• S Gopalakrishnan

      Articles written in Bulletin of Materials Science

    • Synthesis, mechanical, thermal and chemical properties of polyurethanes based on cardanol

      C V Mythili A Malar Retna S Gopalakrishnan

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      Cardanol, an excellent monomer for polymer production, has been isolated from CNSL and allowed to react with formaldehyde in a particular mole ratio in the presence of glutaric acid catalyst to give high-ortho novolac resin. Such characterized polyol has been condensed with diphenylmethane diisocyanate to produce rigid polyurethane. A commercially available polyol, polypropylene glycol-2000 (PPG-2000), has also been condensed with diphenylmethane diisocyanate and polyol to produce tough polyurethane. These polyurethanes were characterized with respect to their resistance to chemical reagents and mechanical properties such as tensile strength, percentage elongation, tear strength and hardness. Differential thermal analysis (DTA) and thermo-gravimetric analysis (TGA) were undertaken for thermal characterization.

    • Influence of polyols on properties of bio-based polyurethanes

      S Gopalakrishnan T Linda Fernando

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      Polyurethane elastomers from cardanol-based polyol, polypropylene glycol (PPG-1200 and PPG-2000) and isophorone diisocyanate were prepared in the form of thin sheets. The sorption,mechanical and thermal properties were studied. The solubility parameter and molecular weight between crosslinks of polyurethane samples were calculated from swelling experiments. The swelling study of polyurethanes revealed that the sorption is found to decrease with an increase in chain length of PPG. The stress–strain data showed that the elastomers obtained using PPG-1200 gave the best mechanical properties. The thermal degradation of all the three elastomers starts almost at 270°C, regardless of the PPG chain length. The value of activation energy of degradation calculated using the Broido method was in the range of 40–70 kJ/mol.

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