Vinyl Ester Resin Modified with Acrylated Epoxidised Soybean (AESO) and Linseed (AELO) Oils: Effect of Additional Urethane Crosslinking

Abstract

Bisphenol A-based vinyl ester resin (VE) was modified with acrylated epoxidised soybean and linseed oils (AESO and AELO, respectively) in 10 wt.%. The double bond/epoxy ratio in these functionalised vegetable oils was practically the same, i.e. 30/70%, allowing us to deduce effects caused by the different unsaturations in the parent oils. The crosslink density of the resins was enhanced by adding polyisocyanate. The glass transition temperature (Tg) of the hybrids was determined by differential scanning calorimetry (DSC) and dynamic mechanical thermal analysis (DMTA). Resistance to thermal degradation was assessed by thermogravimetric analysis (TGA). The fracture toughness and energy (Kc and Gc, respectively) were determined on compact tension specimens at room temperature. Incorporation of AESO and AELO reduced the Tg of VE along with slight reductions in the Kc and Gc data. The Tg reduction was less for AELO than AESO which was attributed to the higher functionality of AELO compared to AESO. Urethane crosslinking of VE (VEUH) prominently enhanced the Tg. Modification of VEUH with AES(L)O enhanced the Tg due to additional crosslinks. Urethane hybridisation was associated with a strong decrease in both Kc and Gc compared to those of the parent VE. Kc and Gc of VEUH did not change practically as a function of blending with AES(L)O. Incorporation of AES(L)O reduced the resistance to thermal degradation of both VE and VEUH.