A one step route synthesis of polyurethane newtwork from epoxidized rapeseed oil

Biobased polyurethane networks were prepared by a one step curing epoxidized rapeseed oil (ERO) with isophorone diisocyanate (IPDI) as a hardener at 130 °C. The in-situ monitoring of the curing process by FTIR has confirmed the progressive consumption of the oxirane ring and the isocyanate function along with the emergence of the urethane groups. Investigation of model systems using phenyl isocyanate confirmed the ring opening of oxirane during the reaction between ERO and the isocyanate. Based on the spectroscopic investigation, it was hypothesised that the reaction started by the condensation between hydroxyl groups of ERO and isocyanate. Then, the oxirane was ring-opened by the urethane group and the hydroxyl group further reacted with isocyanate. The glass transition of the polyurethane network as well as the stiffness and strength were shown to be strongly dependent on the ratio between ERO and IPDI. Polyurethane film from ERO/IPDI in a ratio 80/20 results in a transparent elastic film with a Tg around −20 °C and a tensile modulus and strength of1.5 and 9.4 MPa, respectively.