Influence of aging and wetting on dynamic mechanical properties of multi-functional epoxy resins
Multi-functional epoxy resins with high heat resistance (high glass transition temperature, Tg) were cured with acid anhydrides and diamines. The influence of aging (thermal processing) and wetting (water absorption processing) on the dynamic mechanical properties of these materials was investigated. The aging was carried out by keeping the specimens in air at 130°C for a maximum of 5000 h and wetting was carried out in water at 21 °C for 5000 h. The temperature dependence of multi-functional epoxy resins on the dynamic mechanical properties was measured. The longer the aging time, the larger the weight reduction of the aged multi-functional epoxy resin, which reached a maximum of 3.9% after 5000 h. For the effect of hardeners, the specimens cured with diamines showed larger values. The value of Tg for all the specimens increased. Compared with the unaged materials, the dynamic storage modulus (E') of aged specimens was large at low temperatures (-140 °C) for the samples cured with acid anhydrides and at high temperature (200 °C) for the samples cured with diamines. The maximum water absorption rate of the wetted specimens was 5.1 wt% and those cured with diamines showed larger values while Tg decreased for all the specimens. Compared with the unaged material, some of the wetted specimens showed an increased E' at low temperatures (-140°C) and room temperatures (25°C) but all decreased at higher temperatures (200°C).
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