Synthesis of highly efficient non-lethal repellent for rats from natural capsaicin and its influence on properties of EVA

Abstract A repellent for rats named DC has been successfully synthesized from natural capsaicin and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) via a one-pot procedure. The chemical structure of obtained DC is confirmed by Fourier transform infrared (FTIR), Raman and nuclear magnetic resonance (NMR). Then DC was incorporated into ethylene vinyl acetate copolymer (EVA) by blending, to endow EVA with rat proof property and present the advantage of non-lethal. The influence of DC on the structure and properties of EVA is investigated systematically by theoretical calculations and various measurements. Thermogravimetric analysis (TGA) reveals that the incorporation of 4 wt% DC into EVA can significantly enhance the char residue yield from 2.80 wt% to 6.84 wt%. In addition, limiting oxygen index (LOI) and the char residues analysis suggest that DC could facilitate the formation of char layers, resulting in the improvement of synergistic flame retardancy for EVA/DC compounds. This work provided novel insights into the preparation of highly efficient non-lethal repellent for rats and its potential application for polymer materials.