Investigation on the Inhibition of Discoloration in Methyltin Mercaptide Solution

Abstract

As global demand for sustainable materials grows, the stability of organotin compounds, particularly methyltin mercaptide (MTM) used in plastics, has become a focus of attention. Prolonged exposure of MTM to natural light leads to discoloration, affecting both aesthetics and potential environmental concerns. This study investigates the photo-induced discoloration of MTM and explores strategies to mitigate it. Xenon lamps were used to simulate natural light, and the wavelengths responsible for the color change in the colorless MTM solution were identified. Discoloration occurred only under UV light (200–400 nm), with the solution turning dark brown and reverting to colorless once the light was removed, indicating a reversible process. Spectral analysis confirmed the integrity of functional groups before and after discoloration. DFT analysis showed the discoloration involves redox and photolysis reactions. Furthermore, the addition of UV stabilizers can effectively inhibit solution discoloration. This study provides a theoretical basis for the improvement of the light stability of MTM and offers new ideas for the application of organometallic compounds in environmentally friendly plastic additives.