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In this study, a tunnel model with a length of 20 m, a width of 5 m, and a height of 5 m was used, and an experimental investigation was conducted to examine the impact of high-pressure water mist on the temperature distribution along the tunnel ceiling. Specifically, different experimental settings, such as various nozzle pressures, nozzle positions, and longitudinal ventilation speeds, in the high-pressure water mist system were employed to investigate the smoke-spreading process of tunnel fire under different conditions, and an effective method utilizing a high-pressure water mist system was proposed for blocking smoke and heat. The experimental results reveal that the high-pressure water mist system can be used to effectively improve the ceiling temperature during tunnel fires; when the nozzle pressure is set as 10 MPa, and the nozzle position is located at x7, the highest thermal insulation efficiency in the tunnel is obtained. Additionally, the joint application of the high-pressure water mist system and the mechanical smoke exhaust effectively mitigates the ambient temperature within the tunnel, thereby playing a pivotal role in enhancing the fire safety of the tunnel. [ABSTRACT FROM AUTHOR]

In this research, a series of silicone foam/polytitanosiloxane composites (SF-pTS) were fabricated with hydroxy-, vinyl-, hydrogen-containing polydimethylsiloxanes, and polytitanosiloxane filler in the presence of a platinum catalyst under ambient conditions. The effect of the amount of polytitasiloxane on the micromorphology and flame retardancy of silicone foam was studied, and a relative flame retardancy mechanism was proposed. It could be found that the polytitanosiloxane exhibited a good dispersion level in the silicone foam, thus improving the flame retardancy of the composite. When the content of polytitanosiloxane is 9 wt%, the limiting oxygen index and UL-94 grade of the SF-pTS9 composite are increased to 29.2% and FV-0, respectively. Cone experiment results suggested that the SF-pTS9 possessed relative balanced PHRR (148.9 kW/m2), THR (58.5 MJ/m2), TSP (0.6 m2), and mass residue (83.9%) among the prepared silicone foam materials. This work provides a new avenue to fabricate a silicone foam composite with enhanced flame retardancy. [ABSTRACT FROM AUTHOR]

To manufacture transparent waterborne polyurethane composite coatings that possess desirable mechanical and flame retardancy properties is still a challenge. Herein, we first synthesized phosphorus‐silicon functionalized cellulose nanocrystals (FCNC) filler, and further introduced it into waterborne polyurethane (WPU) matrix to prepare composite. The phosphorus‐silicon‐containing components were grafted covalently on the surface of FCNC, and the FCNC showed good dispersion level in water and WPU matrix. Moreover, the inserted FCNC could not only maintain the high transparency of WPU‐FCNCs composites, but also remarkably enhancing the mechanical and flame retardancy performances. Noticeably, the WPU‐FCNC3 composite containing 3 wt% of FCNC showed balanced mechanical (σb = 16.7 MPa, εb = 557.5%), limiting oxygen index (22.9%), and a UL‐94 rating of V‐2 among prepared films. Additionally, WPU‐FCNC3 composite exhibited significantly reductions in heat release during combustion, and also showed a high transmittance of 92.2%. The present research supplies promising way for developing transparent, toughness, and flame retardant composite coatings. [ABSTRACT FROM AUTHOR]

In this work, we first synthesized vinyl‐terminated polyborosiloxane (pBS) filler, and then incorporated it into silicone rubber foam (SRF) matrix to prepare composite materials through a simple chemical dehydrogenative foaming method under ambient conditions. The pBS filler with reactive groups could form physical and chemical crosslinking networks in SRF, leading to an excellent dispersion level of pBS in the SRF matrix. Moreover, the inserted pBS could remarkably improve the mechanical and flame‐retardancy properties of SRF‐pBS composites. Intriguingly, the SRF‐pBS6 foam containing 6 wt% of pBS possessed a uniform porous structure and balanced mechanical properties (σb = 65.4 kPa, εb = 56.7%, compression stress 97.1 kPa), thermal conductivity (0.102 W (m K)−1), limiting oxygen index (29.8%) and UL‐94 rating (V‐0) among the prepared foams. In addition, the incorporated pBS (6 wt%) could synergistically catalyze the formation of a silicon–boron strengthened ceramic‐like protective layer under fire and was capable of suppressing heat and smoke production in the SRF‐pBS6 foam. The present work provides a promising way for developing high mechanical and flame‐retardant polymeric foam materials with good thermal insulation. © 2021 Society of Industrial Chemistry. [ABSTRACT FROM AUTHOR]

In this work, we first synthesized modified cellulose nanocrystals (MCNC) with 2,4‐toluene diisocyanate and 9,10‐dihydro‐9‐oxa‐10‐phosphaphenanthrene‐10‐oxide via a two‐step in‐situ polymerization method, and then incorporated it with shape memory polyurethane (SMPU) to fabricate composite. It was found that the urethane chains and phosphorus‐containing flame retardant were covalently grafted onto the cellulose nanocrystals surface, and the MCNC exhibited good dispersion level in the SMPU matrix. Due to the crystallization‐induced and flame retardant effects of the prepared MCNC, it could be acted as a multifunctional reinforcer in SMPU composites. Noticeably, the most balanced improvements in crystallization, shape memory, mechanical, thermal stability, and flame retardancy properties of composites were observed with the incorporation of 3 wt% MCNC. Shape memory experiment demonstrated that the SMPU‐MCNC3 composite exhibited admirable thermal induced shape memory behavior, and its shape fixity and shape recovery ratios were maintained above 90% after five cycles. More importantly, the SMPU‐MCNC3 composite showed well balanced mechanical (σb = 13.1 MPa, εb = 189.3%), limiting oxygen index (23.8%), and UL‐94 rating (V‐2) among the prepared polyurethane films. In addition, the representative SMPU‐MCNC3 showed obviously reductions in heat and smoke production during combustion as compared to the neat SMPU. The present work offers a promising route to fabricate shape memory polyurethane composites with versatile functions. [ABSTRACT FROM AUTHOR]