Wei Liu

Vinyl acetate–ethylene copolymer emulsion (VAE) adhesives are widely used in formaldehyde-free wood-based panels and coating systems, but their inherent flammability limits broader application in fire-safety-demanding fields. In this work, fly ash (FA), an industrial solid waste rich in Si- and Al-containing inorganic components, was introduced into a conventional ammonium polyphosphate/melamine/pentaerythritol (APP/MEL/PER) intumescent flame-retardant (IFR) system to prepare flame-retardant VAE emulsion adhesives. The results showed that the incorporation of IFR effectively improved the flame retardancy of VAE, while FA further enhanced the condensed-phase protective effect. The limiting oxygen index (LOI) of VAE/IFR/FA increased to 28.5% from 18.3% for neat VAE, and the sample achieved a UL-94 V-0 rating. Cone calorimetry results showed that the peak heat release rate and total heat release were significantly reduced after flame-retardant modification, accompanied by an increase in residual char. The VAE/IFR/FA sample exhibited the highest char residue and the lowest total smoke production, indicating the positive role of FA in promoting char formation and smoke suppression. The addition of KH403 further regulated the combustion behavior, mainly improving early-stage heat release suppression and fire performance index rather than increasing the final char yield. The KH403-containing formulation also showed improved tensile properties and plywood bonding strength, indicating its potential as a flame-retardant adhesive for wood-based panels. The KH403-containing formulation also showed improved tensile properties and plywood bonding strength, indicating its potential as a flame-retardant adhesive for wood-based panels. SEM-EDS, XPS, Raman, and TG-FTIR analyses confirmed that FA and KH403 contributed to the formation of a phosphorus-rich organic–inorganic hybrid char layer containing Si/Al inorganic structures. This reinforced char layer effectively inhibited heat transfer, oxygen diffusion, and the release of combustible volatiles. This study provides a feasible strategy for developing low-cost flame-retardant VAE adhesives while promoting the high-value utilization of fly ash.

In this paper, recent typical tunnel explosive accidents in China, such as Bamianshan tunnel explosion accident, No. 5 Futuyu tunnel explosion accident, Yanhou tunnel explosion accident, Qidaoliang tunnel explosion accident and so on, have been collected and reviewed. Particular attention has been paid to these direct and indirect causes of explosive accidents, accident tunnel structure, accident process and loss, and subsequent emergency disposal measures. Based on details and information about these accidents, characteristic of various types of explosive accidents, including non-large tunnel explosion accident and large tunnel explosion accident in tunnel has been analyzed and their basic reason has been proposed. It shows that the leakage of mashgas and improper loading of explosives during construction, inflammable and explosive chemicals and materials transportation, vehicle crash and tire spontaneous combustion during operation could cause of explosion accidents in tunnel, while the combination among these causes could finally lead to a series of explosions, large-scale burning, a large number of casualties and massive economic losses. And emergency disposal process for these explosive accidents has been also summarized here. All of these aim to provide reference for the prevention of explosive accidents in tunnel and the formulation of emergency disposal plans in future, which could finally improve the operational safety of the highway tunnel.

In this study, the typical application of supports and hangers in the water supply and drainage system, ventilation and smoke extraction duct system and electric or optical fiber system has been collected and investigated, in order to understand the fire resistance of supports and hangers used for service installation in China, and further optimize the fire testing and evaluating method of these products. A series of fire resistant testing for supports and hangers used in different working condition have been carried out and the effect of bearing load and structure on the fire resistance of supports and hangers has also been discussed in this paper. Moreover, the improved fire resistant testing and evaluating method has been proposed here.

Glass fibers (GFs) reinforced polymer composites display high mechanical performance but deteriorated flame retardancy due to the “candlewick effect” caused by fibers. To solve this problem, novel hierarchal hybrid glass fibers (GF@HBPPA@GO) were prepared by multistep coating of 3‐aminopropyltriethoxysilane (APTES), hyperbranched polyphosphoramide (HBPPA) and graphene oxide (GO) in sequence. Several GFs reinforced poly(lactic acid) (PLA) composites were fabricated with the same GFs loading. PLA/GF@HBPPA@GO composite showed the highest limited oxygen index (LOI) value of 25.2% and much decreased peak heat release rate, total heat release and mass loss rate, corresponding to a drop of 23.2%, 16.6%, and 53.8% respectively compared with PLA/GF‐APTES composite. Meanwhile, it maintained similar tensile and impact strength values. The improved flame retardancy was mainly attributed to the good synergistic effect of HBPPA and GO on generating high‐yield char residues encapsulating GFs perfectly in the condensed phase, which effectively reduced the interface energy and increased the surface roughness of GFs to suppress the wetting and spreading of PLA melt toward the flame zone, and consequently weakened the candlewick effect of GFs and achieved better flame retardancy. This provides new ideas for preparing fiber reinforced polymer composites with encouraging mechanical properties and outstanding fire safety simultaneously.

Polyethylene terephthalate (PET) fabric has been widely used in textile industry for decades. However, it faces poor flame retardant performance and dripping problem during burning. In our study, a novel intumescent flame retardant coating containing bio‐materials ammonium phytate (APA) and cyclodextrin (CD) had been constructed on PET fabrics surface via pad‐dry‐cure method. The fire performance, mechanical properties and bio‐safety of APA/CD coated fabric were evaluated. PET fabric coated with 19%APA/6%CD showed a limiting oxygen index value of 29.5% with self‐extinguish from fire and no melt dripping during the vertical burning test. Cone calorimetry test revealed that treated PET fabric significantly suppressed heat release and mass loss. The peak heat release rate was decreased from 277.1 KW/m² of PET fabric to 158.3 KW/m² of PET‐19%APA/6%CD sample. Furthermore, the residue of treated fabric after combustion was also increased significantly. Tensile strength test showed that the maximum force of fabric was improved by 109.5% in warp direction and 24.2% in weft direction after treatment. Skin irritation test indicated that APA/CD coated PET fabric did not cause erythema and edema to rabbit skin and exhibited satisfactory bio‐safety. All these results suggest that this study proposes a viable way to produce bio‐safety flame retardant PET fabrics.

Phytic acid (IP₆) as the major phosphorus‐containing component of certain plants, such as cereal, oil plant, and bean possesses strong capability of coordinating with metal ion to form complex salt. In this study, low concentration IP₆ was utilized in combination with Al³⁺ ion to in situ form insoluble Al³⁺‐IP₆ complex salt on the surface of the fabric through coordination driven layer‐by‐layer deposition technology without high temperature cure step, which is an attempt to provide a facile bio‐based flame retardant finishing to polyamide (PA) 66 fabric. Surface structure of the treated PA fabric has been analyzed via ATR‐FTIR and SEM characterization. Effect of BLs' number on the flame retardancy and burning behavior of the treated sample has been examined by the limiting oxygen index (LOI) test, the vertical burning test, microcalorimetry, and thermogravimetric analysis. The results show that 20LBL PA fabric has the highest LOI value, highest residual char yield, and lowest THR value in all the samples and no melt dripping behavior could be detected during combustion of 20LBL PA fabric. Moreover, the insolubility of Al³⁺‐IP₆ salt from the surface could promote the durability of the treated fabric after laundering procedure using water single. This is the first time to use coordination driven layer‐by‐layer deposition technology in the fabric's flame retardant finishing.

Recently, traditional flame retardant finishing with a single metal compound has been rarely applied owing to its low effectiveness and durability. This study reports metal ion finishing in combination with surface photografting modification (M/P technology) as a novel approach to incorporate an inorganic–organic hybrid structure containing an Fe³⁺ ion onto the surface of the polyamide (PA) 66 fabric. Specifically, the PA fabric was first surface-modified in the presence of acrylic acid (AA) and N,N′-methylene bisacrylamide (MBAAn) during photografting pretreatment under UV irradiation (step I), then further reacted with the Fe³⁺ ion in the metal ion finishing (step II). After treatment with M/P technology, the fabric exhibits the required excellent flame retardancy and dripping resistance. Here, flame retardant tests show that the treated PA fabric has the highest limiting oxygen index (LOI) value of 33.4 and no melt dripping during combustion. An interesting inorganic/organic composite thermal barrier consisting of an inorganic iron oxide nanoparticle (NP) outer layer and an organic micro-intumescent inner layer can be observed on the surface of the burnt fabric. This structure could be responsible for the significant enhancement in the fire performance of the treated fabric. Importantly, the treated fabric is also highly stable during the laundering procedure, which could retain a high Fe/C ratio and an acceptable LOI value of 27.8 after washing 45 times. This confirms the achievement of durable flame retardancy after treatment with M/P technology, and its possible interaction mechanism has been discussed here.