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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]

Polyhedral oligomeric silsesquioxane (POSS) as an organic–inorganic hybrid at a molecular level, has excellent mechanical properties, thermodynamic properties, dielectric properties and so on. In recent decades, POSS has been extensively used in modification of various polymers to prepare nanocomposites with enhanced comprehensive performances. Biomass materials such as chitosan, cellulose, silk protein, collagen fibers and gelatin have excellent biocompatibility and biodegradability, which have been widely used in the fields such as biomedical, innovative environmental protection and so on. However, deficiencies including insufficient mechanical properties and rapid rate of biodegradation hampered their application. This paper briefly introduced the principal methods to synthesize POSS nanoparticles, and then focused on technologies for preparing biomass‐based composites utilizing diverse functional POSSs. Finally, put forward the prospects of POSS modification technology and its future application direction. This article will have a positive guiding role for the further research and development of biomass/POSS nanocomposites. [ABSTRACT FROM AUTHOR]

A series of novel alkoxy nonionic biosurfactants were synthesized by ring-opening reaction of methoxy poly(ethylene glycols) and alkylene oxide. The chemical structures of these biosurfactants were confirmed by Fourier-transform infrared spectroscopy (FTIR) and 1HNMR spectra. The surface tensions of these nonionic biosurfactants in the aqueous solutions were determined using a surface tensionmeter. The results showed that the critical micelle concentrations decreased with the increase of hydrophobic chain. However, due to the effect of intermolecular hydrogen bonding, the critical surface tensions of these nonionic biosurfactants increased with increasing the hydrophobic chain and were lower than those of conventional nonionic biosurfactants. Meanwhile, the effects of electrolytes on surface tension of these nonionic biosurfactants were slight. Due to the excellent surface activity, these alkoxy nonionic biosurfactants could have great potential in cleansing, oil recovery, and drug delivery. [ABSTRACT FROM AUTHOR]

Silica-gelatin hybrids, particularly GT-G hybrids prepared by crosslinking gelatin (G) with cglycidoxypropyltrimethoxysilane (GT), have attracted much attention in tissue engineering for diverse applications in hard or soft tissue regeneration; however, scaffolds with tunable properties are needed to meet specific requirements. In this work, a silica-gelatin hybrid (ES/GT-G) was synthesized by incorporating epoxy-terminated polydimethylsiloxane oligomer (ES) to modulate the properties of GT-G hybrid. The ES/GT-G hybrid sponge presented a 3D network structure with porosity 86.4%±0.9%, determined by the liquid displacement method, and average pore size 340±36 µm, determined by SEM observation. Compared with GT-G hybrid material, the prepared ES/GT-G hybrid wet film showed a decrease of tensile strength from 2.79±0.04 MPa to 1.87±0.12 MPa, with an increase of elongation at break from 19.96±0.66% to 29.86±0.87%, and the ES/GT-G hybrid sponge exhibited a decline of compressive yield strength from 1.21±0.04 MPa to 0.72±0.06 MPa, based on the tensile and compression tests respectively. The introduction of ES enhanced the thermal denaturing temperature of GT-G by 5°C as determined by a DSC study, and increased in vitro biodegradation slightly, without significantly changing surface wettability and swelling behavior. These findings suggest that silicagelatin hybrids with tunable properties are promising for applications from hard to soft tissue regeneration. [ABSTRACT FROM AUTHOR]

Realizing environmentally friendly polymers that could heal themselves at room temperature is an important challenge for sustainable societies. Herein, environment‐friendly self‐healing waterborne polyurethanes (WPUs) containing diselenide groups were synthesized. The healing efficiency could reach up to more than 90% after exposed to visible light for 48 hours and the fractured location was allowed to be healed repeatedly. Meanwhile, a fast room‐temperature self‐healing could also be achieved in 4 hours with a healing efficiency of ~84%. The healing process was a combination of rapid closure of crack surfaces at the beginning due to the rebuilding of hydrogen bonds and gradual restoration of mechanical property derived from diselenide metathesis across the fractured interface. At the same time, room‐temperature reprocessing could be also achieved with the aid of external pressure under visible light. Moreover, the prepared diselenide‐containing WPUs exhibited excellent emulsion stability. The present work would be hopefully developed into a methodology of design and fabrication of environmentally friendly photo‐sensitive polymers with self‐healing and reprocessing abilities. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47071. [ABSTRACT FROM AUTHOR]