Advanced Materials Research Vols. 29-30

Abstract: Rotational moulding or rotomoulding is a manufacturing process best suited for producing one-piece, hollow plastic products. The raw materials can be in powder or liquid form with linear polyethylene of varying densities being dominant worldwide. Due to the modest material properties of polyethylene, reinforcement in various forms have been incorporated within the rotomoulded components to improve the performance of these products. With the abundance and eco-friendliness of natural fibre resources, this study has focused on the use of sisal and woodfibres along with linear medium density polyethylene (LMDPE) powder to produce rotomoulded composite components. Tensile and impact properties of the rotomoulded natural fibre-reinforced composites have been determined as a function of fibre content.

Abstract: One-dimensional comprehensive mathematical model coupling particle movement and thermal conduction in the casting mould system is developed. A formula for pressure in liquid metal during the centrifuge process is derived. The model takes into consideration the propagation of solidification front and movement of particles due to centrifugal acceleration which takes place either in the same or in opposite direction to that of the solidification front depending on the relative density difference between the particles and melts. In the force balance expression, repulsive force term is incorporated for the particles that are at the vicinity of the solid/liquid interface to calculate the particle segregation pattern in the casting region The effects of various process parameters such as, rotational speed of the mold, size of the reinforcing material, relative density difference between the particle and melt, initial pouring temperature of the liquid melt, mold pre-heating temperature, heat transfer coefficient between the casting/mold interface are studied. It is noted that for a given set of operating conditions, the thickness of the particle rich region in the composite decreases with increase in rotational speed, particle size, relative density difference between the particle and melt, initial pouring temperature and initial mold temperature. With decrease in the heat transfer coefficient between the casting/mold interface, the solidification time increases which, in turn, results in more intense segregation of solid particulates. Again, with increase in the initial volume fraction of the solid particulates, both the solidification time as well as the final thickness of the particulate rich region increase.

Abstract: The effect of accelerated weathering on the chemical and color of wood plastic composites (WPC) made from modified pine wood fiber (control, extractives free and holocellulose) was investigated. WPC were produced from the various wood fibers (60%, weight) and high density polyethylene (40%, weight) as matrix were subjected to accelerated weathering in xenon-arc weatherometer for up to 1200 hours. This study aimed at getting a better understanding of the chemical changes that occur to weathered WPC relative to its material compositions (wood and plastic). Chemical analyses and color measurement of the weathered surface using Fourier transform infrared (FTIR) spectroscopy, pyrolysis gas chromatograph mass spectrometry and colorimetery showed that degradation of WPC had occurred, causing color changes. It was observed that WPC made from holocellulose wood fiber had the lowest color change compared to extractives free wood and control wood fiber based WPC.

Abstract: Industrial hemp fibre was treated with alkali and the influence of this treatment on interfacial shear strength (assessed using the single fibre pull-out test) and composite strength with an epoxy resin, over a range of epoxy resin to curing agent ratios, was investigated. Scanning electron microscopy was conducted to assess the fracture behaviour of the composite tensile test specimens. It was found that alkali treatment increased the interfacial shear strength and composite tensile strength, Young’s modulus and elongation at break. The highest tensile strength was obtained with an epoxy resin to curing agent ratio of 1:1 while the best Young’s modulus was achieved with a resin to curing agent ratio of 1:1.2.

Abstract: This study investigates the effect weathering on composites made from fibre subjected to various stages of a standard Kraft pulping process. Pre-washed, washed and bleached Kraft wood fibre of kappa numbers 27, 17, and 1 was assessed in terms of its surface potential using the streaming potential method and combined with polypropylene (PP) to produce composites. Composites were prepared using a twin screw extruder followed by pelletising and injection moulding. Tensile testing, hardness testing and impact testing were carried out to evaluate the composite mechanical properties. It was found that fibre with higher amounts of residual lignin content led to composites with lower tensile and impact strengths and increased degradability when subjected to accelerated weathering testing.

Abstract: The electrical conductivity studies of chemically crosslinked nano composite membranes consisting of poly (vinyl alcohol) (PVA) and phosphomolybdic acid (PMA) with different blending composition and crosslinking density has been conducted over a wide frequency regime. The conductivity of the systems has been studied within the temperature range 25 oC ø T oe 100 oC for the hydrated membranes. The proton conductivity of the membranes was generally of the order of 10-3 S/cm. The conductivity of these membranes shows a temperature dependence of Arrhenius type. The activation energies for the membranes were calculated from the conductivity measurements. Both the pristine and hydrated membranes were also characterized by X-Ray diffraction studies to observe the effects of blending and hydration on the crystallinity of the composite membranes. The membranes showed comparable proton conductivity and better resistance to methanol permeability than that of Nafion 112 under the same measurement conditions. These properties make them good candidates as polymer electrolyte membranes for direct methanol fuel cell application.

Abstract: Red mud was organophilized by aniline formaldehyde and to know the effect of various filler loading on the properties of PVA-Organophilized red mud composite prepared by a conventional solvent casting technique and comparison of the same with that of the virgin polymer, various characterizations was done. The as-synthesized composite films were typically characterized by FTIR spectroscopy and X-Ray Diffraction.The exfoliation of galleries of organo- red mud was more evident in the composite film containing 2% of filler loading.The morphological image of the composite materials was studied by scanning electron microscopy (SEM) and optical microscope (OM). The thermal properties measured by thermogravimetric analysis (TGA) showed that organored mud enhanced the thermal stability of a series of composite materials freestanding films.The differential scanning calorimetry (DSC) showed increase in glass transition temperature and crystallization of the composite films.

Abstract: The potential of hemp fibre as a reinforcing material for Poly(lactic acid) (PLA) was investigated. Good interaction between hemp fibre and PLA resulted in increases of 100% for Young’s modulus and 30% for tensile strength of composites containing 30 wt% fibre. Different predictive ‘rule of mixtures’ models (e.g. Parallel, Series and Hirsch) were assessed regarding the dependence of tensile properties on fibre loading. Limited agreement with models was observed. Differential scanning calorimetry (DSC) and x-ray diffraction (XRD) studies showed that hemp fibre increased the degree of crystallinity in PLA composites.

Abstract: Composites were made with jute, cordenka and jute+cordenka by extrusion and injection moulding. The matrix material was Polypropylene (PP) and PP maleic acid anhydride grafted copolymer (MAPP) was used as coupling agents. The mechanical tests were performed. The hybrid composite of jute 25% and cordenka 75% showed the enhanced properties. Three types of fire retardants (15%) Mgnifine (Magnesium hydroxide), Exolite AP-750 (Poly-ammonium phosphate) and Expandable Graphite and their mixtures (1:1) were used in the composites and PP. All the fire retardants and their mixture reduced the mechanical properties. Among all fire retardants and their mixtures used, mixture of expandable graphite and magnifine for jute based composite and mixture of expandable graphite and exolite for cordenka based composite was found to be better.

Abstract: Low-k dielectric improves the switching speed by reducing the parasitic capacitance in integrated circuits. However it suffers the problem of copper diffusion. Forming gas (H2 + N2) plasma treatment on the surface of HSG-7000 low-k dielectric thin film has demonstrated to improve copper diffusion resistance. Two techniques using X-ray Photoelectron Spectroscopy (XPS) and Secondary Ion Mass Spectroscopy (SIMS) have been used to examine the copper diffusion on this thin film. A thin layer of 10 nm with C-N bonds near the HSG-7000 surface were believed to be created by the plasma treatment and confirmed with XPS and SIMS and acts as barrier.