Title: PPE TELECHELIC MACROMONOMERS. BROAD PERFORMANCE ENHANCEMENTS OF THERMOSET MATRIX RESINS
Abstract: Fiber-reinforced epoxy systems used in structural composites and advanced electronics have challenges in balancing high glass transition temperatures (Tg), high toughness, reduced moisture sensitivity, and the effects of flame-retardants on performance. Unique polyphenylene ether telechelic macromonomers (PPE-M) were heralded as a breakthrough in the search for materials that broadly enhanced performance of thermoset resins. The use of macromonomer in catalytic and amine cured epoxy resins was studied. The combination of higher glass transition temperatures, impact strength, fracture toughness and compressive strength were observed with increased levels of PPE-M. The dielectric properties were lowered with increased levels of macromer. There were major reductions in shrinkage, which could translate to lower stresses from curing.
Moisture uptake can have adverse effects on composites and alter thermo-mechanical properties. In addition, water can increase hygroscopic stresses through differential swelling and reduced interfacial adhesion. The use of PPE macromer has been shown to offer significant reductions in moisture uptake, growth from absorbed water, and greater retention of flexural strength and modulus after exposure to water. In addition, absorbed water has adverse effects on dielectric properties. The use of the macromer may result in more stable and greater retention of the low dielectric properties.
During combustion, PPE undergoes thermal rearrangements to phenolic like structures, which can lead to char formation. The more char formed, the less fuel produced. PPE-M combined with nonhalogen flame-retardants exhibit reduced burn times. Flame-retardants can have adverse effects on other critical properties such as toughness. Interestingly, as the macromer levels increase the amount of non-halogen flame retardant needed to achieve a certain (UL-94) burn times decreased. With the combination of PPE-M and less flame retardant, the epoxy resin showed increased Tg and impact strength, lower density and dielectric properties.
The broad enhancement of performance by PPE-M suggests that it could be an important reactant for use in epoxy matrix resins.
Authors: Edward N. Peters, Stacy Cashin
Conference: CAMX 2017 –Orlando