Advanced Materials Research Vol. 983

Abstract: The structure and properties of NBR and its composites coupled with different particle size of recycled polytetrafluoetylene (R-PTFE) are investigated. The results show that R-PTFE has a positive effect on NBR enhancing the curing properties of materials, mechanical properties, solvent resistance of NBR when the particle size of R-PTFE less than 200 mesh. However, when it is 200 mesh, R-PTFE is not easily dispersed in the NBR matrix, resulting in decreasing the properties of NBR/R-PTFE composites.

Abstract: Alumina-titanium carbide composite (Al₂O₃-TiC) is one of advance ceramic matrix composites (CMC) that have been used in machining tool and tribology application because of its excellent mechanical properties. Powder processing is often a chosen method to produce this family of material, i.e. hot pressed (HP), hot iso-static pressed (HIP), and pressure-less sintering (PS). These manufacturing techniques convert sub-micron powder into dense bulk component. Al₂O₃-TiC composite has been prepared by HIP process, containing 65%vol Al₂O₃ and 35%vol TiC. The powders were pressured and sintered at temperature between 1250˚C - 1650˚C. Thermal residual stress from Al₂O₃-TiC manufacturing process is conventionally unavoidable. The aim of this study is to investigate the microstructure of HIPped Al₂O₃-TiC composite and its residual micro-strain using transmission electron microscopy (TEM) with selected area electron diffraction pattern (SADP) analysis. The Al₂O₃-TiC composite was prepared by high-precision machining/grinding processes then focus ion beam milling process was used to section the TEM lamella. Microstructures, grain size and phases were determined by TEM and X-ray diffractometry (XRD). Micro-strains of {200}TiC, {111}TiC , {220}TiC and {012}Al₂O₃ were investigated by SADP (Selected Area Diffraction Pattern). Our result revealed there is approximately 0.01 compressive strains distributed in Al₂O₃-TiC composite.

Abstract: Ionic Polymer-Metal Composite (IPMC) has been utilized as an actuator in several robotic applications such as the actuator for its locomotion and gripper of the end effector. However, due to its low actuation force which is normally less than 10gf (depend on dimension), the application has been limited to small scale robot. Hence, in this research we propose a multilayer structure of IPMC actuator and investigate the actuation force increment. Besides, parametric study was also conducted to determine the force-to-weight ratio and the bending displacement. The obtained results had been compared to single ply IPMC actuator at the same thickness. The result shows that the increment of IPMC layer had increased the actuating force up to 30% for two layers and 40% for three layers. In addition, utilizing multilayered IPMC had reduced the stiffness constraint for thicker IPMC. This finding would be useful in designing stage of a small scale robot that require higher actuation force at a higher bending displacement.

Abstract: A novel high-speed photography is introduced to determine the critical fracture strain of a near alpha titanium ally during hot compression deformation. This method precisely captures the nucleation site and propagation process of cracking, and thus is an excellent method to represent dynamically the hot-deformation fracture. Compared with the traditional way, it can significantly decrease the number of trials and improve the accuracy. Based on this method, the critical fracture strain is measured, and a critical fracture model is developed.

Abstract: A novel cheap macromolecular intumescent flame retardants (Mn-MIFR), was synthesized. Epoxy resins (EP) were modified with Mn-MIFR to get the flame retardant EP, whose flammability and burning behavior were characterized by UL 94, limiting oxygen index (LOI), dilatation, char yield, smoke density rating (SDR) and maximum smoke density (MSD). The epoxy resins were obtained for the UL 94 V-0 rating at low Mn contents of 4.0 % get a LOI of 26.5% and char yield of 18.2%. Dilatation, SDR and MSD of EP/Mn-MIFR decreased. The degradation behavior of the EP/Mn-MIFR was studied by TG and EDX analysis. The experimental results exhibited that the initial decomposition temperature (IDT) was decreased, integral procedure decomposition temperature (IPDT) and amounts of Mn and P at the residue were increased.

Abstract: Hemp was treated with guanidine dihydrogen phosphate [GDP] to impart flame retardance. The thermal degradation of the samples were studied by thermogravimetry (TG) and differential thermal analysis (DTA). The flame retardance was determined by LOI. Morphology of the char structure was studied by SEM to obtain information concerning the thermal degradation mechanism. For hemp treated with GDP, which has higher LOI and char yield values, the oxidative decomposition stages include a decomposition stage at lower temperatures (165-240°C) , leading to more carbonaceous residue and small amount of flammable products to get the good flame retardance. The SEM of the chars of hemp treated with GDP also indicate the structure of the charring layer may increase heat insulation, and protect inner matrix materials.

Abstract: Poly-β-hydroxybutyrate-co-β-hydroxyvalerate (PHBV) is a bacterial-synthesized biopolymer. Moreover, PHBV is a biodegradable, it is an interesting biopolymer for disposable products. PHBV is difficult to process due to its low toughness, an elastic polymer such as natural rubber is introduced to develop toughness. In this experiment, PHBV mechanical properties were improved by blending with natural rubber (NR) and epoxidized natural rubber (ENR). The NR/PHBV and ENR/PHBV blends with the same ratio of 10/90 (wt/wt) could be extruded, whereas other conditions could not. This ratio was then used throughout this study to examine effect of maleic anhydride (MA) and benzoyl peroxide (BPO) to improve toughness of the blends. Result showed at composition where 1.0 % (wt/wt) MA and 0.05 % (wt/wt) BPO was mixed (coding EPMB2), several aspects of mechanical properties were improved. The blend, EPMB2 revealed the highest impact strength, significantly improved of elongation but drastically decreased of tensile strength. Storage modulus slightly decreased, tangent delta significantly increased when compared with neat PHBV.

Abstract: The fire retardants were used in epoxy resin (EP) to get fire retardant EP, whose kinetic parameters activation energies (Ea) were calculated by Ozawa integral method and the Kissinger differential method. The results show that the correlation coefficient (R) is above 0.95, which shows good reliability of the two methods for solving Ea. E for the fire retardant foam is decreased by 40 kJ·mol^-1, which shows that the fire retardant can catalyze decomposition and carbonization of EP.

Abstract: Wood has been treated with amino resins and amino resins modified with phosphoric acid to impart flame retardancy. The thermal degradation of samples has been studied by thermogravimetry (TG) in air. From the resulting data, kinetic parameters for different stages of thermal degradation are obtained following the method of Broido. For the decomposition of wood and flame retardant wood, the activation energy is found to decrease from 122 to 72 kJmol^-1.

Abstract: Aiming at the problem that complex systems mechanical model is difficult to set up and analyze accurately, a certain type of electromagnetic high frequency fatigue tester as engineering background, setting up its mechanical model and carrying on the reasonable simplified. Through analyzing the effect of system mechanical properties causing by system main large stiffness parts, and determining the design principle of the engine's stiffness components, it provides scientific theoretical foundation for the design of this type host.