Sol‐gel process of alkyltriethoxysilane in latex for alkylated silica formation in natural rubber

Sol‐gel process of alkyltriethoxysilanes that was dispersed in natural rubber latex was used to generate alkylated silica particles inside the rubber matrix. Three types of alkyltriethoxysilanes were chosen, i.e., vinyltriethoxysilane (VTOS), ethyltriethoxysilane (ETOS), and i‐butyltriethoxysilane (BTOS), as they differed in the type of one substituent group. Together with tetraethoxysilane (TEOS), a typical precursor for silica formation, all silanes were studied for their conversion to silica and subsequent reinforcement capabilities in sulfur‐vulcanized rubber. The in situ generated silicas were fine and well dispersed in the rubber matrix, as analyzed by SEM and TEM. Solid‐state ²⁹Si‐NMR technique was used to confirm the presence of alkyl substituents on the silica particles buried inside the rubber matrix. Tensile and tear properties of the in situ silica‐filled NR vulcanizates were higher than those of the vulcanizate prepared by conventional mixed method. Among the three alkyltriethoxysilanes used, only VTOS, when used as a mixture with TEOS, did not cause a reduction in silica formation. The resulting vinylated silica tended to enhance the tensile modulus and resistant to tear of the rubber vulcanizates. Cure characteristic and swelling behavior in toluene of the silica‐containing vulcanizates were also investigated. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers     

Application of rice husk ash as fillers in the natural rubber industry

Rice husk ash (RHA) obtained from agricultural waste, by using rice husk as a power source, is mainly composed of silica and carbon black. A two‐stage conventional mixing procedure was used to incorporate rice husk ash into natural rubber. For comparison purposes, two commercial reinforcing fillers, silica and carbon black, were also used. The effect of these fillers on cure characteristics and mechanical properties of natural rubber materials at various loadings, ranging from 0 to 40 phr, was investigated. The results indicated that RHA filler resulted in lower Mooney viscosity and shorter cure time of the natural rubber materials. The incorporation of RHA into natural rubber improved hardness but decreased tensile strength and tear strength. Other properties, such as Young's modulus and abrasion loss, show no significant change. However, RHA is characterized by a better resilience property than that of silica and carbon black. Scanning electron micrographs revealed that the dispersion of RHA filler in the rubber matrix is discontinuous, which in turn generates a weak structure compared with that of carbon black and silica. Overall results indicate that RHA can be used as a cheaper filler for natural rubber materials where improved mechanical properties are not critical. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 34–41, 2005     

Experiment and computation multi-fidelity multi-objective airfoil design optimization of fixed-wing UAV

Journal of Mechanical Science and Technology - Optimization with a surrogate model is a popular method used in design to avoid a high computational cost problem and is often encountered in...     

Effects of fluidized bed drying temperature and tempering time on quality of waxy rice

Waxy rice, which is soft and sticky in nature, can be used as a raw material to produce many food products. After being harvested, high-moisture waxy paddy must be dried to appropriate moisture content to prolong its storage life and to achieve higher head rice yield. Fluidized bed dryer could be used to dry waxy rice at high-temperature. However, due to the high heat and mass transfer rates during drying, stresses are generated in a rice kernel, leading to crack and low head rice yield. Tempering is thus recommended to reduce the moisture-induced stresses in the kernel after rapid drying. In this study, the effects of fluidized bed drying temperature (90, 110, 130 °C) and tempering time (30–120 min) on the quality of waxy rice, i.e., head rice yield, thermal properties, pasting properties, color, translucent kernel and microstructure, were investigated. The results showed that head rice yield of waxy rice after drying was significantly lower than that of the reference sample even when tempering was performed. Higher drying temperatures led to higher head rice yield while the tempering time did not have any effect on the head rice yield except when the drying temperature of 90 °C was used. Drying at higher temperatures also affected the starch granule morphology and the pasting properties. Waxy rice changed its appearance from opaque white to translucent when being dried at 130 °C.     

Comparison of rubber reinforcement using various surface-modified precipitated silicas

The reinforcement of a natural rubber compound by various surface-modified precipitated silicas was compared. Compound physical properties were determined for two silicas differing in surface area and were used as controls to evaluate these silicas after surface modification by using either a bifunctional organosilane coupling agent (γ-mercaptopropyl–trimethoxysilane) or a new surface modification process. This new process is based on the in situ polymerization of organic monomers solubilized inside surfactant bilayers that are adsorbed onto the silica surface to afford silicas modified with styrene–butadiene and styrene–isoprene copolymers. Both surface modification processes afford materials that dramatically increase the compound cure rate, thereby significantly reducing T₉₀ cure times, while also improving tensile properties, tear strength, abrasion resistance, and compression set of the cured compound. The silane-modified silica gives a higher flex-cracking resistance than do the silicas modified by the in situ polymerization of organic monomers, whereas these latter silicas significantly increase rebound resilience and offer greater overall improvements in rubber compound performance. The rubber compound physical properties obtained using the modified, higher surface area Hi-Sil® 255 silica are generally improved relative to those obtained using the modified Hi-Sil® 233 silica. © 1996 John Wiley & Sons, Inc.     

Effect of high-temperature fluidized-bed drying on cooking, textural and digestive properties of waxy rice

In this work, changes of the cooking and pasting properties as well as starch digestibility of waxy rice (RD6) during hot air fluidized bed drying were investigated. Re-moistened waxy rice at an initial moisture content of 28% dry basis (d.b.) was dried at 90-150 °C. Semi-dried waxy rice was tempered and dried again by ambient air until the moisture content reached 16% (d.b). It was found that the degree of gelatinization increased with an increase in the drying temperature. At 130 and 150 °C the appearance of some waxy rice kernels changed from opaque to translucent, indicating complete gelatinization. Thermal degradation of amylopectin granules during high-temperature drying caused the starch to be more rapidly digested; this led to lower peak viscosity and setback viscosity. In addition, waxy rice processed at higher drying temperatures (90-150 °C) could adsorb more water and exhibited larger loss of solids during soaking. Such effects subsequently led to samples with lower hardness and higher stickiness. Based on the sensory analysis results, however, waxy rice dried at the above temperatures, when cooked, did not significantly differ in overall acceptability from the reference waxy rice.     

Prevalence and associated risk factors of low‐back pain in textile fishing net manufacturing

This study examined the 7‐day prevalence of low‐back pain (LBP; i.e., pain within the preceding week of the survey) and identified associated factors, including working posture, for a population of fishing net assembly workers. LBP is a serious problem in manual work with high prevalence and affects worker absenteeism. A cross‐sectional survey study was conducted among textile fish net industrial workers using a structured questionnaire (hand delivered by researchers and independently completed by workers). The 7‐day prevalence of LBP in this study was 68.6% (95% confidence interval [CI]: 65 to 72%). Work factors significantly related to LBP included prolonged standing and walking. Workers 35 years old or greater were significantly more likely to experience LBP within the past 7 days preceding the survey than were those 34 years old or less (adjusted odds ratio [ORadj] = 4.9; 95% CI: 2.4 to 10.3; p = .0001). Other significant factors associated with LBP included posture position, specifically stooping (ORadj = 1.6; 95% CI: 1.0 to 2.3; p = .033), lifting (ORadj = 1.6; 95% CI: 1.1 to 2.4; p = .025), and high concentration jobs (ORadj = 1.9; 95% CI: 1.3 to 2.7; p = .001), respectively. LBP among textile fish net workers is a serious problem meriting ergonomic evaluation and design of control measures for reducing worker exposure to risk factors. Work characteristics were more significantly associated with LBP than were individual characteristics. Factories need to consider adjusting work conditions to prevent worker low‐back injuries. © 2012 Wiley Periodicals, Inc.     

Far-infrared radiation assisted drying of longan fruit

Oversupply of fresh longan (Dimocarpus longan Lour.) from seasonal production in Thailand needs to be preserved in the form of dried product (exported value of over US$70 million in 2009) to prevent it from being damaged by microorganism. Due to well known limitations of hot air (HA) drying, a new technique of using far-infrared radiation (FIR) in combination with hot air and heat pump (HP) dryers for longan is proposed in this study. Longan with initial moisture content of approximately 84–86% w.b. was dried to about 18% w.b. at the drying temperature of 55 °C in the case of combined FIR-heat pump drying and 65 °C in the case of combined FIR-hot air drying with 80% recycled air. In both cases, the electric power supplied to FIR rods was set at 250, 350 and 450 W. The experimental results are presented in terms of the drying kinetics, dried product qualities (color, shrinkage, percentage of rehydration, water activity, texture, and microstructure) and sensory characteristics of the dried product. The results show that FIR in combination with hot air and heat pump drying increases the drying rate of longan by reducing the drying time. FIR also helps to create more porous structure in dried longan, with porosity increasing with the power supplied to the FIR heaters. The formation of porous structure results in a product with lower shrinkage, improved rehydration, lower hardness and lower toughness than samples dried in the absence of FIR. In addition, the FIR dried longan had a stronger red color and appeared darker. Dried longans obtained by HP, HA, combined techniques and the product from the local market, were all rated similarly by a sensory panel for color, shape, flavor and taste. It is worth noting that the overall energy used for FIR-assisted drying processes decreased with the increase in the power supplied to the FIR heaters.     

Effect of furcellaran incorporation on gel properties of sardine surimi

Effects of furcellaran, powder (FURP) and solution (FURS), incorporation (2-8% based on surimi solid content) on gel properties of sardine (Sardinella albella) surimi were investigated. Breaking force, hardness, gumminess, chewiness, and whiteness of gels increased with increasing FURP or FURS contents (P < 0.05), where the highest values were observed in gel containing 8% FURS (P < 0.05). Expressible moisture content of gel decreased as levels of furcellaran increased (P < 0.05). The gel deformation, springiness, and cohesiveness were not affected by furcellaran (P > 0.05) as well as the polymerization of myosin heavy chain as visualised by SDS-PAGE. FURP and FURS could enhance the interconnection between chains during heating as indicated by the higher G′. Addition of furcellaran, especially FURS, up to 6% increased sensory property of resulting gel (P < 0.05). Anywise, an abatement in overall likeness score was found in gel with 8% FURS. Finer and denser microstructural network was observed in gel containing 6% FURS when compared to control. Therefore, furcellaran, prepared as solution, at an appropriate level can improve the overall quality of sardine surimi.     

Improving head rice yield of glutinous rice by novel parboiling process

Most commercial parboiled rice is produced from high-amylose content rice. Glutinous rice, which is lacking in amylose content, is generally consumed in Southeast Asian countries. Rare study of parboiling glutinous rice has been observed. In this study, glutinous rice was improved in head rice yield by a novel parboiling process. Two rough glutinous rice, rice department 6 (RD6) and black glutinous rice (BGR) cultivars, were soaked in hot water at 70?±?5°C for 3?h. The ricer 3moisture content after soaking was 50–52% (d.b.), it was dried with hot air and superheated steam (SHS) at 110, 130, and 150°C in a fluidized bed dryer. The results show that SHS at all drying temperatures can improve the high head rice yield in both parboiled glutinous rice cultivars better than hot air drying. Higher temperature drying caused L* value to decrease but the b* value increases in RD6, whereas in BGR, all color values decreased and ΔE* was increased when the drying temperature increased. Increasing drying temperature presented a softer texture of both glutinous rice cultivars. Upper 130°C, completed gelatinization of both varieties can be obtained and seen by scanning electron microscope and differential scanning calorimeter (DSC). This technique of using high-temperature fluidized bed drying can produce completely parboiled glutinous rice in a single process instead of two conventional processes, steaming and drying, in series.