Preparation and Rheological Characterization of Phenolic/Glass Prepregs

Phenolic/glass prepregs are widely used in manufacturing of structuralcomposites. In this work, four types of glass/phenolic prepregs, each with a resincontent of about 40 wt% were prepared by using resole and novolak phenolicresins and satin glass fibre fabric. They were B-staged or pre-cured at 100°C, 110°Cand 120°C in a laboratory-scale prepreg production machine at different processingconditions. The manufactured prepregs were characterized in terms of their volatilecontent, resin content, conversion or the degree of pre-cure, tack and flow behaviourto provide qualitative and quantitative assessments of prepreg processing, structureand properties. The optimum processing conditions were determined and the resultsshow that the level of pre-cure or conversion was in the range of 2 to 55% havingsignificant effect on tack and flow properties of the prepregs. The resole prepregcontaining 15% novolak resin (Re15N) showed the maximum tack of 19.8 kPa whichwas found to be at 6.5% of pre-cure. Nonetheless, the volatile content of prepreg wasvery critical and had a dual effect on tack and processing condition. We studied therheological properties of these prepregs by using a parallel plate rheometer. Thenovolak prepreg displayed a distinct rheological behaviour and by using a mixture ofboth resole and novolak resins a suitable processing condition was achieved.