Use of Dynamical Mechanical Testing and Chromatography to Assess the Degree of Cure of Phenolic Prepreg
Phenolic prepregs are used extensively in aerospace interiors due to their processability, favorable flammability characteristics, and low cost. The extent to which the phenolic matrix is cross-linked, otherwise known as degree of cure, is important to composite manufacturing processes. For solvent-based prepregs, the application of traditional techniques used to determine degree of cure, such as measurement of exothermic heats of reaction using differential scanning calorimetry (DSC), are complicated by the production and evaporation of solvents during the phenolic cure reaction. The purpose of this study was to evaluate alternative methods for measuring phenolic resin degree of cure using gel permeation chromatography (GPC) and dynamic mechanical analysis (DMA). Phenolic prepreg samples with varying levels of degree of cure were manufactured and then analyzed using the methods listed above. DMA was used to measure prepreg glass transition temperature as a relative measure of degree of cure, while GPC was used to directly measure the molecular weight distributions. Good correlation between these two methods was observed, with GPC results being very sensitive to degree of cure.
Author: Mark Peyron
Conference: SAMPE Seattle 2017