EFFECTS OF COUPLING AGENTS ON DYNAMIC-MECHANICAL PROPERTIES OF AGED AND WET MULTIFUNCTIONAL EPOXY-RESINS CURED WITH ACID ANHYDRIDES AND FILLED WITH PITCH-BASED CARBON SHORT FIBERS TREATED WITH COUPLING AGENTS

Pitch-based carbon short fibers (PCF) as functional fillers were treat ed with five types of coupling agents (CA) and were filled with multi- functional epoxy resin (EP) cured with three types of acid anhydrides at 22.2 wt%. The influence of aging and wetting on the dynamic mechani cal properties was studied by use of a non-resonant forced-vibration m ethod. The samples were aged at 130 degrees C for 5000 h or wetted in distilled water at 21 degrees C for 5000 h. The longer the aging time, the larger the weight reduction of the aged specimens: the maximum va lue was 3.6 wt% for 5000 h. The glass transition temperature (T-g) for the CA-treated specimens dropped more compared with the untreated spe cimens (UA). Although CA on the surfaces of PCF was lost by aging, the Storage modulus (E') increased at a lower temperature -140 degrees C and decreased at higher temperatures (over 200 degrees C). The maximum water absorption rate for the wetted specimens was 2.3 wt% and the de crease of T-g was similar to that for the UA specimens. The value of E ' increased at lower temperatures but decreased at higher temperatures . The influence by both aging and wetting on the mechanical dynamic pr operties was similar even though the mechanism for each is different.