Papers by Keyword: Polymer

Abstract: In current ACI 440.1R-06 design guideline, an environmental reduction factor (ERF) is specified to account for long-term durability of GFRP bar used in reinforced concrete structures. Such ERF factor is still lack of confidence to concrete industry prior to deliberate calibrations with in-field real time data. In this paper, a parametric study on the design of GFRP bar RC bridge deck per ACI 440 guideline is presented to investigate the stress level in GFRP bar under ultimate design loads per AASHTO LRFD Specifications. Results show that tensile stress in GFRP under ultimate design loads is always less than 25% of GFRP guaranteed tensile strength f*fu, which is much lower than the design strength per as specified in ACI 440 Guideline (i.e., 0.7 f*fu). It showed that GFRP bar RC bridge deck as designed in accordance with ACI 440 guideline could give sufficient safety margin.

Abstract: In order to reduce the road asphalt fumes in the process of construction, the paper proposed to add some substances in asphalt to reduce the yield of asphalt fumes. Firstly, considering the theory of how the asphalt fumes come into being in the process of construction on the pavement, six possible additives to restrain these fumes havd been screened out. And tests of fumes suppression effect had been done to get the results that: SBS has a good effect of fumes suppression. When added by 3%, the asphalt fumes reduced by the rate of 19.2%; PE has an suppressive effect on asphalt fumes. When added by 3%, the asphalt fumes reduced by the rate of 6.5%; Melamine has a good effect of fumes suppression. When added by 3%, the asphalt fumes reduced by the rate of 45.1%; Ammonium molybdophosphate has an abnormal effect of fumes suppression. When added by 1%, the asphalt fumes not only did not reduce but increases. When added by 3%, the asphalt fumes reduced by the rate of 23.3%; nanoCalcium carbonate has an effect of fumes suppression. When added by 3%, the asphalt fumes reduced by the rate of 4.8%; Activated Carbon has a good effect of fumes suppression. When added by 3%, the asphalt fumes reduced by the rate of 41.6%.

Abstract: Currently, an environmental reduction factor (ERF) is incorporated in design codes/guidelines of Fiber Reinforced-Polymer (FRP) in reinforced concrete (RC) structures to account for the FRP long-term durability. Due to the lack of real time durability data, justification of the ERF is still necessitated. This paper presents a calibration of ERF for GFRP bar to be used in China on the basis of the prediction of GFRP long-term performance with monthly average temperature records from 32 major cities. Research results show that the ERF values vary from 0.49 to 0.58 at 100% R.H. exposure, while ERFs are greater than 0.70 for all cases being studied when R.H. is below 90%. On the basis of this study, ERF can be recommended as of 0.70 and 0.50 for application with R.H. <90% and moisture saturated exposures, respectively.

Abstract: Castor oil and microcrystalline cellulose were employed as biomass feedstock to produce bio-based polymer composites with increased tensile strength. The polymer composites were prepared by curing castor oil with 4,4'-methylenebis (phenyl isocyanate) (MDI) in the presence of microcrystalline cellulose (MC) or modified MC (MMC). The MMC was prepared by reacting MDI with MC to introduce isocyanate groups to the surface of MC. X-ray diffraction spectra suggested the good retention of the crystalline structure of MC or MMC in the composites. SEM analysis showed the well dispersion of MC or MMC in the composites. All of these factors are critical to reinforcing the composites. Mechanical tests of the composites revealed that the reinforcing effect of MMC was more significant than MC at high cellulose content such that the highest tensile strengths of 4.87 MPa was obtained for the composite containing 43% (wt) of MMC. That is almost 5 times higher than that of neat castor oil-based polyurethane.

Abstract: Through the indoor comparative experiments, this paper studied the viscosity and surface tension of surface-active polymer, and calculated the critical micelle concentration, the surface adsorption capacity, molecular occupied area, and other parameters. Through comparing with intermediate molecular weight polymer, it is found out that surface-active polymer has characteristics of high viscosity and its viscosity is higher than common polymer under the same concentration. As a new type of polymer, surface-active polymer can reduce the tension and present a certain activity. The critical micelle concentration of surface-active polymer is 0.2532 g/L, the surface adsorption capacity is 1.678×10 -10mol.cm -2,and the molecule occupies an area of 0.9899 nm 2 .This theme also studied the emulsifying power and the characteristic of static and dynamic adsorption. The results show that the agents have approved emulsifying power with only 38% of the excluded water during 30 days. The static adsorption capacity of surface-active polymer is 1.92 mg/g. Under the same condition, its dynamic retention volume is greater than the amount of polymer retention.

Abstract: An experimental loop was established with API X52 steel pipes to investigate the effect of drag-reducing polymer on heat transfer in gas-liquid two-phase flow. The inner diameter of the steel pipe is forty millimeter and the test loop has four different test sections such as horizontal, inclined upward, inclined downward and vertical upward sections. The experimental results were presented. The relationship between the drag reduction efficiency and heat transfer reduction was analyzed. When the drag reduction induced by drag-reducing polymer is about 60~70%, the heat transfer between the fluid and the pipe wall obviously decreases. The heat transfer reduction can reach up to 80~90%, which is greater than the drag reduction. A new method is proposed for characterizing the effect of drag reducing polymer on the heat transfer in two-phase flow with Stanton Number.

Abstract: A chemical gas sensor for volatile organic compounds (VOCs) detection at trace level is proposed. In this paper, the development and demonstration of the sensor prototype are presented. The prototype is based on a microcantilever resonator that is fabricated from direct bonding silicon-on-insulator (SOI) wafer. The resonant cantilever employs integrated thermal driving and piezoresistive detecting units, and operates in a self-oscillation system. Polyethylenevinylacetate (PEVA) is deposited on top of the cantilever as gas sensitive layer through a spraying method. The responses of the prototype to relative humidity (RH) and six common VOCs: toluene, benzene, ethanol, acetone, hexane and octane have been tested. The PEVA-coated prototype has trace sensitivity to toluene, benzene, hexane and octane, while is insensitive to humidity. The experimental results provide confirmation that the microcantilever resonator is an excellent platform for chemical gas sensor.

Abstract: Both natural and synthetic materials have been utilized to provide three dimensional scaffold environments ideal for bone repair. The biomechanical and biocompatibility characteristics of these scaffolds play a vital role in successful tissue engineering constructs. Polymer/carbonate apatite (CHA) composites have shown to improve cell adhesion and proliferation on the scaffold as well as increase elastic modulus, toughness and strength. The aim of this study is to prepare CHA- polylactic-co-glycolide (PLGA) composites in the form of microsphere, scaffold and disc and evaluate their physico-chemical properties, mechanical properties and in vitro bioactivity. 3-D porous cylindrical composite scaffolds were prepared using PLGA/CHA composites with varying PLGA/CHA ratios (30:70 and 50:50). The CHA was prepared by hydrolysis method and characterized using x-ray diffraction (XRD) and Fourier Transform Infrared spectroscopy (FTIR). The physico-chemical and mechanical properties of the composite scaffolds were evaluated using scanning electron microscopy (SEM), micro-computed tomography (μCT), XRD, FTIR, and thermogravimetry (TGA). Flexural strength was determined using Instron. In vitro bioactivity was determined by the formation of apatite on composite disc surfaces after immersion in simulated body fluid (SBF). SEM and μCT analyses showed high porosity and interconnectivity between microspheres in the composite scaffolds. In vitro bioactivity was observed by the development of an apatite layer on the surfaces of the composite scaffolds after immersion in simulated body fluid. The mechanical strength of the scaffolds was to be dependent on the PLGA-CHA ratio. The elastic modulus, toughness and strength values obtained for the composites were similar to those of reported bone substituted materials. Results from this study provided information on the fabrication of PLGA-CHA scaffolds and their properties that may be useful for their potential application in bone repair and as scaffolds in tissue engineering for bone regeneration.

Abstract: Bragg gratings were inscribed in poled host-guest polymer thin films containing anelectro-optically active chromophore. Probing the grating in reflection, with a transparent con-ducting electrode on one side of the film and a gold-coated electrode on the other, a modulatingelectric field was observed to induce a modulation in the grating efficiency consistent with thatexpected from the measured electro-optic coefficient.

Abstract: Various composite materials have been developed, but in many cases problems arise due to the combined materials such as fabrication becoming difficult because of the significant increase in viscosity, and transparency of the polymer is sacrificed. These issues can be overcome by controlling the nanointerface; however, this is considered as a difficult task since nanoparticles (NPs) easily aggregate in polymer matrices because of their high surface energy. Organic functionalization of inorganic NPs is required to increase affinity between NPs and polymers. For fabricating multi-functional materials, we proposed a new method to synthesize organic modified NPs by using supercritical water. Because organic molecules and metal salt aqueous solutions are miscible in supercritical water and water molecules serve as acid/base catalysts for the reactions, hybrid organic/inorganic NPs can be synthesized under the supercritical condition. The hybrid NPs show high affinity for the organic solvent and the polymer matrix, which leads to the fabrication of these super hybrid NPs. How to release the heat from the devices is the bottle neck of developing the future power devices, and thus nanohybrid materials of polymer and ceramics are required to achieve both high thermal conductivity and easy thin film flexible fabrication, namely trade-off functions. Surface modification of the BN particles via supercritical hydrothermal synthesis improves the affinity between BN and the polymers. This increases the BN loading ratio in the polymers, thus resulting in high thermal conductivity. Transparent dispersion of high refractive index NPs, such as TiO₂ and ZrO₂, in the polymers is required to fabricate optical materials. By adjusting the affinity between NPs and the polymers, we could fabricate super hybrid nanomaterials, which have flexiblility and high refractive index and transparency.