Service life assessment and moisture influence on bio-based thermosetting resins

In this study, three different types of bio-based resins are compared to a conventional oil-based epoxy in terms of moisture uptake, long-term properties and its influence of moisture and glass transition temperature, T (g). Moisture uptake is determined by means of gravimetric method, time temperature superposition (TTSP), and T (g) data obtained in dynamic mechanical thermal analysis (DMTA). Moisture uptake show Fickian diffuison behavour for all resins, saturation level and diffusion coefficient however differ. The long-term properties is characterised by creep compliance master curves created by means of TTSP. The examined bio-based resins are compatible to the reference epoxy in term of stability up to 3-10 years. Comparison between master curves for virgin, wet, and dried material show that moisture present in the specimen increases creep rate, and that some of this increase remains after drying of samples. T (g) measurements show that moisture inside the specimen decreases T (g); this is anticipated because of the plasticizing effect of water. The overall conclusions are that the bio-based resins of polyester, and epoxy type are comparable in performance with oil-based epoxy, LY556 and they can be used to develop high-performance composites.