Paweena Prapainainar

Effect of acid functionalised carbon supports for Pd–Ni–Sn catalyst on ethanol oxidation reaction

The sodium borohydride reduction method was employed to prepare a ternary catalyst with an atomic ratio of 20%Pd10%Ni10%Sn impregnated on four carbon supports, Vulcan XC-72R carbon black (CB), functionalised carbon black (CBsn), multi-walled carbon nanotubes (MWCNTs) and functionalised MWCNTs (MWCNTsn), to improve the catalytic activity for direct ethanol fuel cells (DEFCs). The acid functionalisation was performed using H2SO4 and HNO3. The addition of Ni and Sn metals helped to increase catalytic activity as well as catalyst stability in the ethanol oxidation reaction (EOR). The XRD and XPS results confirmed the presence of Ni(OH)2 and SnO2 compounds. The crystalline size was in the range of 6.4 to 7.4 nm for all samples. TEM images of the catalyst on MWCNTsn confirmed that the catalyst particles were uniformly distributed and dispersed with a particle size in the range of 6 nm. This result was consistent with the highest number of active sites investigated by CO chemisorption. This was due to the highly crystalline structure of MWCNTsn. Moreover, the catalyst on MWCNTs exhibited the highest current density (291 mA cm−2) for EOR, great catalyst stability, the highest electrochemical surface area (77.155 m2 g−1 Pd) and excellent CO tolerance.

Preparation of Graft Copolymer of Natural Rubber and Polystyrene by Electron Beam Irradiation

The simultaneous graft copolymerization between natural rubber (NR) and styrene monomer (St) was induced by electron beam irradiation. The grafted polystyrene in graft copolymer was characterized by Fourier Transform Infrared Spectroscopy (FT-IR). This research investigated the influence of three factors (radiation dose, type of emulsifier and adding of sensitizer; normal butyl acrylate (n-BA)). It was found that the appropriated emulsifier was ammonium laurate which lead to higher monomer conversion and grafting efficiency. The adding of n-BA could notably enhance monomer conversion and crosslink density. Moreover increasing radiation dose, the monomer conversion and crosslink density increased. This technique was a cleaner and faster technology suitable for grafting application.

Synthesis and Characterization of Silaned-Graphene Oxide-Mordenite Grafting

The grafted materials of silaned-graphene oxide-mordenite (s-GO-MOR) were synthesized by grafting graphene oxide (GO) sheets to acid-treated mordenite and followed by functionalization with silane. GO sheets were prepared according to the modified Hummers method. 3-mercaptopropyltriethoxysilane (MPTES) was used as a silane coupling agent. The products were characterized by a Fourier transform infrared spectroscopy, X-ray diffraction, energy-dispersive X-ray spectroscopy and thermogravimetric analysis. The results confirmed the success of s-GO-MOR and showed excellent thermal stability.

The Effect of Ternary Catalyst Atomic Ratios (PtRuSn/C and PtRuNi/C) on Ethanol Electrooxidation for Direct Ethanol Fuel Cell

The effect of the different metal atomic ratios deposited on Vulcan XC-72R on ethanol electrooxidation reaction were investigated by producing of the ternary catalysts (PtRuSn/C and PtRuNi/C) in various atomic ratios (75:20:5, 75:15:10, 75:10:15, 75:5:20). All catalysts were prepared via polyol process. The nominal atomic ratios of the metals on the support were confirmed by EDX-SEM. The cyclic voltammetry was used to investigate the electrocatalytic activity of the catalysts. It was found that PtRuSn/C (75:10:15) showed the highest maximum current density of 3.25 mA/cm2 among all Sn containing catalysts. However, PtRuNi/C (75:5:20) also exhibited the high maximum current density of 2.66 mA/cm2 which was the maximum current density for Ni containing catalysts. Moreover, PtRuNi/C (75:5:20) exhibited the best activity and stability for ethanol electrooxidation reaction as showed in chronoamperometry tests. The current density at 3000 s was 0.54 mA/cm2. The size of the catalysts was about 1.9-3 nm measured by TEM. The catalyst also presented smaller particle size and better catalyst dispersion among all ternary catalysts. The addition of Sn facilitated the C-C bond breaking in molecule of ethanol while the addition of Ni facilitated better stability.

Nafion-Silane Modified Mordenite Composite Membrane Synthesis and Characterization for Direct Ethanol Fuel Cell

Composite membranes, consist of Nafion and surface-modified mordenite as inorganic filler functioned as ethanol barrier, were prepared and used for direct ethanol fuel cell (DEFC). mordenite was modified using gamma-glycidoxypropyltrimethoxysilane (GMPTS) which has the epoxide group and 3-mercaptopropyl-trimethoxysilane (MPTS) which has the mercapto group as coupling agents on mordenite. The composite membranes were fabricated by adding 5 %weight modified mordenite into Nafion by solution casting and hot pressing with catalyst to produce MEA and tested in DEFC single cell stack. XRD, FT-IR, Mastersizer and SEM were used to study the morphology, physical and chemical properties of the filler and the composite membrane. The characterizations also included ethanol permeability and proton conductivity by using the diffusion cell and AC impedance test, respectively. The performance of the cell was evaluated in the DEFC under cell temperature from 30 to 70 °C and ethanol concentration of 1 M to 4 M. It was then compared to the recasted Nafion membrane.

Natural Rubber Reinforced with Silica Nanoparticles Extracted from Jasmine and Riceberry Rice Husk Ashes

Silica nanoparticles were synthesized by rice husk ash (RHA) produced from jasmine rice husk and riceberry rice husk via sol-gel method for the use as reinforcing fillers in natural rubber (NR). The obtained silica nanoparticles are spherical in shape and the particle sizes were observed to be in the 10-20 nm range with uniformly size distribution. The surface of silica nanoparticles was treated with a silane coupling agent confirmed by FTIR. The treated silica nanoparticles were then incorporated into NR and vulcanized with electron beam irradiation. The rubber nanocomposites with silica nanoparticles, produced from jasmine rice husk and riceberry rice husk, resulted in higher mechanical properties (tensile strength and modulus) than neat rubber vulcanizate. The modified rubber vulcanizates revealed rougher surface with tear lines as compared to the neat rubber vulcanizates, indicating the improved strength. Interestingly, the rubber nanocomposites with silica nanoparticles from jasmine rice husk showed higher tensile strength and modulus than silica nanoparticles produced from riceberry rice husk. The micrographs indicated better dispersion of NR composites with jasmine rice husk which leads to a strong interaction between silica nanoparticles and rubber matrix, thereby improving the strength.

Extraction of Nanocellulose from Dried Rubber Tree Leaves by Acid Hydrolysis

Nanocellulose were extracted from dried rubber tree leaves by acid hydrolysis. The dried rubber tree leaves were treated by the alkali and bleaching process to obtain the bleached cellulose powder. Acid hydrolysis from sulfuric acid (H2SO4) at different concentrations (35 wt.% to 65 wt.%) was performed to obtain the nanocellulose. The extracted nanocellulose were characterized by the transmission electron microscope (TEM), atomic force microscope (AFM), Fourier transform infrared spectroscopy (FTIR) and X-ray powder diffraction (XRD). The produced nanocellulose exhibited rod-like shaped cellulose nanocrystals (CNCs), however, the CNCs structure and crystallinity depended on the H2SO4 concentration. It was revealed that the higher H2SO4 concentration led to the shorter CNCs lengths. In addition, the crystallinity was generally found to increase with increasing acid concentration treatments but slightly reduce at 65 wt.% of H2SO4.

Effect of Gamma Radiation on Properties of Cellulose Nanocrystal/Natural Rubber Nanocomposites

Cellulose nanocrystals (CNC) were extracted from corn cob and synthesized by alkaline treatment using 3 wt% sodium hydroxide (NaOH). Acid hydrolysis with 64 wt% sulfuric acid (H2SO4) at different reaction times (30, 45, 60 min) was performed to obtain CNC solutions. CNC was evaluated as a reinforcing agent in natural rubber (NR) at CNC loadings from 1-5 wt%. Gamma-ray radiation was used as vulcanization method and varied at 10 and 20 kGy. The tensile modulus and tensile strength of NR vulcanizates increased with addition of CNC and contents. In addition, radiation by gamma ray impacts the mechanical performance, where CNC/NR composites vulcanized with higher dose of radiation of 20 KGy were found to have the higher values in tensile strength, elongation at break, and modulus than with 10 KGy. Moreover, the tensile strength and elongation at break of the composites after aging were found to slightly increase due to post-curing during the aging process.

Degradation of Silica-Reinforced Natural Rubber by UV Radiation and Humidity in Soil

In this research study, the degradation of natural rubber was applied for applications in agriculture products such as rubber mulch. This work included the synthesis of 20% wt silica/ natural rubber composites from high ammonia concentrate latex (HA) and fresh latex (FL). They were casted by film casting. The experimental study of rubber composite degradation was done by putting the samples underground and above the soil surface under accelerated degradation test box equipped with a solar simulator lamp for a period of 50 days. Samples were characterized by scanning electron microscopy (SEM) to examine the dispersion on cross-sectional area between natural rubber and silica. Thermogravimetric analysis (TGA) was used to analyze the thermal stability of the composites. Tensile strength (MPa), modulus at 100% elongation (MPa), and elongation at break (%) of the samples after aging were tested by focusing on. It was found that thermal degradation of natural rubber compounds consisted of one step of mass loss between 341°C and 455°C. The SEM result showed good dispersion of Si in the rubber samples. Moreover, it was found that before aging, the composite samples had higher tensile strength than that of the rubber. After aging, the composite samples had lower tensile strength than that of the rubber. Elongation @ break value of HA/Si and FL/Si after aging were decreased obviously.

Degradation Test of Natural Rubber/Chitosan Composite

Degradable materials from 20wt% chitosan loading and natural rubber (CS/NR) were prepared by solution casting without surface treatment to study their thermal and mechanical properties after degradation test in aging condition. The test was done in an acrylic degradation box with 600 W light and high humidity for accelerate degradation condition. Samples included high ammonia concentrated latex (HA) with no filler, fresh latex (FL) with no filler, HA with chitosan filler, FL with chitosan filler, and natural rubber with shrimp shell filler to compare the result with chitosan filler. After degradation test, thermal properties from TGA both before and after degradation showed that the fillers effected on these composite materials. TGA result of CS/NR composite with aging at temperature 100 °C for 10 h and 20 h showed that chitosan slightly effected on thermal stability of composites when compare to natural rubber. SEM images were compared before and after degradation of HA and FL with no filler, chitosan filler, and shrimp shell. It was clearly seen that the samples degraded as the shape and size were changed. Tensile testing values showed that longer aging time could lead to the degradation in CS/HA and lower the tensile strength.