Processability studies of silica‐thermoset polymer matrix nanocomposites

Abstract

The aim of this study is to investigate the processability of silica-thermoset polymer matrix nanocomposites in terms of dispersion of silica nanoparticles and their effect on curing. Two thermosetting resins were considered, an epoxy and a polyester resin, with 5 % silica, although 1% silica was also used in preliminary studies in the polyester system. Various combinations of mechanical mixing and sonication were investigated for the dispersion of silica nanoparticles under different processing conditions and times in solvent-free and solvent-containing systems. It was found that the best dispersion route involved a solvent-aided dispersion technique. Consequently, different procedures for the solvent removal were investigated. Optical microscopy and SEM were used to characterize the resulting nanocomposites. DSC and rheological DMTA tests demonstrated that the silica nanoparticles shorten the gel time and promote curing in these thermosetting systems.3

Liquid composite moulding of fibre nanocomposites

“…Rheology DMTA tests in this study and DSC tests in a previous study 24 showed that silica nanoparticles promote the curing of epoxies and accelerate gelling. As a result, the mixture needs to be processed at lower temperatures in liquid composite moulding processes to extend the infiltration time.…”

“…The silica powder was dispersed in the epoxy resin in a solvent aided procedure to ensure homogeneous mixing, 24 where ethanol was the solvent employed. A suspension was produced with 10 g of WACKER HDK N20 powder in 120 mL ethanol and was sonicated in an ultrasonic bath at room temperature for 30 min to disperse the silica nanoparticles.…”

“…It is easily observed that the silica nanoparticles lower the gelling time of the system (324 min for the silica-epoxy system against 440 min for the pure epoxy system at the same high viscosity value), owing to both the locking effect of the rigid silica particles and also the promotion of curing by the silica nanoparticles, as demonstrated in DSC studies. 24 This means that the process time of the silica-epoxy system for the infiltration stage in liquid composite moulding is going to be much shorter than that of the pure epoxy system.…”

“…Figure 2 displays an SEM micrograph of the fracture surface of a 5% silica-epoxy nanocomposite (without fibre reinforcement) where the silica-epoxy system was simply left to cure. The surface consists of features of 50-100 nm that have been attributed 24 to well dispersed silica nanoparticles which led to such roughness characteristics in the fracture surface. Figure 3 presents SEM images from different regions of the glass fibre-silica-epoxy specimens produced by RTM.…”

Hybrid Woven Glass Fibre Fabric-Multi-Walled Carbon Nanotube-Epoxy Composites Under Low Rate Impact

“…Dispersion of CNTs is most important to realise the benefits of the nano-effects [19,20]. For this reason, a solvent is frequently used as an aid for the dispersion at high shear [2,21]. Although the concept of multi-scale reinforcement in composite materials has been thought advantageous, on the basis of biocomposites such as bone, it is very difficult to fully infiltrate MWNTs through a continuous fibre reinforcement, following a feasible and cost-effective process.…”