Pornnapa Kasemsiri

Shape memory polymers from benzoxazine-modified epoxy

Novel shape memory polymers (SMPs) were prepared from benzoxazine-modified epoxy resin. Specimens consisting of aromatic epoxy (E), aliphatic epoxy (N), Jeffamine D230 (D) and BA-a benzoxazine monomer (B) were evaluated. The mole ratio of D/B was used as a mixed curing agent for an epoxy system with a fixed E/N. The effects of BA-a content on the thermal, mechanical and shape memory properties of epoxy-based shape memory polymers (SMPs) were investigated by differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), flexural test and shape recovery test. The results revealed that the obtained SMPs exhibited a higher flexural strength and flexural modulus than those of the unmodified epoxy-based SMP at room temperature and at 20?? C above glass transition temperature (Tg). The presence of 1?mol BA-a as a curing agent provided the specimen with the highest Tg, i.e. about 72?? C higher than that of epoxy-based SMP cured by Jeffamine D230. All SMP samples needed only a few minutes to fully recover to their original shape. The samples exhibited high shape fixity (98?99%) and shape recovery ratio (90?100%). In addition, the recovery stress values increased with increasing BA-a mole ratio from 20 to 38?kPa, when BA-a up to 1?mol ratio was added. All of the SMP samples exhibited only minimum change in their flexural strength at the end of a 100 recovery cycles test.

Optimization of Biodegradable Foam Composites from Cassava Starch, Oil Palm Fiber, Chitosan and Palm Oil Using Taguchi Method and Grey Relational Analysis

The objective of this work was to investigate properties of biodegradable foam manufactured from cassava starch containing the combination of additives. The mix proportions of starch foam composites were designed using Taguchi method. L16 orthogonal array with three factors i.e. oil palm fiber content, chitosan content and palm oil content at four-levels each was chosen for optimization. Based on the signal-to-noise (S/N) ratio results, oil palm fiber and palm oil enhanced the flexural strength and water resistance of starch foam composites. Addition of chitosan reduced the density and increased the flexibility of samples. The analysis of variance of results indicated that chitosan was the major parameter influencing density, flexural strength and water absorption index. The oil palm fiber and palm oil were main parameters affecting water solubility index. The multi-linear regression models were developed to predict the properties of starch foam composites. The best mix proportion of starch foam composite was obtained from Grey relational analysis. The starch foam composite could be used as an alternative packaging for dry material.

A comparison of the withdrawal resistance load of nails using experimental and interference approaches

Abstract The objective of this study was to determine and predict the withdrawal resistance or pull-out load of common wire nails embedded in radial, tangential and cross-sectional grain orientation of Douglas fir (Presudotsuga menziesii) and sugar maple (Acer sacharum) samples. Four lead-hole diameters of 1.5, 2.0, 2.5 and 3.0 mm were used to create various interference fits. Nails with a diameter of 3.38 mm were driven into the samples to a depth of 10 mm for the experiments. The overall withdrawal resistance of Douglas fir samples was found to be lower than that of maple samples. Strength values of each sample increased with decreasing lead-hole diameters. No significant difference was found between withdrawal resistance values from radial and tangential sections in either species. However, significantly lower values were obtained for the cross-sections of the samples than for the two other sections. Ratios between predicted pull-out load values of the nails from both species based on the finite element numerical interference approach were very close to experimental measurements, with ratios ranging from 0.93 to 1.09. The results provide better understanding of the behaviour and performance of pull-out resistance for building systems.

Optimizing Mix Proportion of Lightweight Concrete Containing Plastic Waste by Taguchi Method

In this study, mix proportion parameters of lightweight concrete (LWC) containing ethyl vinyl acetate (EVA) plastic waste from footwear manufacture were investigated by employing Taguchis method and ANOVA statistics. The mixtures were designed in a L9 orthogonal array with four factors viz., water/cement, water content, EVA content and sand/cement. The results showed that EVA content and water/cement ratio had the significant effect on density and compressive strength of LWC. The density and compressive strength of the LWC containing EVA waste ranged from 1172 to 1441 kg/m3 and from 3.5 to 10.8 MPa, respectively. It can be concluded that the obtained LWC can be classified as masonry concrete. The best possible levels for mix proportions were determined to optimize density and compressive strength of the samples.

Optimal Decolorization Efficiency of Reactive Red 3 by Fe-RH-MCM-41 Catalytic Wet Oxidation Coupled with Box-Behnken Design

The reactive red 3 was degraded by catalytic wet oxidation process over Fe-RH-MCM-41 prepared by Direct Hydrothermal Technique (DHT) at Si/Fe molar ratio of 10 using silica from rice husk. The extended reaction conditions were studied as a function of reaction temperatures, initial H2O2 concentrations and initial pH of solutions designed by Box-Behnken design (BBD) based on Response Surface Methodology (RSM) to achieve the optimal condition and interaction of independent variables. The characterizations of catalyst were studied by XRD, BET surface area and TEM to explain the morphology of surface and to confirm the hexagonal structure. The results showed the 2theta peak can be indexed to hexagonal lattice that also confirmed by TEM result and surface area about 650 m2/g. All of independent variables showed significant on the degradation of reactive red 3 except for initial H2O2 concentration.

Thermal Degradation and Fire Retrandancy of Wood Impregnated with Nitrogen Phosphorus Flame Retardant

In this research, the effect of diammoniumphosphate (DAP) as fire retardant additive during thermal degradation of wood samples from shorea obtuse (Dipterocarpaceae) has been investigated. Thermal properties of wood samples impregnated with DAP ranging from 0-40 %wt were characterized by thermogravimetric analysis (TGA) and limiting oxygen index (LOI). Leachability of DAP from impregnated samples kept under running water was also investigated. The results indicated that the rate of weight loss obtained from TGA reveal that impregnation of DAP reduced the degradation rate from 0.95%/°C to 0.56%/°C. Furthermore, LOI of woods specimens trended to be increase from 24.8 to 30.6 when they were treated with DAP having a range of 0-30 %wt. Based on the results of this study, wood samples impregnated with 30%wt of DAP can be classified as self-extinguishing materials and cloud meet the requirement for non-flammability in construction. The leachability test indicated that only trace amount of unreacted DAP leached from the samples.

Reconfigurable Shape Memory and Self-Welding Properties of Epoxy Phenolic Novolac/Cashew Nut Shell Liquid Composites Reinforced with Carbon Nanotubes

Conventional shape memory polymers (SMPs) can memorize their permanent shapes. However, these SMPs cannot reconfigure their original shape to obtain a desirable geometry owing to permanent chemically or physically crosslinked networks. To overcome this limitation, novel SMPs that can be reconfigured via bond exchange reactions (BERs) have been developed. In this study, polymer composites consisting of epoxy phenolic novolac (EPN) and bio-based cashew nut shell liquid (CNSL) reinforced by multi-walled carbon nanotubes (CNTs) were prepared. The obtained composites exhibited shape memory and self-welding properties, and their shapes could be reconfigured via BERs. Their shape memory mechanisms were investigated using variable-temperature Fourier transform infrared spectroscopy and dynamic mechanical analysis. The EPN/CNSL composite containing 0.3 wt % CNTs showed the highest shape fixity and shape recovery ratio. Furthermore, shape memory behavior induced by irradiation of near-infrared (NIR) light was also observed. All samples showed high shape recovery ratios of nearly 100% over five cycles, and increasing the CNT content shortened the recovery time remarkably. The ability of shape reconfiguration and stress relaxation affected the photo-induced shape memory properties of reshaped samples. Additionally, the self-welding properties were also influenced by stress relaxation. The hindrance of stress relaxation caused by the CNTs resulted in a decrease in adhesive fracture energy (Gc). However, the Gc values of EPN/CNSL composites were comparable to those of epoxy vitrimers. These results revealed that the material design concepts of thermal- and photo-induced shape memory, shape reconfiguration, and self-welding were combined in the EPN/CNSL composites, which could be feasible method for advanced smart material applications.

Effects of Surface Hydrophobicity on Functionalization of Oleic Acid on Bombyx mori Silkworm Cocoons

The objective of this study is to provide a method which allows introduction of functional groups onto silk cocoon surface. Plasma irradiation is straight-forward, relatively noninvasive and requires minimal chemical reaction steps to alter surface hydrophilicity of polymeric materials. Introduction of oleic acid on pristine and air-zero irradiated silkworm (Bombyx mori) cocoons was carried out via acid-catalyzed esterification. The reaction was confirmed by ATR-FTIR spectroscopy. Functionalization of oleic acids onto silkworm cocoons favors hydrophilic surface. In addition to the acid-catalyzed esterification, amide hydrolysis takes place as a side reaction. This reaction leads to formation of hydrophilic carboxylic acids and amines. The change in hydrophilic functionalities leads to an increase in cocoon wettability as confirmed by contact angle measurements.

Properties of Cassava Starch-Based Foam Composite Containing Sugarcane Fiber and Origanum vulgare L. Essential Oil

Properties of biodegrdable trays manufactured from cassava starch, sugarcane fibers and Origanum vulgare L. essential oils (OEO) were used as additives. The effect of these additives on water absorption index (WAI), water solubility index (WSI), the density and thermal analysis of the starch trays was determined. Based on the experimental results, the cassava starch incorporated with 8% essential oils and sugarcane fiber exhibited outstanding water resistance, comparing with those of polystyrene foam. It shows that the addition of OEO would have potential to enhance dimensional stability of the trays made from cassava starch.

Properties of Light Weight Concrete Containing Crumb Rubber Subjected to High Temperature

In this study, the compressive strength, unit weight and chemical structure of light weight concrete (LWC) containing crumb rubber after exposure to high temperature are investigated. The crumb rubber was used as light weight aggregate in place of normal aggregate at the content of 3-15 wt% of LWC. For all mixtures, the water/cement ratio and sand/cement ratio were fixed at 0.5 and 0.2, respectively. The experimental results showed that the unit weight of LWC containing crumb rubber decreased with increasing crumb rubber content. The unit weight and compressive strength values are in range of 1566-1761 kg/m3, 12-29 MPa, respectively. The LWCs containing 3-7 wt% and 15 wt% crumb rubber can meet the requirement of ASTM standards for structural light weight concrete and masonry, respectively. After high temperature exposure, the unit weight loss and compressive strength loss were 25% and 75%, respectively. All specimens still complied with the requirement of ASTM standard for masonry.