Radical Scavenging Activity of Tertiary Butyl Hydroquinone and Assessment of Stability of Palm Oil (Elaeis guineensis) by Ultrasonic Studies

The aim of the current investigation is to evaluate the efficiency of tertiary butyl hydroquinone (TBHQ) as an antioxidant in edible oil like palm oil (Elaeis guineensis) by physical, chemical and ultrasonic properties. The effects of the varying amounts of TBHQ on the oxidation stability of palm oil have been investigated. The antioxidant incorporated palm oil system and control oil were subjected to heating at 180 ± 5 °C continuously for a period of 4 h per day for 4 days consecutively. The parameters used to assess the thermal degradation and oxidation properties of the palm oil include ultrasonic velocity, viscosity and density. Adiabatic compressibility, intermolecular free length, relaxation time, and acoustic impedance have been calculated from experimental data. The effect of thermal ageing on the physical properties of the oil was confirmed by chemical analysis, which included free fatty acid, total polar compounds, and estimation of fatty acids profile by gas chromatography (GC). The chemical changes were studied by FT-IR bands. The results obtained from ultrasonic studies have shown improvement in oxidative stability and retardation in thermal degradation of the antioxidant-loaded oil in comparison with the base oil. Hence, the ultrasonic velocity and acoustical parameters used for assessment of stability of frying oil and palm oil with TBHQ can be recommended for repeated frying without adverse effects on the physical properties

Influence of free volume on the mechanical properties of Epoxy/poly (methylmethacrylate) blends

Positron lifetime measurements have been performed to investigate the free volume dependence of the mechanical properties of Epoxy/poly methyl methacrylate (PMMA) blends of varying composition of PMMA (2.5, 5, 7.5, 10, 12.5, 15, and 17.5 wt%). The mechanical properties of the blends have been evaluated according to the (ASTM) standard. The positron results indicate that the mechanical properties like tensile strength and surface hardness have a significant dependence on the free volume of the blends. It is also found that the blends of the present study show positive deviation from the familiar linear additivity rule suggesting the immiscible nature of the blends. Further, up to 5-wt% of PMMA in the blend, an increase in relative fractional free volume correlates well with a decrease of tensile strength

Investigation of gamma radiation effect on chemical properties and surface morphology of some nonlinear optical (NLO) single crystals

The effect of Co-60 gamma irradiation on L-alanine cadmium chloride (LACC), L-alanine doped potassium dihydrogen orthophosphate (KDP) and L-arginine doped KDP nonlinear optical (NLO) single crystals were studied in doses ranging from 100 krad to 6 Mrad. The crystals were grown by slow evaporation method at room temperature. The effects of gamma irradiation on the chemical, surface morphology, DC electrical conductivity, thermal and mechanical properties of the grown crystals have been studied. The functional groups of unirradiated and irradiated crystals have been identified and confirmed by Fourier transform infrared (FTIR) studies. Scanning electron microscopy (SEM) of irradiated crystals shows some morphological changes in the crystals. The dc conductivity of LACC and L-alanine doped KDP crystals were found to increase with increase in radiation dose whereas in case of L-arginine doped KDP crystals, the dc conductivity was found to decrease with increase in radiation dose. Differential scanning calorimetry (DSC) thermograms reveals that there is no significant change in the melting point of the crystals after irradiation and the crystals does not decompose as a result of irradiation. The mechanical behavior of both unirradiated and irradiated crystals is explained with the indentation effects using Vicker's microhardness tester. The Vicker's hardness number H-v and Mayer's index 'n' has been estimated and confirms that LACC belong to the hard materials

Investigation of gamma radiation effect on chemical properties and surface morphology of some nonlinear optical (NLO) single crystals

The effect of Co-60 gamma irradiation on l-alanine cadmium chloride (LACC), l-alanine doped potassium dihydrogen orthophosphate (KDP) and l-arginine doped KDP nonlinear optical (NLO) single crystals were studied in doses ranging from 100krad to 6Mrad. The crystals were grown by slow evaporation method at room temperature. The effects of gamma irradiation on the chemical, surface morphology, DC electrical conductivity, thermal and mechanical properties of the grown crystals have been studied. The functional groups of unirradiated and irradiated crystals have been identified and confirmed by Fourier transform infrared (FTIR) studies. Scanning electron microscopy (SEM) of irradiated crystals shows some morphological changes in the crystals. The dc conductivity of LACC and l-alanine doped KDP crystals were found to increase with increase in radiation dose whereas in case of l-arginine doped KDP crystals, the dc conductivity was found to decrease with increase in radiation dose. Differential scanning calorimetry (DSC) thermograms reveals that there is no significant change in the melting point of the crystals after irradiation and the crystals does not decompose as a result of irradiation. The mechanical behavior of both unirradiated and irradiated crystals is explained with the indentation effects using Vicker’s microhardness tester. The Vicker’s hardness number HV and Mayer’s index ‘n’ has been estimated and confirms that LACC belong to the hard materials

Influence of Moisture Absorption and Content of Graphite Filler on Electrical Property of Sensors and Transducers Enclosures and Phenomena of Electrostriction in Glass- Epoxy Composites

In this investigation E-glass epoxy composite filled with different amount of graphite particles were prepared by compression. Plain waived E-glass cloth with density 200g / meter square was used as reinforcement. Epoxy resin LY556 mixed with Hardener HT907 and accelerator DY063 in the ratio 100:80:2 were used as matrix. The graphite of 50 particle size was used as fillers. Four types of composites were prepared with different amount of graphite fillers viz 0 %, 3 %, 6 % and 9 % with unchanged reinforcement. After subjecting the samples to water absorption up to 96 hours in steps of 24 hrs, dielectric dissipation factor (tan δ), dielectric constant and a. c. conductivity have been measured by using a LCR meter at two different frequencies (100 Hz and 1 kHz). Results show that tan δ direct constant, a.c. conductivity increases with increase in % of graphite in the composites at both high and low frequency for dry samples. Samples with 24 hrs moisture absorption showed approximately same result. After 48 hrs, tan δ values showed variations. However, the fluctuations were less at 6 % of graphite in all samples after 48 and 72 hrs of moisture absorption. Dielectric constant increases with increase in graphite % in composites at higher frequency and there was not much variation at low frequency. In all samples after 24 and 48 hrs of moisture absorption, dielectric constant decreases with increase in graphite loading. It is observed that dielectric constant increases in all samples after 72 hrs of moisture absorption as compared to dry samples. A c. conductivity increases with increase in % of graphite content in dry sample. Up to 6% a. c. conductivity increases after 24 and 48 hrs of immersion, after 72 hrs the trend is reversed. Since Fermi level is initially shifted towards the conduction band and then after 72 hrs of moisture absorption shifted towards the valence band. a. c. conductivity increases with increase in moisture content. The phenomenon of electrostriction was observed in composites without graphite fillers

HIV seropositivity among adult tuberculosis patients in Delhi

We report HIV seropositivity among tuberculosis patients from our hospital between 1994-99. Of the 500 patients with various forms of tuberculosis, two were found to be seropositive (0.4%). This report contrasts with the HIV seropositivity reports from other parts of India where increasing HIV seropositivity has been reported. As the HIV infection is making rapid in-roads in India, it is suggested that continuous HIV sero-surveillance should be done in patients with tuberculosis

Influence of curing agent and compatibilizer on the physicomechanical properties of polypropylene/nitrile butadiene rubber blends investigated by positron annihilation lifetime technique

Abstract A series of thermoplastic vulcanizates of polypropylene (PP)/nitrile butadiene rubber (NBR) (50/50) have been prepared by melt-mixing method, using phenolic resin/SnCl2 as the curing system and maleic anhydride-functionalized PP (PP-g-MA) and carboxylated NBR (NBRE-RCOOH) as the compatibilizing system. Triethylenetetramine was also employed to promote the reaction between the functionalized polymers. The effects of curing agent and compatibilizer on the mechanical and morphological properties have been studied. A novel technique based on positron annihilation lifetime spectroscopy has been used to measure the free volume parameters of these systems. The positron results showed minimum free volume size and free volume fraction at 5.0% of the curing agent suggesting some crosslinking in the rubber phase. The reduction in free volume holes at 2.5% of the compatibilizer is interpreted as improvement in the interfacial adhesion between the components of the blend. The observed variation of free volume fraction is opposite to the tensile strength and exhibits the correlation that, lesser the free volume more is the tensile strength at 2.5% of the compatibilizer in the blend. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 4672–4681, 200

Microcrystalline and kinetic parameters of glass-PEEK hybrid composites

The cowoven hybrid fiber fabric consisting of E-glass and poly(ether ether ketone) fiber was compression-molded to obtain the hybrid composites. The effect of heat aging at different temperatures (400 degrees C and 500 degrees C) for different time intervals (1, 2, and 5 min) on the microcrystalline properties of the composites has been investigated and it was observed that heat aging for short time enhances the structure property relationships as reflected in the changes in crystal size and volume. The microcrystalline parameters such as the nanocrystal size (), lattice disorder (g), interplanar distance (d(hkl)), width of the crystallite size distribution, and surface-weighted crystal size (D-s) were evaluated using wide angle X-ray scattering profiles. The different asymmetric column length distribution functions namely, exponential and Reinhold distribution methods were employed to probe the microcrystalline behavior of the composites and the results were compared. The kinetics of thermal degradation (using Flynn-Wall-Ozawa) revealed that, the activation energy decreased with increase in mass loss up to 15% and remains constant thereafter