Advanced Materials Research Vols. 150-151

Abstract: In combination with the property of the freeze-thaw damage of Qinhuangdao concrete pavement，polymer modified cement mortars were developed through the system's mechanical properties and durability compared laboratory tests; On this basis,the mechanics performance of the polymer emulsion and the bonding tension performance of the new-old concrete are studied; The construction techniques were provided and they have been applied in the projects of Qinhuangdao concrete pavement, and through experiments road more than one year of test result to indicate that they have received good economical and social effects.

Abstract: Wood I-joists is a kind of wood-based engineering material which was widely used in wood construction. As it is in fact, the property of I-joists are influenced not only by normal stress but also by a part of shear stress when they are taking into application. In this study, the effects of different factors were evaluated on the tensile property of the wood I-joists. The factors include the depth of the tanks on the flanges, the length of joint and different kinds of flanges. The method of control test was used in the process of the experiment design, and tensile shear test were taken during the experiment at the aim of testing the bonding property of the I-joists using a universal mechanical testing machine. Ultimately, it has been discovered that the factor of depth of the tanks and the length of the joint influence the bonding property mostly. So this paper offers the optimal fabrication technology of the I-joists to make it is possible for the increase of reliability when wood I-joists are taken into application.

Abstract: In order to obtain correct nonlinear performance of tall building at seismic zone, several typical planar and elevation irregular tall buildings with different structural system are mainly discussed in the paper. Effect on the seismic response of structures due to the hazard bearing structure simplification are analyzed so as to obtain nonlinear performance accurately of structures for the seismic risk analysis, important influencing factors are also discussed followed. The results show that it is efficient to forecast the performance of tall buildings for the seismic risk analysis at seismic zone after Wen-Chuan Earthquake in China cities.

Abstract: After the assessment targets on concrete durability were optimum designed rationally to be assessment parameters, the durability deterioration course of concrete in sulfate environment was characterized using designed assessment parameters. The results show that, every performance deterioration degree of concrete can be compared on the same coordination axis by assessment parameters. The assessment parameters were applicable the same determination criterion, and the determination principle is simple and convenient. The comparing the deterioration course and sensitivity degree of concrete performance is much easy. If concrete performance of anti-sulfate erosion was experimented at laboratory, the result assessment ought to use the two non-destructive test assessment parameters.

Abstract: The glass fiber (GF) reinforced epoxy (EP) composites filled by nano-Al2O3, nano-TiO2, nano-SiO2 and multi-walled carbon nanotubes (MWCNTs) were prepared. The friction and wear behavior of composites under dry condition were evaluated with block-on-ring friction and wear tester. The morphologies of the worn surfaces of the composites were analyzed by scanning electric microscopy (SEM). The results show that 0.5 wt% MWCNTs and nano-TiO2 can significantly lower the friction coefficient and specific wear rate of composites, respectively, while 0.5 wt% nano-SiO2 and nano-Al2O3 can slightly lower the friction coefficient and specific wear rate of the composites.

Abstract: For obtaining materials with high thermal conductivities and suitable thermal expansion coefficient for thermal management applications, diamond/Al composites were fabricated by the low-cost pressureless metal infiltration. The resulting composites exhibited thermal conductivities as high as 518.7 W/m•K and thermal expansion coefficient as low as 4.61×10-6/K friendly matching with semiconductors materials like Si or GaAs. The diamond particles were not only well embedded, but also uniformly distributed in the metallic matrix along with SEM observations of the composites. Fractograph of the composites illustrated that aluminum matrix fracture was the dominant fracture mechanism and the stepped breakage of diamond particles indicated strong interfacial bonding between diamond and the Al matrix. The Si skeleton with coralline morphology in the interface between diamond and the matrix were found to play a role of bridge in the interfacial structure and result in distinctive interfacial bonding. Also a little content of Al4C3 were realized to have positive effect on the improved thermal conductivities for promoting interfacial bonding between aluminum and diamond. In addition, the excellent mechanical behavior of the composite was illustrated. The results shows a superior Young’s modulus of 286 GPa compared with traditional thermal management materials and relatively high bending strength of 306MPa.

Abstract: A series of rigid polyurethane foams are synthesized via the reaction of isocyanate terminated polyimide prepolymers with polyether polyol. Deionized water and n-pentane are used for blowing agents. The prepolymers and polymers are characterized by conventional methods, and physical, mechanical and thermal properties are studied. The results show that in comparison to pure polyurethane foams, these rigid polymer foams exhibit improved thermal stability as well as good compressive property. SEM of the compressed body of rigid polyurethane-imide foams show that the destructive forms are open-type tear of the film and the breakdown of the cell body wall.

Abstract: A novel rigid polyurethane thermosetting foam is synthesized via the reaction of isocyanate terminated polyimide prepolymers with polyether polyol(4110), and deionized water and n-pentane are used for blowing agents simultaneously. The prepolymers and polymers are characterized by conventional methods and -NCO conversion rate, characteristic structure and morphology are also studied. The results show that the optimal condition of polymerization of polyimide prepolymers is under 60 oC for 30min. FTIR data show that the imide groups have been achieved successfully. The rigid polyurethane-imide foams prepared by this technique possess the cell diameter ranging from 1.5mm to 2.5mm and bubbles distributing equably.

Abstract: The polycondensation kinetics of 4,4’-dihydroxydiphenyl sulfide (DHPS) with 4,4’-dichloro diphenylsulfide (DCPS) was investigated in the presence of catalyst 2A. The reaction follows second-order kinetics and the reaction rate is a bimodal, a relatively lower rate initially and a faster rate after 3h. The initially lower rate is attributed to the lower solubility of DHPS salt in organic solvent. The results show higher polymerization temperature leads to higher conversion and finial reaction extent after 7h. In the present work, catalyst 2A/DHPS molar ratio of 0.17 is considered more suitable for PPSE preparation. The activation energy of two-stage polymerization of PPSE is 104.5kJ/mol and 79.33kJ/mol, respectively. According to obtained kinetics parameters, curves of fractional conversion versus reaction time were simulated and compared with experimental curves at different temperatures.

Abstract: This study modified urea-formaldehyde (UF) resin with a modifier, and focused on properties of particleboard manufactured with the modified UF resin. The orthogonal design was used to analyze the effects of different levels of hot-pressing temperature, hot-pressing time, glue content, and waterproof agent content on the modulus of rupture (MOR), internal bonding strength (IB), and formaldehyde emission (FE) of the particleboard, and thus determined the optimum technical parameters of hot-pressing. The conclusions were as follows: (1) the modifier used in this study could significantly reduce the free formaldehyde content of UF resin and the formaldehyde emission of particleboard; (2) the optimum hot-pressing technical parameters of particleboard manufactured with the modified UF resin were hot-pressing temperature 180°C, hot-pressing time 50s/mm, glue content 12%, and waterproof agent content 0.6%. The MOR and IB under the optimum technical parameters could reach 20.7 and 0.47 MPa, and the FE was 0.85 mg/L.