Exploiting Chaos: Should Polymerization Reactors Be Chaotic?

It is known that chaotic fluid element trajectories improve distributive mixing of liquids. This study exploited globally chaotic mixing conditions in a chaotic mixer to expedite rate of polymerization in synthesis of thermoplastic polyurethanes by one-step method from of an aliphatic diisocyanate, polyether and polyester polyols, and butanediol. The reactants were hand-mixed with a tin catalyst before pouring into the chaotic mixer. It was found that the tin catalyst not only catalyzed urethane formation but also helped reduce the size of suspended droplets of aliphatic diisocyanate in reaction mixture. The time-scales of mixing (t_mix) and polymerization reactions (t_rxn) were correlated with the time to reach the maximum torque (t_max) and the molecular weight and polydispersity index of the polymer products were analyzed.