Polyurethane market majorly depends on synthetic materials which are noxious. This stimulated an idea to replace petrochemical resources with renewable resources for polyurethane production. Keeping this in mind, this research focused on the use of sunflower oil for the preparation of polyol and its use in polyurethane composition. The reaction mechanism of epoxidation and ring-opening was approached for the conversion of sunflower oil to polyol. During the conversion of sunflower oil, unsaturated groups of sunflower oil were converted into hydroxyl groups of polyol.
Sunflower oil-based polyol was successfully blended with methylene diphenyl diisocyanate (MDI) to form urethane bonds. Confirmative tests such as fourier transform infrared spectroscopy (FTIR), gel permeation chromatography (GPC), viscosity, and hydroxyl number analysis were performed. Very small amounts of graphene-based fillers such as graphene nanoplatelets (GNPs), graphene nanoribbon (GNR), graphene oxide (GO), and reduced graphene oxide (rGO) were separately dispersed into polyol by ultrasonication method to prepare polyurethane composites to enhance thermal and mechanical strength of the polyurethane. Structure of graphene-based fillers was confirmed by X-ray diffraction study.
Film specimens from polyurethane composites were prepared for mechanical tests such as Shore D hardness, tensile and flexural. In the study of tensile strength, the highest tensile strength was recorded 34.9 MPa for polyurethane/graphene nanoplatelet films. For thermal stability analysis, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and dynamic mechanical analysis (DMA) tests were conducted. Almost all polyurethane composite samples were thermally stable up to 280 oC. The change in thermal stability upon adding graphene-based fillers was analyzed by comparing residual percentages. The surface morphology of the films was studied by water contact angle (WCA), and atomic force microscopy (AFM). The highest WCA was measured at 104.22 for with 0.05 wt.% rGO filler. Hence, this research studied the effect of a very small quantity of graphene-based fillers on the sunflower oil-based polyurethane film
