Preparation and properties of biomass castor oil polyurethane films

Abstract

In order to investigate the optimal conditions for the formation of castor oil-based polyurethane (CO-PU) films and their comprehensive performance, a series of experiments were carried out utilising biomass castor oil (CO) as the main reactant, 4,4-diphenylmethane diisocyanate (MDI) as the other main reactant, benzoyl peroxide (BPO) as the radical initiator, and dibutyltin dilaurate (DBTDL) as the catalyst. The CO-PUs with different R-values (the number ratio of –NCO/–OH substances) were prepared by pre-polymerisation under single-variable control. The effects of different R-values, DBTDL contents and curing temperatures on the mechanical properties and film-forming state of the CO-PUs were then investigated. Finally, the liquid-resistant medium properties and thermo-gravimetric analyses of CO-PU films were investigated. The experimental results demonstrate that when the R value is 2.5, the DBTDL content is 0.1 ‰, and the curing temperature of the film-forming process is 80 °C, the tensile strength and elongation at break of the CO-PU film are 36.4 MPa and 49.05 % respectively, and the hardness of the pencil at this time is 6H. The water absorption rate is 0.01 %, and the contact angle of water is up to 83.5°. CO-PU displays a commendable resistance to sulfuric acid, sodium hydroxide, and ethyl acetate. Additionally, CO-PU exhibits a high thermal decomposition temperature. The comprehensive performance of CO-PU can be enhanced by modifying the film-forming conditions of CO-PU, which paves the way for further expansion of the applications of CO-PU in the future.