Synthesis of Stevia-Quercetin Added Semi-Synthetic Polyurethane Structures and Aluminum Sheet Surface Coating Applications

PU structures containing stevia-quercetin in different ratios (1% stevia-49% quercetin, 3% stevia-47% quercetin, 5% stevia-45% quercetin) were synthesized. Structural characterization of the synthesized PU structures was carried out using Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis-differential thermal analysis (TGA-DTA) and X-ray diffraction analysis (XRD) techniques. Aluminum metal sheet surfaces are covered with synthesized PU structures. The surface morphologies of the coated surfaces were examined by both optical microscope and scanning electron microscope (SEM). The anti-corrosive abilities of the uncoated and coated aluminum metal sheets were tested using the weight loss method in 5% NaCl and physiological saline solutions. Calculation according to the method was carried out as percent weight loss at certain time intervals (1, 2, 3, 4 and 7 days). The weight loss in the control group whose surface was not covered with PU was 38.95% on the 7th day when the most contact was made in 5% NaCl solution. Among the coated groups, the least weight loss was observed as 10.89% in PU structures containing 1% stevia-49% quercetin. The weight loss in the control group was 27.44% after 7 days of exposure in physiological saline solutions. In the coated groups after 7 days of contact, the least weight loss was observed as 9.95% in the PU group containing 1% stevia-49% quercetin. In the current study, anti-corrosive abilities were observed in all the synthesized PU structures. The increased amount of quercetin in the synthesized PU structures increases the anti-corrosive activity, although partially. With the study, semi-synthetic PU structures containing stevia-quercetin were brought to the literature. Synthesized PU structures have the potential to be an important alternative for the surface protection of metallic materials.