Overage Indicator for Graphite Fiber Epoxy Prepreg.

摘要

Prepreg or B-staged products are used extensively in the aerospace, electrical, and communications industries. They consist of a partially reacted mixture of monomers which have been impregnated into the reinforcement. During shipping and storage, prior to use, the reactions will continue. The amount of reaction or age 11 of the prepreg will depend on the conditions (temperature, humidity and time) that it has been exposed to. This report provides data and results of aging studies performed on Hercules 3501-6/As graphite epoxy prepreg under diverse conditions of temperature, time and humidity. At various times during the aging, physical properties of the prepreg were measured and the following methods were used to track the age of the prepreg: (1) dielectric analysis (DA), (2) dynamic mechanical analysis (DNA), and (3) a simple, easy to use time-temperature integrating device (TTW) which is carried with the prepreg and provides a visual observation of the time and temperature exposure of the prepreg. Liquid chromatography (Lc) was used to characterize some of the changes. It was found that DA, DNA, and the TTW can be used to follow the age of the prepreg and that they can be used as overage indicators to tell the user when the prepreg has lost its useful life. The changes in prepreg reactivity caused by aging in a humid environment were also determined using DA and LC. This study was conducted by exposing prepreg to dry and humid conditions at different temperatures. Results indicate that exposure to high humidity will ultimately result in prepreg with much greater reactivity when compared to initial or dry aged prepreg. This change is irreversible and is time and temperature dependent. (MM).