Combustion Calorimeter Research Articles

Flame retardant PP/PA6 blends: A recipe for recycled wastes

AbstractDisposal of plastics in the form of discarded scrap or waste is an environmental nightmare to the developed and under-developing countries. In this sense, modern technologies are every day growing; meanwhile recycling wastes are taking credit for higher performance to pave the way towards a cleaner planet. Recycling of polymer blends is associated with serious complexities in finding appropriate additives acting in each phase or at the interface of non-miscible polymers to attain materials with higher properties. A flame retardant system was designed and intended to play the role of typical recycled flame retardant polypropylene/polyamide (PP/PA6) blends by incorporation of two kinds of talc, sepiolite, and a phosphorus-based flame retardant. First, two types of talcs having different physical properties were added to PA6 in combination with melamine cyanurate (MC) or melamine pyrophosphate (MPP) to find the one acting as a barrier during combustion. Then, high-aspect-ratio talc that appeared more effective in the first-stage survey was then used in combination with MC, MPP and ammonium polyphosphate (APP) together with a compatibilizer for PP/PA6 blend. Then, thermogravimetric analysis (TGA), microcalorimeter of combustion (PCFC) and cone calorimeter measurements were performed to study thermal degradation and flammability behavior. The results are indicative of successful formulation of flame retardant system containing the aforementioned precursors to be intended to the recycled PP/PA6 blends.

Design and characterization of flame resistant blended nondrip PA6/Lenzing FR®/PBI fiber nonwoven fabrics

AbstractIn current thermal protective clothing systems, maximizing the personal protection performance against fire and heat is in great demand. Additionally, minimizing the manufacturing cost by using low-cost materials is also a critical factor. In previous studies [1–3], a new type of low-cost inherently flame resistant (FR) non-drip Polyamide 6 (PA6) nanocomposite fiber was developed. In this paper, this FR non-drip PA6 fiber was tested in blends with two commercially available inherently FR fibers to form FR nonwoven fabrics. Different formulations of varying blending ratios were processed into nonwoven fabrics. The fiber morphology was observed by Scanning Electron Microscopy (SEM). The fabric flammability and combustion properties were characterized using a Microscale Combustion Calorimeter (MCC), and a vertical flame tester, as well as Thermogravimetric Analysis (TGA). Tensile tests were conducted to characterize mechanical properties of these FR nonwoven fabrics. The water vapor permeability test was also performed to measure the wearability of the fabric. Results of several nonwoven blends were compared to find the one with optimum blend ratio which has the potential to be used as low-cost thermal protective fabric.

Rubber toughened flame retardant (FR) polyamide 11 nanocomposites Part 2: synergy between multi-walled carbon nanotube (MWNT) and MMT nanoclay

AbstractIn the previous study, flame retardant (FR) polyamide 11 (PA11) nanocomposites formulations designed for selective laser sintering (SLS)were prepared and characterized. The SEBS-g-MA elastomer successfully improved the material’s ductility. Although the nonhalogenated FR additives and montmorillonite (MMT) nanoclay successfully decreased the heat release capacity (HRC) and peak heat release rate (pHRR) as characterized by microscale combustion calorimeter (MCC). None of the rubber toughened formulations achieved UL 94 V0 rating, which is a bench mark for many FR polymer applications. As part two of this study, we explored the synergism between two nanoparticles, nanoclay and multi-walled carbon nanotubes (MWNTs), to see whether better FR properties can be achieved. TEM micrographs indicate that both nanoclay and MWNTs achieved high level of dispersion. Flammability results showed that all formulations achieved UL 94 V0 rating, which is a significant improvement from the previous formulations without MWNTs. Char morphology characterization indicated that a solid carbonaceous char layer was reinforced by nanoclay and MWNTs.

Enhanced flame retardancy and smoke suppression of polypropylene by incorporating zinc oxide nanowires

In this work, zinc oxide (ZnO) nanowires were prepared via hydrothermal method. They were added into polypropylene (PP) with different mass fractions by melt blending method. Thermal stability of ZnO nanowires/PP nanocomposites was investigated through thermogravimetric analysis (TGA). The flame retardant and smoke suppression performances of the nanocomposites were characterized by microscale combustion calorimeter (MCC) and smoke density tester, respectively. The results showed that the prepared ZnO nanowires/PP nanocomposites possessed good thermal stability, flame retardant and smoke suppression performances. With the 30 wt% addition of ZnO nanowires, the onset degradation temperature (Td5) and maximum weight loss temperature (Tmax) of nanocomposite were increased by 34.6 °C and 20.8 °C compared to pure PP. The peak heat release rate (PHRR) and total heat release (THR) of nanocomposite were decreased by 36.0% and 37.8% in comparison to pure PP. Moreover, the maximum smoke density (MSD) of nanocomposites was reduced by 53.9% compared to pure PP. Lastly, the flame retardant and smoke suppression mechanisms of ZnO nanowires were analyzed according to the morphology of the char layer and calculation of activation energy.

Innovative Approach to Flame Retardant Cotton Fabrics with Phosphorus Rich Casein via Layer-by-Layer Processing

Flame retardant behaviour was imparted using the layer-by layer assemblies of phosphorus rich casein milk protein with eco-friendly inorganic chemicals on cotton fabrics. The cotton twill fabrics were prepared using two solutions; a mixture of positively charged branched polyethylenimine (BPEI) with urea and diammonium phosphate (DAP), and negatively charged casein. Layer-by-layer assemblies for flame retardant properties were applied using the pad-dry-cure method, and each coating formula was rotated for 20 bi-layers. The effectiveness to resist flame spread on treated fabrics was evaluated using vertical (ASTM D6413-08) and 45° angle flammability test (ASTM D1230-01) methods. In most case, char lengths of fabrics that passed the vertical flammability tests were less than 50% of the original length, and after-flame and after-glow times were less than one second. Thermal properties were tested the extent of char produced by untreated and treated fabrics at 600°C by thermogravimetric analysis (TGA). Micro-scale combustion calorimeter (MCC) and Limiting oxygen indices (LOI, ASTM D2863-09) were also assessed. All untreated fabrics showed LOI values of about 21% oxygen in nitrogen. LOI values for the treated casein with BPEI/urea/DAP fabrics were greater than 29-34% between 5.80-9.59 add on wt%. Their structural characterizations were revealed by TGA/FT-IR and SEM methods. The treated fabrics exhibited improved thermal stability, as evidenced by increased ignition times and lower heat release rates. The results of this study show that flame retardant nanocoatings can be readily applied to textile fabrics using a continuous process that is ideal for commercial and industrial applications.

Regioselective ring-opening metathesis polymerization of limonene oxide-substituted cyclooctene: The highly functional ethylene/vinyl ester copolymers

We present a new cyclooctene monomer with abundant biorenewable limonene oxide as side group via simple esterification, which could be polymerized by ring-opening metathesis polymerization (ROMP) using Hoveyda-Grubbs second-generation catalyst (H2) to afford polymer with remarkably high head-to-tail regioregularity and high trans-stereoregularity, as well as precisely placed ether branches on every eighth backbone carbon. Due to the presence of easily functional oxirane in limonene oxide side chain, the polymer can be efficiently modified by thiol, or dibutyl phosphate that shows impart flame-resistant property, even bearing pendent cyclic carbonate groups by CO2 insertion catalyzed by tetrabutylammonium bromide. In all cases, the main chains of the polymer remain intact. Differential scanning calorimetry (DSC), thermal gravimetric analyzer (TGA) and the microscale combustion calorimeter test (MCC) were used to study the thermal properties and flame retardancy.

Thermodynamic investigation of l-carnitine

In the present work temperature dependence of heat capacity of l-carnitine has been measured for the first time over the range from 6 K to 346 K by precision adiabatic vacuum calorimetry. Based on the experimental data, the thermodynamic functions of the l-carnitine, namely, the heat capacity , enthalpy H°(T) − H°(0), entropy S°(T) − S°(0) and Gibbs function G°(T) − H°(0) have been determined for the range from T → 0 to 350 K. The value of the fractal dimension D in the function of multifractal generalization of Debye’s theory of the heat capacity of solids was estimated and the character of heterodynamics of structure was detected. Enthalpy of combustion (−4142.1 ± 2.3) kJ mol−1 of the l-carnitine was measured for the first time using high-precision combustion calorimeter. The standard molar enthalpy of formation in the crystalline state (−756.2 ± 2.5) kJ mol−1 of l-carnitine at 298.15 K was derived from the combustion experiments. Using combination of the adiabatic and combustion calorimetry results the thermodynamic functions of formation of the l-carnitine at T = 298.15 K and p = 0.1 MPa have been calculated. The low-temperature X-ray diffraction was used for the determination of coefficients of thermal expansion.

The synergistic effects of a novel intumescent flame-retardant poly-(4-nitrophenoxy)-phosphazene and ammonium polyphosphate on ABS systems

Novel intumescent flame retardancy acrylonitrile–butadiene–styrene (ABS) composites were prepared by adding poly-(4-nitrophenoxy)-phosphazene (DPP) as charring and inflate agent, and ammonium polyphosphate (APP) as acid and inflate agent. The flame-retardant properties of samples were studied by LOI, UL-94 and microscale combustion calorimeter (MCC), when the ratio of APP and DPP was 1:1 with 30 mass% additive amount, the LOI was 27%, and the UL-94 reached V-0 rating. To further study the synergistic effects of DPP and APP, the charring-forming capability and thermal behavior of ABS composites were extensively studied by thermogravimetric analysis (TGA) under nitrogen and air, respectively. Also the binary system of APP and DPP was investigated by TGA measurements to identify their reaction and the synergistic mechanisms. The char residues were studied by X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) analysis and Fourier transform infrared (FTIR). Meanwhile, the gaseous products generated in degradation process were detected by thermogravimetric analysis coupled Fourier transform infrared (TGA/FTIR).

Microwave Assisted Preparation of Flame Resistant Cotton Using Economic Inorganic Materials

Innovative approaches for preparing flame retardant cotton fabrics were employed by utilizing a microwave-assisted technique with a minimum amount of co-solvent. Our attempts at flame retardant cotton fabrics treated with low cost inorganic formulations, such as urea and diammonium phosphate, were done successfully. The evidence of flame retardant chemical penetrations or surface modification of cotton fabrics was confirmed by scanning electron microscope (SEM) and the treated cotton fabrics were evaluated by flammability tests, such as 45° angle (clothing textiles test), vertical flame (clothing textile test) and limiting oxygen index (LOI). For formulations with urea only, LOI values of treated fabrics were 21.0–22.0% after add-on values for the formulation were 5.16–18.22%. For formulations comprising urea with diammonium phosphate, LOI values were greater than 29.0% after add-on values for the formulation were 1.85–7.73%. With the formulation comprising urea and diammonium phosphate, all treated fabrics passed the vertical flame test for add-on values 5.34–7.73%. Their char lengths were less than half the length of the original fabric and after-flame and after-glow times were less than 3.2 s. Additional thermal properties of desired products will be discussed using thermogravimetric analysis (TGA) and microscale combustion calorimeter (MCC).

Synergetic enhancement of mechanical and fire-resistance performance of waterborne polyurethane by introducing two kinds of phosphorus–nitrogen flame retardant

In this work, a novel hydroxyl-terminated monomer containing phosphorus and nitrogen, tri(N, N-bis-(2-hydroxy-ethyl) acyloxoethyl) phosphate (TNAP), was synthesized successfully with phosphorus oxychloride, hydroxyethyl acrylate, and diethanolamine as raw materials, and then incorporated into flame-retarded waterborne polyurethanes to improve their flame retardancy, thermal behavior, and mechanical properties. Their structures were confirmed by nuclear magnetic resonance (NMR) and fourier transform infrared spectroscopy (FTIR). Besides, the thermal performance and combustion behaviors of crosslinked flame-retarded waterborne polyurethane (CFRWPU) films were evaluated through thermogravimetric analysis (TGA), thermogravimetry-FTIR, limiting oxygen index (LOI) tests, and microscale combustion calorimeter tests (MCC). Additionally, the mechanical properties were investigated by tensile stress–strain tests. These results revealed that the monomer TNAP exhibited remarkable residual char formation ability of 34.98 wt% and that TNAP-embedded FRWPU films attained an LOI value of 25.5% at a TNAP content of 4 wt%. Moreover, there was significant enhancement in tensile strength (15.81 MPa) obtained with the combined incorporation of TNAP into FRWPU. Also, scanning electron microscopy (SEM) and energy dispersive spectrometry (EDS) provided the morphologies and the element distributions of char residues of CFRWPU after LOI tests. Finally, the thermal mechanical properties of CFRWPU were assessed by dynamic mechanical analysis (DMA).

Heat release and flame spread assessment of insulation in External Thermal Insulation Composite System (ETICS) façades

External Thermal Insulation Composite Systems (ETICS) represent a popular modern façade for reducing energy consumption, particularly in retrofit applications. Insulation – typically in the form of either EPS (expanded polystyrene) or mineral wool – is applied to the exterior of buildings using mortar adhesive, and then coated with a final layer of sand-cement render and glass fibre reinforcement. The materials are relatively cheap, and the labour can be easy and inexpensive compared to other solutions.The system does however mean that highly flammable EPS insulation is protected by only a thin layer of render, normally 3–8mm. The addition of this combustible material to the façade of the building represents a change in the fire risk, as the typical fire safety strategy involving compartmentation does not anticipate vertical fire spread on the exterior of a building. It is therefore necessary to characterise the fire risk, and ensure that an optimal fire barrier – namely, the render layer – is defined adequately.In this work, the insulation component of an EPS ETICS façade is tested using micro- to small-scale methodologies. The objective of this is to characterise some of the fundamental thermal material properties, ignitability, heat release, and flame spread of the specific components. The aim is to then extend this to a larger-scale methodology for testing of complete systems, which will be complemented by numerical modelling to enable scaling. Previous attempts at testing ETICS in a small-scale have been largely unsuccessful, and efforts have pointed to large-scale apparatuses – generally 4–8m high – as the only viable solution at present. These are however expensive and time consuming, and deliver little information on how the façade performs. Testing is especially problematic for EPS, which melts and shrinks at low temperatures, leading to difficulties in attempting to extract global flammability properties.MCC (Microscale Combustion Calorimeter) testing has been performed to benchmark the different EPS insulation that can be used in buildings. It is found that black EPS containing expanded graphite used in façades has substantially improved performance compared to ordinary white EPS used as building insulation. The peak heat release was reduced from 1160 W g−1 down to 490–740 W g−1, occurring at a temperature of 430–440 °C. An extra additive to improve the moisture performance of the system also enhances the fire performance slightly by reducing the heat release further.Previous attempts of testing ETICS and EPS using LIFT (Lateral Ignition and Flame spread Test) have in many cases been unproductive. For this experimental series, a sheet of paper has been applied to the surface of the first 100 mm of EPS in order to force ignition. Results for the flame spread velocity near to ignition have then been discarded to minimise the influence of this method. Flame spread results for the white EPS were not satisfactory due to the fact that the flame spread velocity had a weak dependence on the incident heat flux, and that that minimum critical heat flux for flame spread was 0.0 kW m−2, that is, no external energy was required to sustain burning. For black EPS specimens, the addition of the expanded graphite was effective in improving the flame spread performance. The minimum heat flux for flame spread was increased to 0.75–1.09 kW m−2, and the velocity was sufficiently moderate that a reasonable value for the flame spread modulus could be obtained.In future, attempts will be made to correlate the flame spread results of these individual EPS products to the flame spread as part of a complete ETICS façade. This would then provide a more meaningful method to compare different ETICS solutions as a first step without the need for expensive large-scale testing during the main development phase of systems.

Some Key Factors Influencing the Flame Retardancy of EDA-DOPO Containing Flexible Polyurethane Foams.

The role of various additives (emulsifier, anti-dripping agent) and formulation procedures (pre-dispersion of solid additives in polyol via milling) which influence the flame retardancy of 6,6′-[ethan-1,2-diylbis(azandiyl)]bis(6H-dibenzo[c,e][1,2]oxaphosphin-6-oxid) (EDA-DOPO) containing flexible polyurethane foams has been investigated in this work. For comparison, the flame retardancy of two additional structurally-analogous bridged 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO)-based compounds, i.e., ethanolamine-DOPO (ETA-DOPO) and ethylene glycol-DOPO (EG-DOPO) were also evaluated together with EDA-DOPO in flexible PU foams of various formulations. The flame retardancy of these three bridged-DOPO compounds depends on the type of PU formulation. For certain PU formulations containing EDA-DOPO, lower fire performance was observed. Addition of emulsifier and polytetrafluoroethylene (PTFE) to these PU formulations influenced positively the flame retardancy of EDA-DOPO/PU foams. In addition, dispersion of EDA-DOPO and PTFE via milling in polyol improved the flame retardancy of the PU foams. Mechanistic studies performed using a microscale combustion calorimeter (MCC) and its coupling to FTIR showed no difference in the combustion efficiency of the bridged-DOPO compounds in PU foams. From MCC experiments it can be concluded that these bridged-DOPO compounds and their decomposition products may work primarily in the gas phase as flame inhibitors. The physiochemical behavior of additives in PU formulation responsible for the improvement in the flame retardancy of PU foams was further investigated by studying the dripping behavior of the PU foams in the UL 94 HB test. A high-speed camera was used to study the dripping behavior in the UL 94 HB test and results indicate a considerable reduction of the total number of melt drips and flaming drips for the flame retardant formulations. This reduction in melt drips and flaming drips during the UL 94 HB tests help PU foams achieve higher fire classification.

Sensitivity analysis on the microscale combustion calorimeter for polyurethane foam using a full factorial design methodology

A sensitivity analysis on test outcomes from the microscale combustion calorimeter was performed using flexible polyurethane foam as the sample material. Three input factors were investigated: sample preparation, heating rate and pyrolysis chamber atmosphere. The experiments were setup according to the principles of design of experiments and a full factorial design was implemented. In total, 39 experiments were performed as part of this study: 27 unique tests and 12 repeat experiments. Results from the microscale combustion calorimeter showed excellent repeatability in most cases. Sample inhomogeneity was suggested as a possible explanation for the variation observed. A statistical analysis was performed to quantitatively assess how each input factor affected the test results. Analysis showed that all three factors had some effect on the test outcomes, with heating rates and pyrolysis chamber atmosphere proving to be the most influential in regard to the analysed output quantities. Increasing the heating rate from 15 to 180°C/min illustrated the effects of thermal lag, increasing the temperatures at which the sample reactions took place. Interaction effects between input parameters were also observed. The pyrolysis chamber atmosphere, either inert or oxidative, was observed to have the largest effect on the tested output parameters. The energy release was observed to decrease with the introduction of 20% oxygen. Increasing the oxygen levels also produced a drop in the peak reaction temperatures; this was consistent for all tested atmospheres (from 0% to 10% and 10% to 20% oxygen). This study illustrated that outcomes from this apparatus, for materials such as flexible polyurethane foam, can be dependent on sample preparation as well as heating rate and testing atmosphere. In addition, it highlights the importance of apparatus characterisation for less homogeneous materials to understand how input factors choices can influence the outcomes of the tests performed.

Thermochemical Properties of Ph4Sb(OC(O)C10H15) and Ph3Sb(OC(O)C10H15)2

The energy of combustion of crystalline adamantanecarboxylate of tetraphenylantimony and triphenylantimony bis(1-adamantanecarboxylate) is determined at 298.15 K using a combustion calorimeter with a static bomb. The combustion enthalpies of these substances in the crystalline state at 298.15 K are calculated using the obtained experimental data. Such standard functions of formation as ΔfH° and ΔfG° are calculated for the studied compounds in the crystalline state at 298.15 K. The obtained thermochemical properties are analyzed, and their dependences on the molar mass of the substituent with antimony are determined.

Imidazolium based ionic liquids containing methanesulfonate anion: comprehensive thermodynamic study

New experimental vapor pressures and vaporization enthalpies of the ionic liquids [Cnmim][CH3SO3] (with the alkyl chain length n=2, 3 and 4) have been measured by the QCM and TGA methods. Energies of combustion of [C2mim][CH3SO3] and [C4mim][CH3SO3] were measured in a high-precision rotating-bomb combustion calorimeter and used for calculation the aqueous enthalpy of formation of the ΔfHmo(CH3SO3aq−)anion. The solubility parameters of ILs under study have been derived from experimental ΔlgHmo(298.15K) and used for estimation of miscibility of some common solutes in [Cnmim][CH3SO3]. This comprehensive thermodynamic study will facilitate chemical engineering calculations of processes involving ionic liquids.

Diphase flame‐retardant effect of ammonium polyphosphate and dimethyl methyl phosphonate on polyisocyanurate‐polyurethane foam

Building energy consumption is an important component in the total social energy consumption. How to reduce building energy consumption became an important issue in today's society. Therefore, building insulation materials, as a kind of effective energy saving method, has been widely used for the external walls. However, the occurrence of many building fires caused by the ignition of the flammable insulation materials has brought serious damage to people. Consequently, it is significant to develop insulation materials which possess high level of fire safety. The aim of this study was to develop high efficient phosphorus‐based flame‐retardant system for polyisocyanurate‐polyurethane (PIR‐PUR) foam. Ammonium polyphosphate (APP) was used as condensed phase flame retardant and dimethyl methylphosphonate (DMMP) were used as gas phase flame retardant for preparing flame‐retardant PIR‐PUR foam. The flame retardancy, thermal decomposition, and combustion behaviors of PIR‐PUR foams were evaluated by limiting oxygen index (LOI) test, vertical burning test, thermogravimetric analysis, cone calorimeter test (Cone), and microscale combustion calorimeter test, respectively. The LOI results showed that the PIR‐PUR sample simultaneously containing APP and DMMP possessed higher flame retardant efficiency, which indicated that APP and DMMP possessed synergistic flame‐retardant effect in PIR‐PUR foam. Cone results indicated that the presence of DMMP can delay the ignition of specimen and delay the time to reach the maximal peak heat release rate. Moreover, the mechanical performance and thermal insulating properties were evaluated, respectively.

Generalized regression and feed forward back propagation neural networks in modelling flammability characteristics of polymethyl methacrylate (PMMA)

The capability of artificial neural networks in predicting microscale combustion calorimeter (MCC) parameters of polymethyl methacrylate (PMMA) was carried out in this study. Using values of sample mass and corresponding heating rate, feed forward back propagation (FFBP) and generalized regression neural network (GRNN) models were developed to predict MCC parameters. On the whole, GRNN outperformed FFBP in predicting HRC data while FFBP model saw an improvement over GRNN when estimating pTime. It was also discovered that GRNN obtained better THR, pTemp and pHRR predictions during training but generated a relatively poor correlation when estimating the testing data. Sensitivity analysis on the ANN models revealed that heating rate had a more significant effect on the models’ outcome. Also, the ANN models observed the least error deviation when compared with HRC results for PMMA from structure-property models. Hence, ANN presents a reliable method for predicting flammability characteristics of PMMA from MCC test.

Preparation, flame retardancy, and thermal and mechanical properties of polyurethane containing phosphonated bisphenol‐A units

SummaryA novel phosphonated bisphenol‐A glycol (3001‐OH) was synthesized by the ring opening reaction between α,ω‐phenol‐terminated aromatic polyphosphonate and propylene oxide. 3001‐OH was then incorporated into polyurethanes (PUs) as soft segments, and the effects of 3001‐OH on the flame retardancy and thermal and mechanical properties of PUs were investigated. The tensile strength and Young modulus of PUs are improved with the incorporation of 3001‐OH into the PUs. With the increase of 3001‐OH content in the PUs, the glass transition temperature of the soft segments increases, and the phase separation degree between the hard and soft segments decreases. The limiting oxygen index values of PUs increase from 23.1% to 29.6%, while total heat release values from micro‐scale combustion calorimeter decrease from 24.3 to 21.5 kJ g−1. And the PUs containing phosphorus element successfully met UL‐94 V‐0 rating requirements. The thermal degradation behaviors and flame retardant mechanism of 3001‐OH were studied by thermal gravimetric analysis and pyrolysis gas chromatography/mass spectrometry coupled with the morphology and chemical analysis of the char residues. The results confirm that 3001‐OH exerts gaseous‐phase and condensed‐phase flame retardant effects on the PUs.

Recyclable flame retardant paper made from layer-by-layer assembly of zinc coordinated multi-layered coatings

Recyclable flame retardant paper was made by constructing zinc coordinated multi-layered coatings consisting of positively charged polyethylenimine/melamine and negatively charged phytic acid. Herein, with the paper matrix as a carbon source, phytic acid was chosen as the acid source, while polyethylenimine and melamine served as the blowing agent. The successful deposition of zinc ion coordinated coating on the surface of paper fiber was confirmed by scanning electron microscopy and energy-dispersive X-ray. The weight gain of the paper (P) treated with 4 (P–4BL) and 8 (P–8BL) bilayers of coating were 5.5 and 10.1 wt%, respectively. After coordination with zinc ion, P–4BL–Zn and P–8BL–Zn were obtained with weight gains of 6.7 and 13.6 wt%, respectively. The thermal stability and flammability were evaluated by thermogravimetric analysis (TGA), horizontal burning and microscale combustion calorimeter (MCC) tests. TGA results demonstrated that the thermal stability of the treated sample was significantly enhanced at high temperature, as evidenced by the improvement of char residue at 700 °C for P–8BL–Zn to 31.6% as compared with that of untreated paper (1.6%). The P–8BL and P–8BL–Zn samples could achieve self-extinguishing in the horizontal burning test. MCC results showed that the peak heat release rate and the total heat release of P–8BL–Zn were reduced by 43 and 49% as compared to those of the untreated paper, respectively. Furthermore, the zinc ion coordinated coating displayed better in-water durability than the un-coordinated one, which made it possible recyclable flame retardant coating.

One-Pot Synthesis of P(O)-N Containing Compounds Using N-Chlorosuccinimide and Their Influence in Thermal Decomposition of PU Foams.

Synthesis of intermediate containing P(O)-Cl bonds is the key to converting P(O)-H bonds to P(O)-N. In this work we have performed chlorination reactions of different H-phosphinates and H-phosphonates using N-chlorosuccinimide as an environmentally-benign chlorinating agent. The chlorination reaction showed high yield and high selectivity for transformation of P(O)-H bonds into P(O)-Cl analogues, resulting in an easily separable succinimide as the by-product. Using a one-pot synthesis methodology, we have synthesized a series of P(O)-N containing derivatives whose synthesis was found to be dependent on the reaction solvents and the starting materials. The synthesized P(O)-N compounds were incorporated in flexible polyurethane foam (FPUF) and screened for their influence in thermal decomposition of FPUFs using thermogravimetric analysis (TGA) and a microscale combustion calorimeter (MCC). All solid P(O)-N compounds influenced the first-stage decomposition of FPUFs, which resulted in an accelerated decomposition or temporary stabilization of this stage. However, the liquid P(O)-N derivatives volatilize at an earlier stage and could be active in the gas phase. In addition, they also work in condensed phase via acid catalyzed decomposition for FPUFs.