calorimeter (CONE) and thermogravimetric analysis (TGA). All composites could meet the UL94V-0 standard. A synergist effect was observed when kaolin clay is used in combination with the intumescent flame-retardant through the TGA and CONE results. Moreover Scanning Electron Microscope (SEM) was done for the char morphology.

Abstract: Natural rubber (NR) obtained from H. brasiliensis is known to be susceptible to oxidative degradation according to the amount of double bonds in the structure of the polymer, i.e. poly (cis-1,4-isoprene) [1]. However NR has been reported to contain native antioxidants such as phytosterols, phospholipids and tocotrienols [2]. Among those, γ-tocotrienol, present in hevea latex was reported to exhibit “in-vitro” antioxidant activity [3]. However the direct involvement of γ-tocotrienol or other antioxidants naturally present in NR in the protection of NR against oxidation is difficult to assess as the works were carried out with different of rubber types and in different conditions [4,5]. In the framework of a work on the dynamics of γ-tocotrienols in NR samples obtained from coagula maturated during several durations (0 to 15 days) in parallel with measurement of standard properties such as P₀ and PRI, methodological development of the analysis of tocotrienols and derivatives is presented in this study.HPLC-MS has been shown to be an accurate technique for lipid analysis in NR [6]. However, this is a time-consuming technique especially with large number of samples due to a necessary step of saponification. Moreover, the structures of γ-tocotrienol and its dimers were found to be affected by the strong alkali condition of saponification (data not shown). Therefore a rapid quantitative method for γ-tocotrienol from NR using high performance thin layer chromatography (HP-TLC) has been developed. Lipid extracts from NR samples could be simply analyzed by HP-TLC without any derivatization and the detectable quantity could be in nanogram range. Statistical analysis of the data showed that the method is precise, accurate, reproducible and sensitive. Thus the proposed HP-TLC method can be successfully used for the quantification of γ-tocotrienol from NR samples. This technique will be useful to conduct further experiments on antioxidant activity of NR lipids and to relate the results with physical properties of NR, especially those linked to resistance to oxidation.

Abstract: Phenolic compound which was extracted from oil palm leaves is a renewable natural antioxidant (NA) and it was added into rubber compound in order to improve stability during thermo-oxidative ageing. The influence of NA in natural and synthetic rubber was investigated by comparing with TMQ, which is one of the most commonly used synthetic antioxidant in natural rubber (NR) product. Tensile properties, tear strength and crosslink density were investigated to interpret the experimental data related to the oxidation of natural (SMR CV60) and synthetic rubber (SBR). The results indicated that tensile, tear and crosslink density of NR were better than SBR for both compound with the presence of NA and TMQ. The presence of phenolic compound in NA could retard the oxidation activities of NR and SBR. On top of that, the structure of NR which induced strain crystallization had increased the tensile, tear and crosslink density of NR. Meanwhile, the bulky groups in SBR structure were interrupting the crystallization during stretching the rubber chains, resulting in lower mechanical properties. In general, NA was found to have better results on tensile, tear and crosslink density compared to TMQ in NR compound.

Abstract: Hevea brasiliensis natural rubber (NR) latex is a very important commercial source of elastomers. It is not only a source for dry NR rubber but also the feedstock for the latex glove dipping industry. The particles of freshly tapped latex are known to be stabilized by proteins and lipids that come with the latex from the tree. These non-rubbers [, especially proteins and lipids, confer to the rubber and latex excellent properties unsurpassed by any synthetic latex [. Recent structural studies of NR revealed that the NR molecules comprise of 2 trans-isoprene units connected to a long-chain cis-isoprene units. Two terminal groups, referred to as ω and α, have been postulated to link with mono-and di-phosphate groups associated with phospholipids by H-bonding at the α-terminal, whereas the ω-terminal is a dimethylallyl group links to protein by H-bonding [. Although numerous studies have been published on the surface structure of the natural rubber particle [4-, none of these offered a direct in situ visualization of the intact particle surface. This is because of any attempt to remove this surface layer of proteins and lipids results in an immediate destabilization of the latex. The second part focused on the using of Atomic Force Microscopy (AFM) and Confocal Fluorescence microscopy to visualize and delineate the structure of the proteins and lipids layer on the latex particle surface in situ.

Abstract: The highly glycerin-loaded natural rubber (NR) films were fabricated by casting technique with different solvents including dichloromethane (DCM), diethyl ether and tetrahydrofuran (THF) with an addition of 75 phr glycerin. Their mechanical properties, wettability and topography were determined. The highly glycerin-loaded NR films exhibited the continuous porous structure which their tensile strength values decreased whereas their wettability was enhanced. Pore size of the glycerin-loaded NR films prepared by using DCM as a solvent was greatly larger than those of the systems prepared by using diethyl ether and THF, respectively. Some active compounds might be loaded into these modified porous structures of NR films and applied for controlled drug delivery systems.

Abstract: The various triethyl citrate-loaded natural rubber (NR) films were prepared by casting technique employing dichloromethane (DCM) as solvent. The wettability, mechanical properties and topology of prepared dry films were determined. The contact angle of distilled water onto the cast films was measured using the goniometer. Triethyl citrate-loaded NR films exhibited the continuous porous structure. The presence of triethyl citrate in NR films promoted wettability and surface free energy whereas the tensile strength decreased. The unique porous topography of triethyl citrate-loaded NR film exhibited the potential for applying this material as the scaffold or controlled drug delivery devices in the future.