Pyrolysis Combustion Flow Calorimetry Research Articles

Improvement of flame retardancy of silk fabric by bio-based phytic acid, nano-TiO2, and polycarboxylic acid

Abstract This research work reported a novel approach to develop flame retardant silk fabric using naturally occurring phytic acid (PA) rich in phosphorus and TiO 2 nanoparticles through a pad-dry-cure technique. A polycarboxylic acid [1,2,3,4–butanetetracarboxylic acid (BTCA)] was employed to stabilize and improve the adhesion of TiO 2 on silk surface. The flame retardancy of the treated silk fabric was determined in terms of limiting oxygen index, vertical burning, and pyrolysis combustion flow calorimetry, and the durability of flame retardancy to washing was discussed. PA and TiO 2 were found to have a joint flame retardant effect. The combination of PA, TiO 2 and BTCA was able to endow silk fabric with excellent flame retardancy, and the good flame retardant ability was kept even after 25 times of washing. The reasons for the good washing durability of the treated silk fabric were discussed. Finally, a significant condensed-phase flame retardant mechanism of the silk fabric treated with the PA/TiO 2 /BTCA system was revealed by the analyses of thermogravimetry and pyrolysis combustion flow calorimetry.

Thermal Stability and Fire Properties of Salen and Metallosalens as Fire Retardants in Thermoplastic Polyurethane (TPU).

This study deals with the synthesis and evaluation of salen based derivatives as fire retardants in thermoplastic polyurethane. Salens, hydroxysalens and their first row transition metal complexes (salen-M) were synthesized (Copper, Manganese, Nickel and Zinc). They were then incorporated in thermoplastic polyurethane (TPU) with a loading as low as 10:1 weight ratio. The thermal stability as well as the fire properties of the formulations were evaluated. Thermogravimetric analysis (TGA) showed that different coordination metals on the salen could induce different decomposition pathways when mixed with TPU. The Pyrolysis Combustion Flow Calorimetry (PCFC) results showed that some M-salen have the ability to significantly decrease the peak heat release rate (−61% compared to neat TPU) and total heat released (−63% compared to neat TPU) when formulated at 10:1 wt % ratio in TPU. Mass Loss Cone Calorimetry (MLC) results have shown that some additives (salen-Cu and salen-Mn) exhibit very promising performance and they are good candidates as flame-retardants for TPU.

New Flexible Flame Retardant Coatings Based on Siloxane Resin and Ethylene-Vinyl Chloride Copolymer.

This work presents the effectiveness of a phosphorus-containing flame retardant based on siloxane resin and ethylene-vinyl chloride copolymer as a back-coating of fabrics. The possibility of improving flame retardant efficiency of this composition by introducing fumed silica, montmorillonite, carbon nanotubes, and graphite was evaluated. The effect of each additive on the efficiency of the composition was examined separately. Flammability tests of flame retardant-coated fabrics (natural and synthetic) were carried out using pyrolysis combustion flow calorimetry (PCFC), cone calorimetry, and limiting oxygen index determination. An assessment of the ignitability of upholstered furniture containing flame retardant fabric, resistance to washing, antifungal activity, and some of the utility properties of the final newly-developed flame-retardant coating was conducted.

Studying the thermo-oxidative stability of chars using pyrolysis-combustion flow calorimetry

A method to estimate the thermo-oxidative stability of chars is proposed using pyrolysis-combustion flow calorimetry. The temperature of char degradation is measured for different oxygen fractions (from 0.01 to 0.4, i.e. from 0 to 40%) into the pyrolyzer. Then the thermo-oxidative stability versus the oxygen fraction is modelled using a simple phenomenological equation. Two parameters have been calculated: the first one predicts the temperature of char degradation in “pure” oxygen and the second one corresponds to the sensitivity of the char degradation temperature to the oxygen fraction. These two parameters allow comparing the chars obtained from different materials after various pyrolysis procedures. Rough relationships between these two parameters and the elemental composition of char are identified. Phosphorus allows improving the thermo-oxidative stability of chars as expected but its effect is nonlinear. Lignocellulosic materials lead to chars with low thermal stability even when the phosphorus content is high. Finally, the obtained results show that the char elemental composition is not the only parameter influencing its thermo-oxidative stability.

Flame retardancy of phosphorus-containing ionic liquid based epoxy networks

Various amounts of a phosphonium ionic liquid (IL169) were used as curing agents as well as flame retardants of epoxy prepolymer in order to prepare epoxy networks with improved fire properties. The flame retardancy of these resins was investigated using thermogravimetric analysis (TGA), pyrolysis-combustion flow calorimetry (PCFC) and cone calorimetry. Phosphonium ionic liquid significantly reduced flammability without further addition of flame retardants due to the high amount of phosphorus (up to 3.69 wt%). The Peak of heat release rate decreases from 1099 kW/m2 to 300 kW/m2 in cone calorimeter at 35 kW/m2 when incorporating 30 phr of IL169. Phosphorus modifies pyrolysis pathway, promotes charring and may act as flame inhibitor. The char layer protects the underlying polymer, leading to a high unburnt polymeric fraction. Char properties were studied using PCFC, Raman spectroscopy and X-ray tomography. Phosphorus improved the graphitization of the char and its thermo-oxidative stability.

Synergistic effect of carbon nanotubes on the flame retardancy of poly(methyl methacrylate)/zinc oxalate nanocomposites

Carbon nanotubes have incorporated in poly(methyl methacrylate) (PMMA) nanocomposites as a synergist of zinc oxalate nanoparticles in order to enhance the flame retardancy. PMMA nanocomposites filled with the newly developed environmentally friendly zinc oxalate nanoparticles and with multi-walled nanotubes (MWNTs), both serving as flame retardants, were prepared by applying the solution blending method. The fire behavior of these composites was systematically studied by carrying out limiting oxygen index (LOI) and pyrolysis combustion flow calorimetry (PCFC) tests. The introduction of MWNTs into the PMMA/zinc oxalate nanocomposites improved the LOI values and markedly decreased the peak heat release rate. It can be suggested that this improvement in the flame retardancy resulted from the formation of stable protective char layers during the combustion process. Open image in new window

Effect of Individualized Cellulose Fibrils on Properties of Poly(Methyl Methacrylate) Composites

ABSTRACTCellulose fibrils were manufactured from flax fibers using chemical treatments followed by cryo-crushing and ultrasonication techniques. The fibrils, consisting mainly of cellulose free from lignin, pectin and hemicellulose, were exploited as a biofiller in preparing poly(methyl methacrylate) (PMMA) matrix composites. The effects of incorporating cellulose fibrils on the physical and mechanical properties of the polymer matrix were investigated. In particular, the influence of the fibrils on the thermal stability and degradation of the composites was studied by means of thermogravimetric analysis carried out in both inert and oxidative atmospheres. The runs performed under air flow revealed the efficiency of the cellulose fibrils in delaying the polymer decomposition during thermal oxidation. The weight loss was slowed down in the composites of all compositions and the temperature of degradation increased with increasing the amount of the fibrils. The combustion properties of the fibril-based composites were evaluated by means of pyrolysis combustion flow calorimetry. The addition of cellulose fibrils into the PMMA matrix resulted in a noticeable decrease of the primary combustion parameters.

Adsorption and Flame Retardant Properties of Bio-Based Phytic Acid on Wool Fabric.

Bio-based phytic acid (PA) as a nontoxic naturally occurring compound is a promising prospect for flame-retardant (FR) modifications to polymers. In this work, PA was applied to wool fabric using an exhaustion technique, and the adsorption and FR properties of PA on wool fabric were studied. The flame retardancy of the treated wool fabrics depended greatly on the adsorption quantity of PA, which was related to the pH of treatment solution, immersing temperature and initial PA concentration. The Langmuir adsorption of PA took place due to electrostatic interactions between PA and wool fiber. The limiting oxygen index, vertical burning and pyrolysis combustion flow calorimetry tests revealed that the treated wool fabrics exhibited good flame retardancy. The measurements of the phosphorus content of the burned fabric residues and thermogravimetric analyses suggested that a significant condensed-phase FR action was applicable to the PA treated fabrics. PA treatment was found to have little adverse effect on the whiteness and mechanical performance of wool. Additionally, the washing resistance of the FR fabrics should be further improved.

The effect of phosphorus containing polyol and layered double hydroxides on the properties of a castor oil based flexible polyurethane foam

In this work the effect of the addition of a phosphorus containing polyol (E560) and different type of layered double hydroxides (LDH) to flexible polyurethane foams synthesized with a castor oil based polyol (LB50) is reported. A carbonate intercalated commercial synthetic hydrotalcite (LDH-CO3) and modified LDH with intercalated hydrogen phosphate and bis(2-ethylhexyl) hydrogen phosphate (LDH-HPO4 and LDH-HDEHP, respectively) were used. The density and the compression force deflection values of the foams increased with the addition of E560, while the effect of the different LDH depended on their dispersion degree, which was analyzed by X-ray diffraction. It was found by thermogravimetric analysis that E560 catalyzed the first degradation stage whereas LDH, especially those modified with phosphorus, showed a barrier effect which delayed the thermal degradation with respect to unfilled foams containing E560. It was also observed by pyrolysis combustion flow calorimetry that the combination of E560 with LDH led to decrease the total heat release and heat release capacity comparing to foams fully synthesized with LB50. Both E560 and LDH resulted also to decrease the peak heat release rate separately in both stages of degradation.

Mineralization of wood by calcium carbonate insertion for improved flame retardancy

Abstract Wood can be considered as a highly porous, three-dimensional organic scaffold. It can be mineralized to create hierarchically structured organic-inorganic hybrid materials with novel properties. In the present paper, the precipitation of CaCO3 mineral in Norway spruce and European beech wood has been studied by alternating impregnation with aqueous and alcoholic electrolyte solutions. Microstructural imaging by SEM and confocal Raman microscopy shows the distribution of calcite and vaterite as two CaCO3 polymorphs, which are deposited deep inside the cellular structure of the wood. The confined microenvironment of the wood cell wall seems to favor a formation of vaterite, as visible by XRD and Raman spectroscopy. In view of a practical application, the mineralization of wood opens up ways for sustainable wood-based hybrid materials with a significantly improved fire resistance, as proven via pyrolysis combustion flow calorimetry and cone calorimetry tests. Beyond that, this versatile solute-exchange approach provides an opportunity for the incorporation of a broad range of different mineral phases into wood for novel material property combinations.

Morphological characterization and thermal properties of compatibilized poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV)/poly(butylene succinate) (PBS)/halloysite ternary nanocomposites

Blends of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) and poly(butylene succinate) (PBS) at different weight ratios (80/20, 50/50 and 20/80 w/w) and ternary PHBV/PBS/halloysite nanotubes (HNT) nanocomposites were prepared by melt compounding. Typical co-continuous and nodular morphologies were obtained with the neat blends. The effect of maleic anhydride-grafted PHBV (PHBV-g-MA) compatibilizer and HNT on the nodular microstructure and thermal properties of PHBV/PBS/HNT nanocomposites was investigated. Morphological observations using scanning electron microscopy (SEM) showed an improved dispersion of PBS nodules in the immiscible PHBV/PBS 80/20 blends, owing to the diffusion and emulsifying effect of PHBV-g-MA chains at the PHBV/PBS interface. A preferential location of HNTs in the PBS nodules was observed, due to their better wettability with PBS phase. Image analysis showed that combining HNT and compatibilizer led to a reduced emulsifying effect, attributed to the formation of PHBV-g-MA/HNT aggregates that limit the diffusion of PHBV-g-MA chains at the interface. Thermogravimetric analysis (TGA) and Pyrolysis Combustion Flow Calorimetry (PCFC) showed a better thermal stability and fire reaction of PHBV in the PHBV/PBS blends as compared to neat PHBV. Incorporation of HNT in the blends decreased their thermal stability but improved significantly their fire reaction, whereas combining PHBV-g-MA and HNT seems to level the influence of each component.

Gamma irradiation effects on morphology and properties of PHBV/PLA blends in presence of compatibilizer and Cloisite 30B

The effects of gamma irradiation on the morphology and physical properties of various blends based on poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) and polylactide (PLA): 50/50 w/w were studied with and without PHBV-g-MA and organomodified montmorillonite used as the compatibilizer and reinforcement agent, respectively. The different blend compositions prepared by melt compounding were compression molded to thin films of an average thickness of 150 μm, and subjected to 25, 50 and 100 kGy at room temperature; the dose rate being 1.0 Gy/h. Infrared spectra analysis indicated the occurrence of some chemical modifications in the irradiated samples, in particular an absorbed dose of 100 kGy resulted in the formation of a large absorption band in the carbonyl region. Size exclusion chromatography (SEC) data showed a decrease in the average molecular weight for all irradiated samples with increasing absorbed dose due to chain scission. Nanoindentation tests showed that γ-irradiation significantly decreased both modulus and hardness of neat PHBV and neat PLA after 100 kGy, whereas no noticeable changes were observed for PHBV/PLA blends. Thermogravimetric analysis (TGA) and pyrolysis combustion flow calorimetry (PCFC) tests revealed that the organomodified clay can act as a compatibilizer and compensate for the effect of irradiation on both thermal stability and fire retardancy of PHBV/PLA blends.

Water-soluble polyelectrolyte complex nanocoating for flame retardant nylon-cotton fabric

Blends of cotton with synthetic fibers are widely used for various military and industrial applications. Nylon-cotton (NYCO) blends offer high durability and strength from nylon and the softness of cotton, but both fiber types are highly flammable. Previously reported flame retardant coatings for cotton fabric, comprised of a complex of polyethylenimine and a polyphosphate, are not able to protect NYCO textiles, so a new generation of water-soluble polyelectrolyte complex coating is needed. The basis of this new treatment is an aqueous complex of polyethylenimine and ammonium polyphosphate that forms melamine polyphosphate in-situ during exposure to a melamine-containing solution. NYCO fabric was rendered self-extinguishing in a vertical flame test and pyrolysis combustion flow calorimetry showed a 28% reduction in total heat release, and a 65% reduction of cotton's peak heat release, with less than 20 wt% coating. The effectiveness of this halogen-free, flame retardant coating is due to condensed phase activity that includes cooling effects and charring. The ease of this coating procedure and the use of more environmentally benign chemicals deposited from aqueous solutions make this an industrially feasible alternative to current treatments.

How much the fabric grammage may affect cotton combustion?

The present article is addressed to investigating the effect of different fabric grammages (mass per area unit) on cotton combustion. To this aim, 100, 200 and 400 g/m2 cotton fabrics were tested when exposed to (1) two different heat fluxes (25 and 35 kW/m2) under a cone calorimeter, (2) a methane flame in horizontal or vertical flame spread tests or (3) a propane flame in Limiting Oxygen Index tests, and (4) when pyrolysed and further oxidised in pyrolysis-combustion flow calorimetry (PCFC). The collected results demonstrated a precise relationship between fabric grammage and cotton combustion behaviour. Indeed, when exposed to a 35-kW/m2 heat flux, the higher the fabric grammage, the higher the total heat release during combustion was; the opposite trend was observed when the same fabrics were pyrolysed and further oxidised in PCFC. This finding was ascribed to the different scenarios described by these instrumentations; indeed, the cone calorimeter was able to reproduce cotton combustion in a well-ventilated context in the presence of air (thus, oxygen), while PCFC only represented the combustion of pyrolysis products. However, both techniques indirectly evidenced a linear dependence of char formation as a function of fabric grammage: the higher the fabric grammage, the larger the amount of char formed was. The same trend was also observed during horizontal and vertical flame spread tests. In conclusion, the present article is intended to show how cotton combustion may be affected by fabric grammage as well as how such behaviour is influenced by the experimental conditions in which it is investigated.

Effects of laundering on military uniform fabric flammability

SummaryIn this paper, the effects of laundering on the flammability of a military uniform fabric were studied. The flame retardant was incorporated into the fiber prior to fiber spinning, and its ability to maintain flame spread and flame retardancy was evaluated by multiple test methods. Vertical flame spread, cone calorimeter, and pyrolysis combustion flow calorimetry were used to determine how many of the flame retardants were removed as a function of wash cycles and if there was any measurable reduction in heat release/fire safety performance that correlated with a loss in flame retardant from washing. Fire testing showed that flame spread performance was maintained within the normal error for the measurement and heat release testing showed very little difference between samples as a function of laundering. Additional analysis via pyrolysis gas chromatography–mass spectrometry showed that while the flame retardant levels did decrease with washing, enough of the material remained embedded in the fibers so that fire performance could be maintained. The results do indicate that the flame retardant can be washed off, but because of the flame retardant being deeply embedded in the fiber, enough will remain with the fabric after 25 washes to maintain flame retardant performance. Copyright © 2015 John Wiley & Sons, Ltd.

Thermal and flame retardant properties of ethylene vinyl acetate copolymers containing deoxyribose nucleic acid or ammonium polyphosphate

The present study was aimed to compare the effect of the presence of deoxyribose nucleic acid (DNA) or ammonium polyphosphate (APP) in ethylene vinyl acetate (EVA) copolymers, as far as their thermal and flame retardant properties are considered. Indeed, although DNA has been recently discovered as a novel green flame retardant, its performances have not been compared with a conventional flame retardant such as APP yet. With this purpose, EVA compounds containing 10 or 20 mass% of DNA or APP have been melt-blended and their thermal and flame retardant properties thoroughly investigated. The morphology of the samples has proven to be significantly different, as assessed by scanning electron microscopy: indeed, APP gave rise to numerous micro-aggregates homogeneously distributed within the polymer matrix; on reverse, DNA was finely dispersed. Both the additives have favoured the char formation, inhibiting the production of volatile species, as assessed by thermogravimetry and pyrolysis–combustion flow calorimetry. The char features of both the additives turned out to be extremely advantageous for strongly modifying the combustion behaviour of EVA, as clearly demonstrated by cone calorimetry tests.

Synergistic effects occurring between water glasses and urea/ammonium dihydrogen phosphate pair for enhancing the flame retardancy of cotton

Cotton fabrics have been treated with two different finishing compositions based on urea (U) and ammonium dihydrogen phosphate (AP) in order to enhance their flame retardancy properties, particularly referring to the resistance to a flame application (namely, Limiting Oxygen Index tests) and to an irradiative heat flux of 35 kW/m2 (by cone calorimetry). The collected results have proven a remarkable increase of cotton flame resistance: indeed, the fabrics treated with the high concentrated bath showed a LOI increase of 121 % (from 19 for neat cotton, to 42 %) and did not ignite under 35 kW/m2 heat flux. Thermogravimetry coupled with pyrolysis-combustion flow calorimetry has demonstrated efficient features of the proposed flame retardant system as char-promoter for cotton. In order to reduce the amounts of U and AP employed in the selected formulations, the use of water glasses (WG) has been explored. A very low WG amount has proven to be effective in halving U and AP contents, maintaining the same fire performances already provided by the high concentrated finishing bath. Furthermore, WG have turned out to act as synergistic species as demonstrated by evaluating the synergistic effectiveness parameter.

Metallic phytates as efficient bio-based phosphorous flame retardant additives for poly(lactic acid)

In this study, we evaluated the potential flame retardant effect of different metallic phytates as biosourced phosphorous additives for poly(lactic acid) (PLA). Starting from sodium phytate, the sodium cations were replaced by aluminum, iron or lanthanum cations as attested by elemental analysis. PLA-metallic phytate composites containing 20 or 30 wt% of additives were produced by melt blending in an internal mixer and their fire properties, thermogravimetric resistance have been characterized as well as the PLA chain degradation occurring during melt processing. The most significant flame retardant effect, observed by cone calorimeter test, was obtained when aluminum phytate was used. Cone calorimeter testing combined with pyrolysis combustion flow calorimetry (PCFC) analysis indicated that the barrier effect was more significant in the case of PLA filled with aluminum phytate. However, aluminum phytate proved to be responsible for PLA chain degradation during melt processing. Combinations of metallic phytate and native sodium phytate overcame this negative effect and allowed for limiting the thermal degradation of PLA during melt processing while preserving good fire performances, i.e. significant pHRR reduction and V-2 classification in UL-94 test.

Water-based chitosan/melamine polyphosphate multilayer nanocoating that extinguishes fire on polyester-cotton fabric

Polyester–cotton (PECO) blends are widely used in the textile industry because they combine the softness of cotton and the strength and durability of polyester. Unfortunately, both fiber types share the disadvantage of being flammable. The layer-by-layer coating technique was used to deposit a highly effective flame retardant (melamine polyphosphate) from water onto polyester–cotton fabric. Soluble melamine and sodium hexametaphosphate form this water-insoluble flame retardant during the coating procedure. This unique nanocoating imparts self-extinguishing properties to PECO with only 12% relative coating weight. Vertical flame testing, pyrolysis combustion flow calorimetry (PCFC), thermogravimetric analysis (TGA), and scanning electron microscopy were used to evaluate the quality of the coating as well as its flame retardant performance. A combination of both condensed and gas-phase activity appears to be the reason for this effective flame retardancy. Degradation pathways of both cotton and polyester are affected by the applied coating, as shown by PCFC and TGA. Use of environmentally benign and non-toxic chemicals, and the ease of layer-by-layer deposition, making this coating an industrially feasible alternative to render polyester–cotton fabric self-extinguishing.

Pyrolysis Combustion Flow Calorimetry Studies on Some Reactively Modified Polymers

As a part of our continuing work to improve the flame retardance of some chain-growth polymers, by employing a reactive route, we have synthesized several unsaturated compounds containing either phosphorus (P), or both phosphorus (P) and nitrogen (N), bearing groups in different chemical environments. They included: diethyl(acryloyloxymethyl)phosphonate (DEAMP); diethyl(1-acryloyloxyethyl)phosphonate (DE1AEP); diethyl-2-(acryloyloxy)ethyl phosphate (DEAEP); diethyl-2-(metharyloyloxy)ethyl phosphate (DEMEP); acrylic acid-2-(diethoxyphosphorylamino)ethyl ester (ADEPAE); acrylic acid-2-[(diethoxyphosphoryl)methyl amino]ethyl ester (ADEPMAE). Acrylonitrile (AN), methyl methacrylate (MMA) and styrene (S) were free radically copolymerised with the above mentioned comonomers. The recovered polymers were subjected to routine spectroscopic and thermo-gravimetric analyses. In addition, the combustion behaviours of homopolymers as well as the copolymers containing nominal loadings of P-, or P/N-, groups were, primarily, evaluated using pyrolysis combustion flow calorimetry (PCFC). PCFC has been found to be a very useful screening technique, especially, in establishing the efficacies of the different modifying groups towards flame retarding some base polymeric materials. Values of the heat release capacity (HRC) values normalised to the P contents (wt%) can be considered as useful tool in ranking the various P-containing modifying groups in terms of their efficacies to flame-retard non-halogenated chain-growth polymers considered in the present work.