Rigid polyisocyanurate–waterglass foam composite: Preparation, mechanism, and thermal and flame‐retardant properties

ABSTRACT A rigid polyisocyanurate–waterglass foam (PIWGRF) composite was prepared with polyaryl poly(methylene isocyanate) and waterglass (WG) as the main materials; water as a blowing agent, and no polyols. We speculated the formation mechanism of the PIWGRFs on the basis of the analysis of experiment data, scanning electron microscopy characterization, and transmission electron microscopy. The results show that three‐dimensional nanoflakes derived from the cured WG was observed; this was connected with polyisocyanurate by secondary bonding (SiOHN). Thermogravimetric testing indicated that the thermal stability and residual mass (34%) of the PIWGRFs were significantly higher than those of rigid traditional polyurethane foams (T‐PUFs). When the core density of the PIWGRFs was 32.6 kg/m3, the strength was up to 162.9 KPa by excessive filling. The flame retardancy of the PIWGRFs, including the time to ignition, heat‐release rate, total smoke of release, and limiting oxygen index, was obviously better than that of the T‐PUFs. The structure of the residual char was more dense and orderly; this was also an effective barrier layer. The reason was attributed to the fact that the WG did not contain combustible elements. So, the PIWGRFs had excellent thermal stability, flame retardancy, and environmental friendliness. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46182.