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Phase modifications in a partially miscible blend PS/PMMA and an immiscible blend PVC/EVA have been brought about using electron beam and microwave irradiation to improve the interfacial tension. These changes have been characterized by positron lifetime technique through free volume monitoring with support from DSC measurements. the hydrodynamic interaction parameter deduced from free volume data turns out to be a good parameter to characterize the interfacial changes compared with free volume data itself. The free volume data also confirms that the conventional DSC measurements are not adequate to differentiate the level of miscibility or interfacial tension. Present data based on hydrodynamic interaction parameter indicate that microwave irradiation is a better route to stabilize the interfaces than e-beam irradiation. POLYM, ENG. SCI., 48:1495-1503, 2008. ©2008 Society of Plastics Engineers, INTRODUCTION Blending is a widely used technique in polymer research to improve the physical/mechanical properties of homopolymers (1). Polymer blends with exploitable combination of properties are an alternative to meet [...]

Blends of Poly(methyl methacrylate) (PMMA)/Poly(vinyl chloride) (PVC) and Poly(vinyl chloride) (PVC)/Polystyrene (PS) of different compositions were prepared by solution casting technique. The blends were characterized using Differential Scanning Calorimetry (DSC), Fourier Transform Infrared Spectroscopy (FTIR), and Positron Lifetime Spectroscopy. DSC data were found to be inadequate to describe whether PMMA/PVC blends are miscible or not, possibly because of the small gap in their glass transition temperatures. On the other hand, PVC/PS blends were clearly found to be immiscible by DSC. FTIR results for PMMA/PVC indicate the possible interactions between the carbonyl group of PMMA and α-hydrogen of PVC. Free volume data derived from Positron lifetime measurements showed that the PMMA/PVC blends to be miscible in low PVC concentration domain. For the first time, the authors have evaluated the hydrodynamic interaction parameter α, advocated by Wolf and Schnell, Polymer, 42, 8599 (2001), to take into account the friction between the component molecules using the free volume data. This parameter (α) has a high value (-57) at 10 wt% of PVC, which could be taken to read miscibility for PMMA/PVC blends to be high. In the case of PVC/PS blends, the positron results fully support the DSC data to conclude the blends to be immiscible throughout the range of concentration. As expected, the hydrodynamic interaction parameter α does not show any change throughout the concentration in PVC/PS blends, further supporting the idea that α is another suitable parameter in the miscibility study of polymer blends. POLYM. ENG. SCI., 46:1231-1241, 2006. © 2006 Society of Plastics Engineers, INTRODUCTION Polymer blending is a widely used technique to improve the physical/mechanical properties of homopolymers [1]. Blending of two polymers may either result in a compatible (miscible) system or incompatible [...]

Glass-fiber reinforced epoxy nanocomposites are widely used in high voltage outdoor applications. One of the serious problems of outdoor insulation is the surface tracking and erosion that leads to premature failure of insulation. In this paper free-space length, surface energy and surface tracking of epoxy composites with nano alumina, silica and micro alumina trihydrate fillers and unidirectional glass fiber reinforcement are discussed. Quantitative interfacial analysis has been used by determining the freespace length of the composites. The results of tracking are explained on the basis of contact angle measurements and the concept of surface energy is used to substantiate the results. The time-to-track and surface erosion of dry and water treated nanocomposites are determined by the inclined plane tracking and erosion method. The experimental results have revealed that the hydrophobic nature of glass epoxy composites improves with addition of fillers. The surface energy, wettability and interaction parameters show reduction with the addition of fillers. It is observed that the Glass Epoxy composite with combination of nano alumina, silica and micro ATH fillers exhibits good thermal, electrical and mechanical properties with improved tracking and erosion resistance. [ABSTRACT FROM AUTHOR]

ABSTRACT We have investigated the effect of ion implantation on structural modification and the electrical conductivity of Bakelite-resistive plate chamber (RPC) detector material used in high energy physics experiments. Samples of Bakelite polymer were exposed to 100 keV and 150 keV oxygen ions in the fluence of 1012 to 1015 ions cm−2. Ion implantation induced microstructural changes have been studied using positron annihilation lifetime spectroscopy, X-ray diffraction and Fourier transform infrared techniques. Positron lifetime parameters viz., o-Ps lifetime and its intensity showed formation of radicals, secondary ions due to the creation of interior tracks by high-energy ions followed by chain scission at lower fluence of 100 keV implantation. The decreased free volume size at 150 keV ion implantation is an indication of crosslinking and filling up of interior tracks by the implanted ions. Variation of ac conductivity with frequency obeys Jonscher power law at 100 keV and the conduction mechanism is explained by barrier hopping model. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 44962. [ABSTRACT FROM AUTHOR]

The paper reports the results of moisture and filler induced effects on the dynamic mechanical properties of glass fiber reinforced epoxy hybrid composites. The rate of water diffusion into the composites has been determined to understand the effect of moisture on the dynamic mechanical properties. Significant differences in the moisture uptake properties of the composites are observed which induce changes in storage modulus (E′), loss modulus (E″), and damping factor (tan δ). It is also observed that water diffusion depends on the free volume content of the hybrid composites. Results of this study indicate that hybrid composites with combination of micro and nanofillers possess good dynamic mechanical properties in presence of moisture at higher temperatures. [ABSTRACT FROM AUTHOR]

It is well established that copper sulfide is formed due to reaction of sulfur with copper conductors in transformers and reactors. However, there is very little experimental evidence to demonstrate copper sulfide diffusion into bulk of paper. Diffusion experiments have been carried out on three samples of kraft paper having different thickness. Positron Annihilation Lifetime Spectroscopy has been used to investigate the possibilities of copper sulfide diffusion into bulk of paper. This study has demonstrated that copper sulfide can diffuse into the bulk of paper leading to either increase or decrease in free volume of paper. The reasons for changes in free volume of paper due to copper sulfide deposits are explained. The consequences of copper sulfide diffusion on PD, voltage-current characteristics under ac and volume resistivity are discussed. Electric field simulation has been used to explain the effects of Cu ions and copper sulfide formation on electric stress distribution across paper. [ABSTRACT FROM AUTHOR]

Human rights are essential for the protection and maintenance of the dignity of the individuals. They create conditions in which every individual can develop his personality to the fullest extent. In India, the full realization of human rights is a distant dream. It cannot be easily or quickly achieved. Although recent years have seen remarkable efforts by the governments in India to promote human rights like many other developing countries, still much has to be done for the better protection of human rights. [ABSTRACT FROM AUTHOR]

To explore the structural modifications in terms of crosslink density and electrical conductivity in polymer based Bakelite RPC detector material was exposed to 8 MeV electron beam with the irradiation doses of 20 kGy to 100 kGy in steps of 20 kGy. The microstructural changes of Bakelite upon electron beam irradiation have been studied using Positron Annihilation Lifetime Spectroscopy (PALS), X-ray Diffraction (XRD) and Fourier Transform Infrared (FTIR) Spectroscopy. Positron lifetime parameters viz., o-Ps lifetime and its intensity showed chain scission at lower doses (at 20 kGy and 40 kGy) followed by crosslinking due to the radical reactions. These changes are effectively explained with the help of FTIR and XRD parameters. The reduction in electrical conductivity of Bakelite material beyond 60 kGy is correlated between conducting pathways and crosslinks in the polymer matrix. The appropriate dose of electron beam on Bakelite might reduce the leakage current of Bakelite RPC detector material and hence improves the performance of the detector. [ABSTRACT FROM PUBLISHER]