Electron-beam-initiated grafting of triallyl cyanurate onto polyethylene: Structure and properties

Electron-beam (EB)-initiated grafting of triallyl cyanurate (TAC) onto polyethylene (PE) has been carried out over a range of radiation dose (2–20 Mrad) and concentrations of TAC (0.5–3 parts by weight). The grafting level, as determined from IR spectroscopy, is maximum at a 10 Mrad radiation does using 1 part TAC. With increasing TAC level at a 15 Mrad dose, the grafting level is higher only after 1.5 parts TAC. The gel content increases with radiation dose in the initial stages. X-ray studies indicate two peaks at 10.6–10.8° and 11.7–11.9° and the corresponding interplaner distances of 4.15 and 3.80 Å. With increase in radiation dose or TAC level, the crystallinity decreases in the initial stage and then increases. It shows a decreasing trend again at higher radiation dose. The interplanar distance or the interchain distance of the modified polymer does not change. However, the crystallite size increases initially and then decreases. The tensile properties are relatively insensitive to the variation of radiation dose because of the interplay of various factors. The dielectric loss, tan δ, shows a maximum at a 10 Mrad dose and minimum at 5 and 15 Mrad due to changes of polarity and the carrier mobility. © 1994 John Wiley & Sons, Inc.     

Effect of ambient‐temperature and high‐temperature electron‐beam radiation on the structural,thermal, mechanical,and dynamic mechanical properties of injection‐molded polyamide‐6,6

Electron‐beam irradiation of injection‐molded specimens of polyiminohexamethyleneiminoadipoyl (better known as polyamide‐6,6) was carried out in air at ambient temperature (303 K) and a high temperature (393 K). Most of the irradiated specimens were tensile dumbbells, although a few were cylinders for compressive stress relaxation testing. A few representative samples were dipped in triallyl cyanurate (TAC) solution before ambient‐temperature irradiation. The gel content of the specimens increased with radiation dose and the temperature of irradiation. Moreover, the TAC‐treated specimens showed an increase in gel content over the neat specimens irradiated at the same dose levels. Wide‐angle X‐ray scattering and differential scanning calorimetry studies revealed that the crystallinity decreased with increasing radiation dose. Irradiation at the high temperature and treatment with TAC further decreased the crystallinity compared to irradiation at ambient temperature. As determined from compressive stress relaxation and mechanical and dynamic mechanical properties, the optimized radiation dose for ambient‐temperature radiation was 200 kGy. The gels had a stiffening effect, and the rate of relaxation decreased significantly. The water‐uptake characteristics of the tensile specimens were investigated; this revealed a decrease in the water absorption tendency with increasing gel content. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 1633–1644, 2006     

Effect of processing parameters, applied pressure and temperature on the electrical resistivity of rubber-based conductive composites

Carbon black- and short carbon fibre (SCF)-filled conductive composites were prepared from ethylene vinyl acetate (EVA), ethylene propylene diene (EPDM) rubber and their 50:50 blend. The electrical resistivity of carbon black- and SCF-filled composites were measured under different conditions. The electrical conductivity of filled polymer composites is due to the formation of a continuous conductive network in the polymer matrix. These conductive networks involve specific arrangement of conductive elements so that the electrical paths are formed for free movement of electrons. It was found that electrical conductivity of filled conductive composites depends on different processing parameters like mixing time, rotor speed, mixing temperature, vulcanization time and pressure and service conditions like applied pressure and temperature. The results of different experiments have been discussed in light of break down and formation of the continuous conductive network.     

Change in fiber properties due to the heat treatment of nylon 6 tire cords

Nylon 6 is used as a reinforcing material in different rubber products. However, as it is a thermoplastic material, it may undergo some kind of thermal shrinkage during the vulcanization of rubber, which leads to dimensional stability problems in the rubber product. To prevent this, we subjected nylon 6 to some kind of thermal treatment at higher temperatures. During thermal treatment, there was some change in the mechanical properties, shrinkage which may have been correlated with changes in the crystal structure of the polymer. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci 2008     

Effect of electron‐beam irradiation on ethylene–methyl acrylate copolymer

Ethylene–methyl acrylate copolymer (Elvaloy 1330) was irradiated by an electron beam at different levels of radiation both in the presence and absence of a trimethylolpropane trimethacrylate sensitizer at various dosages of incorporation. The mechanical, thermal, and electrical properties of these samples were compared. The mechanical properties were observed to reach an optimum maximum around 6 Mrad of irradiation and 1 phr of sensitizer incorporation. Furthermore, an increase in either the radiation dose or the sensitizer level helped very little to further modify the properties. The thermal properties as determined by the thermogravimetric analysis and differential scanning calorimetry studies were quite supportive of the observation made during the study of the mechanical properties. The thermal stability of the irradiated samples underwent an increase with increasing electron‐beam dosage. In a manner similar to those of the mechanical properties, the increase in thermal stability was found to reach a maximum at a particular level of treatment and sensitizer incorporation, beyond which there was marginal or no effect at all. The α transition temperature underwent a substantial increase with increasing crosslink density, as evidenced by the increase in gel content with increasing proportion of electron‐beam radiation dose. The other glass‐transition temperature, however, appeared to remain unaffected. The electrical properties, as described by the dielectric constant, volume resistivity, and breakdown voltage, appeared to be affected very little by the electron‐beam radiation. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Electromagnetic interference shielding effectiveness of ethylene vinyl acetate based conductive composites containing carbon fillers

Conductive polymeric based composites were derived from ethylene vinyl acetate rubber filled with Vulcan XC‐72, short carbon fiber (SCF), and their blends. The electromagnetic interference (EMI) shielding effectiveness (SE), return loss, and reflection coefficient were studied. The measurements of the SE of the composites were carried out in two different frequency ranges of 100–2000 MHz and 8–12 GHz (X band). It was observed that the SE of the composites was frequency dependent and it increased with increasing frequency. The increasing of filler loading also enhanced the SE of the composites. The 100% SCF filled composites showed a higher SE compared to that of the filler blend or purely carbon black filled composites. The correlation between the SE and bulk conductivity of various composites was also discussed. The compromise between EMI SE, electrical conductivity, and mechanical properties was obtained when the composites contained both types of filler like particulate carbon black and SCF. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 1601–1608, 2001     

Effect of thermal treatment on structure and properties of polyester tire cords

Polyester and nylon are the mostly used reinforcing textile fibers in many industrial rubber applications. Now‐a‐days body ply of a passenger car radial is mostly made up of polyester fiber. Because of its thermoplastic nature, it undergoes some kind of thermal shrinkage during processing and vulcanization, which lead to many problems related to shape, dimension, and dimensional stability. To avoid this, polyester is subjected to thermal treatment at higher temperature. Hence, thermomechanical properties of polyester tire cords become very important. During the thermal treatment, there is not only change in shrinkage, shrinkage force, and mechanical properties but also it affects structural and morphological properties. In this work, the changes in thermomechanical properties due to heat setting have been correlated to structural and morphological changes like crystallinity, crystal size, orientation, crystal perfection, etc. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Effect of electron beam irradiation on the dielectric properties of fluorocarbon rubber

Terpolymeric fluorocarbon rubber (68 wt.-% fluorine, 1.4 wt.-% hydrogen) was subjected to electron beam irradiation using 1,1,1-trimethylolpropane triacrylate (TMPTA), tripropylene glycol diacrylate (TPGDA), and pentaerythritol tetracrylate as radiation sensitizers. Compared to the original sample both the dielectric constant and the dielectric loss factor decrease for samples treated to a certain dose level, beyond which there is an increase. Similar improvement in dielectric properties is observed at relatively higher levels of TMPTA, owing to the increased degree of crosslinking. Among the various polyfunctional monomers used as radiation sensitizers, both the dielectric constant and the dielectric loss factor are higher for systems based on TPGDA due to the reduced crosslink density.     

Tricycloillicinone, a novel prenylated c6-c3 compound increasing choline acetyltransferase (ChAT) activity, isolated from Illicium tashiroi

Tricycloillicinone (1), a novel tricyclic prenylated C6-C3 compound, has been isolated as a neurotrophic substance from the woods of Illicium tashiroi and its structure has been elucidated by spectroscopic analyses. Compound 1 could increase ChAT activity in culture of P10 rat septal neurons.     

Development of the package-reactor (1) -reactor for pioneering new nuclear markets-

A new small reactor concept named Package-Reactor has been developed through a joint research of Mitsubishi Heavy Industries, Ltd. and Hitachi, Ltd. Several key designs have been investigated, taking into account both PWR and BWR technologies. The Package-Reactor is designed to attain high reliability, high safety, good maintainability, good operability and low construction cost. To achieve the aims, its nuclear steam supply system adopts the natural-circulation core cooling system, and the reactivity-control-free system, under normal operation. The core assembly is composed of several sub-cores. Each sub-core is housed in a pressure tube called “cassette”. The cycle length is five years, by using UO₂ fuel with 5wt% enrichment. The containment vessel is small and the nuclear steam supply system can be constructed through ground transportation.