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The surplus entropy of the phase transition is measured for KH2P04 and KD2P04 crystals.

Bariumtitanate/polyvinylidene fluoride (BaTiO 3 ) x (PVDF) 100-x composite samples were prepared and characterized using X-ray diffraction (XRD) and differential scanning calorimetry (DSC) techniques. In this work, the ratio of the constituents of this composite was altered, and the structural and thermal changes were studied. Also, the variation of tetragonality of BaTiO 3 (BT) in the composite samples as a function of BT content was studied for the first time. The results show that all the samples are in the a-phase, and the hindrance to the PVDF crystallization increases with the increase of BaTiO 3 (BT) ratio in the composite. Tetragonal distortion of BT nanoparticles in the composite increases with the increase in BT ratio up to 30%, where it gets a saturation value. Also, it seems that stretching the samples enhances the BT tetragonality. Both melting and crystallization behaviors of the composite samples show double-melting endotherms (reorganization) and crystallization exotherms. The inclusion of BT in the composite samples results in a decrease in the melting temperature of the samples.

Effect of the concentration of four types of carbon black, namely, HAF, FEF, ISAF and GPF, on the electrical conductivity of SBR (1502) was studied. The anomalous behavior of conductivity [σmin in σ(T) curves] becomes more pronounced as we approach a characteristic value of carbon concentration, F0, at which maximum anomaly occurs; F0 was found to depend on the type of carbon black. Moreover, the depth of the valley shape of the σ(T) curve increases with the particle size of carbon black used.

Styrene–butadiene rubber (SBR) charged with 50 phr of HAF carbon black has been found to show a positive temperature coefficient of resistivity close to 0.07/°C at 27°C. Beyond a point (75°C) of minimum conductivity, however, it behaves as a normal noncrystalline semiconductor with a resistivity which decreases with rise of temperature with an activation energy of 0.56 eV. Blending the composition with poly(vinyl chloride) (PVC) shifts the minimum towards lower temperatures. The descending branch of the conductivity versus reciprocal absolute temperature characteristic is probably associated with thermal expansion of tunnelling paths separating the conducting carbon particles.

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SynopsisFollowing a series of experiments on the effect of different factors of the electrical conductivity of carbon-black-loaded styrene butadiene rubber, an attempt was made to study the effect on electrical conduction of changing the sulfur content. It was found that an optimum sulfur content leads to a swelling-resistant composite with good electrical insulation. This was done for dry as well as wet specimens of rubber.

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