Bio-based Resins From Vegetable Oils

In recent years, the research on sustainable and bio-based polymers and their applications has gained considerable attention due to socio-economic factors and environmental concerns. Vegetable oils are ideally renewable, abundant and low-cost resources to obtain sustainable polymers with different structures, properties and applications as they offer a great opportunity to tap into a pool of complex molecules in terms of carbon skeleton and double-bonds and functionalities availability. In this work, vegetable oils with a different composition in terms of fatty acid profile, namely soybean, hempseed and linseed oil, were used as starting materials for the preparation of acrylated monomers and their combination with terpenes (limonene, ?-myrcene and ?-pinene) as co-monomer for the preparation of various thermosetting resins. The acrylated resins were obtained following a three-step process: (1) epoxidation of double bonds of vegetable oil, (2) acrylation of epoxidized oil by acrylic acid and (3) curing in the presence of co-monomer and radical initiator. Thermal, mechanical and dynamic mechanical properties both of the prepared materials and of a reference styrene-based resin were studied. The characterization highlighted high thermal stability, good mechanical performances and glass transition temperatures between 40 and 80 °C. The results showed not only the possibility to compete with the properties of the styrene-based resin based, but even overcoming them. The proper choice of the starting oil and of the co-monomer, in particular as a function of their double bonds availability, allows one to obtain thermosetting resins with tunable properties. Furthermore, preliminary studies on the design and preparation of resins reinforced by natural fibers (hemp fibers) pave the way for the development of renewable composites that respond to sustainability needs. In addition, waste cooking oil was used for the production bio-based materials as a promising alternative to virgin vegetable oils materials since it is far cheaper than pure vegetable oils and pursues waste valorisation and sustainability principles. Lastly, preliminary experiments on the use of epoxidized soybeans oil to obtain non-acrylic thermosetting resins in combination with different dicarboxylic acids such as fumaric, tartaric, succinic, adipic and azelaic acid and monocarboxylic acids such as oleic and sorbic were carried out. The products obtained were characterized by thermal analysis, infrared spectroscopy, and compression tests. Dicarboxylic acids and sorbic acid provided soft materials with shape persistence which showed a glass transition temperature close to -20 °C. Compression tests highlighted superior mechanical properties for the resins obtained by using double bond contained carboxylic acids such as fumaric and succinic ones. In general, the results showed not only the possibility of competing with the properties of fossil building blocks. but even the chance to overcome them in terms of final material properties and performances.