engleski

Kinetics of epoxy-amine reaction of pre-hydrolysed 3-glycidyloxypropyltrimethoxysilane

Hydrolysis of 3-glycidyloxypropyltrimethoxysilane (GLYMO), an organically modified methoxysilane with a reactive epoxy group linked to a silicon atom through a stable Si-C covalent bond, was studied by Fourier-transform infrared spectroscopy (FTIR). Stoichiometric molar ratio for full condensation of GLYMO, of 1.5 mol of water per 1 mol of GLYMO, was used. Hydrolysis was catalysed by addition of varying concentration of hydrochloric acid, HCl. Kinetics of subsequent reaction of hydrolysed GLYMO with poly(oxypropylene)diamine was studied by differential scanning calorimetry (DSC), using varying heating rates to obtain isoconversional kinetics data. Glass transition, of hybrid materials obtained in this manner was characterised by DSC, thermal stability by thermogravimetric analysis (TGA) and hardness by ball-indentation method. FTIR and DSC results have shown that epoxy groups remain stable during hydrolysis. Activation energy of the epoxy-amine reaction was determined by Kissinger and Friedman isoconversional methods from dynamic DSC scans. Obtained plots of Ea vs α indicate a complex reaction mechanism, and the influence of hydrolysis conditions. In all conditions, silanol groups formed by hydrolysis can act as catalysts for the epoxy-amine reaction. Residual chloride ions from acid-catalysed hydrolysis act as scission centers and decrease thermal stability of hybrid materials as determined by TGA. Hardness of hybrid materials was not improved when compared with ones obtained from non-hydrolysed GLYMO.

kinetics; alkoxysilane; epoxy-amine reaction

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