Green fluorescent unsaturated polyester/graphitic carbon nitride quantum dots nanocomposites: Preparation and study of UV-resistance, mechanical and viscoelastic properties

The present study has been conducted to investigate the protective effect of graphitic carbon nitride quantum dots (CNQDs) against high energetic and harmful ultraviolet (UV) rays in addition to strengthening impact of CNQDs over mechanical and viscoelastic properties of unsaturated polyester (UP). To achieve this purpose, CNQDs were synthesized using citric acid and extra urea via microwave-assisted method. Afterwards, several percentages of CNQDs (0.25, 0.5 and 0.75 wt%) were added to UP and after curing process, UP/CNQDs nanocomposites were obtained with different percentages. By certain microscopic and spectroscopic tests, correctness of CNQDs formation and various features of UP/CNQDs nanocomposites were examined. Adding CNQDs to the matrix of polyester resin allowed creation of nanocomposites with fluorescence emission ability, also blockage of UV rays by the strengthened samples. Strengthening UP by CNQDs resulted in growth of thermal stability, improvement of tensile strength, 10%–15% increase in flexibility, and progress in viscoelastic characteristics including storage modulus, T g and cross-linking density.