Papers by Author: Rathanawan Magaraphan

Abstract: Atmospheric pressure plasma treatment was used to improve hydrophilic properties and scaffold/cell interaction of poly(S/EGDMA)polyHIPE highly porous foam, prepared from poly(styrene/ethylene glycol dimethacrylate) using high internal phase emulsion technique. With our synthesis procedure and surface treatment, this bioactive material, featuring highly porous structure and good mechanical strength, can be applied as a scaffold for tissue engineering applications. The treatment time and external plasma parameters were investigated in regards to the polyHIPE foam surface’s appropriate for fibroblast implantation. The changes in surface properties were characterized by contact angle measurement, showing that the exposure to air-plasma induced polyHIPE foam with hydrophilic surfaces, as observed by a decrease in contact angle degree. Enhancement of the interaction between the polyHIPE foam and the L929 fibroblast-like cells would imply the hydrophilic improvement of the polyHIPE foam surface due to the polar-like property of the biofluid cell medium.

Abstract: Organoclay derived from Na-bentonite can offer an alternative used as an inorganic filler for high internal phase emulsiom foams. Two types of organoclay, hybrid organic–inorganic porous clay heterostructures (HPCH), derived from organo–bentonite which prepared through surfactant–directed assembly of tetraethoxysilane (TEOS)/methyltetraethoxysilane (MTS) into galleries of the clay mineral, and organo-modified bentonite (MOD) treated with quaternary alkyl ammonium cation by ion exchange reaction, were used as a reinforcing agent for poly(divinylbenzene; DVB)polyHIPE foams in this study. Poly(DVB)polyHIPE foams filled with organo-bentonite (MOD and HPCH) loadings of 0, 1, 3, 5, and 10 wt% were successfully prepared using the HIPE technique. To study the effects of the organoclay on morphology, surface area, and mechanical properties of the prepared poly(DVB)polyHIPE foams, SEM, N2 adsorption-desorption, and a Lloyd Universal testing machine were employed. It was demonstrated that the addition of organo-bentonite (both MOD and HPCH) into PolyHIPE foams resulted in the enhancement of physical properties of the poly(DVB)polyHIPE foams. The incorporation of layered silicate in the polymer matrix were supported by SEM images, which shown that the roughness of the polymer wall surfaces appeared to increase due to the presence of organoclay. It was established that the use of organo–bentonite, both HPCH and MOD, as inorganic filler for poly(DVB)polyHIPE, has an effect on improving the surface area of the obtained materials. However, higher improvement in surface properties was achieved with poly(DVB)polyHIPE filled with HPCH when compared with poly(DVB)polyHIPE foams filled with MOD. This is because of the surface charateristic of the HPCH which is a combination of micro– and mesoporosity between each layered of silicates and gas molecules might be able to adsorbed into these porous structures. Mechanical properties of the filled poly(DVB)polyHIPE foams were found to improve when compared to the neat poly(DVB)polyHIPE. Highest Young’s modulus and compressive stress were observed at 5 wt% organoclay loading. It was clearly demonstrated in this study that the suitable content of

Abstract: The non-isothermal crystallization and subsequent melting behaviors of poly(trimethylene terephthalate), (PTT)/Vectra A950, (VA) blends with different VA contents were studied by differential scanning calorimetry. The effects of VA on the non-isothermal crystallization kinetics of PTT were discussed based on the Ozawa model. It was found that VA has a nucleation effect on PTT crystallization. The triple melting endotherms were found in the subsequent melting thermograms. The blends are clearly immiscible as verified by the unchanged Tg and morphological results.

Abstract: A wide variety of toxic metals and organic chemicals are discharged to the environment as industrial or laboratory wastes, causing serious water, air, and soil pollution. One of the interesting materials for using as the adsorbents to adsorb these pollutants in wastewater treatment is porous clay heterostructures (PCHs). These porous materials are obtained by the surfactant-directed assembly of mesostructured silica within clay layers. In the present work, the PCHs were synthesized within the galleries of Na-bentonite clay by the polymerization of tetraethoxysilane (TEOS) in surfactant templates (cetyltrimethylammonium ion and dodecylamine). These PCHs were functionalized with 3-mercaptopropyltrimethoxysilane (MPTMS) to obtain the MP-PCH utilizing as heavy metal adsorbent. According to N2 adsorption-desorption data, the results show that PCH has surface areas of 549.7 m2/g, an average pore diameter in the supermicropore to small mesopore range of 3.16 nm, and a pore volume of 0.45 cc/g, while MP-PCH shows pore parameters of 488.7 m2/g, 3.28 nm, and 0.48 cc/g, respectively. Moreover, the MP-PCH was investigated the adsorption properties which concerned with their function as adsorbents for aqueous solution. The results show that the adsorption capacity of MP-PCH was 0.22, 0.24, 0.50 , 0.48 and 0.11 mmol/g for Cd, Cu, Mn, Ni and Pb, respectively. They point out the potential for utilizing as the heavy metal adsorbents in wastewater treatment.

Abstract: The effects of polyacrylamide (PAM) as a capping agent, and zirconium as a dopant, on the structural and optical properties of ZnO nanoparticles were investigated. All the samples were prepared by microwave irradiation in an aqueous system without a post-annealing step. The crystallite sizes were decreased by the incorporation of Zr and PAM. The photoluminescence efficiency was enhanced for samples with PAM-capped ZnO and PAM-capped ZnO doped with Zr, when compared to the pure ZnO. The broad visible luminescence signified the suitability of these nanoparticles as a white phosphor.

Abstract: Porous Clay Heterostructures (PCHs) have been prepared by the surfactant-directed assembly of mesostructured silica within the two-dimensional interlayer galleries of clays. The PCH is an interesting material to use as entrapping system such as ethylene scavenger, owing to its high surface area with uniform and specific pore size. In the present work, the PCH was synthesized within the galleries of Na-bentonite clay by the polymerization of tetraethoxysilane (TEOS) in the presence of surfactant micelles. In addition, a mesoporous clay with organic-inorganic hybrid (HPCH) is modified via co-condensation reaction of TEOS with methyltriethoxysilane (MTS) to enhance hydrophobicity of PCH material for entrapping system. According to pore characterization, PCHs have surface areas of 421-551 m2/g, an average pore diameter in the supermicropore to small mesopore range of 4.79-5.02 nm, and a pore volume of 0.57-0.66 cc/g while HPCHs have surface areas of 533-966 m2/g, an average pore diameter of 4.28-6.38 nm, and a pore volume of 0.42-0.77cc/g.

Abstract: One of weak point of PS/clay nanocomposite is the lack of interfacial adhesion between clay and polystyrene matrix. In this research, the radical sites on the clay surface were induced via the plasma technique. The optimum condition for this process was investigated and used to treat bentonite before grafting styrene on clay structure. The increase of basel-spacing of clay was not noticeable from XRD spectra, but the FT-IR spectra showed characteristic peak of polystyrene implied that the styrene grafting was occurred on the outer surface of the clay. The impact strength is quite improved, especially for the higher ratio of styrene/clay during the grafting step.