A comparison study: The new extended shelf life isopropyl ester PMR technology versus the traditional methyl ester PMR approach

Polymerization of monomeric reactants (PMR) monomer solutions and carbon cloth prepregs of PMR II‐50 and VCAP‐75 were prepared using both the traditional limited shelf life methanol based PMR approach and a novel extended shelf life isopropanol based PMR approach. The methyl ester and isopropyl ester based PMR monomer solutions and PMR prepregs were aged for up to 4 years at freezer and room temperatures. The aging products formed were monitored using high pressure liquid chromatography (HPLC). The composite processing flow characteristics and volatile contents of the aged prepregs were correlated versus room temperature storage time. Composite processing cycles were developed and six‐ply cloth laminates were fabricated with prepregs after various extended room temperature storage times. The composites were then evaluated for glass transition temperature (Tg), thermal decomposition temperature (Td), initial flexural strength (FS), and modulus (FM), long term (1000 h at 316°C) thermal oxidative stability (TOS), and retention of FS and FM after 1000 h aging at 316°C. The results for each ester system were comparable. Freezer storage was found to prevent the formation of aging products for both ester systems. Room temperature storage of the novel isopropyl ester system increased PMR monomer solution and PMR prepreg shelf life by at least an order of magnitude, while maintaining composite thermal and mechanical properties. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 99: 3549–3564, 2006