Presence Of Ammonium Polyphosphate Research Articles

Preparation and properties of APP flame-retardant ramie fabric reinforced epoxy resin composites

Ramie fabrics (RFs) as natural fibers have shown promising potential in the field of fiber reinforced composites, but flammability of RFs limits their application in composites. In this study, ammonium polyphosphate (APP) was first coated on the surface of RFs, and then the flame-retardant RF reinforced epoxy resin composites were obtained. When the weight gain rate of APP in RFs was about 20 %, the limiting oxygen index of the flame-retardant composites reached 33.8 %, and achieved UL-94 V-0 rating. At the same time, the peak heat release rate and total heat release values of the flame-retardant composites were reduced by 26 % and 41 % respectively, and the total smoke production was reduced by 43.9 %. In terms of mechanical properties, the presence of APP had a certain negative effect on the internal compatibility of composites. In this work, the flame-retardant composites show excellent flame retardancy and provide a feasible solution to improve the flammability of natural fiber reinforced composites.

Self-Assembled Serpentine Ni3Si2O5(OH)4 Hybrid Sheets with Ammonium Polyphosphate for Fire Safety Enhancement of Polylactide Composites.

Biodegradable polylactide (PLA) has been widely utilized in people's daily lives. In order to improve the fire safety of PLA, ammonium polyphosphate (APP) was self-assembled onto the surface of serpentine Ni3Si2O5(OH)4 through the electrostatic method, followed by mixing with PLA by melt compounding. The APP-modified serpentine (serpentine@APP) dispersed uniformly in the PLA matrix. Compared with pure PLA, the PLA composite with 2 wt% serpentine@APP reduced the peak heat release rate (pHRR) and total heat release (THR) by 43.9% and 16.3%, respectively. The combination of APP and serpentine exhibited suitable synergistic flame-retardant effects on the fire safety enhancement of PLA. In addition, the dynamical rheological tests revealed that the presence of APP and serpentine could reduce the viscosity of PLA composites. The plasticizing effects of APP and serpentine benefited the processing of PLA. The mechanical properties of PLA/serpentine@APP maintained suitable performance as pure PLA. This study provided a feasible way to enhance the fire safety of PLA without sacrificing its mechanical properties.

Intumescent flame retardant finishing for polypropylene nonwoven fabric

This work reports our recent efforts on improving the fire safety of nonwoven polypropylene fabric by increasing surface polarity followed by a conventional finishing. The fabric was firstly surface treated in a surfactant solution containing cetyltrimethylammonium chloride under ultrasonic to increase the hydrophilicity, and then was treated by a pad-dry process with a water solution of ammonium polyphosphate and pentaerythritol. The contact angle of polypropylene fabric treated with 0.2% cetyltrimethylammonium chloride was decreased to 71° from 130° of the control sample. The flammability was evaluated by limiting oxygen index, vertical flammability test, and cone calorimetry test. The limiting oxygen index value was increased to 23.5% from 18.1%, the peak heat release rate was decreased to 159.1 from 292.5 kW/m2, and the melt dripping was completely eliminated by the finishing treatment. Thermogravimetric analysis showed that treated polypropylene fabric samples had higher thermal stability and formed more char residue in high temperature range (above 450 °C) than the control polypropylene sample. The char morphology observation by scanning electron microscopy demonstrated that the treated fabric sample formed continuous char structure without voids, which effectively isolated underlying polypropylene fabric materials from fire and oxygen. It is proposed that decomposition compounds from both cetyltrimethylammonium chloride and ammonium polyphosphate catch free radicals in the gas phase, and the presence of ammonium polyphosphate and pentaerythritol promote char formation in the condensed phase during the burning process of polypropylene fabric.

The flammability and mechanical properties of poly (lactic acid) composites containing Ni-MOF nanosheets with polyhydroxy groups

This work reports our recent effort on the preparation of α-Phenyl-N-(2-propyl-2-hydroxymethyl-1, 3-dihydroxy)-imine-Nickel (Ⅱ) (Ni-MOF) containing polyhydroxy groups and its application in improving the fire performance of PLA composites in combination with ammonium polyphosphate (APP). The flame retardant evaluation revealed that the presence of 1.7% Ni-MOF and 3.3% APP in PLA increased the LOI value to 31.0%, upgraded the UL-94 level to V-0, decreased the peak heat release rate (pHRR), total heat release (THR) and total smoking production (TSP) by 27%, 19% and 50%, respectively, and substantially delayed the time to ignition (TTI) from 67 to 97 s. It was proposed that the flame retardants take effect in both vapor and condensed phases, and Ni-MOF nanosheets can synergistically improve the flame resistance of PLA with APP. The incorporation of Ni-MOF effectively inhibited the deterioration of mechanical properties for PLA composites caused by the presence of APP.

Synthesis of a Carrageenan-Iron Complex and Its Effect on Flame Retardancy and Smoke Suppression for Waterborne Epoxy.

A k-carrageenan–iron complex (KC–Fe) was synthesized by complexation between degraded KC and FeCl3. Furthermore, KC–Fe and ammonium polyphosphate (APP) were simultaneously added into waterborne epoxy (EP) to improve its flame retardancy and smoke suppression performance. The structure and properties of KC–Fe were assessed using Fourier transform infrared spectroscopy (FTIR), ultraviolet (UV) spectroscopy, thermo gravimetric analysis (TGA), and X-ray powder diffraction analysis (XRD). The analysis showed that KC–Fe was successfully synthesized and exhibited good thermal properties with a 49% char residue at 800 °C. The enhanced flame retardancy and smoke suppression performance of waterborne epoxy were evaluated using a limiting oxygen index (LOI) and UL-94. Moreover, the flame retardancy of waterborne epoxy coated on a steel plate was also investigated using cone calorimetry. The results showed that the flame-retardant waterborne epoxy blend exhibited the best flame retardancy when the mass ratio of APP and KC–Fe was 2:1. The total heat release (THR) and total smoke production (TSP) was decreased by 44% and 45%, respectively, which indicated good fire safety performance and smoke suppression properties. Analysis of the residual char using FTIR, SEM, and elemental analysis (EDS) indicated that the action of KC–Fe was promoted by the presence of APP. The formation of a dense thermal stable char layer from an intumescent coating was essential to protect the underlying materials.

Influence of expandable graphite particle size on the synergy flame retardant property between expandable graphite and ammonium polyphosphate in semi-rigid polyurethane foam

Effect of the difference of expandable graphite (EG) particle size on the synergistic flame retardant effect between expandable graphite (EG) and ammonium polyphosphate (APP) in the semi-rigid polyurethane foam (SPUF) was studied for the first time. Three large-span particle sizes of EG were added into SPUF with different mass ratios of EG/APP. The synergistic effect between EG and APP on the flame retardant property of composites was investigated using the limiting oxygen index test, horizontal–vertical burning test, thermogravimetric analysis (TGA), scanning electron microscope (SEM), etc. Flammability performance tests indicated that the larger particle size the EG possessed, the more obvious will be the synergistic effect exhibited between EG and APP. SEM images and TGA results provided positive evidence for the combustion tests. Synergistic effect was strongly influenced by the compactness of united protective layer. The maximal rate of the degradation of the SPUF composite system further confirmed the relationship between the rate of the composites’ degradation and the compactness of united protective layer. Speculative reactions which were related to the changes of EG in the presence of APP under high temperature were discussed.

Study on in-situ polymerization of PANI/APP and its application in HDPE

An organo-inorganic composite material PANI–APP based on conjugated polyaniline (PANI) and ammonium polyphosphate (APP) was prepared by performing in situ polymerization of aniline with ammonium persulfate in the presence of APP, and then it was doped by P-toluene sulfonic acid (PTSA). PANIPTSA–APP was possessed of flame retardancy and electrical conductivity and it was introduced into high density polyethylene for preparing PE/PANIPTSA–APP composites. The structural and morphological properties of PANIPTSA–APP were analyzed by Fourier transform infrared spectroscopy, X-ray diffraction (XRD) and other analyses. The results showed that PANI doped with PTSA was prepared. The electrical conductivity and flame retardancy of PE/PANIPTSA–APP composites were investigated by measuring the electrical resistance and scanning electron microscope, photomicrography, limiting oxygen index (LOI), thermal gravity (TG) and XRD, respectively. Experimental results showed that the LOI of composite reached to 29.2% and the volume resistivity dropped to 6.80 × 108 Ω cm−1 when the amount of PANIPTSA–APP was 30%. The thermal degradation mechanism of PANIPTSA–APP was explored and we found out that PANIPTSA coupled with APP had a positive synergistic effect on the flame retardancy.

The effect of chitosan on the flammability and thermal stability of polylactic acid/ammonium polyphosphate biocomposites

This work reports our recent efforts on introducing chitosan (CS) in association with ammonium polyphosphate (APP) into polylactic acid (PLA) by melt blending to improve the flame retardancy of the biocomposites. The flammability of the composites was characterized by limiting oxygen index (LOI), UL-94 vertical burning test and cone calorimetry test (CONE). The results showed that the PLA sample containing 2% CS and 5% APP achieved the maximal LOI value of 33.1, passed the UL-94 V-0 rating, and decreased the peak heat release rate to 425.6kW/m2. The morphology characterization of char residue by scanning electron microscope indicated a dense, homogeneous and continuous residue char could be formed by the presence of APP and CS in PLA. Fourier transform infrared spectroscopy and thermal gravity analysis suggested that CS could act as a novel carbon agent owning to its high content of carbon atoms and multi-hydroxyl groups, and the interaction between CS and APP could provide synergistic effects in improving the flame retardancy of PLA biocomposites. X-ray diffraction and differential scanning calorimetry results demonstrated that the presence of APP and CS could promote the crystallization of PLA.

Silica Treatments: A Fire Retardant Strategy for Hemp Fabric/Epoxy Composites.

In this paper, for the first time, inexpensive waterglass solutions are exploited as a new, simple and ecofriendly chemical approach for promoting the formation of a silica-based coating on hemp fabrics, able to act as a thermal shield and to protect the latter from heat sources. Fourier Transform Infrared (FTIR) and solid-state Nuclear Magnetic Resonance (NMR) analysis confirm the formation of –C–O–Si– covalent bonds between the coating and the cellulosic substrate. The proposed waterglass treatment, which is resistant to washing, seems to be very effective for improving the fire behavior of hemp fabric/epoxy composites, also in combination with ammonium polyphosphate. In particular, the exploitation of hemp surface treatment and Ammonium Polyphosphate (APP) addition to epoxy favors a remarkable decrease of the Heat Release Rate (HRR), Total Heat Release (THR), Total Smoke Release (TSR) and Specific Extinction Area (SEA) (respectively by 83%, 35%, 45% and 44%) as compared to untreated hemp/epoxy composites, favoring the formation of a very stable char, as also assessed by Thermogravimetric Analysis (TGA). Because of the low interfacial adhesion between the fabrics and the epoxy matrix, the obtained composites show low strength and stiffness; however, the energy absorbed by the material is higher when using treated hemp. The presence of APP in the epoxy matrix does not affect the mechanical behavior of the composites.

Evaluating the heat resistance of thermal insulated sandwich composites subjected to a turbulent fire

SummaryThe fire structural response of sandwich composite laminates incorporating bio‐derived constituents subjected to a turbulent flaming fire was investigated. Fire structural tests were conducted on thermal insulated sandwich composites incorporating a thin surface‐bonded non‐woven glass fibre tissue impregnated with char‐forming fire retardant, ammonium polyphosphate. The sandwich composite laminates were loaded in compression at 10%, 15% or 20% of the ultimate compressive strength while simultaneously subjected to turbulent flames imposing an incident heat flux of 35 kW/m2. Generally, the failure time increased with the reduced applied compressive load. The thermal insulated sandwich composite laminates had considerably improved fire resistance in comparison to their unmodified counterparts. The unmodified composites failed 96 s earlier than the thermal insulated specimens when the compression load was 10% of the ultimate compressive strength. The presence of ammonium polyphosphate at the heat‐exposed surface promoted the formation of a consolidated char layer, which slowed down heat conduction into composite laminate substrate. The fire reaction parameters measured via the cone calorimeter provided insights into the thermal response hence fire structural survivability of sandwich composite laminates. Copyright © 2015 John Wiley & Sons, Ltd.

Thermal volatilisation analysis of a TDI-based flexible polyurethane foam containing ammonium polyphosphate

In this paper, we report a comprehensive study on a TDI-based foam containing 13% ammonium polyphosphate (APP) in order to examine the effect that this conventional fire retardant has on the thermal and thermo-oxidative degradation behaviour of the polyurethane foam. The results from TVA and TGA analyses show that the APP foam undergoes a significantly different degradation mechanism to the standard foam that we have reported on previously. The TGA results revealed the presence of a two-stage degradation process under a non-oxidative environment. The TVA results, on the other hand, revealed that degradation of the APP foam in fact occurs in four overlapping steps compared to the two-step process which occurs for the standard foam. The additional degradation steps observed for the APP foam are proposed to correspond to degradation of the fire retardant. Evolution of volatile material was also observed to occur at a lower temperature for the APP foam and it is proposed that the primary degradation of the urethane linkages via a depolycondensation reaction is acid-catalysed by the acidic hydroxyl groups which arise from degradation of APP. The sub-ambient differential distillation trace revealed that the nature and distribution of the volatiles evolved from the APP foam were profoundly different to the standard foam, which confirms that the secondary degradation is also altered in the presence of APP.

Polymer/clay aerogel composites with flame retardant agents: Mechanical, thermal and fire behavior

Aerogel is a class of material characterized by its high void content and extreme lightness. Different polymer/clay aerogels have been prepared by a simply freeze–thaw process from a suspension with poly(vinyl alcohol) (PVOH) and clay (Na+-MMT). Low density polymer/clay aerogels modified with flame retardant agents were prepared using a similar approach. The addition of flame retardant agents slightly increased the apparent density of the final composites whereas the compression properties were reduced due to the decrease in the polymer/clay interfacial bonding. An exception was the sample containing Al(OH)3 that exhibited higher modulus and stress at maximum deformation. Regarding thermal properties, the presence of ammonium polyphosphate (APP) or silica gel (SG) significantly slowed the rate of aerogel decomposition at the temperature range from 250°C to 500°C while the onset of polymer decomposition was not affected. Fire behavior was analyzed through cone calorimeter suggesting that either the presence of Al(OH)3 or APP reduced the heat release rate of PVOH/clay systems.

Flammability Characteristics and Performance of Flame-Retarded Epoxy Composite Based on Melamine Cyanurate and Ammonium Polyphosphate

The flammability characteristics and thermal performance of epoxy compounds containing ammonium polyphosphate (APP) and melamine cyanurate (MCA) were studied by LOI, UL-94, TG, FTIR and SEM. The compounds containing 12 wt% APP and 3 wt% MCA can pass V-0 in the UL-94 test, while neat EP can't pass any rating. The SEM images show that dense and compact multicellular char residues are produced on the surface of the test bars after combustion, while Fourier transform infrared spectra confirm a phosphorus char resulting from the presence of APP and MCA. TGA results illustrate that the thermal stability of EP/4APP:MCA at high temperature was noteworthy and leaves about 17.1% residue at 800°C. The use of APP together with MCA is better than using either APP or MCA alone.

Synthesis of aromatic–aliphatic polyamide acting as adjuvant in polylactic acid (PLA)/ammonium polyphosphate (APP) system

A potential adjuvant for polylactic acid (PLA)/ammonium polyphosphate (APP) system, a novel polyamide (PA) containing aromatic and aliphatic groups, was synthesized from a polycondensation reaction of adipic acid with 4,4-diaminodiphenyl sulphone. The synthesized PA was characterized by Fourier transform infrared spectra (FTIR), nuclear magnetic resonance (1H NMR, 13C NMR), size exclusion chromatography (SEC) and thermogravimetric analysis (TGA), respectively. As a potential adjuvant, this PA has been used in a PLA system combined with and without APP in order to investigate the flame retardancy. The flammability of PLA and PA are studied by microscale combustion calorimeter (MCC). The flame retardant properties and thermal decomposition behaviors of PLA-PA composites were investigated by cone calorimeter test (CCT) and TGA, respectively. In the presence of APP, in some extent PA shows a synergistic effect on improving the flame retardancy of PLA composites at the fixed mass ratio 2:1 of APP and PA, reflecting delayed time to ignition (TTI) and slight decrease in the peak heat release rate (pHRR) in the cone calorimeter test. In order to further improve the flame retardancy, 1wt% clay was introduced to the PLA-PA-APP system while the total loading of additives kept at 15 wt%. The results of PLA-PA-APP-clay composite from cone calorimeter test showed significant decrease in heat release rate (HRR), total heat release rate (THR) and total smoke release (TSP).

Effect of phosphorous flame retardants on the thermal decomposition of vinyl polymers and copolymers

The effect of ammonium polyphosphate (APP) and tris(2,4-di- ter-butylphenyl)phosphite (TBP) flame retardants and polyphosphoric acid (PPA) was examined on the thermal decomposition reactions of polystyrene (PS), styrene-acrylonitrile copolymer (SAN), acrylonitrile-butadiene-styrene copolymer (ABS) and polyacrylonitrile (PAN) by pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) and thermogravimetry (TG) techniques. The effect of APP and PPA proved to be significant on the thermal decomposition of polymers investigated. The char formation from each polymer-APP and polymer-PPA mixture increases considerably. The thermal stability of PS increases in the presence of APP and PPA by 17 and 28 °C, respectively. Analogous and significant changes were observed in the pyrolysis product distribution of PS, SAN and ABS in the presence of APP and PPA, indicating, that the polyphosphoric residue of APP modifies the thermal decomposition mechanisms of these polymers even during fast pyrolysis when the chemical processes take place simultaneously. The presence of PPA promotes hydrogen shifts resulting in isomerisation and formation of indene compounds from PS, moreover, development of a conjugated ladder structure from PAN chain even during fast pyrolysis. This is the first time that a GC/MS evidence can be presented directly confirming the first step of carbonization reaction of PAN. The results also give an insight into the influence of PPA on the electron donating ability of phenyl side groups having a significant effect on the thermal decomposition product distribution of PS and styrene copolymers.

Flame retardancy of polyisocyanurate–polyurethane foams: use of different charring agents

The influence of different charring agents on physical-mechanical properties and fire behaviour of polyisocyanurate–polyurethane (PIR–PUR) foams has been investigated. In particular the use of varying amounts of ammonium polyphosphate, melamine cyanurate and expandable graphite has been analysed; all, when involved in fire, lead to the formation of a char layer on the polymer surface, but their ways of flame retardancy are different. The results obtained show that the higher the filler content the lower the compression strength; in particular the worst results have been obtained in the presence of melamine cyanurate. Moreover, the presence of ammonium polyphosphate or melamine cyanurate causes any significant worsening on thermal conductivity, while expandable graphite leads to a quite marked increase of the thermal conductivity. The fire behaviour has been studied by means of cone calorimeter apparatus and oxygen index test; it has been observed that the best results, i.e. the lowest rate of heat release and the highest oxygen index, are achieved with expandable graphite. Also the ammonium polyphosphate brings slight improvement in fire behaviour, whereas the effect of melamine cyanurate is negligible.

Mechanism of fire retardancy of polyurethanes using ammonium polyphosphate

AbstractIn this work, we studied the mechanism of the fire retardancy of ammonium polyphosphate (APP) in polyurethane (PU). Indeed, according to the limiting oxygen index test, the efficiency of APP in PU coating was proven. On the one hand, thermogravimetric analyses showed that the addition of APP to PU accelerates the decomposition of the matrix but leads to an increase in the amount of high‐temperature residue, under an oxidative or inert atmosphere. This stabilized residue acts as a protective thermal barrier during the intumescence–fire retardancy process. On the other hand, spectroscopic analysis of the charring materials using infrared spectroscopy, MAS NMR of the solid state, and ESR enables better understanding of the carbonization process and, consequently, of the intumescence phenomenon. It has been shown that the char resulting from PU consists of an aromatic carbonaceous structure which condenses and oxidizes at high temperature. In the presence of APP, a reaction between the additive and the polymer occurs, which leads to the formation of a phosphocarbonaceous polyaromatic structure. Moreover, this char is strongly paramagnetic. The presence of large radical species, such as a polyaromatic macromolecule trapping free radicals, was demonstrated. Both of these characteristics help to explain the fire‐retardant performance of PU/APP. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 3262–3274, 2001

Diode Laser Measurements of HF Concentrations Produced from Heptane/Air Pan Fires Extinguished by FE-36, FM-200, FE-36 Plus APP, or FM-200 Plus APP

Tunable diode laser absorption spectroscopy (TDLAS) is used to measure the time evolution of hydrogen fluoride (HF) concentrations produced from a series of enclosed heptane/air pan fires extinguished by either FE-36, FM-200, FE-36 plus ammonium poly-phosphate (APP), or FM-200 plus APP. For the fires studied, the change in HF gas concentration with time is dependent upon the fire-fighting chemical used to extinguish the re. The presence of APP is observed to reduce HF concentrations in the re enclosure. Visible attenuation spectroscopy is also used to measure the amount of light attenuation (obscuration) that occurs as a hand-held re extinguisher containing powdered fire fighting agent is released in the crew space of a M1-Abrams land combat vehicle.

Effect of the fire-retardant ammonium polyphosphate on the thermal decomposition of aliphatic polyamides. Part III—Polyamides 6.6 and 6.10

Polyamides 6.6 (PA-6.6) and 6.10 (PA-6.10) decompose on heating by scission of the N-alkylamide bond (CH 2NHCO), with the formation of vinyl chain ends and primary amide groups which dehydrate to nitriles at the temperature of degradation. In PA-6.6 scission of the alkylamide bond (CH 2CONH) also takes place, resulting in methyl and isocyanate chain ends which can further dimerize to carbodiimides with elimination of CO 2 or trimerize to isocyanurate structures. In the presence of ammonium polyphosphate (APP), flammability, as measured by oxygen index, decreases because APP induces intumescent behaviour. The chemical interaction between APP and PA-6.6 and PA-6.10 leads to chain scission of the polyamide, with formation of a primary amide group and a phosphate ester which thermally degrades to give a vinyl chain end. APP also catalyses the alkylamide bond scission in PA-6.6. The intumescent behaviour might be due to blowing of the thermally stable polyphosphoric acid layer on the surface of the material by the gases evolved by the degradation of the polyamides, which occurs at lower temperature in the presence of APP.

Primary thermal degradation mechanisms of PET and PBT

The primary thermal degradation mechanisms of polyethyleneterephthalate (PET) and polybutyleneterephthalate (PBT) have been studied by direct pyrolysis mass spectrometry using negative chemical ionization (NCI). The NCI mass spectra of PET and PBT are dominated by series of ions which might be assigned either to cyclic or open-chain oligomers with olefin and carboxylic end-groups. The structures of the pyrolysis products have been identified by comparison of their daughter ion spectra with those of authentic samples of cyclic and open-chain oligomers with olefin and carboxyl end-groups. The authors' results provide strong evidence that cyclic oligomers are the primary pyrolysis products of PET and PBT, formed by intramolecular exchange (ionic) reactions. These further decompose by a β-CH hydrogen transfer reaction, which involves a six-membered cyclic transition state, and generates open chain oligomers with olefin and carboxylic end-groups. The pyrolysis of PET and PBT was also carried out in the presence of ammonium polyphosphate (APP) (an acid precursor). APP affects the pyrolysis by increasing the rate of decomposition and lowering the Polymer Decomposition Temperatures (PDT)s of both polymers. However, it does not change the nature of the compounds obtained in the pyrolysis of the pure polymers. This fact provides a firm argument in favour of the belief that the β-CH hydrogen transfer occurs by an ionic process.