Epoxy composites with silica hardened with 1-ethylimidazole
Ryszard Pilawka, Teofil Jesionowski
Quarterly No. 1, 2011 pages 14-17
DOI:
keywords: epoxy resin, epoxy composites, silica fillers, tensile and bending strength
abstract Epoxy compositions and composites hardened with 1-ethylimidazole (1EI) with different silicas have been investigated. The epoxy resin used was Epidian 6 (product of Chemical Works “Organika Sarzyna” in Nowa Sarzyna) and as a filler, different silicas were applied: a product of the precipitation reaction from solutions of sodium silicate and ammonium salts and modified with 3 wt./wt. of 3-glicydoxypropyltrimethoxysilane (SiO2-EP) or 3 wt/wt./wt. of 3-aminopropyl-trimethoxysilane (SiO2-NH). The filler was introduced to the compositions in the amounts of 1.0; 2.5; 5.0 and 7.5 g per 100 g of the epoxy resin and the hardener was added - 1 g 1-ethylimidazole per 100 g of epoxy resin. The dispergation time of the fillers was 120 minutes at 70°C. The epoxy composites were hardened at a temperature of 140°C for 4 hours. The particle sizes of the obtained powders using the laser diffraction method (Mastersizer 2000, Malvern Instruments Ltd.) were determined. The investigations of the viscosity of the epoxy composition were carried out with the use of an ARES rheometer, Rheometric Scientific: the diameter of the plates - 50 mm, the thickness between the plates - 1 mm. The tensile and bending strengths were measured corresponding to standards PN-EN ISO 527-1 (speed rate 5 mm/min) and PN-EN ISO178 (speed rate 1 mm/min) by using the testing machine Instron 4206, Instron Corporation. The particle size remains in the range of 350 to 840 nm for the unmodified silica. The modified nanosilicas are in a higher particle size range of 530 to 1050 nm for the aminosilane-grafted silica and from 450 to 900 nm for the modified silica with epoxysilane. The addition of a filler increases the viscosities of the epoxy composition from 12.74 Pa•s (epoxy resin Epidain 6) to 15.78 Pa•s for a composition with 7.5 phr silica modified with epoxysilane. The epoxy composites with the nanofiller have higher tensile and bending strength than unfilled systems. The introduction of silica increased both the Young’s and elasticity modulus and additionally the tensile and bending strength of the epoxy composites.