Papers by Wanvimon Arayapranee
Polymers
Polylactide (PLA) polymer, polypropylene (PP) polymer, and a PLA/PP (70:30 wt%) blend, with liqui... more Polylactide (PLA) polymer, polypropylene (PP) polymer, and a PLA/PP (70:30 wt%) blend, with liquid natural rubber−graft−methy methacrylate (LNR−g−MMA) of 0.0, 2.5, 5.0, and 10.0 phr as compatibilizers, were prepared by internal mixing and compression molding. The effect of LNR-g-MMA content on the morphology, mechanical properties, water absorption, thermal degradation, and a lifetime of blends based on PLA and PP was investigated. Scanning electron microscopy (SEM) revealed that the PLA/PP blend underwent phase separation, and the presence of LNR−g−MMA in the PLA/PP blend showed a more homogenized and refined blend morphology. Hence, the addition of LNR−g−MMA was used as a compatibilizer to induce miscibility in the PLA/PP blend. The values of tensile strength, elongation at break, and impact strength of the polymer blends increased, whereas water absorption values decreased with increased LNR−g−MMA content. Thermal degradation kinetics was studied over a temperature range of 50–80...
Polymers
Liquid natural rubber (LNR), a depolymerized natural rubber (NR) consisting of shorter chains, wa... more Liquid natural rubber (LNR), a depolymerized natural rubber (NR) consisting of shorter chains, was prepared via oxidative degradation using NaNO2 and H2O2 degrading agents in the presence of HCOOH. The influence of reagent concentrations, temperature, and reaction time on the number-average molecular weight (Mn) was studied. Results showed the higher concentration of H2O2 and HCOOH employed faster degradative rates. However, a higher concentration of NaNO2 decreased the Mn reduction. Prolonged reaction time and high temperature resulted in a product with low Mn. FTIR spectra indicated the synthesized LNR contained hydroxyl end groups resulting from the breaking of the NR chains at an acidic pH, whereas a carboxyl terminated LNR was formed at an alkaline pH. SEM micrographs showed the latex particles of LNR were spherical and smaller compared to NR. The experimental results showed the reaction orders of [H2O2], [HCOOH], and [NaNO2] were 1.58, 0.79, and −0.65, respectively. In additio...
Mechanical and Aging Properties of Hydrogenated Epoxidized Natural Rubber and Its Lifetime Prediction
ACS Omega
ACS Omega
Epoxidized natural rubber (ENR) with 50% mol of epoxide groups was synthesized using performic ac... more Epoxidized natural rubber (ENR) with 50% mol of epoxide groups was synthesized using performic acid generated from the reaction of formic acid/hydrogen peroxide in latex form followed by hydrogenation using diimide generated from hydrazine (N 2 H 4) and hydrogen peroxide (H 2 O 2) with boric acid (H 3 BO 3) as a catalyst. The resulting products (hydrogenated epoxidized natural rubber, HENR) were characterized by proton nuclear magnetic resonance spectroscopy (1 H-NMR), gel testing, transmission electron microscopy (TEM), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). The effects of reaction parameters such as N 2 H 4 amount, H 2 O 2 amount, H 3 BO 3 amount, gelatin amount, reaction time, and reaction temperature on the percentage of hydrogenation degree and gel content were investigated. The transmission electron micrographs of the particles confirmed a core/shell structure consisting of a highly unsaturated concentration region as the core encapsulated by a low carbon−carbon double bond concentration region as the shell, which indicated that the rubber particle seemed to be modified from the outer layer to the center of the rubber particle. Overall, the data showed that an increase in the amount of the individual chemicals, reaction time, and temperature increased the hydrogenation degree. However, a higher level of gelatin retarded an increase in the percentage of hydrogenation degree. As the hydrogenation degree increased, the gel content increased due to the ether linkage and the crosslinking reaction triggered through hydroxyl radicals. From DSC measurements, the glass transition temperatures of hydrogenated products increased above those of original rubbers. The thermal stability of hydrogenated products was improved, demonstrated by a decomposition temperature shift to a higher temperature than ENR, as shown by the results from the thermogravimetric analysis. Therefore, the hydrogenated ENR (HENR) exhibited good thermal stability, which could extend the applications of ENR in the automotive and oil industries.
Diimide Hydrogenation of In-situ Epoxidized Natural Rubber Latex
The effects of filler loading and size on curing characteristics and mechanical properties of ste... more The effects of filler loading and size on curing characteristics and mechanical properties of stearic acid-coated CaCO 3 filled natural rubber (NR) compounds have been studied. A two-stage conventional mixing procedure was used to incorporate two particle sizes, 1 and 5 m, of stearic acid-coated CaCO 3 into natural rubber. Filler loading was varied from 0-60 parts per hundred of rubber (phr) at 15 phr intervals. The cure time (t 90) of both filler sizes decreased with increasing stearic acid-coated CaCO 3 loading. At a given filler loading, larger particle size coated CaCO 3 showed shorter t 90. The Mooney viscosity increased with an increase in filler loading and smaller particle size showed higher viscosity. Tensile strength of the coated CaCO 3 filled NR compounds increased with filler loading until a maximum level was reached (at approximately 30 phr) and then started to decrease with further increase in filler loading. As the coated CaCO 3 loading increased, the compounds became stiffer and harder. Thus, an increase in the modulus at 300% elongation with increasing filler loading was obtained. Again, the compounds filled with smaller coated CaCO 3 size showed higher tensile strength and 300% modulus.
in Natural Rubber Compounds
Rice husk ash obtained as agricultural waste from using rice husk as a power source contains a co... more Rice husk ash obtained as agricultural waste from using rice husk as a power source contains a considerable amount of silica. Two-stage mixing, using a dispersion kneader machine and a two-roll mill, was used to incorporate rice husk ash as a filler into natural rubber over a loading range from 0 to 40 phr. For comparison, a commercial silica filler was also used. The effect of filler loading on the cure characteristics and mechanical properties such as tensile strength, tear strength, Young’s modulus, and hardness, both before and after heat aging, was investigated. Scanning electron microscopy of the fracture surfaces was used to investigate the interaction between the filler and the natural rubber matrix.
The graft copolymerization of styrene/methyl methacrylate mixtures onto dienebased polymer seed l... more The graft copolymerization of styrene/methyl methacrylate mixtures onto dienebased polymer seed latex has been carried out using cumene hydroperoxide redox initiator. The diene-based polymers were natural rubber, styrene-butadiene rubber and polybutadiene. The experiments were designed using two fractional factorial design techniques. The monomer conversion, graft copolymer composition and grafting efficiency were determined. The synthesized graft copolymers were purified and then characterized by proton nuclear magnetic resonance (1 H-NMR) analysis and differential scanning calorimetry (DSC). Transmission electron microscopy (TEM) was used to study the morphology of the graft copolymers. Grafting efficiency is discussed with respect to the influence of six process factors and the interaction of these factors. The factors studied include the amount of initiator, emulsifier and chain-transfer agent, styrene-tomethyl methacrylate ratio, monomer-to-rubber ratio, and temperature. The analysis of the results from the design showed that only the amount of chain transfer agent and temperature in the range of test had significant effects on grafting efficiency. The mechanism of graft copolymerization has been studied. It appears that the formation of graft copolymers occurs on the surface of the latex particles through a chain-transfer process. The graft copolymer products could be used as an impact modifier for PVC, thus, blends of the graft copolymer products and PVC were prepared. Izod impact strength and tensile properties of the graft copolymer products were investigated.
Application of lime kiln dust as a filler in the natural rubber industry
Journal of Applied Polymer Science, 2010
ABSTRACT
CHAPTER 5. Natural Rubber Blends and Based IPNs: Manufacturing Methods
Polymer Chemistry Series, 2013
Blending natural rubber (NR) with other polymers is a popular technique to enhance its mechanical... more Blending natural rubber (NR) with other polymers is a popular technique to enhance its mechanical, dynamic and thermal ageing properties, processability and oil resistance. To improve the desired properties of the final product, rubber based blends have to be mixed with various additives, shaped and cured. Rubber blends are difficult materials to process, because in both the raw and the compounded state they have both viscoelastic properties. Therefore, mixing of the additives with the rubber is a very important step in the rubber compounding. The primary functions of mixing are incorporation, dispersion and distribution of the other ingredients in rubbers. The latex-mixing method is an alternative to the conventional dry-mixing method which is to combine dry solid rubber and other compounding ingredients in mixing equipment. To soften the rubber, the long polymer chains must be partially broken by passing the rubber between rollers or rotating blades. The ingredients can be thoroughly mixed with the rubber to achieve uniform dispersion of ingredients. The quality of the compound are as a consequence of the combined effect of the unit processes of mixing, which would be dispersion of the filler, chain scission of the polymer, and bound rubber formation.
Polymer Composites, 2014
Material waste from the production of autoclaved aerated concrete, a porous material, should be c... more Material waste from the production of autoclaved aerated concrete, a porous material, should be considered as a valuable byproduct for use as a filler material for the rubber industry. Natural rubber (NR) composites filled with different loading (over the range of 0-60 phr) of autoclaved aerated concrete waste (AACW) as a new eco-friendly material were produced using two roll mills and then were studied for their cure characteristics, mechanical and aging properties, and morphology, and also compared with commercial fillers, calcium carbonate (CaCO 3), and silica (SiO 2). In most cases, the cure characteristics and mechanical and aging properties of the SiO 2-filled NR composites were significantly better than those of the AACW-and CaCO 3-filled NR composites. However, these properties for AACW-filled composites appeared to be higher than CaCO 3-filled composites. The reason for this could be due to a larger surface area which is both porous and of an irregular shape of the AACW filler used. Scanning electron microscope images showed that the morphology of the rubber filled with SiO 2 was finer and more homogenous compared with the rubber filled with AACW or CaCO 3. Overall results revealed that the reinforcement ability of AACW-filled NR composites was generally better when compared with CaCO 3-filled NR composites; therefore, AACW can be used effectively as a cheaper filler for production of rubber products where end-use properties of a rubber product is specifically required.
The effect of blend ratio on curing characteristics of epoxidized natural rubber (ENR) blended wi... more The effect of blend ratio on curing characteristics of epoxidized natural rubber (ENR) blended with natural rubber (NR) was studied. Also, a systematic study of tensile properties of the blends was carried out before and after immersion in oil at room temperature and 100C for 72 h. The cure time (t 90) increased with increasing ENR content in the blend. The results indicate that tensile strength decreased with increasing ENR content in the blends until a minimum level was reached and then the property started to increase with an increase in ENR content. Increasing ENR content in the blend resulted in enhancement of tensile modulus. At a similar immersion temperature, blends with higher content of ENR exhibited better oil and thermal resistances.
Journal of Polymers, 2013
The grafting of an olefinic monomer like acrylonitrile (AN), methyl methacrylate (MMA), and styre... more The grafting of an olefinic monomer like acrylonitrile (AN), methyl methacrylate (MMA), and styrene (ST) onto natural rubber (NR) was carried out to enhance the polarity of the new chemical groups on the NR backbone and, in turn, to improve the filler-rubber interaction. The grafted natural rubber (GNR) produced was compounded and then vulcanization was carried out in the presence of silica as a reinforcing filler. The physical properties and aging resistance provided by the presence of the polar functional groups of the GNR composites were investigated and compared with other rubbers such as SBR, NBR, and NR. The GNRs provided significant improvements in resistance of the composites to thermal, oil, and ozone while maintaining the mechanical properties of the rubber. Therefore, these properties can be controlled as a function of the polarity of functional groups on the NR backbone. Morphological studies confirmed a shift from ductility failure to brittle with the presence of the po...
Korean Journal of Chemical Engineering, 2015
A graft copolymerization model for using cumene hydroperoxide/tetraethylenepentamine (CHPO/TEPA) ... more A graft copolymerization model for using cumene hydroperoxide/tetraethylenepentamine (CHPO/TEPA) as a redox initiator was developed to describe the grafting of methyl methacrylate onto natural rubber latex as a coreshell particle. The model allows estimating the effects of the initiator concentration, monomer-rubber weight ratio, and temperature on the properties of graft product, e.g., % grafting efficiency and the % monomer composition in the graft copolymer and free polymer. The rate expressions of polymer chain formation are developed by taking into account a reduction of CHPO by TEPA and a population event of radicals between core/shell phases. The parameter estimation is performed to find the kinetic parameters. Validation with experimental results demonstrates a good applicability of the proposed model. The model results reveal that the formation of grafted polymer chains rather form by the chain transfer reaction to rubber chains from homopolymer radicals and the initiation reaction of cumyloxy radicals to rubber chains.
Kinetic study of styrene and methyl methacrylate emulsion polymerization induced by cumene hydroperoxide/tetraethylenepentamine
Journal of Polymer Research, 2015
ABSTRACT The redox initiator, cumene hydroperoxide/tetraethylenepentamine (CHPO/TEPA), was used t... more ABSTRACT The redox initiator, cumene hydroperoxide/tetraethylenepentamine (CHPO/TEPA), was used to initiate the emulsion polymerizations of styrene and methyl methacrylate (MMA). The hydrophobic CHPO acting as oxidizer would interact with the hydrophilic TEPA employed as the reducer at the particle-water interface where the vinyl monomer is present. The kinetics of the styrene and MMA polymerizations were studied under a temperature range of 30–70 °C. The polymerization rate, the concentration of monomer in the particles, the average number of latex particles and the number of radicals per particle were investigated to evaluate the propagation rate constant during interval II of the polymerization. With increasing temperature, the number of latex particles increases while the monomer concentration in the particles slightly decreases. The observed number of radicals per particle, calculated from the number average volume of the particles and the relation between the entry rate coefficients of free radicals into the particles and the exit rate coefficients of free radicals from the particle, was found to be approximately 0.47 and 0.5 in case of styrene and MMA polymerization, respectively. The calculation shows that the propagation rate constant, k p = 6.84 × 107e−37.65/RT and k p = 3.4 × 107e−31.05/RT L/mol∙s for styrene and MMA polymerizations over the temperature range studied, respectively.
Factorial experimental design for grafting of vinyl monomers onto natural rubber latex
Journal of Applied Polymer Science, 2004
Graft copolymerization of styrene (St) and methyl methacrylate (MMA) in the presence of natural r... more Graft copolymerization of styrene (St) and methyl methacrylate (MMA) in the presence of natural rubber latex using cumene hydroperoxide/tetraethylenepentamine redox initiator system was prepared at various process variables. The synthesized graft copolymers were purified and then characterized by Fourier transformed infrared spectroscopy analysis. A full 24 factorial experimental design was applied to study the effect of various process variables on grafting efficiency. The following four independent variables considered to be mainly affecting the grafting efficiency were reaction temperature, rubber-to-monomer ratio, St-to-MMA ratio, and initiator amount used in the secondary polymerization. It was shown in this study that the reaction temperature significantly influenced the grafting efficiency, increasing as the temperature was increased. The amount of grafting increased with increasing rubber-to-monomer ratio and St-to-MMA ratio, whereas the amount of grafting decreased with increasing amount of initiator. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 455–463, 2004
Journal of Applied Polymer Science, 2008
The mechanical properties of natural rubber latex (NRL) modified with styrene-grafted natural rub... more The mechanical properties of natural rubber latex (NRL) modified with styrene-grafted natural rubber (styrene-GNR) latex were investigated. Styrene-GNR was first synthesized via emulsion copolymerization using cumene hydroperoxide/tetraethylene pentamine as an initiator. The styrene-GNR latex produced was mixed with NRL with various latex compounding contents and then prevulcanization was carried out. The mechanical properties and heat, weathering, and ozone resistance of the natural rubber (NR) and styrene-GNR latex compounds were investigated as a function of the grafted NR content. The results indicated that the tensile and tear strength were decreased, whereas Young's modulus and hardness were increased at high content of styrene-GNR. Addition of sty-rene-GNR improved the resistance of the compounds to heat and weathering ageing. The ozone resistance of the compound containing styrene-GNR is superior to that of the NR-rich compound. The results indicated that NR/styrene-GNR latex compounds maintained good antiageing properties required for outdoor applications. The tensile fracture surface examined by scanning electron microscopy confirmed a shift from ductility failure to brittle with an increase of the styrene-GNR content in the compounds.
Synthesis and mechanical properties of diimide-hydrogenated natural rubber vulcanizates
Journal of Applied Polymer Science, 2009
ABSTRACT
Factorial experimental design for graft copolymerization of styrene and methyl methacrylate onto styrene–butadiene rubber
Journal of Applied Polymer Science, 2006
The graft copolymerization of styrene (ST) and methyl methacrylate (MMA) onto styrene–butadiene r... more The graft copolymerization of styrene (ST) and methyl methacrylate (MMA) onto styrene–butadiene rubber (SBR) latex prepared by seeded emulsion polymerization has been studied under various reaction conditions using cumene hydroperoxide redox initiator. The mechanism of graft copolymerization has been investigated. The synthesized graft copolymers were purified and then characterized by proton nuclear magnetic resonance (1H NMR) analysis. A 2 2 fractional factorial experimental design was applied to study the effects of the process variables such as the amount of initiator and emulsifier, the presence or absence of chain-transfer agent, ST to MMA ratio, monomer to rubber ratio, and reaction temperature on the grafting efficiency. The analysis of the results from the design showed the sequence of the main effect on the observed response of the grafting of ST and MMA onto SBR and that the amount of chain-transfer agent had a significant effect. Transmission electron microscopy was used to study the morphology of the graft copolymers. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 2867–2874, 2006
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Papers by Wanvimon Arayapranee