Pranut Potiyaraj

Deposition of Polyelectrolyte Multilayers to Improve the Color Fastness of Silk

The color fastness to washing of silk fibers dyed with scarlet dye was improved by the deposition of a thin polymer film which prevented desorption of the dye in standard soap solution. Dyed silk fibers were coated with polyelectrolytes multilayers (PEM) by following the so-called layer-by-layer deposition method in which up to 30 layers of cationic poly(diallyldimethylammonium chloride) and anionic poly(sodium 4-styrene sulfonate) were deposited. The growth of the film was confirmed using attenuated total reflectance Fourier transform infrared spectrophotometry and the dye exhaustion from the silk fiber was monitored using UV-Vis spectroscopy. The ability of the PEM to act as an electrostatic barrier against the release of the negatively charged dye was investigated as a function of the terminating top layer. The results showed that the negative layer-terminated PEM is more efficient at preventing the release of the dye than the positively terminated PEM.

Recognition and re‐visualization of woven fabric structures

Purpose – The purpose of this paper is to develop a computerized program that can recognize woven fabric structures and simultaneously use the obtained data to 3D re‐visualize the corresponding woven fabric structures.Design/methodology/approach – A 2D bitmap image of woven fabric was initially acquired using an ordinary desktop flatbed scanner. Through several image‐processing and analysis techniques as well as recognition algorithms, the weave pattern was then identified and stored in a digital format. The weave pattern data were then used to construct warp and weft yarn paths based on Peirces geometrical model.Findings – By combining relevant weave parameters, including yarn sizes, warp and weft densities, yarn colours as well as cross‐sectional shapes, a 3D image of yarns assembled together as a woven fabric structure is produced and shown on a screen through the virtual reality modelling language browser.Originality/value – Woven fabric structures can now be recognised and simultaneously use the obt...

Synthesis of nano zinc hydroxide via sol-gel method on silica surface and its potential application in the reduction of cure activator level in the vulcanization of natural rubber

In this article, we have described the synthesis of nano zinc hydroxide on the surface of precipitated silica via the sol–gel precipitation method. The studied zinc hydroxides have been tested as novel cure activators on the vulcanization of natural rubber. The aim of this paper was to reduce the cure activator level in the vulcanization of natural rubber. Synthesized zinc hydroxides were characterized by Fourier transform infrared spectroscope, X-ray diffraction, and field-emission scanning electron microscope, and the results clearly indicate the formation of nano zinc hydroxide with a plate-like structure on the surface of silica. Curing and tensile properties in the presence of synthesized zinc hydroxides as cure activator were compared with those of conventional zinc oxide as a cure activator on the vulcanization of natural rubber. The curing study indicated that lowering the concentration of zinc hydroxide on the silica surface improves the cure rate index to a large extent and it is greater than 360 % for 0.18 g of zinc hydroxide per gram of silica-accelerated vulcanizates compared with that of conventional 5 g zinc oxide-accelerated vulcanizates. However, lower concentrations of zinc hydroxide form fewer number of cross-links, which merely affects the tensile strength. Considering both curing and mechanical properties, 0.5 g of zinc hydroxide per gram of silica, which was synthesized in this experiment, is the suitable choice for activator for the vulcanization of natural rubber.Graphical Abstract

Intumescent flame retardant finishing of polyester fabrics via the layer-by-layer assembly technique

Purpose The purpose of this paper is to investigate the potential use of the layer-by-layer (LbL) assembly as an intumescent flame retardant for polyester, cotton and their blended fabrics. Design/methodology/approach In this study, polyester (PET), cotton and their blends were applied with the flame retardant coating via the LbL assembly technique. The flame retardancy, melt dripping, thermal properties and morphology of coated polyester fabrics were then examined. Findings The scanning electron micrograph of uncoated and coated fabrics revealed that the LbL assembly coating on the fabric surface was successful. The assessment of the flame retardancy and thermal properties of the coated fabrics showed that the after-flame time and melt dripping during the vertical burning test decreased. The char residue at temperatures ranging from 450 to 800°C during thermogravimetric analysis was enhanced as compared with the uncoated fabric. Furthermore, the morphology of the char residual of coated fabrics was rougher and bulkier than the uncoated fabrics, suggesting the typical behavior of intumescence. Social implications The LbL technique generally uses much fewer chemicals, thus making this flame retardant finishing much more environmentally friendly. It is also expected that these fabrics will show better touch characteristics. These fabrics may be tested for their comfort compared to that of conventional coating to enable their use on an industrial scale. Originality/value This work demonstrated the ability to apply an effective intumescent coating on polyester, cotton and blend fabric. In order to maintain fabric handle property, the Lbl coating technique is also employed.

Preparation of Thermoplastic Elastomer from Epoxidised Natural Rubber and Polystyrene

The aim of this research was to prepare and investigate the behaviour of thermoplastic elastomers (TPE) from epoxidised natural rubbers (ENR) blended with polystyrene. ENRs with different amounts of epoxide groups were prepared via in situ epoxidation method and denoted accordingly as ENR25, ENR35 and ENR50. Polystyrene (PS) was prepared by emulsion polymerisation. The obtained ENRs were blended with commercial and prepared PS at room temperature in the latex state at the amounts of dry PS of 0, 20, 40, 60, 80 and 100 phr (parts per hundred rubber). The mechanical and thermal properties of the blend sheets were investigated. It was found that the tensile strength and elongation at break increased as the amount of PS increased, then decreased later at higher amounts of PS. However, these values decreased as the amount of epoxide groups increased. The hardness of the specimens increased with the increase of epoxide groups and PS content. For the determination of blend compatibility, a shift in glass transition temperature to a lower temperature was revealed by DSC analysis. According to the results, the ENR/PS blends could be described as partially miscible blends.

Composite materials from unsaturated polyester/rice husk ash/ natural rubber -g -polystyrene

Composite materials from unsaturated polyester (UPE) resin, black rice husk ash (BRHA), and natural rubber grafted polystyrene (NR-g-PS) were prepared. NR-g-PS was synthesised by emulsion copolymerisation with a NR/styrene molar ratio of 80/20 using tert-butyl hydroperoxide/tetraethylene pentamine (t-BHPO/TEPA) as an initiator. Grafting efficiency of the copolymer product was about 54%. Initially, UPE was blended with BRHA at UPE/BRHA weight ratios of 100/30, 100/40 and 100/50. Each blend was subsequently mixed with NR-g-PS in the proportions of 5, 10 and 15 parts per hundred of UPE resin (phr). After curing, the cast specimens were examined for their physical properties, thermal expansion coefficient and morphology. It was found that the composite of 100UPE/30BRHA/5NR-g-PS exhibited the highest flexural and impact strength but the lowest water absorption. The thermal expansion coefficient of 100UPE/30BRHA/5NR-g-PS composite measured by thermomechanical analysis (TMA) was as low as 0.00005/°C. The morphology of the composites was investigated by scanning electron microscopy (SEM), which disclosed that NR-g-PS particles were well dispersed in the UPE matrix whereas the RHA was agglomerated and poorly dispersed in the composites. The higher the amount of NR-g-PS the more agglomeration of BRHA. This was due to the very high viscosity of the systems.

Exploring the comparative effect of silane coupling agents with different functional groups on the cure, mechanical and thermal properties of nano-alumina (Al 2 O 3 )-based natural rubber (NR) compounds

AbstractThe surface of sol–gel-synthesized nano-alumina (Al2O3) was modified by three types of silane coupling agents with different specific functionalities, namely 3-aminopropyltriethoxysilane (APTES), triethoxy(octyl)silane (OCTEOS) and bis[3-(triethoxysilyl)propyl]tetrasulfide (TESPT). The aim of the present study was to explore the effect of both unmodified and surface-modified nano-Al2O3 on the cure characteristics, mechanical properties, cross-link density and thermal stability of natural rubber (NR) nanocomposites. Results revealed that silane coupling agents were very effective to enhance maximum rheometric torque (R∞) and mechanical properties like modulus and tensile strength of nano-Al2O3-based NR nanocomposites. APTES offered higher value of cure rate index for NR compounds as compared to two other silane coupling agents. Among three silane coupling agents, TESPT provided highest improvement in the mechanical properties of NR/nano-Al2O3 composites. This might be explained by considering excellent improvement in the cross-link density of NR compounds in the presence of TESPT-treated nano-Al2O3. The incorporation of both TESPT- and OCTEOS-modified nano-Al2O3 into the NR matrix markedly improved the thermal stability of NR composites. Moreover, bi-functional silane TESPT not only increased the hydrophobicity of nano-Al2O3, but also improved the probability of sulfur cross-linking during cure process of NR compounds.

Graphene/Thermoplastic Polyurethane Composites

Thermoplastic polyurethane/graphene nanocomposites were successfully prepared by mixing masterbatches with neat polymers using the melt compounding process. Graphene was obtained from graphite by the chemical mean. Graphite was initially converted into graphite oxide which was then converted to graphene oxide. Graphene oxide was then reduced by L-ascorbic acid to obtain graphene. The effects of graphene addition on thermal and morphological properties of nanocomposite were studied by a differential scanning calorimeter, a thermal gravimetric analyzer and a scanning electron microscope. TPU/graphene nanocomposites showed higher melting temperature compared to TPU. On the other hand, heat of fusion of nanocomposites was lowered. TPU and TPU/graphene nanocomposites have two steps of decomposition. The first degradation of TPU occurred at higher temperature compared with nanocomposites but the second degradation showed the opposite results. The percentage of residue after thermal degradation of nanocomposites was lower than that of TPU. For surface morphology, nanocomposite exhibited the rougher surface comparing with TPU and well graphene dispersion in TPU phase was achieved. Nevertheless, there were some agglomeration of graphene.

Tuning of HDPE Properties for 3D Printing

The objective of this study is to improve high density polyethylene (HDPE) properties for 3D printing by addition of graphene and low density polyethylene (LDPE). Graphene was prepared by modified Hummer’s method. The prepared graphene was characterized by the infrared spectroscopy and the X-ray diffraction analysis (XRD). Graphene/HDPE and LDPE/HDPE composites were successfully prepared through the melt-blending technique using a twin-screw extruder. The melt flow index (MFI) and differential scanning calorimetry (DSC) were employed to characterize neat HDPE and the modified HDPE. FTIR and XRD results show that graphite was successfully changed into graphene completely and MFI of graphene/HDPE and LDPE/HDPE decreased as the amount of graphene and LDPE in the composite blends increased. DSC results show that the addition of low crystalline polymers can reduce a crystallization temperature and crystallinity content.

Poly(Lactic Acid)/Poly(Vinyl Alcohol)/Graphene Nanocomposites

Poly(lactic acid) (PLA) is an interesting material as an environmentally-friendly replacement of petroleum-based polymers. However, some properties need improvements in order to commercially utilized PLA. In this work, graphene is used as a reinforcing filler and poly(vinyl alcohol) is used as a carrier to enhance dispersion of graphene in PLA matrix. The addition of graphene aims at improving the mechanical and thermal properties of PLA. The functional groups of graphene were characterized by Fourier transform infrared (FTIR) spectroscopy and X-ray diffraction (XRD). The mechanical property testing was performed using a universal testing machine. The thermal properties were measured through differential scanning calorimetry (DSC). As a result, the Young’s modulus and the thermal properties of PLA composites increased as the amount of graphene in the composites increased due to improved dispersion of graphene in PLA matrix.