Smoke suppression properties of epoxy crosslinked structure and intumescent fire retardant in epoxy‐based intumescent fire‐retardant coating

In this article, the smoke production behaviors of crosslinked epoxy/polyamide resin (EP/PA) and intumescent fire retardant (IFR) in epoxy‐based intumescent fire‐retardant coating (IFR‐EP) have been investigated using cone calorimeter, smoke density instrument, and thermogravimetric analysis and Fourier transform infrared spectroscopic measurement. The static and dynamic smoke production behaviors of EP/PA and IFR‐EP indicate that the IFR has an excellent smoke suppression effect on EP/PA by forming protective char layer in the late combustion stage, while the epoxy crosslinked structure in IFR‐EP can enhance the thermal stability and reduce smoke production in the early combustion stage. In addition, according to the discussion of pyrolysis gas products, the IFR can effectively suppress the production of toxic and inflammable gases during the combustion process. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43912.     

Investigations of thermal degradation behavior and fire performance of halogen‐free flame retardant poly(1,4‐butylene terephthalate) composites

This work aims to develop halogen‐free poly(1,4‐butylene terephthalate) (PBT) composites with enhanced flame retardancy using ecofriendly flame retardants, aluminum hypophosphite (AHP) and melamine derivatives (melamine polyphosphate and melamine cyanurate). Microscale combustion calorimetry and thermal gravimetric analysis/infrared spectrometry (TG‐IR) technique were used to investigate the potential fire hazards of these PBT composites. For the PBT composites with the incorporation of AHP and melamine derivatives, the heat release capacity (HRC) which is an indicator of a material fire hazard was significantly reduced, and the intensities of a variety of combustible or toxic gases detected by TG‐IR technique were remarkably decreased. Moreover, a loading of 20 wt % flame retardant mixture fulfilled the PBT composites high limited oxygen index (LOI) and V‐0 classification in UL 94 testing. An intumescent flame retarded mechanism was speculated in this work, because numerous bubble‐like char residues were found on the surface of the samples containing flame retardant mixture after LOI testing. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

New fire‐protective intumescent coatings for wood

Polyurethane coatings are highly flammable, and because of their widespread applications on different substrates (wood, steel, and building materials), there is a need to increase their fire‐safety properties. Intumescent additives sharply suppress the flammability properties of polyurethane coatings. Two problems accompany intumescent additives: their high loading percentage and incompatibility with polyurethane coatings. In this research, we succeeded in increasing the compatibility by mixing intumescent additives with a butyl acrylate polymer and in lowering the flame‐retardant additive loading (up to 20%) by incorporating newly modified montmorillonite. The flammability properties of the new intumescent coatings were characterized with a cone calorimeter. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Effect of boron‐containing materials on the flammability and thermal degradation of polyamide 6 composites containing melamine

Three different boron‐containing substances—zinc borate (ZnB), borophosphate (BPO₄), and a boron‐ and silicon‐containing oligomer (BSi)—were used to improve the flame retardancy of melamine in a polyamide 6 (PA‐6) matrix. The combustion and thermal degradation characteristics of PA‐6 composites were investigated with the limiting oxygen index (LOI), the UL‐94 standard, thermogravimetric analysis (TGA)/Fourier transform infrared (FTIR) spectroscopy, and differential scanning calorimetry (DSC). A slight increase was seen in the LOI values of a sample containing BSi (1 wt %). BPO₄ at high loadings showed a V0 rating (indicating the best flame retardancy) and slightly lower LOI values in comparison with samples with only melamine. For ZnB and BSi, glassy film and char formation decreased the dripping rate and sublimation of melamine, and this led to low LOIs. According to the TGA–FTIR results, the addition of boron compounds did not change the decomposition product distribution of melamine and PA‐6. The addition of boron compounds affected the flame retardancy by physical means. The TGA data showed that boron compounds and melamine reduced the decomposition temperature of PA‐6. According to the DSC data, the inclusion of boron compounds increased the onset temperature of sublimation of melamine and also affected the flame retardancy negatively. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Fire‐retardant copolymer of acrylonitrile with O,O‐diethyl‐O‐allyl thiophosphate

A novel halogen‐free flame retardant, O,O‐diethyl‐O‐allyl thiophosphate (DATP), which simultaneously contained phosphorus and sulfur, was synthesized through a simple method. The structure of DATP was characterized by Fourier transform infrared spectroscopy, ¹H‐NMR, and mass spectroscopy. The flame‐retardant copolymer was obtained by the free‐radical copolymerization of DATP with acrylonitrile. The flammability and thermal degradation characteristics of the copolymer were assayed by limiting oxygen index measurement, thermogravimetric analysis, and differential scanning calorimetry. The results show that the incorporation of a small percentage of DATP into the copolymer had a significant effect on the retarding combustion of the copolymer, with the limiting oxygen index of the copolymer reaching 28.5% and the char yield being 68.63 wt % at 554°C. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Photopolymerization and thermal behavior of phosphate diacrylate and triacrylate used as reactive‐type flame‐retardant monomers in ultraviolet‐curable resins

Tri(acryloyloxyethyl)phosphate (TAEP) and di(acryloyloxyethyl)ethyl phosphate (DAEEP) were used as reactive‐type flame‐retardant monomers along with commercial epoxy acrylate and polyurethane acrylate oligomers in ultraviolet (UV)‐curable resins. The concentrations of the monomers were varied from 17 to 50 wt %. The addition of the monomers greatly reduced the viscosity of the oligomers and increased the photopolymerization rates of the resins. The flame retardancy and thermal degradation behavior of the UV‐cured films were investigated with the limiting oxygen index (LOI) and thermogravimetric analysis. The results showed that the thermal stability at high temperatures greater than 400°C and the LOI values of the UV‐cured resins, especially those containing epoxy acrylate, were largely improved by the addition of the monomers. The dynamic mechanical thermal properties of the UV‐cured films were also measured. The results showed that the crosslink density increased along with the concentrations of the monomers. However, the glass‐transition temperature decreased with an increasing concentration of DAEEP because of the reduction in the rigidity of the cured films, whereas the glass‐transition temperature increased with the concentration of TAEP because of the higher crosslink density of the cured films. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 185–194, 2005     

Synthesis of phospholipidated β‐cyclodextrin and its application for flame‐retardant poly(lactic acid) with ammonium polyphosphate

In this study, phospholipidated β‐cyclodextrin (PCD) was obtained by the condensation between β‐cyclodextrin and phenyl phosphonic acid dichloride, which was characterized by Fourier transform infrared (FTIR) spectra, ¹H‐NMR, and thermogravimetric analysis (TGA). The thermal stability and flame retardancy of the poly(lactic acid) (PLA) blends [PLA–ammonium polyphosphate (APP)–PCD] were measured by TGA coupled to FTIR spectroscopy, vertical burning test (UL‐94), limiting oxygen index (LOI), and cone calorimetry tests. The results show that the mass ratio and loading amount of APP and PCD affected the properties of PLA. When the loading of APP and PCD was 30 wt % and the mass ratio of APP to PCD was 5:1, the highest LOI value of 42.6% (that of neat PLA was 19.7%) and a UL‐94 V0 rating were achieved, and the reduction of the total heat release was greater than 80%. Even when the total amount of APP and PCD was decreased to 20 wt % with the same mass ratio, the flame‐retardant PLA still can achieved a UL‐94 V0 rating. The improved performance was explained by the formation of an intumescent, continuous, contact char layer. Moreover, the reaction between APP and PCD contributed to the improvement of the thermal stability of the char residue. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46054.     

Effect of expandable graphite on the properties of intumescent flame‐retardant polyurethane foam

Water‐blown rigid polyurethane foam (PUF) with two different particle sizes (180 and 300 μm) of expandable graphite (EG) as a flame‐retardant additive were prepared, and the effects on the mechanical, morphological, water absorption, thermal conductivity, thermal, and flame‐retardant properties were studied. In this investigation, EG content was varied from 5 to 50 php by weight. The mechanical properties of PUF decreased with increasing EG loading in both cases. The water absorption of the PUF increased with an increase in the EG loading mainly because of the collapse of foam cells, as evidenced from the scanning electron microscopy pictures. The thermal conductivity of the EG‐filled PUF showed that the insulation properties decreased with EG loading. The flame‐retardant properties (limiting oxygen index and char yield measurement) of the PUF improved with increasing EG loading. PUF filled with the higher particle size EG showed better mechanical properties and fire‐retardant properties than the PUF filled with the lower particle size EG. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Improving the flame‐retardant efficiency of aluminum hydroxide with fullerene for high‐density polyethylene

The influence of fullerene (C₆₀) on the flame retardancy and thermal stability of high‐density polyethylene (HDPE)/aluminum hydroxide (ATH) composites was studied. After the addition of three portions of C₆₀ to an HDPE–ATH (mass ratio = 100:120) composite, a V‐0 rating in the UL‐94 vertical combustion test was achieved, and the limiting oxygen index increased by about 2%. The results of cone testing also showed that the addition of C₆₀ effectively extended the time to ignition and the time to maximum heat‐release rate while cutting down the peak heat‐release rate. Thus, fewer flame retardants were needed to achieve a satisfactory flame retardance. Consequently, the adverse effects on the mechanical properties because of the high level of flame‐retardant loading was reduced, as evidenced by the obvious enhancements in the tensile strength, elongation at break, and flexural strength. Electron spin resonance spectroscopy proved that C₆₀ was an efficient free‐radical scavenger toward HO· radicals. Thermogravimetric analysis coupled to Fourier transform infrared spectroscopy demonstrated that in both N₂ and air atmospheres, C₆₀ increased the onset temperature of the matrix by about 10 °C because of its enormous capacity to absorb free radicals evolved from the degradation of the matrix to form crosslinked network, which was covered by aluminum oxide. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44551.     

Effects of two kinds of THEIC‐based charring agents on flame‐retardant properties of polylactide

Two charring agents tris (2‐hydrooxyethyl) isocyanurate terephthalic acid ester, (dimer/trimer mixture TT23, and tetramer TT4) were synthesized by using tris (2‐hydrooxyethyl) isocyanurate (THEIC) and terephthalic acid (TPA) as raw materials. These two charring agents were combined with ammonium polyphosphate (APP) to form intumescent flame retardants (IFR) for polylactide (PLA). The thermal stability of IFRs were tested by TGA, it is found that APP/TT4 mixture has a higher thermal stability and a better char forming ability than that of APP/TT23 mixture. The combustion properties and thermal stability of PLA/APP/TT23 and PLA/APP/TT4 composites were evaluated by UL‐94 burning tests, limiting oxygen index (LOI), cone calorimeter tests and TGA, the chemical structure of char residues were analyzed by FTIR and XPS. It can be concluded that PLA with 30 wt % of APP/TT4 (weight ratio 5 : 1) achieved the greatest flame retardancy. Moreover, the continuous and expansionary char layer observed from SEM images proved better char forming ability of TT4 than that of TT23. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42086.     

Effect of nano‐titanium nitride on thermal insulating and flame‐retardant performances of phenolic foam

In this work, titanium nitride (TiN) nanoparticles were employed to achieve enhanced thermal insulation and flame retardance of phenolic foam (PF)/TiN nanocomposites (PFTNs) via in situ polymerization. The morphologies of PFTNs were observed by scanning electron microscope and the images showed that the PFTNs have more uniform cell morphologies compared with pure PF. Thermal insulating properties of PFTNs were evaluated by thermal conductivity tests. The introduction of TiN obviously decreased the thermal conductivities of PF over a wide temperature range (?20 to 60 °C). Significantly, the thermal conductivity of PFTNs gradually decreased as the temperature increased from 30 to 60 °C, showing a contrary tendency with that of pure PF. Moreover, the thermal stability and flame‐retardant properties of PFTNs were estimated by thermogravimetric analysis (TGA), UL‐94 vertical burning and limited oxygen index (LOI) tests, respectively. The TGA and LOI results indicated that PFTNs possess enhanced thermal stabilities and fire‐retardant performances with respect to the virgin PF. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43765.     

Preparation of flame‐retardant leather pretreated with pyrovatex CP

Resistance to burning is one of the most useful properties that can be imparted to leather. Pyrovatex CP is rich in phosphorus and nitrogen and has been successfully used as a flame‐retardant agent in the presence of etherified methylolated melamine (EMM). The effects of a finishing formulation containing Pyrovatex CP and EMM on the flame retardancy and other properties of modified leather have been studied under different conditions. The synergistic effect of the N/P ratio has been thoroughly investigated through the estimation of the nitrogen and phosphorus contents, and their impact on the flame retardancy, tensile strength, and elongation at break of the treated leather has been studied. An investigation of the different factors has led to the following conclusions: (1) the P and N percentages increase with increasing curing temperature and time, (2) increases in the Pyrovatex CP and EMM concentrations are accompanied by an enhancement of the P and N percentages, and (3) all samples exhibit loss in their tensile properties but within an acceptable range (20%). © 2005 Wiley Periodicals, Inc. J Appl Polym Sci, 2006     

Preparation and properties of transparent copolymers based on cyclotriphosphazene and styrene as potential flame‐retardant optical resins

Transparent copolymers composed of hexa(allyl 4‐hydroxybenzoate) cyclotriphosphazene (compound 1 ) and styrene as potential halogen‐free, flame‐retardant optical resins were prepared by radical copolymerization. The thermal performances of the cured resins were studied with thermogravimetric analysis; the decomposition mechanism of the copolymers was investigated with integrated thermogravimetry–Fourier transform infrared analysis. Compared with conventional polystyrene, the synthesized copolymers exhibited a higher refractive index and a higher thermal stability both under nitrogen and air atmospheres at elevated temperature, and the visible‐light transmittance of the copolymers decreased slightly. With increasing ratio of compound 1 to styrene in the copolymers, the onset decomposition temperature and the char yield both increased gradually. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Influence of fumed silica on the flame‐retardant properties of ethylene vinyl acetate/aluminum hydroxide composites

The flammability and synergistic flame‐retardant effects of fumed silica (SiO₂) in ethylene vinyl acetate (EVA)/aluminum hydroxide (ATH) blends were studied with limiting oxygen index measurements, UL 94 testing, cone calorimeter testing (CONE), and thermogravimetric analysis (TGA). The results show that the addition of a given amount of fumed SiO₂ can apparently improve UL 94 rating. The CONE data indicated that the addition of fumed SiO₂ greatly reduced the heat release rate. The TGA data showed that this synergistic flame‐retardant mechanism of fumed SiO₂ in the EVA/ATH materials was mainly due to the physical process. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Effect of charring agent THEIC on flame retardant properties of polypropylene

Tris(2‐hydroxyethyl) isocyanurate (THEIC) was used as charring agent and combined with ammonium polyphosphate (APP) to form an intumescent flame retardant (IFR) for polypropylene (PP). The flame retardancy and combustion performance of PP/IFR composite was tested by limiting oxygen index (LOI), UL‐94 vertical burning test and cone calorimeter. The results showed that PP/IFR composite had highest LOI of 34.8 and obtained V‐0 rating when 30 wt % IFR was loaded and mass ratio APP/THEIC was 2 : 1. The peak heat release (PHRR) and total heat release (THR) values of PP composite containing FRs were remarkably reduced compared with that of pure PP. However, water resistant test demonstrated the PP/IFR composite had poor flame retardant durability, both the LOI value and UL‐94 V‐rating decreased when PP/IFR composite was soaked in water at 70°C after 36 h. The degradation process and the char morphology of IFR and PP/IFR composite were investigated by TGA and SEM images. The possible reaction path between APP and THEIC in the swollen process was proposed. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41214.     

Synergistic flame retardant effect of piperazine salt and ammonium polyphosphate as intumescent flame retardant system for polypropylene

Amino trimethylene phosphonic acid piperazine (ATPIP) salt, as a novel charring agent, is prepared via a simple ionic reaction in distilled water using amino trimethylene phosphate (ATMP) and piperazine as raw materials. The synergistic flame retardant effect of ATPIP and ammonium polyphosphate (APP) as an intumescent flame retardant (IFR) is investigated by various characterization and testing methods. The results show that the polypropylene (PP)/modified APP with piperazine (MAPP)/ATPIP ternary blend passes UL-94 V-0 rating and achieve a limiting oxygen index (LOI) of 30% at a loading level of 25 wt% IFR (MAPP:ATPIP = 3:1). Meanwhile, the total smoke production (TSP) value of IFR-PP samples is 3.3 m², which decreases by 93.2% compared with that of pure PP, exhibiting excellent smoke suppression performance. Besides, the analysis of gaseous pyrolysis products and char residue indicates that the IFR-PP samples show a synergistic flame-retardant mechanism including the gas phase and the condensed phase.     

Melamine amino trimethylene phosphate as a novel flame retardant for rigid polyurethane foams with improved flame retardant,mechanical and thermal properties

Melamine amino trimethylene phosphate (MATMP) as a novel nitrogen‐phosphorus flame retardant, was synthesized by the reaction of melamine with amino trimethylene phosphonic acid (ATMP) in aqueous solution. The structure of MATMP was characterized by Fourier transform infrared spectroscopy, solid state 31 P nuclear magnetic resonance, and thermogravimetric analysis. Rigid polyurethane (RPU) foams were prepared by one‐shot and free‐rise method, using MATMP as a flame retardant. The flame retardant, mechanical and thermal properties of MATMP in RPU foams were studied. It is found that the RPU foam containing 15 wt % MATMP (sample RPUMA‐15) can pass the UL‐94 V0 test with a limiting oxygen index of 25.5%. The cone calorimeter test results show that the peak heat release rate of RPUMA‐15 is reduced about 34% compared with that of untreated RPU foam. SEM results indicate that the RPU foams with MATMP can form the good and compact char during burning which provides better flame retardancy. The compressive strength of the RPU foams filled with MATMP first increases and then slightly decreases with an increase in the MATMP content comparing with that of untreated RPU foam. Moreover, thermal conductivities of the MATMP filled RPU foams are about 0.03 W/m K. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45234.     

Fire retardance and smoke suppression of polypropylene with a macromolecular intumescent flame retardant containing caged bicyclic phosphate and piperazine

A macromolecular intumescent flame retardant (FR) named PPPAP was designed and synthesized with phosphorus chloride (the acid source), 2,6,7-trioxa-l-phosphabicyclo[2.2.2]-octane-4-methanol (the charring agent), and anhydrous piperazine (the blowing agent). Then, it was used to prepare an intumescent flame-retardant polypropylene (FR-PP). The thermal stability, flame retardancy, and fire performance of the FR-PPs were investigated. The results show that the initial decomposition temperature and char residue at 700 °C of PPPAP were 260.8 °C and 31.8%, respectively. The limiting oxygen index (LOI) value of polypropylene (PP) was enhanced with increasing PPPAP content. With the addition of 40 wt % PPPAP, the LOI value of FR-PP was 29%, and it passed the vertical burning UL-94 V-0 rating. The cone calorimetry results indicate that not only the peak heat-release rate but also the total smoke production of PP significantly decreased to 65.7 and 79.5%, respectively, with the incorporation of only 20 wt % PPPAP. The FR mechanism suggested that PPPAP played a part in both the gas and condensed phases, and the formation of the intumescent char layer during combustion was the dominant FR mechanism. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47593.     

Halogen‐free flame‐retardant rigid polyurethane foams: Effect of alumina trihydrate and triphenylphosphate on the properties of polyurethane foams

Rigid polyurethane foam (PUF) filled with mixture of alumina trihydrate (ATH) and triphenyl phosphate (TPP) as fire retardant additive was prepared with water as a blowing agent. In this study, the ATH content was varied from 10 to 100 parts per hundred polyol by weight (php), and TPP was used at a higher loading of ATH (75 and 100 php) in a ratio of 1 : 5 to enhance the processing during PUF preparation. The effects of ATH on properties such as density, compressive strength, morphological, thermal conductivity, thermal stability, flame‐retardant (FR) behavior, and smoke characteristics were studied. The density and compressive strength of the ATH‐filled PUF decreased initially and then increased with further increase in ATH content. There was no significant change in the thermal stability with increasing ATH loading. We determined the FR properties of these foam samples by measuring the limiting oxygen index (LOI), smoke density, rate of burning, and char yield. The addition of ATH with TPP to PUF significantly decreased the flame‐spread rate and increased LOI. The addition of TPP resulted in easy processing and also improved FR characteristics of the foam. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Green synthesis and characterization of phosphorus flame retardant crosslinking agents for epoxy resins

The flame‐retardant efficacy of phosphorus‐containing reactive amine hardeners for epoxy resins is well‐known; however their synthesis often applies hazardous, objectionable reagents. The aim of this work is to develop an effective synthesis method for the preparation of P‐containing amines, which can act as flame‐retardant crosslinking agent in epoxy resins. The syntheses and testing of an aliphatic and two aromatic amines are described: curing properties, glass transition temperature, thermal stability, and flame‐retardant performance of the amines are studied. On the basis of these results, the scaling‐up and the optimization of the synthesis of the phosphorus‐containing aliphatic amine hardener in ReactIR? in situ FTIR apparatus is discussed. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40105.