Materials Science Forum Vol. 815

Abstract: A novel superplasticizer with a multi-arm structure, i.e., a “core” connected with multiple copolymer “arms”, was synthesized through two steps including an esterification reaction between polyhydric alcohols and acrylic acid and a copolymerization reaction in an aqueous solution among the esterification product, isobutenyl polyethylene glycol and acrylic acid. The reaction conditions were determined, and the results showed that the esterification rate can reach above 95% with a water-carrying agent of 70g, a catalyst/alcohol molar ratio of 0.07, an inhibitor/monomer molar ratio of 0.03, and a reaction time of 7 hrs. The reaction products were characterized by ¹H Nuclear Magnetic Resonance (¹H NMR) and Fourier Transform infrared spectroscopy (FTIR). It is confirmed to be the multi-arm structure, and the self-synthesized superplasticizer with a multi-arm structure exhibited higher energy efficiency, which was in accordance with its excellent paste fluidity performances and adsorption behavior in cement paste

Abstract: Using supercritical CO₂ as the foaming agent, rigid polyvinyl chloride (R-PVC) foam sheets were prepared in a continuous extrusion foaming system. The effects of dioctyl phthalate (DOP) on the rheological properties of PVC were investigated using a Brabender torque rheometer while other basic formula remained unchanged. The influences of DOP content on microstructure, mechanical properties and density of PVC micro foamed sheet were investigated with scanning electron microscopy (SEM). The results showed that the addition of DOP resulted in increased flexibility and the elongation at break of the foamed PVC sheet, while the mechanical properties of foamed PVC sheet decreased with the increase of DOP content, implying that excessive addition of DOP will cause gas escape and bubble coalescence in the foaming process. Low density PVC foam sheets with fine cell morphology were obtained when 2 phr DOP was added in PVCformula.

Abstract: In this paper, epoxy resin was used as matrix to prepare composite cryomilling at liquid nitrogen temperature in which the content of CNTs powder vary from 25 wt% to 40 wt%. The microstructure and dielectric properties of the composite were analyzed by SEM and RF impedance material analyzer. The result showed that permittivity of the composites turned negative after the CNTs reached certain content. The plasma oscillation of delocalized electrons in CNTs conductive networks causes negative permittivity phenomenon.

Abstract: The microstructure and dielectric properties of the graphene–epoxy composites prepared by cryomilling at liquid nitrogen temperature were studied by SEM and RF impedance material analyzer. The result indicated that both the dielectric constant and conductivity of the composites increased with the increase of the graphene content. The value of the dielectric constant of the composite with about 8 wt % of graphene was as high as 200. Moreover, the frequency dispersion behaviors of the conductivity within a certain frequency range accorded with the Jonscher's power law demonstrating that the conductive mechanism is hopping conduction. The negative reactance decreased with the increase of the testing frequency which indicated a capacitive character

Abstract: We develop an ultra-thin, highly filled, neutron-shielding material. This material exhibits a desirable neutron-shielding performance, and also has certain advantageous mechanical properties and uses. We study the physical properties of shielding materials with different polyolefins as base materials, and investigate the neutron-shielding performance of boron-containing and lithium-containing shielding materials. We furthermore report on the effect of additive amounts of functional additives on shielding properties and physical-chemical properties. We additionally study the effect of radiation crosslinking technology on shielding material properties. We show that, using ethylene-octene copolymer (POE) modified low-density polyethylene (PE-LD), the additive amounts of boron carbide (B₄C) and nano-montmorillonite (OMMT) are 60–70% and 4%, respectively. The optimal radiation dose is 160 kGy, and the shielding materials exhibit good neutron-shielding performance and mechanical strength.

Abstract: Poly p-phenylene benzobisoxazole (PBO) fiber is a kind of organic fiber with high performance, but the properties of the interface between PBO fiber and resin are poor, which limit its application in the field of composite materials. Therefore, the surface modification methods were employed to enhance the interface properties, which could damage the fiber. This article assessed the influence of plasma modification, γ-ray irradiation, coupling agent, acid treatment and combined treatments on the strength of PBO fiber filament, and investigated its tensile strength with Weibull analysis. Through observation of fiber surface by SEM，it can be found that some combined treatments caused less damage to PBO fiber compared to the individual treatments. This indicates that if combining the different treatments appropriately, the interface energy of PBO fiber will increase, with the excellent mechanical properties well retained

Abstract: The fabrication of multi walled carbon nanotube (MWNT) buckypaper and its silver nanoparticle (AgNP) hybrid is studied with the assist of a high-performance polymer, polybenzimidazole (PBI) by filtration-method. The result of Raman spectra demonstrates the strong π-π interaction between MWNT and PBI. Because of the coordination effect of imidazole groups to metal ions, AgNPs are then deposited on the surface of MWNTs/PBI buckypaper. The Ag/buckypaper hybrid (MPBA) is found to be super-hydrophobic after being treated by 1-Octadecanethiol.

Abstract: Polyester fabric was pretreated with 3-aminopropyltrimethoxysilane (APTMS) through supercritical carbon dioxide (scCO₂) process before electroless copper plating. APTMS pretreated polyester fibers were characterized by contact angle. Deposit weight, surface morphology and electromagnetic interference (EMI) shielding effectiveness (SE) of electroless copper plated polyester fabrics were investigated. The results show that polyester fibers are covered with APTMS after APTMS modification in scCO₂ medium. Copper coatings on the polyester fibers are uniform after copper plating. Electromagnetic interference shielding effectiveness of the copper plated polyester fabric arrives at 60-80dB at frequencies ranging from 2 to 18 GHz.

Abstract: Phenolic fiber is a versatile material. This article focused on introduction of the progress of generating phenolic fibers using solution electrospinning method and its applications, as well as the trail exploration of preparing phenolic fibers by melt electrospinning. For the research on preparation of phenolic fibers using solution electrospinning, researchers added polymers or additive agents to adjust the viscosity and electrical conductivity of the spinning solution. Then they cured and carbonized the electrospun fibers to reach their varied aims. After these two processes, the brittle nature of the phenolic fibers has been greatly changed. What’s more, the modification makes it easier to be dealed with in the analysis tests and be more suitable to be applied as adsorbent materials, nonconductive materials, and flexible materials.

Abstract: The effect of heat setting methods on the structures and mechanical properties of high strength polyvinyl alcohol (PVA) fibre is studied in this article. The microstructure and mechanical properties of heat treated PVA fibre is investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD), and single fibre electronic tensile strength tester. Results show that the heat setting method with constant tension is a good heat setting method which can largely enhance the tensile strength of PVA fibre. During the heat setting process, the mechanical properties of PVA fibre are greatly affected by the temperature, tension and setting time. When the temperature is 220°C, tension is 5cN/dtex and setting time is 90sec, the tensile strength of PVA fibre increases from 12.0cN/dtex to 16.4cN/dtex in compare with the PVA fibre without heat setting