Vegetable-oil based thermosetting polymers

In the search for sustainable chemistry, there are increasing demands for replacing petroleum derived raw materials with renewable raw materials in the production of polymers. The importance of natural products for industrial applications becomes very clear from a social, environmental and energy standpoint, with the increasing emphasis on issues concerning waste disposal and depletion of non renewable resources. Vegetable oils are one of the cheapest and most abundant, annually renewable natural resources available in large quantities from various oilseeds and are now being used in an increasing number of industrial applications. In recent years, extensive work has been done to develop polymers from triglycerides of fatty acids as the main component.

The purpose of our research is to develop new biobased thermosetting polymers from vegetable oils as renewable resources. Vegetable oils are triglycerides of different fatty acids with varying degrees of unsaturation. Although they possess double bonds, it is generally considered difficult to polymerise vegetable oils themselves due to its low reactivity. Our research focuses on improving the physical properties of triglyceride based materials, because they demonstrated low molecular weights and light crosslinking, incapable of displaying the necessary rigidity and strength required for structural applications by themselves. In this way, polymers ranging from soft rubbers to hard plastics can be obtained by cationic copolymerisation with styrene and divinylbenzene. Like other organic polymeric materials, the flammability of vegetable oil based materials is a shortcoming in some applications. The concept of sustainable development requires fire retardant technologies to be developed which have minimum impact on health and the environment through the life cycle of the fire-retardant material; that is to say, its synthesis, fabrication, use, recycling and disposal. To further extend the application of renewable resources and to obtain flame retardant polymers, we synthesized polymers from vegetable oils, styrene, divinylbenzene and silicon, phosphorus or boron-containing reactive modifiers.

The presence of double bonds makes possible to attach some functional groups through chemical modification and we described various chemical pathways for functionalising triglycerides and fatty acids. An enone-containing triglyceride was obtained by an environmentally friendly chemical procedure from high oleic sunflower oil that could be an interesting alternative to epoxidized vegetable oils to produce thermosets by crosslinking with conventional aromatic diamines. In a similar way, triglycerides containing secondary allylic alcohols can be obtained, that can be further functionalised with acrylate or phosphorus-containing derivatives to obtain flame retardant themosets. We also obtained organic-inorganic hybrid materials with promising properties for optical applications by the hydrosilylation of alkenyl-terminated fatty acid derivatives and biobased polyhedral oligomeric silsesquioxanes-nanocomposites. Moreover, we described the preparation of a new family of epoxidized methyl oleate-based polyether polyols which were used in the synthesis of polyurethanes with specific applications: silicon-containing polyurethanes with enhanced flame-retardant properties and polyurethane networks with potential applications in biomedicine.