Advanced Materials Research Vols. 750-752

Abstract: Carbon nanotubes (CNTs) treated with an alkali solution were used to toughen epoxy resin (EP) by in-situ polymerization.The effects of different CNTs contents on the impact strength of EP were discussed. The morphology of impact section was investigated too.The results indicated that a certain amount of hydroxy groups were introduced on the surface of CNTs.The impact strength of EP is greatly enhanced with the increase of CNTs/EP weight ratio, and exhibited a maximum when ratio was 0.5.The toughness of CNTs/EP composites was remarkably improved.SEM showed that the fracture pattern of CNTs/EP composites was changed from brittle fracture to ductile fracture.

Abstract: Polyacrylic acid butyl ester (PBA) / poly (methyl methacrylate - maleic anhydride) [P(MMA-MAH)] was synthesized by emulsion polymerization. We got three core-shell particles of core-shell ratio 2/8,3/7 and 4/6 by the method, and blend them with PA6 in proportion of 5%,10% and 15%. Two-layer structure under the TEM proves the existence of core-shell particles, and the core-shell particles disperse uniformly under the SEM. The core-shell rate is 4/6 and PA6 ratio in the 10%, toughening effect is the best. The impact strength and tensile strength increase by 187% and 13.8% respectively, showing the unique nature of the core-shell particles.

Abstract: High performance thermal insulating ethylene-propylene-diene monomer (EPDM) composites were obtained with the addition of hollow phenolic micro-sphere. The effects of the pretreatment and content of micro-sphere on various properties of EPDM composites were evaluated. Experimental results showed that thermal conductivity and specific gravity of EPDM composites significantly decreased, which was due to the intact and uniform dispersion of pretreated micro-sphere throughout the EPDM matrix. With the content increasing of pretreated micro-sphere, the specific gravity of EPDM composites linearly decreased while the thermal stability increased. Specifically, EPDM composites showed the three-layer structure after ablation and the addition of pretreated micro-sphere distinctively enhanced thermal insulating properties of EPDM composites, which was attributed to multi-type heat conductivity resulted from hollow micro-spheres. Hollow phenolic micro-sphere exhibited great potential in preparing new generation of light-weight and high thermal insulating materials.

Abstract: PP/PA6/APP/OMMT Nanocomposites were Prepared via One-Step and Two-Step Melt Intercalation. the Flame Retardation, Thermostability, Structure Characters and Hygrothermal Aging Properties of PP/PA6/APP/OMMT Nanocomposites were Studied by UL-94, OI, TG and TEM. the Results Show that Two-Step can Improve the Flame Retardation of PP/PA6/APP/OMMT Nanocomposites; when OMMT Content is 4% or 6%, the Flame Retardation Gets Tofv-0, and the Lois are 32.2% and 32.8% Respectively; OMMT Doesn’t Play an Obvious Role to Hygrothermal Aging of PP/PA6/APP/OMMT Nanocomposites.

Abstract: Laponite-armored polystyrene (PS) particles were fabricated by Pickering emulsion polymerization. Emulsions of styrene dispersed in water were stabilized by hydrophobic modified Laponite nanodiscs. The properties of PS particles were investigated by TEM, SEM and DLS. The results show that these particles have narrow size distribution with diameter around 160 nm, which attributes to the improvable wettibility of modified Laponite stabilizer. TEM result proves that Laponite nanodiscs are on the surface of PS particles.

Abstract: Based on the mechanism of processing and molding of multivariate polypropylene composite system, this paper studies the effect of the screw length-to-diameter ratio and the wedge angle of the helix angle of the twin-screw extruder on the properties of elongation at break of polypropylene composite. The relationship between injection temperature and injection pressure of injection molding machine is also analyzed. Experiments show that when length-to-diameter ratio is 30, and wedge angle is 16±5^o, the elongation at break of test sample reaches its maximum value and tends to be stable. When melting pressure is 40 MPa and the injection temperature at 190 °C-220 °C, injection molding machine can improve the process flowing property of composite materials.

Abstract: ZnS was coated on carbon nanotubes (CNTs) that had been previously functionalized with Fe₃O₄ nanoparticles. The as-synthesized products were characterized by X-ray diffraction (XRD), transmission electronic microscope (TEM) and physical properties measurement system (PPMS). ZnS nanoparticles with sphalerite structure are successfully assembled on the surface of CNTs/Fe₃O₄ nanocomposites. The CNTs/Fe₃O₄-ZnS nanocomposites exhibit superparamagnetic behavior with saturation magnetization of 21.25emug1. The as-synthesized nanocomposites have great potential for applications in the field of wastewater treatment, electronic devices, sensors and biotechnology.

Abstract: The purpose of this study is to determine the correct estimation of the mechanical property between epoxy resin and PEEK sheet as the composites and its validity has been tested with the alternative materials of the metal-based materials for artificial hip joint. Moreover, this work evaluated the mechanical properties according to the temperature of heat treatments for sizing removal of carbon fiber and the fractured surfaces of Carbon/Epoxy and Carbon/PEEK composites were also evaluated. First, the sizing removal of carbon fiber were conducted at 300°C for 4 hours and 400°C for 2 hours. The fractured surface in the specimen of tensile test made from PEEK and epoxy resin was observed by SEM. the fracture surface of the tensile test specimen of the Carbon/Epoxy composites heat-treated to 400°C showed that the resin did not bury nearly in the fiber surface and pull out was observed. It is shown that 400°C is suitable for the sizing removal of the carbon fiber. The mechanical test result showed that there was no significant differences in short beam strength. However, the tensile strength and compressive strength of the Carbon/PEEK composites was higher than those of the Carbon/Epoxy composites in the case of the Vacuum Bag process. In addition, this result showed that the sizing material did not have a significant effect on the strength of the Carbon/PEEK composites.

Abstract: Generally, the moisture absorbed in the composites plasticizes the resin. And it makes the composites expansion in volume and generates the cracking at the same time, So, the fracture is often generated in the composites by those reason. Therefore, in this study, the change of mechanical properties due to the moisture-absorption for the carbon fiber reinforced composites in comparison with basalt fiber and glass fiber reinforced composites are investigated. The specimens for the carbon, basalt, and glass fiber reinforced composites manufactured with the ASTM standard. The specimens immersed in distilled water at 80°C during 100 days and the coefficient of moisture was measured in according to the Fick's law. In addition, after drying process, the humidity-absorbed specimen under 80°C for 1 day, the recovery rate was measured. As a result, the coefficient of moisture-absorption of carbon fiber reinforced composite material was the lowest at approximately 3 % because the interface coherence with the fiber and resin are the most strong. Also, after drying process, the recovery rate was 20 percent higher than the others.

Abstract: High-Energy Ball Milling was used to disperse carbon nanotubes (CNTs) in Al-5wt%Mg matrix and hot-pressing were used to consolidate the composite powders with different CNTs contents. The results showed that a certain weight of CNTs can be homogeneously dispersed in the matrix through the high-energy ball milling, the most of CNTs are embedded in the Al-5wt%Mg matrix and have a close bonding with the Al-5wt%Mg matrix. In addition, CNTs can play the role of grinding aids to prevented agglomeration of particles. Tensile strength and hardness of the CNTs/Al-5wt%Mg composites increase by 47.9% and 37.25% respectively when the CNTs was 2wt% in the Al-5wt%Mg composites. The fracture surfaces of the composite with 2wt% CNTs involved in the pulling out and breakage of CNTs. In this case, both Orowan looping and load transfer were proved to be the strengthening mechanisms of the CNTs/ Al-5wt%Mg composites.