engleski

Epoxy-based hybrid materials

Epoxy resins are high-performance polymer materials with wide application, ranging from bulk materials to protective coatings and high-performance binders. In order to improve their already excellent properties, epoxy-based nanocomposites are being investigated. To avoid aggregation of nanoparticles, inorganic phase was formed in situ by sol-gel process, producing organic-inorganic hybrid materials. Presence of bonds between the phases improves interphase contact and end-properties of hybrid materials. The hybrid materials were prepared from diglycidyl ether of bisphenol A (DGEBA), with modified silicon alkoxide with a reactive epoxy group, 3-glycidyloxypropyltrimethoxysilane (GLYMO) as an inorganic precursor, and a poly(oxypropylene)diamine Jeffamine D230 as a curing agent for epoxy. Influence of amine/epoxy ratio and conditions of hydrolysis of GLYMO were investigated. Hybrid materials were cured either 24 hours at room temperature or 1 hour at 60 °C, and postcured 24 hours at 120 °C to complete the organic cure. Morphology of hybrid materials was found to depend both on hydrolysis conditions and cure temperature. Base catalysis caused formation of larger inorganic particles inside epoxy matrix. Materials cured at 60 °C show finer morphology compared to those cured at 25 °C, since higher temperature favours formation of polymer network over condensation of inorganic phase. Hybrid materials from hydrolysed GLYMO show visibly improved mechanical properties. Storage modulus is increased both in glassy and viscoelastic state due to strengthening effect of inorganic network. Truly hybrid system prepared from acid-catalysed GLYMO and cured at 60 °C shows improvement in all properties when compared to non hydrolysed one. This indicates positive influence of silanol Si-OH groups formed by hydrolysis. Presence of uncondensed silanol groups enabled formation of additional hydrogen bonds with polymer matrix, further improving interphase contact and consequently mechanical properties of the hybrid material. On the other hand, residual HCl in the material can act as a centre of chain-scission, and these materials were found to start degrading at somewhat lower temperatures.

epoxy resin; organic-inorganic hybrid materials; sol-gel process;

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