The biobased chain extended polyurethane (PU) was synthesized by reacting castor oil based polyol with different diisocyanates [toluene-2,4-diisocyanate (TDI) and hexamethylene diisocyanate (HMDI)] and chain extender such as glutaric acid. Biocomposites have been fabricated by incorporating the silk fiber into both TDIand HMDI-based PUs. The effect of incorporation of silk fiber into TDI-and HMDI-based neat PU on the physicomechanical properties such as density, surface hardness, tensile strength, and percentage elongation have been investigated. The dynamic mechanical properties and the thermal stability of neat PUs and the silk fiber incorporated PU composites have been evaluated. The TDI-based neat PU has showed higher mechanical properties compared to HMDI-based PU. The incorporation of 10% silk fiber into TDI-and HMDIbased PU resulted in an enhancement of tensile strength by 1.8 and 2.2 folds, respectively. The incorporation of silk fiber into biobased chain extended PU increased the glass transition temperature (T g ) of the resultant biocomposites. The morphology of tensile fractured neat PUs and their biocomposites with silk fiber was studied using scanning electron microscope (SEM). POLYM. ENG. SCI., 50:851-856,

Castor oil based chain extended polyurethanes (PUs) have been prepared using citric acid and maleic acid as chain extenders. Molecular transport of n‐alkanes into prepared carboxylic acid chain extended PUs has been studied at different temperatures, viz., 25, 40, and 60°C using a gravimetric sorption method. The sorption (S), the diffusion (D), and the permeation (P) coefficients for n‐alkane penetrants have been calculated. Transport data are affected by the nature of the interacting solvent molecules, molar volume, solubility parameters, temperature, and the structural variation of the chain extended PUs. The temperature dependence of the transport coefficient has been used to estimate the kinetic parameters for the processes of diffusion (ED) and permeation (EP) from the Arrhenius plots. The van't Hoff relation was used to obtain enthalpy (ΔH) and entropy (ΔS) of sorption process. POLYM. ENG. SCI., 47:2057–2064, 2007. © 2007 Society of Plastics Engineers

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Castor oil-based polyurethane (PU)-polyester nonwoven fabric composites were fabricated by impregnating the polyester nonwoven fabric in a composition containing castor oil and diisocyanate. The effects of different diisocyanates such as toluene-2,4-diisocyanate (TDI) and hexamethylene diisocyanate (HMDI) on the mechanical properties have been studied for neat PU sheets and their composites with polyester nonwoven fabric. Chemical resistance of the PU composites has been assessed by exposing the specimens to different chemical environments. Percentage water absorption of composites and neat PU sheets has been determined both at room temperature and in boiling water. Both TDI-and HMDI-based PU composites showed a marginal improvement in tensile strength retention at 1008C heat ageing. Water sorption studies were carried out at different temperatures, viz, 30, 50, and 708C, based on immersion weight gain method. From the sorption results, the diffusion (D) and permeation (P) coefficients of water penetrant have been calculated. Attempts were made to estimate the empirical parameters such as n, which suggests the mode of transport (non-Fickian), and K, a constant which depends on the structural characteristics of the polymer in addition to its interaction in boiling water. The temperature dependence of the transport coefficients has been used to estimate the activation energy parameters for diffusion (E D ) and permeation (E p ) processes from Arrhenius plots.

Exfoliated graphite was prepared by chemical route and then further subjected to thermal oxidation and sonication for size reduction and increased interlayer spacing in natural flake graphite. Exfoliated graphite/ABS composites were prepared with varying filler concentration by solution casting method. Exfoliated graphite and composites were characterised by scanning electron microscopy and energy dispersive X-ray analysis, Fourier transform infrared spectroscopy and X-ray diffractometry techniques. After thermal exfoliation significant peak of graphite at 2 = 26.4˚ disappeared completely, confirming successful exfoliation of graphite. SEM images revealed homogeneous dispersion of exfoliated graphite in the matrix and EDAX confirmed successful reduction of graphite oxide.