Investigation of the effects of amino silane-based sizing on the mechanical properties of sized glass fibre mat epoxy composites

Sizing is the surface treatment of glass fibres (GFs) to protect them from wear, handle with ease and to create a good interface with the polymer matrix. This paper reports on the discernible procedure for the synthesis of epoxy- compatible amino silane sizing formulation for E-GF and its efficacy based on inter-laminar shear strength (ILSS) and flexural strength of in-house sized GF (SGF) woven roven mat (WRM) reinforced epoxy composites and compared to commercially available sized WRM [0°/90°]. The formulations of sizing were prepared by varying the proportions of aminopropyltriethoxy silane (APS, coupling agent) and polydimethylsiloxane (PDMS, anti-foam agent), for a fixed proportion of film former, surfactant and lubricant. Commercially available sized GF WRM were heat cleaned prior to sizing with prepared formulations. Interestingly, sizing with formulation of 0.65 wt% APS and 0.35 wt% of PDMS, coded as S6, showed homogeneous coating morphology and the loss on ignition (LOI) is comparable to commercially available SGF. Also, Fourier transform-infrared spectroscopy of SGF6 indicated the formation of silanol interphase by the presence of bands corresponding to Si–O–Si and Si–OH functional groups. The contact angle with epoxy hardener solvent by sessile drop method demonstrated good wetting favourable for better interphase with epoxy matrix. Thermogravimetric analysis indicated that sizing pick up and thermal stability were best for S6 formulation SGF. The mechanical testing shows that S6-sized WRM composite (SWC) yielded the best ILSS and flexural strength due to the effect of better wetting and good interfacial adhesion between SGF and matrix as revealed from fractography. The discernible recipe formulation and the better mechanical properties exhibited by SWC-reinforced SGF WRM sized with S6 comparable to that of commercial GF WRM epoxy composite indicate plausible industrial applications. (author)