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The introduction of biobased carbon sources in intumescent flame retardant formulations is extensively explored, particularly for biopolymers such as poly(lactic acid) (PLA). In this work, the flame retardant efficiency of alginate, a favorable renewable charring agent candidate, is enhanced by chemical modification with a phosphorus‐ and silicon‐containing compound and subsequent coagulation in the presence of Ca2+ ions. The simultaneous presence of P and Si atoms in the reactive compound is shown to be an effective way to avoid thermal stability issues related to the biobased carbohydrate. The newly synthesized PSilAlg additive boosts the flame‐retardant effectiveness of ammonium‐polyphosphate (APP) at low loadings. Adding 5 wt% PSilAlg to 15 wt% APP containing PLA composite increases the limiting oxygen index from 26.0 to 34.0 vol% and decreases the total heat emission during combustion by 46%, accompanied by significantly (by 66%) reduced smoke production. The outstanding flame retardant performance of PSilAlg is attributed to the high amount and thermally stable carbonaceous fire‐protecting layer that forms as a result of the enhanced charring, catalyzed by the high oxidation state P, and the strengthening mechanism of inorganic silicates and calcium salts. [ABSTRACT FROM AUTHOR]

The mixture of ammonium polyphosphate and pentaerythritol is a very efficient intumescent system suitable for polyolefins, especially polypropylene. In this article, the intumescence mechanism of this intumescent system with and without zeolite 4A used as a synergy agent is revisited. The intumescent system was investigated in depth using continuous-wave electron paramagnetic resonance spectroscopy, solid-state nuclear magnetic resonance, and the advanced technique, namely hyperfine sublevel correlation pulsed electron paramagnetic resonance. It was observed that the char generated between 250°C and 350°C is made of polycyclic heterocyclic radicals with nitrogen atoms and that free radicals are mainly generated at these temperatures with a spin concentration relatively stable at least up to 500°C. Moreover, the presence of hydrogen, carbon, nitrogen, and phosphorus was clearly evidenced in the chemical environment of free electrons at 350°C (hyperfine sublevel correlation pulsed electron paramagnetic resonance). Besides, it was also evidenced that 4A totally collapses below 250°C. Contrary to previous works suggesting the presence of aluminosilicophosphate complexes, this work demonstrated that distinct alumino- and silicophosphate complexes are generated and protected the residue at high temperatures. [ABSTRACT FROM AUTHOR]

Intumescent fire-retardant coatings, which feature thinner layers and good decorative effects while significantly reducing heat transfer and air dispersion capabilities, are highly attractive for fire safety applications due to their effective prevention of material combustion and protection of materials. Particularly, the worldwide demand for improved environmental protection requirements has given rise to the production of waterborne intumescent fire-retardant polymer composite coatings, which are comparable to or provide more advantages than solvent-based intumescent fire-retardant polymer composite coatings in terms of low cost, reduced odor, and minimal environmental and health hazards. However, there is still a lack of a comprehensive and in-depth overview of waterborne intumescent fire-retardant polymer composite coatings. This review aims to systematically and comprehensively discuss the composition, the flame retardant and heat insulation mechanisms, and the practical applications of waterborne intumescent fire-retardant polymer composite coatings. Finally, some key challenges associated with waterborne intumescent fire-retardant polymer composite coatings are highlighted, following which future perspectives and opportunities are proposed. [ABSTRACT FROM AUTHOR]

After the period of halogenated compounds, the period of nano-structured systems, and that of phosphorus (and nitrogen)-based additives (still in progress), following the increasingly demanding circular economy concept, about ten years ago the textile flame retardant world started experiencing the design and exploitation of bio-sourced products. Indeed, since the demonstration of the potential of such bio(macro)molecules as whey proteins, milk proteins (i.e., caseins), and nucleic acids as effective flame retardants, both natural and synthetic fibers and fabrics can take advantage of the availability of several low-environmental impact/“green” compounds, often recovered from wastes or by-products, which contain all the elements that typically compose standard flame-retardant recipes. The so-treated textiles often exhibit flame-retardant features that are similar to those provided by conventional fireproof treatments. Further, the possibility of using the same deposition techniques already available in the textile industry makes these products very appealing, considering that the application methods usually do not require hazardous or toxic chemicals. This review aims to present an overview of the development of bio-sourced flame retardants, focusing attention on the latest research outcomes, and finally discussing some current challenging issues related to their efficient application, paving the way toward further future implementations. [ABSTRACT FROM AUTHOR]

Copyright of Industria Textila is the property of Institutul National de Cercetare-Dezvoltare pentru Textile si Pielarie and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The soft nap and deep pile that impart comfort and warmth to cotton fleece also amplify its flammability. Using ambient aqueous processing, an environmentally benign polyelectrolyte complex (PEC), consisting of poly(allylamine hydrochloride) and sodium hexametaphosphate, was deposited on cotton fleece. This treatment adds only 12.5% weight, reduces peak heat release by 68% and total heat release by 74%, and protects from fire via intumescence. Without treatment, fleece burns aggressively with long afterburn and afterglow times, leaving no residue. With the applied PEC, the fabric self-extinguishes within a few seconds and exhibits no afterglow. In addition, it withstands at least five simulated laundering cycles in alkaline detergent, maintaining a 57% reduction in fire growth capacity afterward. The original soft surface can be restored to the fleece by manual brushing. This simple and environmentally benign treatment provides an opportunity to effectively protect highly flammable textured cellulosic textiles in a safe way. [ABSTRACT FROM AUTHOR]

Abstract Silica hydrogels are used as fire-retardant materials due to the occurrence of intumescence that limits heat and mass transfer. They act as heat-sink, through continuous endothermic condensation reactions, meantime shrinking to a more connected network, towards the correspondent crystalline compound. Which compositions and treatments amplify this phenomenon is still of interest. To this aim, two silica sols containing two different complexing agents: ethylene glycol and glycerol has been prepared and analyzed. The samples were subjected to different treatments to induce gelation and densification: exposure to ultraviolet or microwave or infrared irradiation. Thermogravimetric analysis coupled with differential scanning calorimetry (TG-DSC) and scanning electron microscopy analyses has been also carried out. Moreover, dynamic mechanical spectroscopy (DMS) let to evaluate simultaneously the mechanical and intumescence behavior of the gels at increasing curing times for each type of irradiation. Intumescence of gels occurs up to 200 °C and appears as an endothermal group of peaks visible on the heat-flux DSC curves. DMS analyses let to assess that a MW cured glycerol-containing gel (GL-0-MW 6d) shows a glass transition above 150 °C, measured as the maximum of damping peak. Accordingly, this sample is a good option for the application: a few bubbles nucleate and grow fast at high temperature. Article Highlights Transparent fire doors contain silica gel, which absorbs heat and releases water by foaming. Two different silica gels were synthetized using different chelating agents. The foaming depends on the reagents used to produce the gel, on the treatments for stabilizing it and also on ageing. Both foaming and consolidation of the gel were studied with thermogravimetric and dynamic-mechanical analysis.

Silica hydrogels are used as fire-retardant materials due to the occurrence of intumescence that limits heat and mass transfer. They act as heat-sink, through continuous endothermic condensation reactions, meantime shrinking to a more connected network, towards the correspondent crystalline compound. Which compositions and treatments amplify this phenomenon is still of interest. To this aim, two silica sols containing two different complexing agents: ethylene glycol and glycerol has been prepared and analyzed. The samples were subjected to different treatments to induce gelation and densification: exposure to ultraviolet or microwave or infrared irradiation. Thermogravimetric analysis coupled with differential scanning calorimetry (TG-DSC) and scanning electron microscopy analyses has been also carried out. Moreover, dynamic mechanical spectroscopy (DMS) let to evaluate simultaneously the mechanical and intumescence behavior of the gels at increasing curing times for each type of irradiation. Intumescence of gels occurs up to 200 °C and appears as an endothermal group of peaks visible on the heat-flux DSC curves. DMS analyses let to assess that a MW cured glycerol-containing gel (GL-0-MW 6d) shows a glass transition above 150 °C, measured as the maximum of damping peak. Accordingly, this sample is a good option for the application: a few bubbles nucleate and grow fast at high temperature. Article Highlights: Transparent fire doors contain silica gel, which absorbs heat and releases water by foaming. Two different silica gels were synthetized using different chelating agents. The foaming depends on the reagents used to produce the gel, on the treatments for stabilizing it and also on ageing. Both foaming and consolidation of the gel were studied with thermogravimetric and dynamic-mechanical analysis. [ABSTRACT FROM AUTHOR]

Intumescence occurs on the leaves and stems of tomato (Solanum lycopersicum Mill.) seedlings grown under ultraviolet (UV) deficient light environments, such as in a plant factory with artificial lighting (PFAL). Supplemental UV-B alleviates intumescence incidence and modulates plants mophology and photomorphogenic responses. UV-B supplementation is required to suppress intumescence injury and determine the morphological and growth responses for each tomato cultivar cultivated in PFAL. 'Doterang Dia' and 'B-blocking', which were cultivars used as scion and rootstock, were grown in a PFAL with white light emitting diodes (LEDs) at a light intensity of 180 µmol m−2 s−1 for 16 h d−1, an air temperature of 25/20oC and a relative humidity of 70/90% (photo/dark periods) for 21 days. UV-B light was supplemented to each cultivar at 0 (Control), 0.05, 0.10, or 0.15 W m−2 for 3 h per day. The intumescence incidence rate was measured by the percentage of intumescent leaflets for all leaflets. The intumescence incidence of 'B-blocking' decreased significantly under UV-B radiation. The incidence rate was lower than 1% under supplemental UV-B radiation with an intensity of 0.1 W m−2 and 0.15 W m−2. The stem length, leaf area, and dry weights of shoots and roots were greater at UV-B intensities of 0.05 and 0.1 W m−2 than those in control and decreased at 0.15 W m−2 to the same level as the control. In comparison to 'B-blocking', intumescence incidence rates for 'Doterang Dia' showed low values, but it also showed a decreasing tendency with supplemental UV-B light similar to that of 'B-blocking'. The stem lengths of 'Doterang Dia' were greater at a UV-B intensity of 0.05 W m−2 than those in control and decreased with higher UV-B radiation. The result suggests that supplementing of the small range of UV-B radiation can reduce the intumescence incidence while modulating growth promotion in tomato seedlings. The different cultivar-specific responses to UV-B light between scion and rootstock cultivars could be due to the genetic differences among their major breeding resources developed from other areas with different levels of UV-B radiation. [ABSTRACT FROM AUTHOR]

Generally, pentaerythritol (PER) and melamine are, respectively, used as charring agent and blowing agent to combine with ammonium polyphosphate (APP) to establish an intumescent flame retardant (IFR). As for IFR system, the intumescent volume and compactness of char residues are the keys to enhance the flame retardancy of polymers. In this work, hydroxylated melamine (MOH) was synthesized and used as both charring agent and blowing agent to replace pentaerythritol and melamine simultaneously, and it was combined with APP to develop an excellent intumescent flame retardant for epoxy resin. This APP/MOH intumescent flame retardant at the mass ratio of 3:1 significantly improved the LOI value of epoxy resin to 32.5% and reached UL 94 V-0 by 15 mass% loading contents. However, both APP and APP/PER system failed to pass UL-94 vertical burning test and lower LOI was obtained. Additionally, the peak of heat release rate and peak of smoke production rate of APP/MOH based epoxy resin were reduced by 68.3% and 39.0%, respectively, compared with those of neat epoxy resin. After analysis of the pyrolysis products from the gaseous and condensed phases, it was found that APP/MOH system produced higher intumescent volume and better compactness of char, which is a good barrier to hinder the transfer of fuels and heats. [ABSTRACT FROM AUTHOR]

Copyright of Electroplating & Finishing is the property of Electroplating & Finishing Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In the flame retardancy of the biopolymer matrix and natural fibre reinforcement containing green composites, researchers face multiple challenges, such as low thermal stability, the candlewick effect of fibres and compatibility issues. Cellulosic fibres have been shown to have char-promoting properties and to advantageously interact with intumescent systems. In this work, melamine-polyphosphate was combined with neat or flame-retardant-treated cellulosic fibres differing in fibre length to obtain intumescent flame retarded poly(lactic acid) composites. The effect of the cellulose fibre length was evaluated in both forms. The structure-property relationships were evaluated by thermal and flammability test methods. It was found that the formation and the structure of the fire-protecting char are influenced by the length of the cellulose fibres, and thus it noticeably affects the effectiveness of the flame-retardant system. Cellulose fibres with an average length of 30–60 µm were found to contribute the best to the formation of an integrated fibrous-intumescent char structure with enhanced barrier characteristics. [ABSTRACT FROM AUTHOR]

• Aromatic free radicals are mainly generated during the intumescence of the system between 250 and 350 °C. • A structural shift occurs at a temperature range of 350 to 400 °C, transitioning from a predominantly carbonaceous material to a phosphorated one. • Aromatic residues protected by alumino- and silicophosphates derived from zeoliothe 4A. The mixture of ammonium polyphosphate (APP) and pentaerythritol (PER) is a very efficient flame retardant (FR) intumescent system suitable for polyolefins such as polypropylene (PP). The mechanisms of intumescence of this FR system in this polymer was investigated using different spectroscopic techniques including continuous wave (CW) electron paramagnetic resonance (EPR) spectroscopy and solid state nuclear magnetic resonance (NMR) technique. In this work, the intumescence mechanism of PP/APP/PER formulations with and without 4A is revisited. The intumescent system was in-depth investigated using NMR, CW EPR and pulsed EPR. The CW EPR technique confirmed that free radicals are mainly generated during the intumescence of the system between 250 and 350 °C. Thanks to the pulsed EPR and solid state NMR, it was evidenced that a key structural shift from a predominantly carbonaceous residue to a predominantly phosphorated residue. Besides, it was also evidenced that zeolite 4A totally collapses during extrusion of PP/APP/PER formulations reacting with APP to generate aluminophosphates. Then, silicophosphates are generated between 350 and 400 °C. Both alumino- and silicophosphates contribute to protect aromatic structures in the residue at high temperatures. [ABSTRACT FROM AUTHOR]

This work focuses on the investigation of the fire protection of steel using inorganic intumescent alkali silicate and geopolymer (alkali aluminosilicate) coatings at temperatures relevant for hydrocarbon fires, as described in the UL1709 standard. Pure alkali silicate coatings based on Na, K, or a mixture of these with Li exhibited high initial expansion followed by melting. In comparison, Li-silicate coatings expanded less but demonstrated significantly higher thermal stability. Increasing the SiO2/Na2O molar ratio prolonged the fire protection time, explained by the lower melt formation proposed by global equilibrium calculations. The presence of melting in the high expanding alkali silicate systems limits their use in hydrocarbon fire conditions. In comparison to pure alkali silicates, geopolymer coatings with kaolin, metakaolin, and fly ash and additional CaCO3 displayed a higher thermal stability confirmed by global equilibrium calculations. The kaolin-based coating provided the best fire protection with a critical time of 37.6 min, explained by its high expansion compared to metakaolin and fly ash-based coatings. Examining the influence of CaCO3 and kaolin content suggests that an optimum exists for the kaolin coatings in terms of expansion, fire protection, and thermal stability. The best performing kaolin coating (37.6 min) had a lower fire protection compared to a state-of-the-art commercial organic hydrocarbon coating (44.2 min), caused by their differences in internal structure. The commercial coating expanded to a more compact microporous solid, while the kaolin coating qualitatively displayed a higher proportion of macropores. This in turn suggests that future work must be performed to further improve the internal structure of the kaolin-based coatings to ensure good fire protection. [ABSTRACT FROM AUTHOR]

With certain formulations, Geopolymer (GP) exhibits intumescence (expansion upon heating), forming a porous structure, providing a thermal barrier effect. However, there have been no studies demonstrating the mechanism of the intumescence and the corresponding structural changes before and after heating. In this study, GPs are made based on metakaolin and silica fume. Then, GP with two aluminum-to-silicon molar ratio (Al/Si = 0/0.55) are investigated under heating conditions. The GP (Al/Si = 0) exhibits initial softening followed by hardening of the structure (from 50°C to 175°C), with intumescence observed within this temperature range. In contrast, the GP (Al/Si = 0.55) does not exhibit softening or expansion. Solid-state Magic Angle Spinning Nuclear Magnetic Resonance (MAS NMR) analysis of 29Si and 1H were then conducted on both GPs at ambient temperature and after heating at 105/200/300°C for 24 h. Results show that GP softening is due to the transition from Si(Q2) to Si(Q3) silicate units, while hardening is caused by the transition from Si(Q3) to Si(Q4) silicate units. Additionally, the proton mobility of GP is higher for lower Al/Si ratios after curing. During heating, the mobility decreases for both GPs due to the removal of free water and the breaking of hydrogen bonds. Our results extend the knowledge of GP intumescence mechanism and call attention to low Al/Si GP for fire/high temperature application. • As the temperature rises, intumescence is observed in GP (Al/Si=0). • The conversion from Q2 to Q3,4 induces material softening. • The mobility of protons is high in GP (Al/Si=0), but low in GP (Al/Si=1.5). [ABSTRACT FROM AUTHOR]

• Cotton, polyester, and blends thereof are self-extinguished by a single polyelectrolyte complex. • Intumescence is observed on natural, synthetic, and blended fabrics. • Char yield, heat release, and volatile emission are improved for each textile. Inhibiting the flammability of natural, synthetic, and blended textiles with a single treatment is challenging because of differing fiber properties and chemistries. Intumescent surface treatments that promote char formation can be applied in the form of a polyelectrolyte complex (PEC) containing nitrogen and phosphorus compounds that combat burning in both the condensed and gas phase. Poly(allylamine hydrochloride) (PAH) and poly(sodium phosphate) (PSP) comprise a PEC that reduces the flammability of cotton, polyester, and polyester/cotton (PECO). The incorporation of melamine renders each substrate self-extinguishing. The degradation of PAH is seen to differ between substrates, with gas phase degradation being more prevalent on polyester and heterocyclization occurring on cellulose. Quantitatively, cotton flammability is reduced more than that of polyester, but significant improvements are made to the char yield, heat release, and volatile emission for all fabric types. This water-based coating is rapidly applied in two steps for fire protection. These results demonstrate the versatility of PEC coatings as environmentally-benign fire protection for a variety of chemistries. [ABSTRACT FROM AUTHOR]

Intumescence is a physiological disorder in tomato and other plant species that encompasses callus formation on leaves and stems. Next to a genetic predisposition, it has also been shown to be influenced by environmental factors like light spectrum. We grew tomato plants of four different recombinant inbred line (RIL) populations under high‐pressure sodium (HPS) and red/blue LED supplemental lighting in a greenhouse and determined the severity of intumescence on 4‐week‐old plants, in three subsequent replicates. The intumescence severity was scored on a scale from 0 to 3. The severity of intumescence was highly genotype dependent in three out of the four tested tomato populations, with the heritability ranging from 54% to 83%. In those three populations, two to eight QTL for intumescence were identified. One major effect quantitative trait locus (QTL) on the top of chromosome 1 was at a similar position in two genetically different RIL populations. The amount of genetic variation explained for these QTL ranged from 30% to 70% depending on the population. Next to chromosomal influences, we also identified differences in effects from maternal plastids on intumescence, by using reciprocal crosses. The cultivation of the tomato plants under HPS lamps or under red/blue LED supplemental lighting had no significant influence on intumescence score. All major QTLs appeared to be reproducible among the three replicates and among the two light conditions. Significant, though, low negative correlations were identified between the intumescence score and the area of leaves, chlorophyll content index, photosynthesis efficiency and fresh weight to dry weight ratio, which can reflect possible effects of the disorder on multiple aspects of plant performance. [ABSTRACT FROM AUTHOR]

This review provides an intensive overview of flame retardant coating systems. The occurrence of flame due to thermal degradation of the polymer substrate as a result of overheating is one of the major concerns. Hence, coating is the best solution to this problem as it prevents the substrate from igniting the flame. In this review, the descriptions of several classifications of coating and their relation to thermal degradation and flammability were discussed. The details of flame retardants and flame retardant coatings in terms of principles, types, mechanisms, and properties were explained as well. This overview imparted the importance of intumescent flame retardant coatings in preventing the spread of flame via the formation of a multicellular charred layer. Thus, the intended intumescence can reduce the risk of flame from inherently flammable materials used to maintain a high standard of living. [ABSTRACT FROM AUTHOR]

Fireproof inorganic coatings based on sodium silicate solution with intumescent additions were prepared and tested to assess their ability to limit the negative effect of a fire. The intumescent materials were obtained by the alkali activation of waste glass powder (obtained by the grinding of recycled soda-lime culet) and slag (waste resulting from the metallurgical industry). The replacement of talc (used as filler in paint formulation) with the intumescent materials obtained by the alkaline activation of waste glass powder (WGP), determined an increase in the intumescence coefficient (up to 65%) and decreased the activation temperature of this process. To evaluate these coatings' abilities to prevent or delay the temperature increase in metal structures, the paints were applied on steel plates and tested in direct contact with the flame of a butane burner for 60 min. The coatings prevented the increase in the steel substrate temperature over one considered critical (500°C) for steel mechanical properties; the combination of two coatings, with different intumescence activation temperatures, correlated with the increase in the coating's thickness, sensibly reduced the rate of temperature increase (up to 75%) in the steel substrate. [ABSTRACT FROM AUTHOR]

Summary: To decrease the reaction to fire of a highly flammable plastic, polypropylene (PP), the concept of intumescence was applied. Two intumescent systems were designed on the basis of different mechanisms: physical expansion with expandable graphite (EG) and chemical expansion with modified ammonium polyphosphate (AP). Fire behavior of PP containing EG, AP, or an AP/EG mixture with a total loading of 10 wt% was evaluated by cone calorimetry at 35 kW·m−2. Thermocouples allowed measuring the temperature at the backside or inside samples over time and evaluating the thermal barrier of these intumescent materials. Two grades of AP (difference in composition) and several grades of EG (difference in expansion characteristics) were compared. Mixing AP and EG does not create a synergistic effect in studied conditions. Contrarily, the incorporation of small amount of EG in PP‐AP modifies heat transfer in the coating, creating a strong anisotropy. Graphite worms are trapped vertically into the expanded AP, which increases the transverse heat conductivity (lower efficiency of the thermal barrier) and decreases the fire performance. This phenomenon disappears in thicker specimens. While a higher expansion volume of graphite worms improves fire performances of PP with only small amount of EG (1 wt%), this effect is not noticeable with AP/EG mixtures. [ABSTRACT FROM AUTHOR]

The thermal degradation behaviour of various spirophosphates synthesized using SDP (phenol), SDOC (o-cresol), SDMC (m-cresol), SDPC (p-cresol), SDDMP (2,4-dimethylphenol) and SDTMP (2,4,6-trimethylphenol) with 3,9-dichloro-2,4,8,10-tetraoxa-3,9-diphosphaspiro-[5,5]-undecane-3,9-dioxide (SDCDP) are investigated using thermogravimetric analyzer. The spirophosphates show multistage degradations in the temperature range 180–550°C. The second stage of degradation is more prominent and the substituent effect is clearly reflected at this stage of degradation. The compound SDP showed superior performance since it has the greatest char yield value (44%) and LOI value (27%). The model free kinetic methods of Flynn-Wall-Ozawa and Vyazovkin methods are used to calculate the apparent energy of activation for the thermal degradation (Ea-D) of these spirophosphates. The material SDTMP showed the highest Ea-D values. [ABSTRACT FROM AUTHOR]

Silica-epoxy nanocomposites were prepared via an “in-situ” sol-gel synthesis process and a phosphorus (P) flame-retardant i.e. 6H-dibenz[c,e][1,2]oxaphosphorin,6-[(1-oxido-2,6,7-trioxa-1-phosphabicyclo[2.2.2]oct-4-yl)methoxy]-, 6-oxide (DP) and melamine (Mel) were further added to the matrix to improve its fire performance. The main components of epoxy resin were bisphenol A diglycidyl ether (DGEBA) and isophorone diamine (IPDA) hardener. The addition of DP as well as silica alone into the epoxy system stopped the melt dripping phenomena in the vertical fire test (UL 94), however, the addition of melamine was crucial for achieving the highest fire classification (UL 94-V0 rating). The presence of DP and Mel in the silica-epoxy nanocomposite promoted a large reduction (ranging from 53% up to 80%) in the heat release rate (HRR) and a delay (up to 31%) in the ignition time in the cone calorimetry experiments. Improved fire performance of the epoxy system was attributed to i) a condensed phase activity of silica, DP and melamine to form a protective thermal barrier during combustion and ii) a minor gas phase flame inhibition activity of DOPO component of DP. The mechanical characterization of the epoxy nanocomposites through tensile tests showed that the addition of DP increases the stiffness of the epoxy resin, resulting in a strong increase of Young modulus (up to 32%) and in a slight decrease of fracture strength, elongation at break and toughness. An increased glass transition temperature (up to 8%) of the epoxy system possibly due to hydrogen bonds and polar interactions of DP with the matrix was also observed.

In this paper, we present the results of studying the mechanism of the fire-retardant action of a new class of bioantipyrenes obtained based on oxidized wood. The intumescent behavior of bio flame retardant under pyrolysis and combustion conditions is studied using thermogravimetric and thermomechanical analysis, differential scanning calorimetry, and gas chromatography-mass spectrometry. A formal mechanism of the intumescence process is proposed with allowance for the chemical aspect of the pyrolytic transformation of bio flame retardant. [ABSTRACT FROM AUTHOR]

A quantitative understanding of the thermal transport within a growing intumescent char layer remains largely unsolved. The development of improved techniques to analyze charring and intumescent materials is necessary to investigate the physics of heat transfer within the char. To aid in this endeavor, a systematic methodology to parameterize comprehensive pyrolysis models for charring and intumescent materials is presented. Thermogravimetric analysis, differential scanning calorimetry and microscale combustion calorimetry were conducted on 4–7 mg samples to analyze the kinetics and thermodynamics of thermal decomposition and determine heats of complete combustion of gaseous pyrolyzates. A multi-step reaction mechanism, consisting of sequential first-order reactions, was constructed to capture the physical transformations and chemical reactions observed in the milligram-scale experiments. 0.07 m diameter disk-shaped samples were gasified in the Controlled Atmosphere Pyrolysis Apparatus II to characterize the thermal transport within the condensed phase material and evolving char layer. ThermaKin2Ds was employed to interpret the experimental data using inverse analysis techniques. Bisphenol A polycarbonate and poly(ether ether ketone), widely used intumescent materials, were analyzed within this study. The resulting two-dimensional models of bisphenol A polycarbonate and poly(ether ether ketone) were capable of predicting the experimental gasification mass loss rates with a mean error of 17.8% and 16.9%, respectively. An analysis of the char pore structure was also conducted from which quantitative relationships were subsequently developed between relevant thermal transport quantities and physical descriptors of the char's physical structure. Two prominent linear correlations were discovered: the char's effective thermal conductivity increased as a function of increasing volume-weighted mean pore diameter and the product of density and thermal conductivity increased with an increasing char porosity based on image analysis. Finally, a brief sensitivity analysis of the polycarbonate and poly(ether ether ketone) burning rates was conducted to determine which key material properties were responsible for the observed differences in flammability. [ABSTRACT FROM AUTHOR]

The concept of intumescence was applied to make flame retarded polypropylene (PP). This paper examines two types of intumescence in PP based on expandable graphite (EG, physical expansion) and on modified ammonium polyphosphate (AP760, chemical expansion). Reaction to fire of PP containing EG and AP760 was first evaluated by cone calorimetry. The incorporation of intumescent additives at relatively low loading (10 wt%) in PP permits the reduction by 70% of peak of heat release rate (pHRR). The mode of action occurs via the formation of an expanded carbonaceous layer in all cases. The protective coating acts mainly as heat barrier in the case of the formulations containing AP760 or as heat dissipater with EG. The incorporation of small amount of EG in PP-AP760 modifies heat transfer in the coating creating a strong anisotropy. Upon expansion, graphite worms align normal to the surface increasing the transverse heat conductivity (lower efficiency of the heat barrier) and hence, decreasing the fire performance (decrease by only 30% of pHRR). Kinetic analysis was then performed to quantify the thermal stability of the intumescent systems. It reveals that the intumescent additives do not modify the reactional scheme of the PP thermal decomposition but they increase slightly the thermal stability of the intumescent systems. For all materials, the decomposition model follows a reactional scheme at two successive reactions. This model was determined in dynamic conditions (conditions of thermogravimetry with linear heating rates) but it is able to simulate the decomposition of the materials in isothermal conditions (excellent agreement between the simulated and experimental curves). Image 1 • 70% of HRR reduction using only 10 wt% intumescent additive in polypropylene. • Worms of EG (physical expansion) come up normal to the surface when combined with APP-based additive (chemical expansion). • Worms of expandable graphite create high anisotropic heat conductivity. • X-ray tomography reveals the inner part of intumescent chars. [ABSTRACT FROM AUTHOR]

Highlights • Systematic method to parameterize pyrolysis model for charring material is presented. • Two-dimensional pyrolysis simulator is developed to take into account char swelling. • Method is demonstrated by developing accurate model for rigid poly(vinyl chloride). • Char pore structure analysis is performed to relate the structure to heat transfer. Abstract A quantitative understanding of an intumescent material's reaction to fire is largely an unsolved challenge in the field of fire science. To advance fire modeling, a systematic methodology to fully parameterize a comprehensive pyrolysis model for charring and intumescent materials is presented. Thermogravimetric analysis, differential scanning calorimetry and microscale combustion calorimetry were employed to characterize the kinetics and thermodynamics of thermal decomposition and heats of complete combustion of gaseous pyrolyzates. A multi-step reaction mechanism, consisting of sequential steps, was constructed to capture the physical transformations and chemical reactions observed in all milligram-scale experiments. Controlled Atmosphere Pyrolysis Apparatus II gasification experiments were conducted on 0.07 m diameter disk-shaped samples to parameterize the thermal transport within the undecomposed material and developing char layer. A recently expanded fully verified and validated numerical framework, ThermaKin2Ds, was employed to inversely model the gasification experimental results. The model accounted for spatially non-uniform swelling of the sample and associated changes in the radiant heat exposure. Rigid poly(vinyl chloride), a widely used intumescent material, was analyzed in this work. The resulting two-dimensional model was shown to reproduce the gasification experimental unexposed surface temperatures and mass loss rates with a mean error of 3.9% and 12.6%, respectively. A preliminary analysis of the char pore structure was also conducted to determine the pore size distribution and char porosity. The resulting porosity based on the density of graphite and the porosity based on image analysis (including only the pores that are greater than 1 × 10−4 m in diameter) was found to be 0.96 and 0.53, respectively. [ABSTRACT FROM AUTHOR]

Abstract The concept of intumescence was applied to flame retard ethylene vinyl acetate copolymer (EVA). The paper examines two types of intumescence based on expandable graphite (EG, physical expansion) and on modified ammonium polyphosphate (AP760, chemical expansion). The incorporation of expandable graphite (EG) at relatively low loading (10 wt%) in EVA permits the reduction up to 65% of peak of heat release rate (pHRR) measured by cone calorimetry. The mode of action occurs via the formation of an expanded carbonaceous layer acting mainly as heat barrier limiting heat and mass transfer as evidenced by the temperature measurement as a function of time during cone calorimetry. The incorporation of small amount of ZnCO 3 in EVA-AP760 enhances strongly the performance: pHRR was not reduced using the sole AP760 while it is decreased by 54% when only 2 wt% of AP760 is substituted by ZnCO 3. A strong synergistic effect was therefore observed. Solid state NMR of 31P and 13C on cone residues prepared at different characteristic times evidenced the mechanism involved is the reinforcement of the protective char by the formation of phosphate glass limiting the creation of cracks and increasing the char strength. Graphical abstract Image 1 Highlights • Two types of intumescence: physical and chemical expansion. • Low loading of expandable graphite provides lower pHRR (lower than that of EVA/ATH at 65 wt%). • Zinc carbonate is a superior synergist for conventional intumescent EVA (chemical expansion). • Zinc carbonate: reinforcement of the protective char by the formation of phosphate glass. [ABSTRACT FROM AUTHOR]

In this paper, we discuss promising systems for reducing the combustibility of polymeric materials taking the environmental safety of the polymer usage into account. Polymer nanocomposites containing nanocarbon fillers and layered silicates as additives that exhibit a synergistic effect on reducing the combustibility of traditional polymer thermoplastics are described. Particular attention is paid to a new direction in reducing combustibility due to the use of intumescent flame retardants based on oxidized renewable raw materials that can be successfully implemented in the manufacture of wood and polymeric structural materials of wide use. [ABSTRACT FROM AUTHOR]

This study aimed at investigating the influence of the crystalline structure of a series of clay minerals on the flame retardancy of ethylene based polymer materials with and without an intumescent formulation. The clay minerals tested were mica, kaolinite (Kaol) and palygorskite (Pal). K-feldspar (K-Fsp) was also tested. The intumescent formulation used was composed of ammonium polyphosphate (APP) and pentaerythritol (PER). The flammability was evaluated using UL-94 classification, limiting oxygen index (LOI) and cone calorimeter analyses. The addition of Pal to the intumescent formulation led to the highest LOI value and a rate of heat release (RHR) close to zero, indicating that a great synergy occurred from the interaction of this clay mineral crystalline structure with the polymer chains and the intumescent formulation. The K-Fsp showed the lowest performance. The TGA and heating microscopy analyses showed that the addition of mica, Kaol or Pal led to the formation of a more thermally stable intumescent layer, and the crystalline structure of the clay minerals' appears to affect the synergy with APP/PER. The presence of the tetrahedral SiO 4 sheets on both sides of the interlayer space, as in the mica structure, or in the internal face of the channels, as in the Pal, seems to lead to a greater synergistic action. [ABSTRACT FROM AUTHOR]

Flame-retardant-treated cellulose (FR-cell) was used as bio-based charring agent in combination with ammonium polyphosphate (APP) based intumescent flame retardant (IFR) system to reduce the flammability of poly(lactic acid) (PLA) foams produced by supercritical carbon dioxide (sc-CO 2 ) assisted extrusion. FR-cell was obtained by surface treatment of cellulose with diammonium phosphate (DAP) and boric acid (BA). To enhance foamability, the inherently low melt strength and slow crystallization rate of PLA was increased by adding epoxy-based chain extender (CE) and montmorillonite (MMT) nanoclay, respectively. The morphology of the foams was examined using water displacement method, scanning electron microscopy (SEM) and energy dispersive X-ray spectrometry (EDS). Thermal properties were assessed using differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). Flammability was evaluated by limiting oxygen index (LOI) measurements, UL-94 tests and pyrolysis combustion flow calorimetry (PCFC). The continuous extrusion foaming technique allowed the preparation of low density PLA foams with uniform microcellular structure and void fractions higher than 90% accompanied with increased crystallinity of up to 19%. Despite the high expansion ratios (i.e. high surface area), the PLA foams showed excellent flame retardancy, UL-94 V-0 rate and LOI value of 31.5 vol% was achieved with an additive content as small as 19.5%. However, the flame retardant synergism evinced between IFR and MMT proved to be less pronounced in the expanded foams compared to bulk materials with identical additive contents. [ABSTRACT FROM AUTHOR]

The genus Alouatta hosts species popularly known as red-handed howler, presenting wide geographic distribution and being found in several biomes. The objective is to describe the anatomy of the spinal cord of Alouatta belzebul specimens, focusing on the topography of the medullary cone, stressing the cervical and lumbar intumescences and cauda equina, to provide anatomical data and compare it with other species to assist in anesthetic and surgical procedures. Four animals were received for scientific research, post mortem, from the fauna rescue program of the Hydroelectric Plant of Belo Monte - Pará, and they were fixed in 10% formaldehyde solution. Structures such as the medullary cone, cervical and lumbar intumescence, and cauda equina were photographed (Sony a200-10.2 mpx). After thawing, we measured the specimens and observed a size of 80 to 82 cm from head to toe. After the skin and musculature were removed, it was observed that the spine of all specimens presented 7 cervical, 13 thoracic, 5 lumbar and 3 fused sacral vertebrae. The spinal cord was exposed after the removal of vertebral arches, it has 22 cm length in all animals, presenting the cervical intumescence between C3 and C6 vertebrae, with average of 2.2 cm and lumbar intumescence between T11 and T12 vertebrae, with average of 1.65 cm. The medullary cone is located between T12 and L1 vertebrae, with average of 1.5 cm, and the cauda equina between L1 and S3, with an average of 15 cm. This study has an important role as the basis for epidural anesthesia in the species. [ABSTRACT FROM AUTHOR]

In the current study, the effects of four different POSS nanoparticles on the flame retardant properties of intumescent PP were investigated through mass-loss calorimetry (MLC), limiting oxygen index (LOI) test and UL-94 ratings. In addition, the structure-property relationship was enlightened via thermal, morphological and mechanical tests. The four different POSS types, namely aminopropyl isobutyl-POSS (A-POSS), octaphenyl-POSS (OP-POSS), octaammonium-POSS (OA-POSS) and trissulfonic acid propyl-POSS (TS-POSS), were used. The ratio of ammonium polyphosphate (APP) to pentaerythritol (PER) was kept constant and the POSS content was varied as 0.5%, 1% and 3%. The MLC, LOI and UL-94 tests revealed that the addition of POSS particles had adjuvant on the flame retardant properties of PP/IFR system. All POSS nanoparticles showed their highest adjuvant effect at the lowest concentration of 0.5 wt%. The highest UL-94 rating and the highest LOI values were achieved in the presence of OA-POSS and TS-POSS. The ceramic layer formation was monitored using scanning electron microscopy (SEM) and FTIR on the char residues. The thermal properties of PP/IFR/POSS composites were obtained via differential scanning calorimeter and thermo-gravimetric analysis. The inline melt flow properties were observed via vertical force measurements. The fracture morphology was investigated using SEM. Mechanical tests showed that the yield strengths of the composites were lower than that of pristine PP; in contrast, the elongation at break and the impact strength of composites enhanced in A-POSS and TS-POSS based composites. [ABSTRACT FROM AUTHOR]

• Phosphorylated methacrylate photopolymer complexes with polyethylenimine. • Two-step treatment process renders wood self-extinguishing. • Flame retardancy of wood improved, while preserving mechanical properties. • Treatment permeates the wood, protecting interior as well as exterior. The use of wood in home and commercial structures has continued to grow in recent years, but its flammability poses a threat to lives and property. Previous attempts to flame retard wood have utilized harmful halogenated chemistries or required complex deposition methods. In this work, a UV-cured flame-retardant treatment is deposited on plywood and natural whitewood through in situ photopolymerization of an anionic phosphate-containing methacrylate, in the presence of cationic polyethylenimine (PEI), to form a polyelectrolyte complex. The influence of PEI molecular weight, PEI and methacrylate concentrations, and deposition time were investigated. The best version of this treatment, deposited in only two steps, renders natural wood and plywood flame retardant without affecting mechanical properties. Cone calorimetry reveals a significant reduction in the total heat release, average heat release rate, and maximum average rate of heat release for both substrates. This environmentally benign and facile system represents a significant advancement for safe and effective flame retardant treatment of wood. [Display omitted] [ABSTRACT FROM AUTHOR]

The objective of this study is to assess the efficiency of biobased carbonization agent in intumescent formulations (IFRs) to examine the flame retardant properties of polylactic acid (PLA) composites and to investigate their melt-spinnability. We used phosphorous-based halogen free flame retardant (FR) and kraft lignin (KL) as bio-based carbonization agent. After melt compounding and molding into sheets by hot pressing various fire related characteristics of IFR composites were inspected and were characterized by different characterization methods. It was fascinating to discover that the introduction of 5–20 wt% FR increased the limiting oxygen index (LOI) of PLA composites from 20.1% to 23.2–33.5%. The addition of KL with content of 3–5 wt% further increased the LOI up to 36.6–37.8% and also endowed PLA/FR/KL composites with improved anti-dripping properties. Cone calorimetry revealed a 50% reduction in the peak heat release rate of the IFR composites in comparison to 100% PLA and confirmed the development of an intumescent char structure containing residue up to 40%. For comparative study, IFR composites containing pentaerythritol (PER) as a carbonization agent were also prepared and their FR properties were compared. IFR composites were melt spun and mechanical properties of multifilament yarns were tested. The analysis of char residues by energy dispersive X-ray spectrometry (EDS) and SEM images confirmed that PLA/FR/KL composites developed a thicker and more homogeneous char layer with better flame retardant properties confirming that the fire properties of PLA can be enhanced by using KL as a carbonization agent.

Intumescent coatings have been used for fire protection of steel for decades, but there is still a need for improvement and adaptation. The key parameters of such coatings in a fire scenario are thermal insulation, foaming dynamics, and cohesion. The fire resistance tests, large furnaces applying the standard time temperature (STT) curve, demand coated full-scale components or intermediate-scale specimen. The STT Mufu+ (standard time temperature muffle furnace+) approach is presented. It is a recently developed bench-scale testing method to analyze the performance of intumescent coatings. The STT Mufu+ provides vertical testing of specimens with reduced specimen size according to the STT curve. During the experiment, the foaming process is observed with a high-temperature endoscope. Characteristics of this technique like reproducibility and resolution are presented and discussed. The STT Mufu+ test is highly efficient in comparison to common tests because of the reduced sample size. Its potential is extended to a superior research tool by combining it with advanced residue analysis (μ-computed tomography and scanning electron microscopy) and mechanical testing. The benefits of this combination are demonstrated by a case study on 4 intumescent coatings. The evaluation of all collected data is used to create performance-based rankings of the tested coatings. [ABSTRACT FROM AUTHOR]

A new gasification apparatus has been developed to enable a comprehensive analysis of pyrolysis of charring and intumescent materials. This apparatus provides well defined boundary conditions and highly resolved measurements of mass, temperature and sample profile evolution of a disk-shaped 0.07 m diameter material sample exposed to radiant heat. All measurements are collected simultaneously, in a single experiment, and recorded as a function of time. The oxygen concentration in the pyrolysis zone is controlled and can be reduced below 1 vol% to ensure that the measurements are free of oxidation effects. The radiation from an external conical heater has been carefully characterized to account for changes in the sample surface position, including the surface's angular orientation. Using an empirical expression, the radiation heat flux can be predicted with less than 2% error based on the known surface position and heat flux set point. The NIST Fire Dynamics Simulator (FDS) has been utilized in the direct numerical simulation mode to investigate convective losses from the sample surfaces. The convective heat transfer coefficient computed for the top (radiation exposed) surface has been found to be dependent on the surface position; its space-averaged value has been validated against experimental measurements. The capabilities of the apparatus are demonstrated using poly(vinyl chloride). It is shown that the apparatus provides repeatable data necessary for modeling of transport processes inside pyrolyzing intumescent solids. Non-one-dimensional nature of these processes is discussed. [ABSTRACT FROM AUTHOR]

Thermal insulation and mechanical resistance play a crucial role for the performance of an intumescent coating. Both properties depend strongly on the morphology and morphological development of the foamed residue. Small amounts (4 wt%) of fiberglass, clay and a copper salt, respectively, are incorporated into an intumescent coating to study their influence on the morphology and performance of the residues. The bench scale fire tests were performed on 75 × 75 × 2 mm coated steel plates according to the standard time-temperature curve in the Standard Time Temperature Muffle Furnace (STT Mufu). It provided information about foaming dynamics (expansion rates) and thermal insulation. Adding the copper salt halved the expansion height, whereas the clay and fiberglass change the height of the residue only moderately. The time to reach 500°C was improved by 31% for clay and 15% for the other two fillers. Nondestructive micro computed tomography is used to assess the inner structure of the residues. A transition of the residue from a black, carbonaceous foam with closed cells into an inorganic, residual open cell sponge occurs at high temperatures. This transition is due to a loss of carbon; the change in microstructure is analyzed by scanning electron microscopy. Additional mechanical tests are performed and interpreted with respect to the results of the morphology analysis. Adding clay or copper salt improved the mechanical resistance tested by a factor 4. The additives significantly influence the thickness and foaming dynamics as well as the inner structure of the residues, whereas their influence on insulation performance is moderate. In conclusion, different modes of action are observed to achieve similar insulation performance during the fire test. [ABSTRACT FROM AUTHOR]

Model polymer poly(vinyl acetate) (PVAc) was combined with melamine isocyanurate (MIC) as intumescent flame retardant composite. This work emphasises on the study of the decomposition mechanism and compared with a single fire test in order to show its performance as flame retarded composite. As such, mass loss cone calorimetry tests were performed and compared with it inert and oxidative decompositions in lab tests. PVAc/MIC composites cannot be ignited with high loadings MIC. Difference curves in oxidative conditions revealed that the composites with MIC show only positive differences, indicating a high stabilisation, especially in the temperature region of a mild flame (500-700 °C). Experiments performed with TG coupled with mass spectroscopy and analyses on partially degraded residues with solid-state C-NMR enabled the construction of the complete decomposition mechanism. MIC has both a heat-sink FR activity as well as a crosslinking role in the stabilization of the polymer. The latter then creates a highly stabilised char at elevated temperatures in oxidative environments. The formed char starts to degrade only 100 °C higher than the pure polymer within a heating. The degradation of formed char of pure PVAc is autocatalytic; this behaviour disappears upon addition of sufficient amount of MIC. Therefore, the transport of fuel towards the gaseous phase is limited, creating an efficient flame retardant system. [ABSTRACT FROM AUTHOR]

In this work, a semi-empirical pyrolysis model is developed to predict the thermal decomposition behavior of an intumescent fire retardant (IFR) system consisting of ammonium polyphosphate/pentaerythritol (APP/PER) with the ratio 3:1 (wt/wt) in a low-density polyethylene (LDPE) matrix. This work is based on a previously developed semi-global reaction mechanism for the degradation of LDPE and APP/PER, which consists of two consecutive first-order reactions for the LDPE and five first and second-order reactions for the APP/PER combination. The apparent properties that define heat transport inside the pyrolyzing solid are determined via inverse modeling of cone calorimeter experiments for the pure LDPE and then for the complete IFR system. This is achieved by using the Shuffled Complex Evolution optimization algorithm. The flame heat flux in the cone calorimeter experiments is also evaluated by targeting the heat release rate (HRR) data in the optimization process of one of the cone radiative heat setups. The optimized parameters and flame heat feedback are in line with the literature and the robustness of the model is assessed by a comparison with the experimental data for a wide range of cone heat fluxes. Ignition times and peaks of HRR and total HRs are within the engineering accuracy whatever the flux conditions for both pure LDPE and the IFR system. [ABSTRACT FROM AUTHOR]