Influence of aging and wetting on dynamic mechanical properties of multi-functional epoxy resins cured with diamines and filled with pitch-based carbon short fibers treated with coupling agents

Abstract

Pitch-based carbon short fibers (PCF) as functional fillers were treated with five types of coupling agents (CA) and were filled in multi-functional epoxy resin (EP) cured with two types of diamines at 22.2 wt%. The influence of aging and wetting on the dynamic mechanical properties was studied by use of a non-resonant forced-vibration method. The samples were aged at 130° for 5000 h or wetted in distilled water at 21° for 5000 h. The maximum weight reduction of the aged specimens was 5.1 wt% for 5000 h. Although CA on the surfaces of PCF was lost by aging, the storage modulus (E′) increased at a lower temperature -140° and decreased from 25° to 200° compared with untreated specimens (UA). The maximum water absorption rate for the wetted specimens was 5.6 wt%. The value of E′ increased at lower temperatures but decreased above room temperatures. The influence by both aging and wetting on the mechanical dynamic properties was similar even though the mechanism for each is different. These results are compared with specimens cured by acid anhydrides.