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/sub g/ of Scotchply 1009. Cure temperature high enough to ensure sufficiently high T/sub 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.<>