Abstract: The scratch damage resistance and impact strength of PMMA sheets are necessary factors that have to be concerned by manufacturers. The aim of this work is to investigate the influences of silica (Si) from tetraethoxysilane on scratch damage resistance of the sheet surfaces for optical applications. The polymeric composites including PMMA, polyurethane (PU) and Si were produced via a bulk polymerization in a casting process. The technique creates semi-interpenetrating polymer networks (IPNs) between PMMA and PU. The percentage of IPNs and surface morphology of the composite sheets were observed. Furthermore, scratch resistance, impact strength, ultraviolet and thermal degradations of PMMA-PU-Si sheets were measured and compared with those of neat PMMA-PU sheets. The results revealed that the optimal Si amount (0.039 phr) provided 2B of the scratch resistance (2B of pencil range). This composite formula gave the highest impact values of 24.27 kJ/m2 for an Izod type and 24.94 kJ/m2 for a Charpy type. Composite sheets showed increases in ultraviolet and heat resistance by increasing the content of Si. However, the PMMA-PU-Si sheets were useable at temperature lower than 180 ⁰C.
Abstract: The silicate glass was prepared using rice husk as the source of silica. The base glass formula is composed of SiO2 (from rice husk ash), Na2CO3, K2CO3, ZnO, H3BO3, CaO and Al2O3 or Al. CuO was used as the colorant in the glass matrix in the absence and presence of reducing agent. The color of the glass obtained was varied from dark blue to blue depending on the amount of CuO and reducing agent. The expansion coefficients of copper doped glass are in the range of 12.43 x 10-6 - 14.35 x 10-6 (°C-1) which is common for the silicate glass. The finger prints of the bond vibrations were studied using IR spectroscopy. While the oxidation state and the coordination information of the copper ion in the glass matrix were investigated using X-ray absorption spectroscopy. In the absence and presence of reducing agent, Cu+ and Cu2+ exist in the glass matrix. However, in the presence of reducing agent, the amount of Cu+ in the glass matrix is higher.
Abstract: The polymer blend was prepared from natural rubber (NR) and polyethylene (PE) powder blended with epoxidized natural rubber (ENR) by using an internal mixer. In this study, epoxidized natural rubber (ENR) was used as compatibilizer for the blends. Blending ENR with PE powder and NR were prepared at various compositions from 0-20% by weight. Then, specimens from the blends were produced by compression molding at 150 °C. The mechanical and morphological properties of the composites were investigated. It was found that the addition of ENR content has improved the tensile strength, compression set and hardness for the ternary compositions composed of NR/PE powder/ENR compared to the binary one (i.e. NR/PE powder). ENR contributed to a better dispersion between the NR and PE phases as observed in the scanning electron microscopy.
Abstract: Various Thai manuscripts, commonly made from Khoi, suffer the severe deterioration primarily from the degradation of cellulose. Temperature, light, humidity, oxygen, pollution, and microorganisms are the main environmental factors for the conditions of manuscript collections. The degree of the cellulose deterioration can be studied by scanning electron microscopy (SEM), attenuated total reflectance Fourier transformed infrared spectroscopy (ATR-FTIR) and X-ray diffraction (XRD). The morphology of the sample was revealed by Scanning Electron Microscopy. The fiber disintegration and the presence of inorganic particles can be found on the paper surface. The ATR-FTIR results showed the characteristic functional groups of cellulose as follows: nOH (3650–3100 cm-1), nCH (3000–2850 cm-1), dOH (~1640 cm-1), dCH (1420-1300 cm-1), nC-O-C of the b-glucosidic linkage (~1100 cm-1), and dCO or CC (~910 cm cm-1). The presence of inorganic filling, CO32- salt (~1400 cm-1) could not be determined explicitly due to the signal overlap with dCH. The relative intensities of the absorption peaks in dCH of the ancient paper samples are different to those of the new khoi paper. The X-ray diffraction of each sample showed the characteristic peaks of crystalline fraction at 2q between 22.0º and 23.0º and the amorphous fraction at 2q between 15.0º and 16.0º. However, the intensity ratio of the crystalline and amorphous phases for the ancient paper is less than that of the new paper.
Abstract: The Cordon of the Most Illustrious Order of Chulachomklao was one of the insignia that King Rama the fifth gave to the ladies of the court to present their goodness. One component of this object was made from silk and decorated by needled the silvered and golden thread as the laurel and the initial of King’s royal name. This ancient silk suffers from discoloration, low strength and severe deterioration. Amino acids in fibroin were photo-degraded under UV-irradiation and heat. Three silk samples, S-Raw, S-White and S-Ancient, were selected for ATR-FTIR and XRD analyses. FTIR spectroscopy can be used for the determination of the molecular structure of silk fibroin. The characteristic bands of silk fibroin corresponding to amide I, II, and III were found in all silk samples. The skeletal vibrations were also observed. Two degradation estimators, EAmideI/II and EcC=O2 were calculated and used to qualitatively estimate the degree of degradation due to oxidation and crystallinity of silk fibroin respectively. The results showed the higher degree of degradation and lower crystallinity of A-Ancient. The X-ray diffraction of S-Ancient showed the broader and weaker characteristic peaks at 2 theta of ∼ 20o indicating the lower crystallinity.
Abstract: An original equipment market (OEM) in Thailand mainly imports thermoplastic vulcanizates (TPV) from abroad that leads to a high manufacturing cost. To reduce the cost and to create value-added products from a plastic scrap, therefore, this research aim is to observe a possibility of using TPV and recycled polypropylene (rPP) blends as a raw material for OEM. The blends with various rPP loadings were successfully prepared through a traditional twin-screw extruder. Proportions between TPV and rPP were adjusted to determine the optimal flow and mechanical properties for productions of different auto parts. The blends were tested for studying rheology and mechanical properties: tensile; hardness; flexural; and creep behavior. All tests resulted in discussions about the feasibility of using TPV/rPP blends with respect to auto part specifications in real applications. Test results suggested that the TPV/rPP blends meet the requirements of specific automotive applications. Thermal property and morphological analysis were also carried out to have more understanding about changes in mechanical properties.
Abstract: In this paper, effects of incorporation of dry grass on the properties of clay bricks were investigated. Clay bricks fabricated with 0, 2.5, 5 and 7.5 % (w/w) of dry grass were tested. The clay brick specimens were fired at 900, 1000 and 1100 °C to study for bulk density, apparent porosity water absorption and compressive strength of brick samples were investigated. Results revealed that the bulk density of clay bricks were reduced when dry grass dosages increased. Results also shown that the increasing in bulk density were obtained when the firing temperature increased. The compressive strength of clay bricks was decreased when dry grass dosages increased. The addition of 2.5 % (w/w) dry grass fired at 1100 °C showed the optimal condition which indicated 11.6 MPa of compressive strength and 1.78 g/cm3 of bulk density. However, results indicated that a decrease in water absorption and apparent porosity were found when the firing temperature increased. Test results also revealed that the addition of dry grass for clay brick production lead to utilize a potential material as the additive to raw clay-bricks in the manufacturing of lightweight clay bricks.
Abstract: In this research work, natural fiber reinforced composites of bagasse fiber-epoxy resin were prepared. The chemical treatments using sodium hydroxide (NaOH) at 1,3,5,7 wt% were carried out to modify the fiber properties. Thermogravimetric analysis (TGA) was used to study the thermal stability of treated and untreated fibers. The effects of fiber treatment and fiber contents on mechanical properties of bagasse-epoxy composite were investigated. The characteristics of bagasse-epoxy resin composites exposed to high temperature as well as water absorption behavior were determined. The results from the TGA revealed that alkalization improved thermal stability of bagasse fiber. Treated bagasse fibers also had lower moisture content as compared to untreated fiber. The experimental results showed that the flexural properties of composites prepared from treated bagasse fibers were enhanced as compared to the untreated fiber composite. Thermal degradation study demonstrated that treated bagasse fiber composites experienced lower weight loss than untreated fiber composites. From water absorption study, it was observed that the treated bagasse fiber composites had lower water absorption values than those of untreated fiber based composites.
Abstract: Three-dimensional (3D) porous alginate/soy protein isolated (Alg/SPI) tissue engineering scaffolds were achieved by freeze-drying. The physico-chemical attributes of the scaffolds including morphology, chemical structure, mechanical properties and in vitro cytotoxicity were investigated for different SPI blends. Results indicated that increasing SPI content to 40 wt% in the blends resulted in the partial existence of closed pores and reduced pore size. The mechanical values of the scaffolds under compression also reduced with increasing SPI in the blends. The addition of SPI did not significantly enhance the cell viability of the scaffolds investigated for in vitro culture with human fibroblasts, which remained in the high (90 – 100%) range. Results demonstrated that Alg/SPI scaffolds have potential for use as tissue engineering scaffolds.