Papers by Keyword: Water Uptake

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Authors: Sugiman, Ilham Akbar, Emmy Dyah Sulistyowati, Paryanto Dwi Setyawan
Abstract: The paper presents the static strength of adhesively bonded steel joints aged in deionized water at a temperature of 60°C for 15 days at various adhesive thicknesses from 0.1 mm to 0.5 mm. Water uptake and the bulk adhesive tensile properties after aged in the same environment as the joints were also presented. It has been shown that water diffusion into the adhesive is non Fickian. The absorbed water in the adhesive significantly decreases the mechanical properties and it affects the static strength of the bonded steel joints. The effect of water is shown to be significant when the adhesive thickness is thicker than 0.2 mm as the static strength decreases sharply. This information is useful when designing the adhesive joints using thick adhesive layer exposed in moist environment.
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Authors: Mohaddeseh Saffarzadeh, Mohammad Reza Masteri Farahani
Abstract: In this research, the water absorption of polypropylene-pistachio twig flour composite with different content pistachio twig flour were investigated. For this purpose, water absorption was determined according to modified D570 standard. The results indicated that the water absorption of composites increased with increasing of wood flour content.
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Authors: Hai Gang Wang, Qing Wen Wang, Yan Jun Xie, Yong Ming Song
Abstract: Waste wood particles of different shapes were used to reinforce high density polyethylene (HDPE) to prepare high performance wood/plastic composites (WPC). The wood particles showed a needle-, flake-, strand-, and powder-shape, respectively. The mechanical and water-uptake properties of the composites manufactured using extrusion were tested. The wood needles/HDPE composites (WN-WPC) exhibited slightly higher mechanical strengths and lower density than the composites with the other shapes of wood particles. When the flake-, strand-, and powder-shaped wood particles were replaced by wood needles, the flexural, tensile and impact strengths were increased approximately by 4.24%, 7.61%, and 16.6% on average, respectively, and the density was decreased by about 7.34%. The length and width of WPC specimens changed little when soaked in water, with the thickening on the edge area only. WN-WPC performed the best waterproof stability. Based on the experimental results, the wood needles with lager length-to-diameter ratio would be the most suitable for producing high performance WPC.
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Authors: Shakira Md. Akhir Farhana, Dzulkifli Mohd Haziq, Nik Nurfatmah Pz, Rohah A. Majid
Abstract: Polyurethane (PU) foams are widely used today in automotive and as insulation system. Due to environmental issues, efforts have been made to replace petrochemical polyol with natural-based polyol in PU foam production, without sacrificing any properties. This study aims to produce palm oil-based PU rigid foam for non-load bearing applications such as wall panel or insulation for buildings. Two parameters studied were percentage of water uptake and surface foam morphology. Palm oil-based polyol (POP) was reacted with polymeric 4,4-diphenylmethane diisocyanate (p-MDI) at 1:1 NCO:OH ratio. Water was used as blowing agent and silicone surfactant was added to produce stable rigid PU foam. The content of silicone surfactant was varied at 2 and 3 part by weight (pbw). The percentage of water uptake increased slightly with increasing surfactant contents due to siloxane portion of the surfactants, is thought able to reduce the surface tension of the cell, thus absorbing more water than 2 pbw surfactant content. The findings were supported with micrographs of scanning electron microscope (SEM) that showed a larger cell window area and thicker strut.
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Authors: Sohibatul Muizzah Mohamad Izhar, Ku Zilati Ku Shaari, Zakaria Man, Yon Norasyikin Samsudin
Abstract: Starch is highly promising biopolymer for the production of packaging material since it gives films a good tensile and gas barrier properties. However, non-plasticized starch films are brittle and their hydrophilic character results in poor moisture barrier properties and high water sensitivity. In order to improve films formation and material properties of starch, plasticization and chemical modification such as cross-linking of the starch is required. The cross-linking reaction able to improve thermal stability, tensile strength and decreased the dissolution of starch films in water and formic acid. From the study, the percentage of water uptake reduced when the blending ratio of citric acid increased.The percentage of water uptake highly affected by curing time compared to blending ratio. Increasing the curing time from 1 hour to 2 hour significantly reduced the percentage of water uptake. At 4 hour curing time, the percentage water uptake reached equilibrium faster than 3 hour curing time. This shows that more citric acid molecules were chemically bonded with the starch chains, resulting in higher cross link degree and thus, reduced the percentage of water uptake.
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Authors: Yasir Ali, Muneer Al-Qadhi, Nesar Merah, Ahmad Rafiq
Abstract: The mechanical and physical properties of epoxy-clay nanocomposites are known to be significantly affected by the dispersion and distribution of the clay particles in the epoxy matrix. The degree of dispersion of the clay particles in the epoxy matrix depends mainly on the processing parameters used to synthesize the nanocomposite.In this paper, the optimized high shear mixing parameters determined in an earlier work were used to disperse five different loadings of Nanomer I.30E nanoclay (1, 1.5, 2, 3 and 5 wt%) into DGEBA epoxy matrix. A systematic approach was adopted to optimize the degassing process of the mixture. X-Ray Diffraction (XRD) analyses showed that the optimum nanoclay dispersion was achieved for a degassing temperature of 120 °C. The flexural strength of the developed nanoclay/epoxy composite is found to increase by 15% for 1.5 wt% and due to the high stiffness of the clay, as compared with epoxy resin, the flexural modulus improved continuously with clay loading. The observed reduction in strength and fracture strain at high clay loadings is mainly attributable to the presence of clay agglomerations and voids formation. The diffusion of water molecules and maximum moisture uptake of epoxy are reduced considerably by the presence of nanoclay.
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Authors: L. De Rosa, T. Monetta, Francesco Bellucci
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Authors: Fu Chun Zhao, Ai Bin Wu, Li Yue Zhang, Chao Qun Niu, Xiao Hui Wang, Kai Mei Chen, Shuang Quan Liao
Abstract: Nitrogen fertilizer is an important nutrition for the crops. However, the majority of common nitrogen fertilizers have not been absorbed by the plant, which causes great economical loss and environment pollution. In order to solve the above problem, the biodegradable slow-release coating materials for urea was prepared by introducing the active free radical of short chain cassava starch into concentrated natural rubber latex. The effects of the amount of starch, modifier dosage on the water absorption kinetics of natural rubber latex slow-released film, and the mechanical properties, slow-released performance, thermal stability and mildew characteristics in the tropical climate conditions was also examined. The results showed that the swelling rate of natural latex composite film increased with the increment of starch content. However, the water modifier imposed a different effect on the initial swelling rate and the equilibrium-swelling ratio of latex composite film. The preliminary swelling was slow but the time for achieving a basic balance state of the swelling was short. In addition, the thermal degradation process of the natural rubber latex slow-released composite film was divided into two stages. The maximum heat loss temperature of each stage shift toward the each other due to the increasing dosage of water modifier. The biodegradability of the composite film improved but the release rate of urea got faster when the starch content increased.
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