Styrene-free thermosetting resins from vegetable oils

Research and application of biobased polymers is an ever increasing field due to both environmental and socio-economical reasons. Among the pursued ways, the use of vegetable oils as starting materials is certainly a convenient one. These feedstocks can be used as starting reagents for the preparation of traditional monomers or otherwise used as themselves via different kind of functionalization reactions. The latter possibility is the one used for the preparation of thermosetting resins. In this work, oils with different unsaturation degree (soybean, hempseed and linseed oils) as starting materials for the preparation of acrylated monomers and their combination with terpenes (limonene, ?-myrcene and ?-pinene) as co-monomer, were used to obtain thermosetting resins according to the following procedure: the first step is the epoxidation of double bonds of vegetable oil, followed by addition of acrylic acid and by the curing process in the presence of co-monomer and radical initiator. Thermal, mechanical and dynamic mechanical properties both of prepared materials and a reference styrene-based resin were studied. The characterization highlighted high thermal stability, good mechanical performance and glass transition temperatures between 40 and 80°C. The results showed not only the possibility of replacing the properties of the resin based on styrene, but even to overcome them. The choice of starting oil and co-monomer, in particular as function of their double bonds availability, allows obtaining thermosetting resins with tunable properties. Moreover, a preliminary research focused on the design and preparation of sustainable composites based on the aforementioned resins and reinforced with natural fibers provides a feasible way to develop renewable fiber-polymer composites to satisfy sustainability demands.