Hathaikarn Manuspiya

Thermal conductivity and mechanical properties of BN-filled epoxy composite: effects of filler content, mixing conditions and BN agglomerate size

Thermal conductivity and mechanical properties of boron nitride (BN)-filled epoxy composite as a function of filler content, mixing conditions, and BN agglomerate size were studied. Both thermal conductivity and mechanical properties of the composite were found to increase with increases in filler content, mixing speed, mixing time, and mixing temperature, but with decrease in BN agglomerate size. Sonication was found to be more effective in decreasing the BN agglomerate size than mechanical mixing. Viscosity of the BN—epoxy mixture was also studied under various mixing and sonicating conditions. A maximum thermal conductivity of 1.97 W/mK was obtained at 28 vol.% filler content and the mixing conditions of 80 rpm, 30 min, followed by sonication.

Deposition of PEDOT: PSS nanoparticles as a conductive microlayer anode in OLEDs device by desktop inkjet printer

A simple microfabrication technique for delivering macromolecules and patterning microelectrode arrays using desktop inkjet printer was described. Aqueous solution of nanoparticle of poly (3,4-ethylenedioxythiophene) (PEDOT) doped with polystyrene sulfonic acid (PSS) was prepared while its particle size, the surface tension, and the viscosity of the solution were adjusted to be suitable for deposition on a flexible cellulose nanocomposite substrate via inkjet printer. The statistical average of PEDOT: PSS particle size of 100nm was observed. The microthickness, surface morphology, and electrical conductivity of the printed substrate were then characterized by profilometer, atomic force microscope (AFM), and four-point probe electrical measurement, respectively. The inkjet deposition of PEDOT: PSS was successfully carried out, whilst retained its transparency feature. Highly smooth surface (roughness ∼23-44 nm) was achieved.

Thermo-Responsive Poly(N-Isopropylacrylamide)-Cellulose Nanocrystals Hybrid Hydrogels for Wound Dressing

Thermo-responsive hydrogels containing poly(N-isopropylacrylamide) (PNIPAAm), reinforced both with covalent and non-covalent interactions with cellulose nanocrystals (CNC), were synthesized via free-radical polymerization in the absence of any additional cross-linkers. The properties of PNIPAAm-CNC hybrid hydrogels were dependent on the amounts of incorporated CNC. The thermal stability of the hydrogels decreased with increasing CNC content. The rheological measurement indicated that the elastic and viscous moduli of hydrogels increased with the higher amounts of CNC addition, representing stronger mechanical properties of the hydrogels. Moreover, the hydrogel injection also supported the hypothesis that CNC reinforced the hydrogels; the increased CNC content exhibited higher structural integrity upon injection. The PNIPAAm-CNC hybrid hydrogels exhibited clear thermo-responsive behavior; the volume phase transition temperature (VPTT) was in the range of 36 to 39 °C, which is close to normal human body temperature. For wound dressing purposes, metronidazole, an antibiotic and antiprotozoal often used for skin infections, was used as a target drug to study drug-loading and the release properties of the hydrogels. The hydrogels showed a good drug-loading capacity at room temperature and a burst drug release, which was followed by slow and sustained release at 37 °C. These results suggested that newly developed drugs containing injectable hydrogels are promising materials for wound dressing.

Dielectric properties improvement of polymer composite prepared from poly(vinylidene difluoride) and barium-modified porous clay heterostructure

Significant improvements in dielectric properties of poly(vinylidene difluoride) (PVDF) can be achieved by adding small amounts of barium-modified porous clay heterostructure (Ba-PCH). In this article, composite films of PVDF with various amounts of Ba-PCH were fabricated by the compression method. SEM images indicated good dispersion of Ba-PCH in the PVDF matrix, as island-like particles caused improvement in the mechanical and thermal properties in the composite films. The films were highly heat resistant between 446°C and 452°C, depending on the amount of Ba-PCH added. The addition of Ba-PCH in the PVDF matrix reduced the non-polar phase, α-phase, of the PVDF, which resulted in the presence of a polar-phase, β-phase. There was a decrement of the non-polar phase of PVDF after adding small amounts of Ba-PCH, the dielectric constant (at 1 kHz) was dramatically increased from 6.0 of the neat compressed PVDF film to 34.1, 44.8, 47.1, and 56.0 of the compressed PVDF film with 3 wt. %, 5 wt. %, 7 wt. %, and 10 wt. % of Ba-PCH in the PVDF matrix, respectively.

Dielectric Properties Enhancement in Polybenzoxazine Composite at Multi-Frequency Range

This research proposed a novel nano barium strontium titanate (BST) powder- polybenzoxazine composite as a new dielectric material. In this work, the dielectric properties of a surface-treated BST powder-polybenzoxazine composite were studied. The surface of the BST powders were modified by using three different chemicals: 3-aminopropyl-trimethoxysilane, benzoxazine monomer and phthalocyanine. The distribution of the BST powders in the polybenzoxazine matrix was observed by SEM. The dielectric constants of the composites with a function of frequency (1 kHz–10 MHz) were investigated. It was found that the composites with modified BST powders showed good distribution in the polybenzoxazine matrix, and the dielectric constants were also much enhanced than those with untreated BST powders. In comparisons among the three modification methods, the composite with the silane coupling modified BST powder showed significantly in dielectric constant improvement while the composite with the benzoxazine and phthalocyanine modified BST powders displayed lower dielectric loss due to the modified powder dispersed well in the polybenzoxazine matrix.

pH-Sensitive PP/Clay Nanocomposites for Beverage Smart Packaging

The modification of clay by ion exchange reaction with cationic surfactants plays an important role in the greater interlayer spacing of Na-bentonite. Four types of quaternary alkyl ammonium ions, DO AM, DOEM, DCEM and DTDM, were introduced into the clay in order to investigate the effects of intercalation of the cationic surfactants. The organobentonites were characterized by XRD, FTIR and TGA. From WAXD patterns, DOEM-B exhibited the largest interlayer spacing, promissing the most suitable choice for producing PP/clay nanocomposites. The nanoclay composites incorporating pH indicator were melt compounding through a twin screw extruder using Surlynreg as a reactive compatibilizer. Subsequently, the nanoclay composites were fabricated into the sample sheet for pH-sensitive test.

Functionalized Porous Clay Heterostructure for Heavy Metal Adsorption from Wastewater

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.

Physical structure variations of bacterial cellulose produced by different Komagataeibacter xylinus strains and carbon sources in static and agitated conditions

The morphology, crystallinity, crystallite size, and production yield of bacterial cellulose (BC) produced with six different carbon sources (glucose, fructose, lactose, maltitol, sucralose, and xylitol) in static and agitated fermentation conditions by five strains of Komagataeibacter xylinus (KX, TISTR 086, 428, 975, and 1011) which are locally available, were studied. In static condition, the BC pellicle was formed as a membrane sheet at the medium surface exposed to air, while in agitated condition, the spherical or asterisk-like shape BC particles were obtained in the culture media. The XRD and FT-IR analyses found no significant differences in the cellulose crystallinity, crystallite size or polymorphic distribution within the carbon sources. However, changes in crystallinity and mass fraction of the Iα allomorph were observed in BC produced from the different bacterial strains and incubation conditions. The BC samples produced by the same bacterial strain with the varying culture conditions showed the alteration of physical properties more clearly than the BC samples prepared by the opposite situation. These findings suggested that the strains of bacteria and fermentation conditions strongly affected on the physical structures of BC.

Surfactant-Templated Synthesis of Modified Porous Clay Heterostructure (PCH)

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.

Surface-Modified Porous Clay Heterostructure Synthesized by Introduction of Cationic Ions: Effects on Dielectric Behavior

The dielectric enhancement of solid state materials was easily leading by adding the small amount of cationic ion in processing step. In this work, porous clay heterostructure (PCH) derived from bentonite was doped with various cationic solutions. The cationic-modified PCHs were characterized by SEM, BET and Zeta potential. The result suggested that metal ion was trapped into mesoporous structure of PCH, leading to the localized cationic charge along modified clay structure. Thus, the dielectric properties were enhanced. It can be noted that cationic-modified PCH would be one candidate material as excellent filler for dielectric properties enhancement in polymer based nanocomposite.