Advanced Materials Research Vols. 123-125

Abstract: The curing reaction of the system bisphenol-A glycidol ether epoxy resin modified by poly (ethylene glycol) (PEO) and flexible amine (D-230) as curing agent has been studied by means of differential scanning calorimetry (DSC) and thermal scanning rheometry. The curing kinetic parameters have been calculated from the non-thermal DSC curve. The kinetic analysis suggests that the two-parameter autocatalytic model is more appropriate to describe the kinetics of the curing reaction of the system. Increasing the PU content leads to an increase in the heat of curing and has a little effect on the kinetic parameters apparent activation energy (Ea), pre-exponential factor (A), and order of the reaction (m and n). The rheological properties were measured by isothermal curing evolution. Introduction of PEO flexible chains delayed the polymerization. It has been confirmed that the introduction of PEO chains in the structure of the epoxy resin increases the mobility of the molecular segment of the epoxy networks and results in the decrease in glass transition temperature.

Abstract: Composites containing various amounts of LLDPE (Linear Low Density Polyethylene) and clay (0, 1, 5, 10, 20 and 30% of clay) were prepared using two different types of clay (Bijoypur white clay and China clay) by extrusion technique followed by compression molding. Tensile strength (TS) & tensile modulus (TM) of pure LLDPE were found to be 9.8 MPa & 175 MPa respectively. For both types of clay TS, Eb% was gradually decreased but TM was gradually increased with increasing the percentage of clay in LLDPE/clay composites. The effects of ionizing (gamma) and non-ionizing (UV) radiations on the mechanical properties of LLDPE/clay composites were studied. The composites irradiated under UV & gamma radiation showed higher TS than that of non-irradiated one. Thermal degradation of the composites was studied at different temperatures. Water uptake of the composites was found negligible.

Abstract: We introduced a simple experimental set-up and determined the effective cutoff wavelength of bend-insensitive optical fibers by applying the longitudinal misalignment loss with spectral transmission method.

Abstract: The preparation of metallic lead films by electrochemical deposition was reported. Although primary deposits at fresh state (also referred to as fresh deposits) were indeed metallic lead films, the fresh lead films could be rapidly oxidized to lead oxide in air. To obtain long stable metallic lead films, the key process is how to prevent the oxidization of fresh lead films. Our studies indicate that the washing of fresh metallic lead films in absolute alcohol is a simple but effective method to protect the lead films from the oxidization for an extended period of more than 20 days.

Abstract: TaN-Cu nanocomposite thin films used as materials for thin-film resistors (TFR) were prepared by magnetron pulsed dc reactive sputtering. Structural and morphological properties of films deposited on (100) Si as a function of nitrogen flow rate and substrate temperature is investigated. With the introduction of N2 gas flow indicated with different phases of nanocrystalline h-Ta, Ta2N, TaN, Ta4N5 and Cu. XRD analysis of the films deposited with increasing substrate temperature at constant flow rate of nitrogen 10 sccm indicated that the nanocrystalline with bi-phasic (fcc-TaN and fcc-Cu). The microstructure of the films was investigated by scanning electron microscopy and high-resolution transmission electron microscopy.

Abstract: The relationship between metal-induced chemical bonding and the mechanical properties of Me/a:C-H (Me- Ti and Ni) films are discussed. Nanocomposite films were deposited onto the Si substrates via biased target ion beam sputtering of metal combined with reactive ion beam deposition of a:C-H using CH4/Ar gas mixture. The chemical composition, microstructure and mechanical properties were characterized using X-ray photoelectron spectroscopy (XPS), Raman spectroscopy and nanoindentation. XPS analysis revealed that both Ti and Ni atoms were preferentially bonded to carbon to form its metal carbide phase. Irrespective of its kind, both the metal carbide clusters induces more graphite like bondings in a:C-H matrix. From the nanoindentation analysis it was found that there is no crack propagation and damage around the indent region even at very high indentation loads. Additionally, it was found that a:C-H film shows higher hardness compared to that of Ti/a:C-H and Ni/a:C-H films.

Abstract: Nanoscale and crystalline morphology of TPU nanocomposites bearing MMT and laponite clays were studied. Laponite was dual modified using ionic and covalent modifications by different silanes. TPU-clay nanocomposites having variegated modified clays, prepared by solution casting, were characterized using TEM, SAXS, variable temperature XRD (VTXRD), and MDSC. TEM show the uniform clay dispersion in MMT nanocomposites as compared to laponite composites. SAXS showed satisfactory fitment of Guinier eqn. at lower q values. Fitment of Porod eqn. is inferior owing to contribution of internal microstructures and interfacial roughness. VTXRD (1400C to 250C at constant cooling rate) and MDSC studies revealed crystalline morphology development in annealed samples that can be related to the aspect ratio, microstructure, and functional grs of clays. The overall crystallinity development is less effected in laponite based composites.

Abstract: There have been growing demands of high performance metal matrix composites in advanced engineering applications in virtue of their high specific strengths. This paper is to report an assessment of the mechanical properties of LC4/SiCp metal matrix composites using an innovative testing technique, small punch test. The composite materials of this study were produced by stir casting method with particulate reinforcements of 7wt.% and 14wt.% of SiC respectively. Small punch testing was performed on the LC4 base alloy and the two composites materials. The small punch test is a relatively new mechanical testing technique capable of utilizing small disk-shaped samples to determine the mechanical properties of the test materials. In this study, the equivalent fracture strain, εqf of the LC4/SiCp MMCs was characterised and compared with the base alloy. The fracture mechanism of the test samples was examined using scanning electron microscopy.

Abstract: Product-packaging system must survive the environmental hazards experienced during transport and distribution. This paper deals with the design and evaluation method for transport packaging protection. Firstly, just right transport packaging evaluation system is studied and established, which includes four evaluation sub-modules such as packaging reliability, packaging convenience, packaging cost rationality, and environment protection. Then, the improved design method for transport packaging protection with just right transport packaging evaluation system is put forward on the basis of the concept of just right transport packaging and the requirement of environment protection. The improved design and evaluation method can effectively predict and control over-packaging and under-packaging, and is useful to realize just right transport packaging. The research work would provide instruction for the design and evaluation of transport packaging protection of product.

Abstract: Extrinsically conductive polymer composites can be developed by incorporation of conductive filler in suitable polymer matrix. The formation of conductive network in insulating matrix due to filler aggregation at and above percolation is responsible for electrical conductivity of such composites. The present investigation deals with effect of temperature on conductive composites made from different blends of Ethylene-Vinyl copolymer (EVA) and Acrylonitrile-Butadiene copolymer (NBR) filled with particulate carbon filler. The electrical properties of these composites depend on blend composition and filler loading. High temperature (303-393K) DC-resistivity against temperature for EVA and EVA blends composites show positive coefficient of temperature (PCT effect) followed by negative coefficient of temperature (NCT effect) thus passing through a maxima which corresponds to crystalline melting temperature(~348K) of EVA phase. Further the variation of conductivity during heating cooling cycle does not coincides and leads to some kind of thermal hysteresis due to change in conductive network structure. However in low temperature region (10-300K), the resistivity is found to increase with decrease in temperature (NCT effect) and hysteresis effect is also marginal compared to that observed in high temperature region. This difference resistivity/conductivity vs temperature behavior in two different temperature zones suggests that different two mechanisms are operative in the system.