Effect of 3-Glycidoxypropyletrimethoxysilane on Thermal and Mechanical Properties of Epoxy-based Nanocomposites

Adeel Afzal*, Humaira M. Siddiqui

Department of Chemistry, Quaid-i-Azam University, Islamabad-45320, Pakistan

E-mail: aafzal@qau.edu.pk

ABSTRACT

Epoxy-silica nanocomposites not only possess the advantage of higher tensile strength and modulus, better adhesion properties, and good chemical and corrosion resistance, but the incorporation of silica at nanoscale improves their dimensional stability, processing ability, and their physical and thermal properties. However, interphase bonding between the constituents of a nanocomposite is a prerequisite to significantly multiply the advantage of such materials. Current piece of work is an exploratory study into the effects of 3-glycidoxypropyltrimethoxysilane on thermal and mechanical behavior of epoxy-silica nanocomposites based on a diamine cured DGEBA type epoxy resin, and sol-gel derived SiO­­₂. Two types of epoxy-silica nanocomposites ESN-1 and ESN-2 were prepared as transparent coatings with different amounts of silica i.e. (0-20) wt%. Hydrolysis of tetraethyl orthosilicate (TEOS) was carried out in situ with water and the reaction mixture was cured. 5wt% of 3-glycidoxypropyltrimethoxysilane was added to all samples of ESN2 type of nanocomposites to compare the property benefits. Characterization of ESN1 and ESN2 nanocomposites via FTIR spectroscopy confirmed the presence of three dimensional networks of epoxy-amine and silica. Morphological features of nanocomposites were as studied by atomic force microscopy (AFM), and suggest fine dispersion of SiO₂ nanoparticles in the epoxy-amine matrix. Thermal and mechanical properties of nanocomposite films were determined by thermal methods i.e. TGA, DSC, and static mechanical analysis. An appreciable increase in glass-transition temperatures ‘Tg’ and thermal stability of nanocomposites was observed at higher silica loadings. Static mechanical analysis also demonstrated ~50% increase in the modulus of nanocomposites. Consequently, ESN2 nanocomposites were found to be superior to their ESN1 equivalents with similar silica loadings due to enhanced compatibility between the two phases achieved through 3-glycidoxypropyltrimethoxysilane.

Keywords: epoxy resin, nanocomposites, AFM, DSC, TGA

* Corresponding Author: Adeel Afzal
Department of Chemistry, Quaid-i-Azam University, Islamabad.45320, Pakistan
Tel.: (00) 92 51 9064 2234; Fax: (00) 92 51 9064 2241; E-mail: aafzal@qau.edu.pk