Effect of Solid Epoxy Resin on Properties of an Epoxy/Glass Prepreg

The desirable tack and viscosity in prepregs are mostly obtained by pre-curing, but the main problem with this method is the decremental storage life of prepreg because of the ongoing curing reaction. One of the appropriate strategies to overcome this problem is to eliminate the pre-curing stage in the prepreg process and achieve the appropriate viscosity through epoxy formulations with different molecular weights. With this method, it is possible to obtain a prepreg with single-stage curability and longer storage life.

By using low molecular weight epoxy resin (Epon828) and solid epoxy resin with high molecular weight (Ker3003) in the presence of MEK as solvent, DICY as curing agent and diuron as accelerator, two types of formulations including 3S7L (30% (wt) Ker3003 and 70% (wt) Epon828) and 4S6L (40% (wt) Ker3003 and 60% (wt) Epon828) were designed. Based on the obtained formulations, prepregs were manufactured and then cured to obtain the final composites. Different characterization techniques including FTIR, DSC, DMTA, ILSS, tensile strength, viscosity and drapability were used to determine the properties of formulated resins, prepregs and composites.

Appropriate prepregs were obtained based on the designed resin formulations without pre-curing stage. The results showed that the curing initiation temperatures of the formulated resins were about 15°C higher than that of Epon828 epoxy resin. The 4S6L formulation maintains the desired tack and viscosity of the prepreg up to 45°C. ILSS for composites based on 3S7L formulation was about 14% and 11% higher than the values obtained for composites based 4S6L and Epon828 resins, respectively. Flexural rigidity as representative of the drapability of the prepregs was obtained 3230 and 3460 μJ/m, respectively. For prepregs based on 3S7L and 4S6L formulations, there is an indication of high drapability of the prepregs based on designed formulations..