Tin-Containing Crystalline Copolymers as Latent Catalysts for Polyurethanes

For many applications, polyurethanes (PUs) need to have a fast curing speed and long pot life. Latent catalysts are seen to be one of the approaches that can fulfill this need. In this article, we have synthesized a series of copolymers with n-alkyl acrylates and a reactive tin catalyst, dibutyltin maleate, by conventional free radical polymerization using azodiisobutyronitrile (AIBN) as an initiator and dodecanethiol as a chain transfer agent. The copolymers with crystalline side chains were characterized by gel permeation chromatography (GPC), 1H NMR, 13C NMR, differential scanning calorimetry (DSC), and ion chromatography. The tin-containing copolymers showed high crystallinity. The melting temperature of the copolymers decreases slightly with the decrease of molecular weight (Mw), while the crystallinity remains almost unchanged. The catalytic performance and latency of the crystalline copolymers with different particle sizes were characterized by rheological measurement and Fourier transform infrared spectroscopy (FTIR). The crystalline copolymers showed quite good latency at 30 °C and high reactivity above the melting point. Both the particle size and the Mw of the copolymers had effects on the latency of crystalline catalysts. The PU adhesive with copolymers showed a higher peel strength at the initial stage than the noncatalyzed one and comparable final properties as compared with the samples with dibutyltin dilaurate and dibutyltin maleate.