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Density is an important parameter that influences the properties and performances of rigid polyurethane foam (PUF). Rigid PUF with different densities were prepared by varying the amount of distilled water as blowing agent. This investigation reports the mechanical, morphological, water absorption, thermal conductivity, and thermal behavior of rigid PUF varying with the density, which controls the foam architecture. The density of the PUF decreased from 116 to 42 kg/m 3 with an increase in the amount of water from 0.1 to 3.0 parts per hundred polyol by weight (phr), respectively. It was found that the mechanical properties of the PUFs changed with the foam density. The results of water absorption of the PUFs showed that water absorption increased with decrease in density, due to increase in the cell size and decrease in the cell-wall thickness. The thermal conductivity measurements showed that the thermal conductivity decreased with increase in density. It was due to the decrease in cell size. The thermal analysis of the PUFs shows that the glass transition temperature increases with the decrease in foam density, but the thermal stability decreases with the decrease in foam density.

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The synthesis of polyaniline (PAni) powder was carried out from 0.15M of aniline and 1M of HCl in distilled water at room temperature in a single compartment electrochemical cell. The PAni was again synthesized chemically keeping the composition and temperature same as electrochemical process but adding equimolar amount of ammonium peroxydisulfate as an oxidizing agent. Then the PAni obtained from these two methods were characterized by the conductivity, solubility, X-ray, FTIR, TGA, UV, and SEM, and compared. Result shows that the electrochemically synthesized PAni (ECS-PAni) has somewhat lower conductivity, higher solubility, more benzenoid rings than quinoid rings, lower crystallinity, higher band energy, and higher particle size than that of chemically synthesized PAni (CS-PAni).

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Water-blown rigid polyurethane foam (PUF) with two different particle sizes (180 and 300 lm) of expandable graphite (EG) as a flame-retardant additive were prepared, and the effects on the mechanical, morphological, water absorption, thermal conductivity, thermal, and flame-retardant properties were studied. In this investigation, EG content was varied from 5 to 50 php by weight. The mechanical properties of PUF decreased with increasing EG loading in both cases. The water absorption of the PUF increased with an increase in the EG loading mainly because of the collapse of foam cells, as evidenced from the scanning electron microscopy pictures. The thermal conductivity of the EG-filled PUF showed that the insulation properties decreased with EG loading. The flame-retardant properties (limiting oxygen index and char yield measurement) of the PUF improved with increasing EG loading. PUF filled with the higher particle size EG showed better mechanical properties and fire-retardant properties than the PUF filled with the lower particle size EG.

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The comparative study on the effect of different type of dopants on the properties of polyaniline (PANI) is relative less although dopant has profound effect of the properties of PANI. So, the aim of the present work is to study the effect of different type of dopant, namely strong inorganic hydrochloric acid (HCl), organic and aromatic acids containing different aromatic substitution, namely p-toluene sulfonic acid (PTSA), dodecylbenzenesulfonic acid (DBSA), organic and aliphatic acids having long hydrocarbon chain, namely lauric acid (LA), on the properties of PANI. The PANI was prepared through oxidative polymerization methods and doped with HCl, PTSA, DBSA, and LA and then characterized through different methods like conductivity measurement, UV, X-ray, DSC, TGA, and SEM. It was found that the properties of doped PANI depend on the type and molecular size of the dopant. With the increase in dopant chain length, the crystallinity is decreased, whereas the d-spacing, interchain separation, and solubility are increased. The bond formation of water molecules with the backbone nitrogen of the polymers is much less in presence of aromatic dopants when compared with those of inorganic or aliphatic dopants. All the doped polyanilines under investigation do not decompose up to 500 C.