Materials Science Forum Vols. 675-677

Abstract: In this paper, the effects of carbon black (CB) mass fraction on volume resistivity and electromagnetic shielding effectiveness (SE) of CB/Acrylonitrile Butadiene Styrene (ABS) composites were studied. The results indicated that when CB mass fraction was over 15 wt%, the volume resistivity dropped sharply and when it rose to 35 wt%, the volume resistivity achieved the lowest value about 103Ω·cm. In addition, there are two obvious percolation effect at 15~20 wt% and 25~35 wt% CB respectively in the course of the volume resistivity changing. Titanate coupling agent could greatly improve conduction and SE of CB/ABS composites. Lastly, the SE of CB/ABS composites was investigated by experimental observation.

Abstract: Piezoelectric polymer, polyvinylidene fluoride (PVDF) film, has been widely investigated as sensor and transducer material due to its high piezo-, pyro-, and ferroelectric properties. However, there are many limitations for PVDF film as human-related tactile sensor, such as non-breathability, stretching, requirement of additional process like poling, etc. In this paper, PVDF nano-fibrous membrane which is light, flexible, and wearable was prepared by electrospinning technique. The electrospinning parameters such as the voltage, feeding rate, tip-tocollector distance, etc, were well controlled. More than 4 hours electrospinning time was needed for a certain thickness of PVDF nano-fibrous membrane. The morphology of PVDF nanofiber was determined by scanning electron microscopy (SEM), the diameter distribution was calculated and crystal structure was evaluated by FTIR spectroscopy. We found the feasibility of developing piezoelectric PVDF fibrous membranes through electrospinning technology, which is a good candidate for flexible human-related tactile sensors to sense garment pressure, blood pressure, heartbeat rate, accidental external impact on human body, etc.

Abstract: The mixture of asphalt and filler called asphalt binder is an adhesive and packing material in asphalt mixture. In this paper, the influence of different filler sorts such as limestone dust and hydrated lime, and different rates of limestone dust and hydrated lime such as 2:1, 1:1 and 1:2 at the same mass ratio of filler/asphalt (1.0) on the asphalt binder’s properties has been studied. The paper gives a description of the most commonly used conventional tests, such as Penetration and Softening Point, and a more detailed description of the viscoelastic behavior and dynamic testing of bitumen by way of Brookfield viscometer and Dynamic Shear Rheometer (DSR). The contrasts among different test results were presented. It is found that there are a decrease in penetration and an increase in softening point with increasing hydrated lime content. The viscosity also increases obviously with the mass of hydrated lime increases. The DSR results show that hydrated lime can increase asphalt binders' anti-shear stress and G*/sinδ, and are helpful to its properties at high temperature. The four tests results were also incorporated to evaluate the temperature susceptibility and the rheological characteristics of asphalt binders.

Abstract: The TiB2/AZ31 magnesium matrix composite was fabricated via self-propagating hightemperature synthesis (SHS) and then hot extruded. The influence of hot extrusion on the microstructure and property of TiB2/AZ31 composites was investigated. The results show that hot extrusion and synthesized TiB2 particles could refine the grain size obviously. The synthesized TiB2 particles are micro- and nano-sized, dispersing homogenously in the matrix. The interface between the matrix and the particles are good bonding. Meanwhile, slip and twinning are the main deformation modes during the hot extrusion. The fracture surface of hot-extruded TiB2/AZ31 magnesium matrix composite has more dimples than the as-cast AZ31 magnesium alloy. The improvement of microstructure seems to be beneficial for the fracture ductility of TiB2/AZ31 magnesium matrix composite.

Abstract: In this work analytical solutions are developed to study the free vibration of composite beams under axial loading. The beam with a single delamination is modeled as four interconnected Euler-Bernoulli beams using the delamination as their boundary. The continuity and the equilibrium conditions are satisfied between the adjoining beams. The studies show that the sizes and the locations of the delaminations significantly influence the natural frequencies and mode shapes of the beam. A monotonic relation between the natural frequency and the axial load is predicted.

Abstract: Epoxy/polyurethane interpenetrating polymer network coatings(EP/PU IPNs) modified by organic montmorillonite(oMMT)were prepared by interpenetrating polymer technology and in situ intercalative polymerization methods. TEM analysis showed that there is interaction between the oMMT and EP, PU phase, and the oMMT plays a role of "cross-linking point", changing the EP/PU matrix microstructure. Electrochemical analysis showed that oMMT and IPNs of EP and PU exhibits synergistic effect on improving anticorrosive properties of pure EP. When PU content is 30%, oMMT content is 3%, the EP/PU IPNs coatings has the best corrosion resistance.

Abstract: Alloy Mg-10Gd-3Y-0,4Zr in as-cast, as-extruded, cast-T6 (peak aged) and extruded-T5 (peak aged) state was tensile creep tested at 200, 250 and 300 °C and stress 50, 80 and 120 MPa. Comparison of minimal creep rate shows that alloy Mg-10Gd-3Y-0,4Zr in cast-T6 conditions is characterized by an excellent creep resistance, which is higher than that of commercially available Mg-alloys. Creep resistance of as-cast, as-extruded and extruded-T5 alloy Mg-10Gd-3Y-0,4Zr is lower. Cavity nucleation is heavily affected by the amount of secondary phases on the grain boundaries and also by the initial grain size of the microstructure. After extrusion and in the extruded-T5 conditions creep cavitation was not observed, whereas in the as-cast and cast-T6 conditions creep cavitation occurred on the high fraction of grain boundaries.

Abstract: A novel biomass composite, wood-polymer composite with potential good mechanical properties, durability and environmental characteristic capable of applying in fields of construction and traffic as structural material, was prepared by generating high-performance polymer from in situ polymerization of styrene in wood porous structure. The vinyl monomer, styrene, combing with 1wt% AIBN as an initiation, was first impregnated into wood porous structure under a vacuum/pressure condition, and then in situ polymerized through a thermal treatment. The structure of the resultant composite was characterized by SEM, FTIR and XRD. Results show that styrene polymerized into polystyrene through free radical polymerization, and the resultant polymer fully filled in wood porous structure in a column form, partly contacting wood matrix. FTIR analysis indicates that polystyrene generated into wood pores, indicating weak interaction between them. XRD analysis suggests that the polystyrene generated into wood pores mainly existed in an amorphous form.

Abstract: Bio-based materials such as wood, bamboo, bio-straw material are vulnerable to degradation by microorganisms and susceptible to change in dimension under humidity, which greatly reduced their service life. In this study, a novel thought was inspired from the unique porous structure of bio-based material that durability of wood may be capable of being improved by generating polymer in situ the special structure. Maleic anhydride (Man) and Styrene (St) were used to penetrate into wood for further copolymerization. SEM observation shows that polymer filled in wood porous structure and tightly contacted wood matrix (i.e. biopolymers), indicating strong interaction between them. FTIR analysis indicates that polymer chemically grafted onto wood matrix by reaction of anhydride group and hydroxyl group. As the amount of hydroxyl groups greatly reduced for their reacting with polymer, the dimensional stability of wood immersing in water was improved; and as the reaction of wood with polymer, the biopolymers were wrapped by resultant polymer, preventing the sample from attack of microorganisms, thus decay resistance of treated wood against microorganisms was greatly improved. Both of them contributed to the improvement of wood durability.

Abstract: The extensional rheology of low density polyethylene (LDPE) is studied bymelt spinning technique. Melt spinning mastercurves for LDPE are plotted for the measurement results of various temperatures and extrusion velocities. Linear relations between scaling factor b and T, Logb and Logv0 have been found. The analysis indicates that b can be regarded as a useful index of combination effects on the pre-orientation before extension, and on the unwrapping and orientation of macromolecular chains during extension. By using the values of b and the data from reference curve, extension viscosity curves of any setting temperature and extrusion velocity can be calculated, which will effectively enlarge the measurement range of melt spinning technique.