Effect of moisture exposure before curing in epoxy-glass B-stage composites

Effects of moisture exposure before cure of Scotchply 1009 composite material have been studied by three thermal analysis methods. These studies revealed the need for state-of-the-art analytical tools as well as increased attention to detail in packaging (by supplier) and improved handling (by user to reduce moisture exposure). It is shown that water definitely has a detrimental effect on the cure of Scotchply 1009 prepreg containing a boron trifluoride monoethylamine curing agent. Exposure to moisture greater than 70% RH (relative humidity) can be detrimental and lower the T_g of Scotchply 1009. Cure temperature high enough to ensure sufficiently high T_g in 1009 material which has been exposed to moisture can result in degradation of the thermosetting resin. In the manufacture of stator coils, this could cause degradation of electrical properties