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To ensure fire safety, polymers are filled with flame retardants and smoke suppressants. To meet the highest requirements, it is essential to understand the decomposition of those polymeric materials. This study reveals interactions between polymer, smoke suppressants, and flame retardants, and discusses their impact on the materials’ flame retardancy, smoke emission, smoke toxicity, and particle emission in conventional loadings to provide deeper general understanding. Low melting oxide glass, melem, spherical silica, sepiolite, melamine polyphosphate, and boehmite in an aluminum diethylphosphinate flame-retarded polyamide 6.6 were investigated. All smoke suppressants improve the protective layer and act as an adjuvant. Silica and melem performed best under forced flaming conditions. Spherical silica reduces the peak of heat release rate by 39% and the total heat evolved by 14%, whereas 10 wt% melem lowers the total smoke production by 41%. Melem alters the mode of action of aluminum diethylphosphinate from gas to more condensed phase activity. This change reduces flame inhibition and hence smoke toxicity, but further improves the protective layer due to charring reactions in the decomposition mechanism. In addition, the sizes of the smoke particles decrease because of the prolonged time in the pyrolytic zone. This study highlights that interactions between polymer, flame retardants, and smoke suppressants can significantly determine the smoking and burning behavior.
Replacing antimony trioxide (ATO) in flame retardant formulations is an urgent task due to its toxicity. There are indications that calcium hypophosphite (CaP) may be a promising replacement. This study investigates the decomposition, fire behavior, and smoke release of brominated flame-retarded acrylonitrile butadiene styrene (ABS) under various fire scenarios like ignition, developing fire and smoldering, while replacing ATO with CaP and CaP/talc. Adding 4 wt.-% of talc to CaP formulations showed beneficial effects on flammability due to changes in the viscosity and barrier properties. Synergism between 8 wt.-% talc and CaP improved the protective layer in the developing fire scenario, resulting in a ∼60 % decrease in the peak of heat release rate and reduction of ∼21 % in total smoke production (ref. ABS+Br+ATO). With a conventional index of toxicity (CIT) of below 0.75, ABS+Br+CaP passes the highest requirements according to EN 45545-2. Overall, the CaP/talc materials improve flame retardancy, show less smoke emission under forced flaming conditions, and prevent chronic intoxication and environmental pollution through smoke particles contaminated with antimony.
As most of polymeric materials are inherently flammable, flame retardants (FR) are commonly used to reduce their fire risks. Nevertheless, these flame retardant materials are often detrimental to smoke parameters like specific optical density or smoke toxicity. The influence of several smoke suppressants (SP)-zinc stannate, zinc phosphate, titanium oxide and hydrotalcite-were investigated with respect to flame retardancy, smoke emission, particle emission and smoke toxicity in a diethyl aluminum phosphinate (AlPi) flame retardant polyamide 6.6 (PA6.6). It was shown that the interaction between SP, FR and polymer is crucial for smoke and fire properties and can change the mode of action of the FR as well the decomposition mechanism of the polymer. Small amounts of SP show less effect on forced flaming behavior and the optical density, but they can influence flammability and the particle size distribution of the soot particles. The flame retardancy was significantly enhanced by 5 wt.-% zinc stannate in PA6.6 under forced flaming conditions. The charring mechanism was improved, and the mode of action of AlPi switched from the gas to the condensed phase. This resulted of in a reduced PHRR and TSP and an increase in residue yield. The smoke toxicity and optical density were reduced in the smoke density chamber as well. The smoke particles shifted to smaller sizes as the time in the pyrolytic zone increased. The formation of a dense char is assumed to be the key factor to enhance smoke suppression and flame retardancy properties.
Nowadays there are intumescent coatings available for diverse applications. There is no established assessment of their protection performance besides the standard time-temperature curve, but natural fire scenarios often play an important role. A reliable straightforward performance-based assessment is presented. The effective thermal conductivity per thickness is calculated based on intermediate-scale fire tests. The optimum thermal insulation, the time to reach it, and the time until contingent failure of the coating are used for an assessment independent of the heating curve. The procedure was conducted on four different commercially intumescent coatings for steel construction, one solvent-based, one waterborne, one epoxy-based, and a bandage impregnated with a waterborne coating. The performance was studied under four different but similar shaped heating curves with different maximum temperatures (standard time-temperature curve, hydrocarbon curve and two self-designed curves with reduced temperature). The thermal protection performance is crucially affected by the residue morphology. Therefore, a comprehensive morphology analysis, including micro-computed tomography and scanning electron microscopy, was conducted on small-scale residues (7.5 x 7.5 cm2). Two different types of inner structures and the residue surface after different heat exposures were discussed in terms of their influence on thermal protection performance.
Purpose – The purpose of this paper is to investigate the performance of intumescent coating on tension rod systems and their components. Steel tension rod systems consist of tension rods, fork end connectors and associated intersection or gusset plates. In case of fire, beside the tension rods themselves, the connection parts require appropriate fire protection. Intumescent fire protection coatings prevent a rapid heating of the steel and help secure the structural load-carrying capacity. Because the connection components of tension rod systems feature surface curvature and a complex geometry, high demand is placed on the intumescence and thermal protection performance of the coatings.
Design/methodology/approach – In this paper, experimental studies were carried out for steel tension rod systems with intumescent coating. The examined aspects include the foaming and cracking behaviour, the influence of different dry film thicknesses, the heating rate of the steel connecting parts in comparison to the tension rods, and the mounting orientation of the tension rods together with their fork end connectors.
Findings – The results show that a decrease in surface curvature and/or an increase inmass concentration of the steel components leads to a lower heating rate of the steel. Moreover, the performance of the intumescent coating on tension rod systems is influenced by themounting orientation of the steel components.
Originality/value – The findings based on fire tests contribute to a better understanding of the intumescent coating performance on connection components of tension rod systems. This subject has not been extensively studied yet.
The thermal degradation behavior of poly(vinyl chloride) (PVC) and poly(N-vinylpyrrolidone) (PVP) blends was investigated using potentiometric measurements of the released HCl gas during the degradation process, estimating the degree of discoloration of the degraded samples and measuring the thermal stability values (Ts) values. The influence of the PVP percentage in the blend and, moreover, the addition of commercial dibasic lead carbonate stabilizer to the blend on its thermal stability was studied. It was found that the dehydrochlorination rate of the blend was promoted by increasing the PVP concentration in the blend.
This study aims at investigating the use of coal fly ash-based alkali activated mortars as passive fire protection system for steel structures. These systems are used to slow down the temperature rise of the steel substrate in case of fire. In addition, the protective system should guarantee the ability to prevent and/or mitigate steel corrosion phenomena. The behavior of a light-weight mortar was compared to that of a normal-weight mortar. Density and porosity were measured to better characterize the physical properties of the mortars. The degree of protection in case of fire was assessed by performing medium-scale fire tests. Acoustic emission measurements were conducted to analyze cracking phenomena during the high temperature exposure. The corrosion process was evaluated using an electrochemical approach in order to monitor the durability of the developed material. Preliminary results show that a 20 mm-thick layer of light-weight mortar is able to protect the steel substrate from reaching the critical temperature of 500 °C for 38 minutes in case of cellulosic fire. In addition, alkali activated mortars provide protection for carbon steel in presence of aggressive environment (i.e. presence of chlorides). The corrosion resistance is strictly related to the physical properties of the developed mortars.
Alkali-activated fly ashes have been proposed for various applications where resistance against high temperatures is required, yet several details regarding the response of these materials to heat-exposure need to be clarified. In the present study, heat-induced cracking in fly ash-based alkali-activated pastes and lightweight mortars was analyzed by in-situ acoustic emission (AE) detection during complete heating-cooling cycles (up to ∼1100 °C), augmented by thermogravimetry and ex-situ SEM and XRD analyses. The applicability of the lightweight mortars as passive fire protection coatings was assessed by recording temperature-time curves of mortar-coated steel plates. Cracking during heating was limited and associated exclusively with the dehydration of the materials in the temperature range ∼90–360 °C. However, samples heated to temperatures above ∼600 °C exhibited intense cracking on cooling. This was attributed to differential deformations caused by local sintering and partial melting at the glass transition temperature, and subsequent quenching on cooling.
This paper is intended to be the first study to discuss the fire suppressing performance of the four most common extinguishing media under the same reproducible conditions. The tests were performed in bench-scale and used standardized 5A wood cribs as well as a miniature extinguishing system with a liquid flow rate of 1.4 lmin−1. The tests results present a consistent overview of the fire suppression efficacies of water, water with a foaming agent, nozzle-aspirated foam and compressed air foam. Depending on their jet types, the cooling capabilities of the extinguishing media water and water with a foaming agent were compared to the cooling capability of a full Jet of wet, general and dry foams. The results show that compressed air foam suppressed fire most effectively under the test conditions. Because of the convoluted crib structure, water and water with foaming agents used from a distance are more effective in the form of a full jet rather than a spraying jet. At close range, spraying jets multiply their effectiveness. A slight difference can be observed in the cooling performance of extinguishing foams that use foaming agents from different manufacturers. The paper establishes a link between the foaming agent's cooling capability and its wetting power by relating the results of wood crib fire tests according to DIN EN 3–7 and findings from laboratory immersion tests compliant with DIN EN 1772.
Compressed natural gas (CNG) is a widely used automotive fuel in a variety of countries. In case of a vehicle fire where the safety device also malfunctions, a failure of the CNG automotive cylinder could occur. Such a cylinder failure is associated with severe hazards for the surrounding environment. Firstly, a comprehensive analysis is given below, summarizing various accidents involving CNG automotive cylinders and their consequences. In an extensive experimental program, 21 CNG automotive cylinders with no safety device were tested. Of the 21, burst tests were carried out on 5 Type III and 5 Type IV cylinders. Furthermore, fire tests with 8 Type III and 3 Type IV cylinders were conducted. Apart from cylinder pressure, inner temperature and cylinder mantle temperature, the periphery consequences, such as nearfield blast pressure and fragmentation are documented. The maximum measured overpressure due to a Type III cylinder failure was p = 0.41 bar. Each traceable fragment was georeferenced. All-in-all, fragment throw distances of d > 300 m could be observed. As one key result, it can be stated that the tested Type IV CNG cylinders showed less critical failure behavior then the Type III cylinders under fire impingement.