bluuebunny/crossref_metadata_2025 huggingface dataset:
Starch Synthesis and Mobilization in Wood and Bark of Rubber Tree, in Relation with Latex Production, (1) Methodological Approach
Authors: Ketkakomol Salinda , Lerksomlan Tucksin , Clement-Vidal Anne , Chantuma Pisamai , Klanarong Sriroth , Liengprayoon Siriluck , Thaler Philippe , Drevet Practicia , Kasemsap Poonpipope , Piyachomkwan Kuakoon , Gohet Eric , Lacote Regis
Published: November 2013

In rubber tree, starch reserves are necessary for growth and latex regeneration when the demand exceeds supply from photosynthesis. It tends to accumulate in the wood near the tapping cut [1,2] whereas sucrose remains rather stable in the wood and decreases in the latex vessels where it is used to regenerate the exported latex [3].Thus higher starch ability could sustain higher latex yield. However the enzymatic processes driving the dynamics of starch synthesis and hydrolysis as related to tapping are not known. The objective of the study is to analyze the effects of tapping on the enzymes involved in starch and sucrose metabolism in the wood of rubber trees. The first approach of this study was to set up the most adapted methodology on measurement of total nonstructural carbohydrates (NSC) and related enzymes activities. The experiment was conducted in Heveabrasiliensis (rubber tree), clone RRIM600. Treatments include untapped trees (Control) and yielding trees tapped with Ethephon stimulation (ET). Each treatment includes 6 trees. Samples have been collected along the trunk and separated into 2 parts, wood and bark, from both side of the tree tapped and untapped panel. The activity of acid invertase (AI), amylase (AMY), sucrose phosphate synthase (SPS) and sucrose synthase (SuSy) were assessed in the part of soft bark with amethod of sample preparation recoveringmore protein and concentrated enzyme with acetone precipitation. The method has increased enzyme activities of SuSy and SPS. On another hand, starch, sucrose, fructose and glucose concentrations have been enzymatically measured.The results showed that starch was the major component in wood and sucrose was mostly found in bark. There was no difference between the former drainage area and resting area after 2 untapped years before restarting tapping.
The Drying Kinetics of Natural Rubber Sheets under Hot-Air Drying with Forced Convection: Experiments and Modeling
Authors: Werapun Warit , Pianroj Yutthapong , Khongchana Pinpong
Published: November 2013

This study investigated the drying kinetics of the natural rubber sheets under hot air drying, with various heat sources, and included modeling of the kinetics. The heat was generated by combustion, either of charcoal briquettes from coconut shell (biomass) or of liquid petroleum gas (LPG). The hot air entering the drying chamber had its initial temperature controlled at 40, 50, or 60 Centigrade. Five rubber sheets within the chamber were observed during their drying. Howerver, in the case of biomass, the fuctuation of temperature due to charcoal adding. Therfore, the non-linear regression analysis was performed only LPG data with a Weibull distribution and a Modified Handerson and Pabis. They represented the drying kinetics with parametric fits; moreover, an effective diffusion coefficient was determined for each experimental condition.
Feasibility Studies of Magnesium (II) Removal from Fresh Field Natural Rubber Latex Using Macroporous Cationic Exchange Resin
Authors: Puangmanee Sineenart , Taweepreda Wirach
Published: November 2013

The presence of magnesium ions (Mg2+) in fresh field natural rubber latex (FF-NRL) is a major concern for concentrated production. In general, Mg2+ is reduced by adding diammonia hydrogen orthophosphate (DAP) to FF-NRL. The reaction rate between DAP and Mg2+ in NRL is very slow and is the cause of waste latex sludge, waste time for more than 12 hours, and chemicals loss. Moreover, the waste latex sludge is toxic and has to be treated. In this research, the possibility of using cationic exchange resin to remove Mg2+ from the FF-NRL was investigated. The experiment was carried out by comparison the efficiency of difference commercial exchange resin on Mg2+ reduction rate after immersing in FF-NRL. The results were found that macroporous cationic exchange resin adsorped Mg2+ with highest rate. The Mg2+ content of NRL reduced to 100 ppm after immersing macroporous cationic exchange resin in FF-NRL for 6 hours. The performance of cationic exchange resin was increased after regenerate process with acid and can be used for further to reduce Mg2+ in FF-NRL. The morphology of cationic exchange resin was investigated using scanning electron microscope (SEM).
A Simple Water Balance Model of Rubber Tree Plantations under Different Evaporative Demand Regimes
Authors: Sopharat Jessada , Sdoodee Sayan , Tanavud Charlchai , Gay Frederic , Thaler Philippe
Published: November 2013

Drought constraints and transpiration of rubber (Hevea brasiliensis) plantations under different evaporative demand regimes were assessed by the simple water balance model. A lump water model, BILJOU (BILan hydrique JOUrnalier), is the daily water balance model. This model requires daily potential evapotranspiration (ETo) and rainfall as input climatic data, also requires site and stand parameters are maximum extractable soil water and leaf area index (LAI). The study was carried out two sites; namely Songkhla and Chachoengsao province, Thailand, traditional and new plantation area, respectively. The calibration of this model was done with sap flow measurements. Soil water derived by tensiometer for Songkhla and soil sampling for Chachoengsao were used to validate the model. Under non limiting soil water and full canopy, transpiration of rubber was influenced by evaporative demand. Consistently, under limited soil water represented as threshold of relative extractable water (REWc < 0.4), transpiration was influenced by REW. In the new plantation area; Chachoengsao, drought constraints were evident annually from the beginning of senescence until the new accomplished flushing; December to June. However, at Songkhla site, transpiration and soil water was mainly driven by evaporative demand. And the limitation of soil water represented shortly during the plateau stage of LAI.
Influence of Epoxide Levels in Epoxidized Natural Rubber (ENR) Molecules on Cure Characteristics, Dynamic Properties and Mechanical Properties of ENR/Montmorillonite Clay Nanocomposites
Authors: Yokkhun Piriyapol , Thongnuanchan Bencha , Nakason Charoen
Published: November 2013

Nanocomposites based on epoxidized natural rubbers (ENRs) with various levels of epoxide groups (i.e., 10, 20, 30, 40 and 50 mol%) and organoclay were prepared by melt mixing process. The organoclay employed in this study was montmorillonite clay modified by octadecylamine (OC-MMT). Cure characteristics, dynamic properties and mechanical properties of ENRs nanocomposites filled with 5 phr of OC-MMT were studied. In all cases, X-ray diffraction results indicated intercalation of ENRs into the silicate interlayer as an increase in the interlayer distance of layered silicates was observed. The maximum torque and torque difference of ENRs nanocomposites increased with increasing levels of epoxide groups in ENRs. Additionally, it was also found that the tan δ value at Tg of the ENR-50 nanocomposite was much lower than those of other types of ENRs nanocomposite. This indicates stronger interaction between ENR-50 and OC-MMT. However, ENR-50 nanocomposite showed the poorest elasticity in term of the tan δ value at the ambient temperature compared to other types of ENRs nanocomposites. A good balance between strength and elasticity was also observed in the ENR-30 nanocomposite. These results are also consistent with the observation that tensile strength and elongation at break of ENR-30 nanocomposite were higher than those of other types of ENRs nanocomposites.
Electrostriction of Natural Rubber Latex/Carbon Black Nanocomposites
Authors: Jaaoh Darika , Putson Chatchai , Muensit Nantakan
Published: November 2013

The purpose of this paper is to investigate an electrostrictive behavior of natural rubber (NR) and NR composites filled with carbon black (CB) nanopowders below percolation threshold. These NR elastomers present advantageous features such as a high productivity, elasticity, and ease of processing. In addition, such materials also exhibit the high induced strain and low young modulus for electrostrictive materials that can be used as actuators and energy harvesting. The NR and all composites were prepared by using solution casting method. The electrostrictive property of the composites was evaluated at low electric field (E 5 MV/m) by measuring the electric field induced strain Sz with the photonic displacement apparatus. The surface morphology of the samples was observed by the atomic force microscopy (AFM) and their electrical properties were analyzed as function of concentration and frequency in a range of 102105 Hz. The results show that the dielectric constant and the dielectric loss decrease when the frequency was increased. Moreover, the dielectric constant and the electrical conductivity strongly increase with increasing the CB contents, relate to interfacial charge distribution. While the dielectric loss slightly increases with increasing filler concentration. The electrostriction coefficient tended to increase with a higher CB loading. In comparison at CB 1 wt%, it was found that the electrostriction coefficient of NR composites is approximately 7 times larger than the pure NR. The NR nanocomposites thus seem to be very attractive for low frequency electromechanical applications.
Comparison of Thermal Stability of Sulfur, Peroxide and EB Irradiation Cured NR Compounds Containing Ground EPDM Waste
Authors: Nabil Hayeemasae , Ismail Hanafi , Azura A. Rashid
Published: November 2013

This article described concerning to the effect of sulfur, peroxide and electron beam irradiation cured on the thermal stability of natural rubber compounds containing ground EPDM waste. Semi-efficient vulcanization (semi-EV), dicumyl peroxide (DCP) and the EB irradiation at 200 kGy were used and applied in the compounds. Thermal analysis namely thermogravimettric analysis (TGA) and its kinetics of degradation process were investigated. Results indicated that the EB irradiation revealed superior thermal stability by shifting the decomposition temperature at various weight loss and maximum derivatives followed by peroxide and sulfur vulcanizing systems. The activation energies of degradation of the vulcanizates were determined by applying the Coats-Redferns method. It can be verified that the activation energies observed in the vulcanizates were in good agreement with the thermogram results. The highest thermal stability obtained from EB irradiation might be due irradiation-induced-crosslinking resulting to more thermal energy is supplied to overcome the apparent activation energy of the vulcanizates.
Surface Modification of TiO2 Nanoparticles by Grafting with Silane Coupling Agent
Authors: Toh-Ae Pornsiri , Junhasavasdikul Banja , Lopattananon Natinee , Sahakaro Kannika
Published: November 2013

Titanium dioxide (TiO2) possesses excellent photocatalytic activity and provides UV protection for polymeric materials. The nanosized TiO2 particles with larger surface area to volume ratio and an increased surface reactivity shall impart better photocatalysis and UV protection efficiency to the rubber compounds, compared to the use of conventional micron-sized particles. Direct incorporation of TiO2 nanoparticles (n-TiO2) into non-polar rubbers faces incompatibility problem between the two phases. One of the solutions to overcome this problem is to treat the nanoparticle surface by using silane coupling agent such as bis-(3-triethoxysilylpropyl) tetrasulfide (TESPT). This work prepared n-TiO2 from commercial micron sized-TiO2 by ultrasonication technique. Particle size of TiO2 was measured by laser light scattering particle size analyzer. The morphology of TiO2 nanoparticles was characterized by field emission scanning electron microscope (FESEM). The grafting reaction of silane on TiO2 nanoparticles surface was studied at varying reaction temperatures and times. The purified grafted materials were characterized by energy dispersive X-ray analysis (EDX), thermogravimetric analysis (TGA) and Fourier transform infrared spectroscopy (FTIR). The characterization data confirm a presence of grafted silane on the TiO2 nanoparticles surface. The result shows that ultrasonication technique can effectively decrease particle size and the grafting reaction of silane coupling agent onto TiO2 nanoparticles can be successfully carried out at 140°C for 8 h.
Properties of Fire Retardant Thermoplastic Vulcanizates from NR/PP Blends Filled with Aluminium Trihydrate and Magnesium Hydroxide with Reference to the Effect of Mixing Methods
Authors: Walong Alif , Kaesaman Azizon , Sakai Tadamoto , Lopattananon Natinee
Published: November 2013

Blends of natural rubber (NR) and polypropylene (PP) with composition of 60/40 %wt were prepared by using an internal mixer to obtain thermoplastic vulcanizate (TPV). Aluminium trihydrate (ATH) and magnesium hydroxide (MH) were used as fillers to improve thermal stability and fire retardant properties. Three different mixing methods were used to incorporate the fillers into the TPVs, which were (1) compounding of NR and filler followed by dynamic vulcanization of NR during blending with PP, (2) compounding of NR with a half part of filler (and oil) followed by dynamic vulcanization of NR when blending with PP before adding another half part of filler into the blend (3) melt mixing of PP, NR and filler followed by dynamic vulcanization during mixing. The incorporation of ATH and MH decreased tensile strength and elongation at break of the TPVs, but increased the thermal stability and LOI%. From this work, the mixing of filler with NR/PP blend by using method 3 provided better balance of tensile, thermal and fire resistant properties and processing cost reduction.
The Current Status and Future Trends of Farm Production and Marketing of Para-Rubber in the Upper East Coast Provinces of Southern Thailand
Authors: Choengthong Suthijit , Kongrithi Weerasak , Choengthong Suchart , Chuaymuang Benyapa
Published: November 2013

The research aimed to: 1) describe the current status and future trends of para-rubber production and marketing in the study area; 2) identify the marketing costs of farmers; and 3) study the marketing system of para-rubber. Data were collected from 462 farmers, 108 middlemen, and 17 processors. The study area was 4 provinces in the Upper East Coast of Southern Thailand: Chumpon, Suratthani, Nakhonsrithammarat, and Patthalung. The surveys were conducted by using structured questionnaires, in-depth interviews, and workshops. The data were analyzed by descriptive statistics, cost analysis, and marketing channel analysis. From 2005 to 2010, planting areas increased but total yields declined, due to heavy rains and floods. The rubber prices fluctuated but had an increasing trend. On an average, the planting area was 2.7 ha and had been cultivated for 17 years. The major variety was RRIM 600. The majority of farmers (63%) sold most of their para-rubber in latex form, while rubber sheets (31%) or cup lumps (18%) dominated less often. Hired help was often paid by a split of sales revenue. The product price, relationship, and shipping distance affected selecting the sales channel. Most preferred self-transportation to middlemen (81%), who usually set the price lower than the central market price. The marketing costs were from sheet making, transportation, and deductions for low quality. Sheet making at 3.65 THB per kg was mainly labor costs (72%). The transportation cost of cup lumps, latex and, sheets were on average 1.04, 0.86, 0.48 THB per kg, respectively. The cup lumps had quality deductions of 11% average from full price, and cup lump wetness and contamination had affected 65% of farmers, while 46% had sold sheets with deductions averaging 2%. Fluctuating prices and lack of knowledge about market channels and prices were the major problem for 45% of the farmers. Farm producers mainly sold latex or dry rubber (sheets, cutting scraps, and cup lumps). The latex marketing channel was through collectors for processing plants, that could both be local or larger scale. The dry rubber marketing channels included also collectors, central market, and processing plants. Rubber processed to primary products (smoked sheets, block, and compound rubber) was mainly exported. The latex marketing channels are gaining importance because farmers prefer to sell in latex form. They are likely to sell to a local village collector close to the farm. The demand for local processing plants that transform latex to rubber sheets or block rubber as well as the latex processing plants will likely increase.
Effect of Modified Natural Rubber and Functionalization of Carbon Nanotubes on Properties of Natural Rubber Composites
Authors: Nakaramontri Yeampon , Kummerlöwe Claudia , Nakason Charoen , Vennemann Norbert
Published: November 2013

The intention of this work was to prepare natural rubber filled with carbon nanotubes (CNT). Various types of natural rubber, including unmodified natural rubber and epoxidized natural rubber with 25 mol% epoxy groups (i.e., ENR-25) were exploited. The state of CNT dispersion in the unmodified natural rubber matrix was improved by the modification of CNT surface with silane coupling agent (Si-69). The modification was carried out byin-situmethod, i.e., the silane was directly added during the preparation process of the composites in the internal mixer. The interaction between CNT surface and rubber molecules, with and without silane modification, was characterized by ATR-FTIR measurements. The mechanical properties and crosslink densities were investigated, the electrical conductivity was characterized to determine the percolation threshold.
Dynamic Mechanical Properties and Tensile Behavior of Oil Palm Ash Filled Natural Rubber Vulcanizates
Authors: Ooi Zhong Xian , Ismail Hanafi , Bakar Azhar Abu
Published: November 2013

The potential of utilizing low cost filler, i.e. oil palm ash (OPA) as a new filler in natural rubber (NR) compounds using conventional laboratory-sized two roll mills. The NR compound was cross-linked using sulphuric system. The variations of tensile and dynamic properties were examined in the NR vulcanizates with the OPA filling at low loading. In the view of reinforcement, the tensile strength and elongation at break was improved with the low loading of OPA (<10 phr). Dynamic mechanical properties of OPA filled NR vulcanizates was investigated with respect to the storage modulus and mechanical loss factor (Tan δ). Result showed that the storage modulus of the OPA filled NR vulcanizates became higher than that of gum NR vulcanizates whereas the peak height of tan δmax was reduced as the OPA loading was increased. This phenomenon manifested a strong rubber-filler interaction with the low loading of OPA.
Preparation of Polymer Composite: Low Natural Rubber, Cassava Starch and Palm Fiber
Authors: Riyapan Duangporn , Riyajan Sa Ad , Tangboriboonrat Pramuan
Published: November 2013

The objective of this present work was to the preparation of polymer composite from low grade natural rubber (LNR), cassava starch (CSt) and palm fiber by using two-roll mill and then compression molding. The surface of palm fiber with different palm fiber lengths was analyzed by SEM. The tensile strength of the LNR/CSt composite containing 10% palm fiber with <425 µm fiber length was improved by addition of the 0.5 phr K2S2O8. After addition of K2S2O8, the swelling ratio in toluene of this composite was dramatically decreased. This is due to higher interaction between polymer matrix and fiber. The highest tensile strength and lowest swelling ratio in toluene of this composite was obtained with using palm fiber of < 425 µm in length.
Comparative Study on Natural and Synthetic Antioxidants on Thermo-Oxidative Aging of Natural and Synthetic Rubber Vulcanizates
Authors: Shuhaimi Nor Hasmaniza Husna , Othman Nadras , Ismail Hanafi , Sasidharan Sreenivasan
Published: November 2013

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.
Gel Polymer Electrolyte from Ozonolysis of Poly(3-(trimethoxysilyl)Propyl Methacrylate) Graft on Natural Rubber Latex for Natural Dye Sensitized Solar Cell Application
Authors: Silakul Pensiri , Magaraphan Rathanawan
Published: November 2013

The dye sensitized solar cell (DSSC) is devices for converting solar energy to electricity. The gel polymer electrolyte is the main component in the cell. It is used for complexation with liquid electrolyte to generate iodide ions and support the ion transportation. The gel polymer electrolyte of poly(3-(trimethoxysilyl) propyl methacrylate) (PMPS) coat on the surfaces of natural rubber (NR) particles (PMPS-g-NR) was prepared by surface grafting emulsion polymerization method using the redox couple initiator, tetraethylenepentamine (TEPA) and cumenehydroperoxide (CHP). Then, this gel was treated by ozone at different treatment time (5 min, 10 min, 20 min, 25 min, and 30 min) and voltage of ozonolysis (0.7 kV, 1.5 kV, 2.4 kV, and 3.2 kV) on PMPS-g-NR (ozonolysed PMPS-g-NR) to obtain the optimum condition for generating the active species e.g. carbonyl or aldehyde structures. The synthesized materials were characterized by the degree of swelling (%DS), ionic conductivity, and solar cell efficiency, having red cabbage as dye sensitizer. By ozonolysis on PMPS-g-NR, the treatment condition of voltage at 3.2 kV and treatment time at 30 min showed the maximum %DS of 74.2, which is higher than that of PMPS-g-NR without ozonolysis of 65.5. The maximum ion conductivity of PMPS-g-NR and ozonolysed PMPS-g-NR at 2.4 kV and 20 min were 0.240 mS/cm and 0.775 mS/cm, respectively while their maximum solar cell efficiency was 6.738 m% and 10.340 m%, respectively.
Influence of Reaction Conditions on the Properties of Nano-matrix Structure Formed by Graft-Copolymerization of Acrylonitrile onto Natural Rubber
Authors: Prukkaewkanjana Kontapond , Kawahara Seiichi , Sakdapipanich Jitladda
Published: November 2013

Natural rubber (NR) is one of the most important agriculture products of Thailand, which is an important material with unique and special characteristics used in wide range of applications such as mechanical properties, excellent strength, and elasticity. However, it is inferior in oil resistance due to the presence of hydrogen and carbon in its structure. This inherent drawback of NR has limited its application in industry. In order to expand the use of NR, this research is interested to improve the oil resistance of NR without loss of outstanding properties by grafting NR with acrylonitrile (AN) monomer to form the nano-matrix structure. The influences of the initial monomer concentration and initial initiator concentration were investigated. These effects on structure, mechanical properties and oil resistance properties were studied by Fourier transform infrared spectroscopy and proton nuclear magnetic resonance spectroscopy, tensile machine, and swelling in toluene, respectively. It was found that the tensile strength and oil resistance properties of graft copolymerization of AN onto NR increased with increasing the percentage grafting efficiency of acrylonitrile monomer.
Dielectric Studies of Admicelled Natural Rubber with Poly(3-Trimethoxysilylpropyl Methacrylate)
Authors: Nooma Suparat , Magaraphan Rathanawan
Published: November 2013

In this work, 3-trimethoxysilylpropyl methacrylate (MPS) was used as a substrate for coating on natural rubber (NR) particles by admicellar polymerization. The incorporation of MPS monomer, consisting of silicon element and 3 reactive methoxy groups (R-Si(OCH3)), is expected to increase dielectric properties of NR. Under the admicellar polymerization, the R-Si(OCH3) groups can be hydrolyzed and condensed into polysiloxane existed on NR particles. This method aims to prepare composite materials from NR and MPS with various amounts of MPS. The effects of microwave frequency and chemical modification by admicellar polymerization were studied. The dielectric properties of admicelled natural rubber (adNR) with PMPS were investigated at 20 °C in a frequency range extended from MHz to GHz. The results showed that the dielectric constant of adNR increased with PMPS contents. To study the effect of crosslinking on the dielectric properties of adNR, the dielectric spectroscopy measurements were performed on prevulcanized and non-prevulcanized adNR. The investigation showed that the dielectric constant of non-prevulcanized adNR was less than prevulcanized adNR.
A Study on the Graft-Copolymerization of 2-Acryloyloxyethyl Acid Phosphate onto Natural Rubber
Authors: Sorarutayangkoor Chadchai , Boonyasiri Jirapong , Sakdapipanich Jitladda
Published: November 2013

Nowadays, natural rubber (NR) is one of the most important agricultural product of Thailand, which is an important substance with special characteristics such as mechanical properties, excellent strength, and low heat build-up. However, NR is non-polarity that limited its application in industry. To expand the use of NR, this research is interested to improve the polarity of NR by grafting NR with 2-acryloyloxyethyl acid phosphate (P-1A(N)) monomer. The influences of the monomer concentration, dry rubber concentration (DRC) and reaction time were investigated. The best condition of the graft co-polymerization was 10% DRC, 20 phr of monomer and 3h of reaction time. NR was successfully grafted with P-1A(N) monomer by using this condition. It can be confirmed by Fourier Transform Infrared spectroscopy (FT-IR).
Adsorption Characteristics of Direct Violet Dye by Natural Rubber Chips
Authors: Utara Songkot , Phataib Piaw
Published: November 2013

The study examined the adsorption behaviour of Direct Violet 51 (DV 51) dye from aqueous solution onto natural rubber chips. The effects of various operational parameters such as adsorbent dose, contact time, pH and dye concentration were investigated using the batch adsorption technique. The natural rubber sheet (thickness 2mm) was prepared by compression moulding and cut into 5 mm square pieces. The point of zero charge (pHpzc) of the rubber chips was determined using the pH drift method. Equilibrium adsorption data were analysed by means of Langmuir and Freundlich isotherms, and adsorption data by spectrophotometer. It was found that the optimum adsorbent dose was 3g and optimum contact time was 120 minutes. The highest removal efficiency was found at pH 7. The explanation may be understood in terms of the pHpzc of the rubber chip (pHpzc=7.45), at which point the rubber surface is neutral. The surface charge of the rubber chip is therefore positive when the solution pH is below pHpzc. Because of its basicity, Direct Violet therefore tends to be adsorbed onto the surface of natural rubber chips. In addition, at pH 7 common salt (NaCl) was also found, which is believed to reduce the repulsion between the rubber chips and the dye, allowing the dye to diffuse more easily on to the surface of the rubber chip fibres, thereby improving their dyeability. The adsorption data correlated well with the Langmuir isotherm model, suggesting the monolayer adsorption behaviour.
Maturation of Cup Lump Natural Rubber: Growth of Microorganisms and Effects on Quality Properties under Alternative Storage Conditions
Authors: Intapun Jutharat , Sontikun Naridsara , Khowaien Arthit
Published: November 2013

Natural rubber is the main raw material in various rubber products. STR 20 is the most produced type of raw natural rubber in primary rubber production, due to its high global demand for tire production. In the STR 20 standard process, mainly raw cup lump is used, and the microbial populations in the cup lump affect the properties of the raw material during intermediate storage that cannot be avoided. The goal of this study was to evaluate the extent of such maturation effects, and to examine alternative practical storage condition extremes to determine which one is the best, based on quality characteristics.
We screened microorganisms in matured cup lump, and evaluated the key properties determining raw material quality, under various maturation conditions. Maturing cup lump under closed air conditions gave a high population (1.69x1010 CFU/ml) of microorganisms at 3 to 7 days, and the population decreased with further maturation to 3.45x105CFU/ml at 28 days. Raw rubber quality properties (pH, Initial Plasticity and Plasticity Retention Index) were best when stored under shade in spraying water, and worse with storage under closed bag conditions. The best thermal stability and the smallest microorganism population were found in acid coagulated cup lump. The results suggest that cup lump should be acid coagulated, and stored in the shade in spraying water, for best results in STR20 production.
Electrical Properties Characterization and Numerical Models of Rubber Composite at High Frequency
Authors: Nilboworn Salakjit , Wounchoum Phairote , Wichakool Warit , Thongruang Wiriya
Published: November 2013

This paper presents a numerical model of rubber composite using a COMSOL multiphysics program to simulate electrical properties of the rubber composite in the frequency range of 300 kHz to 30 MHz. The rubber composite was made of natural rubber vulcanized with carbon black and carbon nanotube. The chracterization was done by setting up a parallel plate capacitive structure in a shape of circular disk with a diameter of 38 mm and using the RF vector network analyzer to measure electrical properties in term of electrical impedance, specifically resistance (R) and reactance (X). Three different thinknesses of rubber composite sheets were used in the experiment, specifically 0.7 mm, 1.7 mm, and 2.9 mm. From the physical dimension of the test setup, capacitance (C), dissipation factor (D), relative permitivity (εr), and conductivity (σ) can be calculated. These extracted parameters together with the physical dimension of the test structure were used to create COMSOL multiphysics simulation models. The program can simulate non-linear modeling of the rubber composite under different electromagnetic constrains. The simulation results were compared to the measured results for all samples. Comparison results show that all electrical parameters were closly matched, indicating that the COMSOL multiphysics models were correctly generated. The results also indicate that the conductivity and the relative permittivity of the tested rubber composite change dramatically at the frequency above 10 MHz. The results indicate the physical limit of the tested rubber composite in the sensing application. The simulation model proposed in this paper can be used to design and possibly predict the geometical and electrical properties of the rubber composite in future applications.
Compliant Natural Rubber Latex Electrodes for Electrostrictive Polyurethane Actuation
Authors: Putson Chatchai , Jaaoh Darika , Muensit Nantakan
Published: November 2013

Improvement of the electrostrictive polymer with natural rubber (NR) compliant electrodes can potentially offer advantages for enhancement electromechanical efficiency of elastomer actuators. The NR elastomers are capable of advantageous features such as a high productivity, elasticity, and ease of processing. In this work, the NR composites filled with carbon black (CB) nanopowders at high conductivity was used as compliant electrodes on polyurethane electrostrictive polymer. The compliant NR composites electrodes were fabricated by using spin coating technique. The morphology of the NR composites was observed by the scanning electron microscope (SEM). The mechanical, electrical and electromechanical properties of NR composites were investigated. The electric field-induced strain of sample with compliant NR composites electrodes, and comparison with metallic electrodes was determined by using the photonic displacement apparatus. The results show that the thickness strain of polyurethane electrostriction with compliant NR was higher that with metal electrodes, depending not only on compliance between sample and electrodes, but also good conductivity and adhesion of electrodes. Correlation of the electromechanical properties and the mechanically coupled in stretching and compressing to volume incompressibility of polymer are also discussed.
The Influence of Zinc Dimethacrylate on Crosslink Density, Physical Properties and Heat Aging Resistance of Sulfur Vulcanized Styrene Butadiene Rubber
Authors: Naebpetch Weerawut , Junhasavasdikul Banja , Saetung Anuwat , Tulyapitak Tulyapong , Nithi-Uthai Nattapong
Published: November 2013

In this work, to study the utilization of zinc dimethacrylate (ZDMA) in sulfur vulcanized styrene butadiene rubber (SBR). The compounds were prepared by two roll mill mixer. Crosslink density and crosslink types were determined with an equilibrium swelling method. Physical properties and heat aging resistance were studied. The results shows that increase of ZDMA will decrease cure rate index and crosslink density which lead to decreased in 300% modulus and hardness. However, the addition of ZDMA can improve tensile strength, tear strength, elongation at break and heat aging resistance.
An Application of Lean Supply Chain Management for Cost Reduction in Block Rubber Industry
Authors: Promngurn Jaruwan , Sirivongpaisal Nikorn , Suthummanon Sakesun , Kongkaew Wanatchapong , Penchamrat Pallapat
Published: November 2013

Application of a lean concept to supply chain management for the block rubber industry is presented. It seeks to reduce the total systemwide cost by reducing wastes throughout the supply chain. Value stream mapping is used to identify non value added activities in the chain. Four major stakeholders are included: rubber grower, minor collector, major collector, and manufacturer. Four study steps are involved: 1) collection of data for a supply chain model constructed; 2) creation of a value stream map and identification of non value added activities; 3) analysis of root causes of non value added activities, or wastes, identified in the first two steps; and 4) proposal of practical guidelines to reduce or eliminate the wastes. Results show that transportation contributes the second highest cost after personnel cost, but is more practical to be trimmed. Hub-spoke concept along with vehicle routing analysis is recommended to be further explored in depth for practical implementation.
Effect of Foaming Temperature and Blowing Agent Content on Cure Characteristics, Mechanical and Morphological Properties of Natural Rubber Foams
Authors: Pechurai Worawan , Muansupan Tatsanee , Seawlee Petcharat
Published: November 2013

Influences of foaming temperature (i.e. 150 and 160OC) and blowing agent content on cure characteristics, mechanical and morphological properties of natural rubber (NR) foams were investigated. The blowing agent used in this study was oxybis (benzene sulfonyl) hydrazide (OBSH). The expandable rubber samples were prepared using a conventional compression molding technique via a heat transfer foaming process and an air-circulating oven. For cure behavior, it was found that maximum torque and torque difference tended to decrease with increasing the OBSH content for both processing temperatures. Decreasing of cure time was observed at 3 phr of the OBSH content and then it tended to increase. Moreover, cure time and scorch time decreased with increasing foaming temperature. As a result, the NR foam with large cell size and non-uniform foam cell distribution was observed. Mechanical properties of the NR foam in a term of hardness gradually decreased upon increasing the OBSH content. Whilst compression set increased with increasing the OBSH content up to 6 phr after that it decreased.
Novel Process in Preparation of Deproteinized Natural Rubber Latex
Authors: Boonme Prapaporn , Taweepreda Wirach , Pichayakorn Wiwat
Published: November 2013

Natural rubber latex (NRL) tapped from Hevea brasiliensis is composed of cis-1,4-polyisoprene as the major polymer which provides several desirable physical properties which make it to be interesting in pharmaceutical formulations. However, the International Union of Immunological Societies (IUIS) has reported about latex allergies caused by 14 NRL proteins (Hev b1-14). This problem can be coped with deproteinization of NRL in order to obtain deproteinized natural rubber latex (DNRL). This study aimed to prepare DNRL by novel process which was easy to perform and used pharmaceutical acceptable agents. The obtained DNRL was assayed for remained protein amount in form of nitrogen content by Kjeldahl method. Its physical properties were characterized. Its stability was also physically investigated. The DNRL was tested for the skin irritation in 3 rabbits. It was found that the protein amount of DNRL was 0.257% while the initial protein amount of fresh NRL was 1.531%. Hence, the protein was removed for 83.21%. DNRL had the average pH of 7.27. Both protein content and pH value implied that DNRL should be safe for skin application. DNRL possessed Newtonian flow with low viscosity which should be easy for mixing with other components in the further pharmaceutical formulations. The particle size, polydispersity index (PI), and zeta potential of DNRL were 441.0 nm, 0.240, and -42.53 mV, respectively, indicating narrow size distribution and physical stability. The dry rubber content and total solid content of DNRL were controlled as 39.55% and 40.72%, respectively. The suitable storage condition of DNRL was at 2-8°C in tight containers where DNRL could be kept for longer than 4 months. Very slightly irritation with no allergy caused by DNRL was observed in the tested rabbits. It could be concluded that this deproteinization process was easy and the prepared DNRL by this process was suitable and safe for using in further pharmaceutical and cosmetic formulations.
Determination of Crosslink Density and Network Structure of NR Vulcanizates by Means of TSSR
Authors: Vennemann Norbert , Schwarze Christina , Kummerlöwe Claudia
Published: November 2013

Unfilled vulcanizates based on natural rubber (NR) were investigated by temperature scanning stress relaxation (TSSR) measurements. Different sulfur based cure systems, i.e. conventional (CV), semi-efficient (SEV) and efficient (EV) vulcanization system, were used to prepare the vulcanizates. It was found that sulfur/accelerator - ratio has a strong impact on the shape of the relaxation spectrum, deduced from TSSR measurements. By deconvolution of the relaxation spectra, peak separation was performed and 3 different peaks were found in case of CV - cured samples. In contrast, only a single peak was found, in case of the EV-cured sample. After thiolamine treatment the shape of the relaxation spectra altered significantly in case of the CV-cured sample whereas the spectra of the SEV-and EV-cured sample exhibited only slight differences. Additionally, the crosslink density of the samples decreased after thiolamine treatment. This is due to selective cleavage of polysulfidic crosslinks. It has been concluded, that the significant peak in the relaxation spectrum at about 120 °C can be attributed to the cleavage of polysulfidic crosslinks. Furthermore, a linear relationship between the percentage of polysulfidic crosslinks and the sulfur/accelerator - ratio is assumed.
Effect of Unmodified and Modified Epoxidized Soyabean Oils on Properties of Black-NBR Compounds and Black-NBR Vulcanizates
Authors: Chanpon Kannika , Thitithammawong Anoma , Nakason Charoen , Kaesaman Azizon
Published: November 2013

In this study, feasibility of using epoxidized soyabean oil (ESO) and n-phenyl-p-phenylenediamine modified ESO (pA-m-ESO) as rubber processing oil in a formulation of carbon black filled acrylonitrile butadiene rubber (NBR) compound was investigated. It is seen that properties of the NBR compounds (i.e., total mixing energy, dump temperature, Mooney viscosity and curing characteristic) with using the DOP and the ESO were comparable, unlike the compound with using the pA-m-ESO. However, after vulcanization the NBR vulcanizate with using the DOP showed superior modulus, tensile strength and hardness than those of the others. This is due to interaction between the processing oil and the NBR phases as well as reinforcing effect of the carbon black on NBR molecules. However, no differences of dispersion and distribution of carbon black in the NBR vulcanizates with varying types of processing oil were observed.
Electrospun Epoxidized Natural Rubber with Poly(vinyl chloride) (ENR-PVC) Nanofibrous for PEMFC Applications
Authors: Phatcharasit Kritsada , Taweepreda Wirach , Boonkerd Kanoktip , Kim Jin Kuk
Published: November 2013

Various electrospun epoxized natural rubber / poly (vinyl chloride) (ENR/PVC) blend nonwoven membranes were prepared by electrospinning technique. Various concentration of epoxidized natural rubber (ENR) solution in N,N-dimethylformamide (DMF) were directly added to PVC solution for plasticization of the electrospun nanofibrous. Differencial thermal analysis (DTA), thermogravimetry analysis (TGA), fourier transfrom infrared spectroscopy (FT-IR), and scanning electron microscopy (SEM) were used to characterize the pristine and plasticized nanofibrous. DTA results indicated that the addition of ENR resulted in the shifting of glass transition temperature (Tg) towards lower temperatures. The blending of PVC with ENR is thermodynamically incompatible.
Effect of NR/ABS Ratio on Mechanical, Dynamical and Morphological Properties of Vulcanized NR/ABS Blends
Authors: Wongthong Pinyo , Nakason Charoen , Pan Qin Min , Rempel Garry L. , Kiatkamjornwong Suda
Published: November 2013

Dynamically vulcanized NR/ABS blends by phenolic curing were carried out using an internal mixer at 180 °C. The effect of NR/ABS ratio (i.e., 50/50, 60/40, 70/30) on mechanical, dynamical and morphological properties was investigated. It was found that the tensile strength and hardness increased with an increase in ABS loading whilst the elongation at break decreased, indicating that the strength and hardness attributed to thermoplastic component whereas the elasticity of the blends contributed to the vulcanized NR. The results showed that the 60/40 NR/ABS blend provided the well-balanced mechanical properties. The storage modulus of thermoplastic vulcanizates (TPVs) increased with increasing contents of rubber. This is due to that a higher content of vulcanized NR domain was dispersed in the ABS matrix. The results agreed well with the tan δ and complex viscosity of the TPV at various blend ratios. SEM micrographs of 60/40 NR/ABS blend showed that vulcanized rubber domains were dispersed in a continuous ABS phase and it contributed to greater interfacial adhesion between the two phases and thus provided superior properties.
Changes in Mixing Torque, Mechanical and Dynamic Rheological Properties of Epoxidized Natural Rubber and Copolyester Blends as Affected by Epoxidized Natural Rubber Contents
Authors: Kaewkabpet Densak , Nakason Charoen , Kaesaman Azizon , Thitithammawong Anoma
Published: November 2013

Thermoplastic natural rubber (TPNR) based on epoxidized natural rubber with 30 %mol epoxide (ENR-30) and copolyester (COPE) blends was prepared in a molten state by using roller rotor internal mixer. Effect of various ENR contents on mixing torque together with mechanical and dynamic properties of the ENR-30/COPE blends was investigated. It was found that the mixing torque and complex viscosity increased with increasing contents of the ENR in the blends. This was due to higher polarity the ENR molecules caused interaction and entanglement of the ENR molecular chains with higher viscosity. Furthermore, improvement of elastomeric properties of the ENR-30/COPE blends was clearly observed, especially in the blends with higher proportion of the ENR. These improved elastomeric properties with high elongation at break, low tension set and high storage modulus together with low tan δ. This observation correlated to higher elastic component in the blend caused promoting higher elastic response in combination with increasing of interaction between the ENR and the COPE phases.
The Method to Produce Light-Color Natural Rubber
Authors: Boonyang Hathaichanok , Sakdapipanich Jitladda
Published: November 2013

It is known that natural rubber (NR) has a naturally occurring color, which restricts to some applications of NR, especially for producing light-colored NR products. Thus, this present work was an attempt to find the appropriate method for promoting the light color NR. First, the color substances in NR were extracted by a certain method and subjected to analysis by Thin layer chromatography (TLC). They were separated by hexane/diethyl ether (7:3 v/v). The separation was detected using 3% cupric acetate in 8% phosphoric acid (H3PO4) and heated at 180 degree C. It was found that the color extracts from NR comprise of various compounds such as carotenoids, free fatty acids, tocotrienols, oxidized proteins, etc. Developments of light color NR were carried out by the addition of enzymatic browning inhibitors, i.e., sodium metabisulphite (SMS) in latex and the employment of some chemicals, i.e., proteolytic enzyme, sodium hydroxide, to discolor the rubber. It was found that the color index of NaOH-treated rubber or saponified rubber (SP) was lightest, whereas the color of urea-treated rubber or deproteinized rubber (DP) was close to the centrifugation rubber. The treatment of SMS showed an insignificant effect on the decoloring of NR. DP and SP showed very low nitrogen content, so these may be effective methods to produce light-color NR.
Deformation and Fracture of Hydrogenated GaSe and InSe Layered Crystals
Authors: Balitskii Olexiy A. , Eliasz Jacek , Gryshchenko Sergiy A. , Polishchuk Natalia M.
Published: November 2013

In the present work we establish some specific features of the fracture and behavior of anisotropic semiconductor crystals GaSe and InSe under mechanical loading and hydrogenation, which undergoes in the course of preparation of the specimens, their cutting, spalling, and other technological operations of the production of future semiconductor solar energy devices.
A Contribution to the Physical Interpretation of the Morphology of Fatigue Fracture Surfaces
Authors: Lauschmann Hynek , Kovářík Ondřej
Published: November 2013

The reference texture is a subset of the image texture in SEM fractographs of fatigue fractures. It is common to all fractures caused by loadings in which significant events occur sufficiently regularly and frequently. The reference crack growth rate is unambiguously related to the reference texture. A particular loading is characterized by the ratio of the reference and conventional crack growth rates called reference factor. Its value may be related to the sequence of successive sizes of cyclic plastic zone, while the mechanism of the effect of overloads follows the models of Wheeler and Willenborg. Application to a set of three test specimens from stainless steel AISI 304L loaded by various loading regimes is shown.