Influence of siloxane co-segment length and content of waterborne polysiloxane-urethane copolymers on their water resistance, thermal stability and mechanical properties

A series of stable waterborne polysiloxaneurethane (WPSUR) dispersions were prepared using amino-terminated polydimethylsiloxane (NS), dimethylolpropionic acid (DMPA), castor oil, polypropylene glycol and toluene diisocyanate. Meanwhile, NS with different molecular weights was synthesized and used as the soft co-segment. Effects of types and contents of soft co-segments as well as chain extenders on the thermal degradation and stability for WPSUR films were examined. Results reveal that WPSUR films exhibit excellent water resistance and mechanical properties as compared with pure polyurethane (PU) films, and the NS soft co-segment possesses a remarkable effect on the second stage (stage II), while the content of the hard segment is propitious to the initial stage (stage I). Moreover, the highest temperature of stage II (T (2m)) for WPSUR films using NS as soft co-segment is 413A degrees C, approximately being 30A degrees C higher than that of those typical PUs using HDA and APDMS as the chain extenders, respectively.