Trimethylnonylammonium bromide is primarily used as a surfactant and phase transfer catalyst in various chemical reactions. Its ability to stabilize emulsions makes it valuable in the formulation of industrial cleaning agents and detergents, where it enhances the removal of oils and greases. In organic synthesis, it facilitates the transfer of reactants between immiscible phases, improving reaction efficiency. Additionally, it finds application in the textile industry as a softener and antistatic agent, improving fabric handling and quality. Its antimicrobial properties also make it useful in certain disinfectant formulations.