Preparation and flame retardancy of reactive flame retardant for cotton fabric

Journal of Thermal Analysis and Calorimetry - Monochlorotriazine aminopropyl silanol phosphate (MCASP) was synthesized as a novel flame retardant agent for cotton fabric. It was characterized by...     

Study on intumescent flame retarded polystyrene composites with improved flame retardancy

The flame retardancy and thermal stability of ammonium polyphosphate/tripentaerythritol (APP/TPE) intumescent flame retarded polystyrene composites (PS/IFR) combined with organically-modified layered inorganic materials (montmorillonite clay and zirconium phosphate), nanofiber (multiwall carbon nanotubs), nanoparticle (Fe₂O₃) and nickel catalyst were evaluated by cone calorimetry, microscale combustion calorimetry (MCC) and thermogravimetric analysis (TGA). Cone calorimetry revealed that a small substitution of IFR by most of these fillers (≤2%) imparted substantial improvement in flammability performance. The montmorillonite clay exhibited the highest efficiency in reducing the peak heat release rate of PS/IFR composite, while zirconium phosphate modified with C₂₁H₂₆NClO₃S exhibited a negative effect. The yield and thermal stability of the char obtained from TGA correlated well with the reduction in the peak heat release rate in the cone calorimeter. Since intumesence is a condensed-phase flame process, the MCC results showed features different from those obtained from the cone calorimeter.     

Thermal and flame retardant properties of novel intumescent flame retardant polypropylene composites

Novel intumescent flame retardant polypropylene (PP) composites were prepared based on a char forming agent (CFA) and silica-gel microencapsulated ammonium polyphosphate (Si-MCAPP). The thermal and flame retardancy of flame retardant PP composites were investigated by limiting oxygen index, UL-94 test, cone calorimetry, thermogravimetric analysis, scanning electron micrograph, and water resistance test. The results of cone calorimetry show that the flame retardant properties of PP with 30 wt% novel intumescent flame retardants (CFA/Si-MCAPP = 1:3) improve greatly. The peak heat release rate and total heat release decrease, respectively, from 1,140.0 to 156.8 kW m^?2 and from 96.0 to 29.5 MJ m^?2. The PP composite with CFA/Si-MCAPP = 1:3 has the excellent water resistance, and it can still obtain a UL-94 V-0 rating after 168 h soaking in water.     

A novel intumescent flame retardant imparts high flame retardancy to epoxy resin

Intumescent flame retardant (IFR) has received the considerable attention ascribed to the inherent advantages including non‐halogen, low toxicity, low smoke release and environmentally friendly. In this work, a novel charring agent poly (piperazine phenylaminophosphamide) named as PPTA was successfully synthesized and characterized by Fourier transform infrared spectra (FTIR) and X‐ray photoelectron spectroscopy (XPS). Then, a series of flame‐retardant EP samples were prepared by blending with ammonium polyphosphate (APP) and PPTA. Combustion tests include oxygen Index (LOI), vertical Burning Test (UL‐94) and cone calorimeter testing,these test results showed that PPTA greatly enhances the flame retardancy of EP/APP. According to detailed results, EP containing 10 wt% APP had a LOI value of 30.2%,but had no enhancement on UL‐94 rating. However, after both 7.5 wt% APP and 2.5 wt% PPTA were added, EP‐7 passed UL‐94 V‐0 rating with a LOI value of 33.0%. Moreover, the peak heat release rate (PHRR) and peak of smoke product rate (PSPR) of EP‐7 were greatly decreased. Meanwhile, the flame‐retardant mechanism of EP‐7 was investigated by scanning electron microscopy (SEM), thermogravimetric analysis/infrared spectrometry (TG‐IR) and X‐ray photoelectron spectroscopy (XPS). The corresponding results presented PPTA significantly increased the density of char layer, resulting in the good flame retardancy.     

Thermal stabilities and flame retardancies of nitrogen-phosphorus flame retardants based on bisphosphoramidates

Various nitrogen-phosphorus (P-N) compounds based on phosphoramidate were synthesized as model compounds to investigate the relationships among the chemical structure of linker connecting diphenylphoryl groups between the phosphoramidates, the N content, thermal stability, and flame-retarding ability. The flame-retarding efficiencies were evaluated by the limiting oxygen index (LOI) and UL-94 vertical test methods. It was found that bisphosphoramidates are more thermally stable and produce more charred residues when compared to the corresponding bisphosphate compounds. Aromatic phosphoramidates show fairly good flame retardancy for PC and UL-94 V-0 ratings are achieved with addition of as small amount as 3-5 wt%. However, no rating is found for ABS at 30 wt% loading of bisphosphoramidate FRs which leave the remarkably high residues at 600 °C. The thermogravimetric analysis (TGA) results indicate that these compounds work in condensed phase rather than in gas phase. The effect of chemical structure of linker on the flame retardancy is also discussed.     

Thermal degradation and flame retardancy of epoxy resins containing intumescent flame retardant

Pentaerythritol diphosphonate melamine-urea-formaldehyde resin salt, a novel cheap macromolecular intumescent flame retardants (IFR), was synthesized, and its structure was a caged bicyclic macromolecule containing phosphorus characterized by IR. Epoxy resins (EP) were modified with IFR to get the flame retardant EP, whose flammability and burning behavior were characterized by UL 94 and limiting oxygen index (LOI). 25 mass% of IFR were doped into EP to get 27.2 of LOI and UL 94 V-0. The thermal properties of epoxy resins containing IFR were investigated with thermogravimetry (TG) and differential thermogravimetry (DTG). Activation energy for the decomposition of samples was obtained using Kissinger equation. The resultant data show that for EP containing IFR, compared with EP, IFR decreased mass loss, thermal stability and R _max, increased the char yield. The activation energy for the decomposition of EP is 230.4 kJ mol⁻¹ while it becomes 193.8 kJ mol⁻¹ for EP containing IFR, decreased by 36.6 kJ mol⁻¹, which shows that IFR can catalyze decomposition and carbonization of EP.     

Solubilities,thermostabilities and flame retardance behaviour of phosphorus-containing flame retardants and copolymers

Thirteen phosphorus-containing flame retardants were synthesized in this work. The solubilities of flame retardant [(6-oxide-6H-dibenz[c,e][1,2]oxaphosphorin-6-yl)-methyl]-butanedioic acid (DDP) in selected solvents are measured. TGA measurements of the 13 phosphorus-containing flame retardants were carried out and thermal stabilities of three flame-resistant PET (FRPET) resins were investigated. A FRPET incorporated by DDP with terephthalic acid and ethylene glycol reported in literature was also discussed and compared. The thermal stability of the FRPET is improved by the incorporation of phosphorus-containing flame retardants. The LOI values of all phosphorus-containing polyesters are higher than 27%. The improvement of the flame-resistant ability is due to the formation of the char that is not only caused by the existence of phosphorus elements in the resin but also by the relative large number of carbon atoms of the phenyl group in the flame retardants.     

Synthetic hydromagnesite as flame retardant. Evaluation of the flame behaviour in a polyethylene matrix

Synthetic hydromagnesite obtained from an industrial by-product was evaluated as a non-halogenated flame retardant. It was used in combination with aluminium hydroxide (ATH) and compared with commercial flame retardants like magnesium hydroxide (MH) and natural hydromagnesite-huntite (U) in a polyolefin system of low-density polyethylene/poly(ethylene-co-vinyl acetate) (LDPE/EVA).The thermal stability and flame behaviour of the halogen free flame retarded composites were studied by thermogravimetric and differential thermal analysis (TG-DTA), limiting oxygen index (LOI), epiradiateur and cone calorimeter. It has been shown that synthetic hydromagnesite could be an alternative solution to the use of MH in non-halogenated flame retardant systems in EVA.     

A biobased flame retardant towards improvement of flame retardancy and mechanical property of ethylene vinyl acetate

A new biobased flame retardant (MHPA) with remarkable compatibility was synthesized via a facile and low-cost neutralization reaction of magnesium hydroxide (MH) and phytic acid (PA). By blending the prepared MHPA into ethylene vinyl acetate (EVA), the fire retardancy, smoke suppression and mechanical properties of the composites were significantly improved. When 50 wt% of MH was added into EVA matrix, the value of limiting oxygen index (LOI) reached 26.1%. Whereas, when 10 wt% MH in the EVA composites (with initial 50 wt% MH) was replaced by MHPA, the resulted EVA composites had a LOI value of 30.8%, indicating high efficiency of addition of MHPA to improve flame retardancy. Moreover, the heat release rate (HRR) and total smoke production (TSP) of the EVA composites reduced by 54.4% and 27.6%, respectively, suggesting that incorporation of MHPA could effectively hinder rapid degradation of EVA composites during burning process. The fire-retardant mechanism may reside in that the MHPA combined with MH can present the excellent carbonization and expansion effects. This study illustrates that the biobased MHPA has a broad application prospect to develop flame-retardant EVA composites.     

Synergistic effect of flame retardants and graphitic carbon nitride on flame retardancy of polylactide composites

In order to improve the flame retardant of polylactide (PLA), the synergistic effect of graphitic carbon nitride (g‐C₃N₄) with commercial‐available flame retardants melamine pyrophosphate (MPP) and 9,10‐dihydro‐9‐oxa‐10‐phosphaphenanthrene‐10‐oxide (DOPO) was investigated. The PLA composites containing 5 wt% g‐C₃N₄ and 10 wt% DOPO had a highest limited oxygen index (LOI) value of 29.5% and reached the V‐0 rating of UL‐94 test. The cone calorimeter tests exhibited that DOPO had a better synergistic effect with g‐C₃N₄ than MPP to improve flame retardancy of PLA. The peak heat release rate (pHRR) and total heat release (THR) of PLA composites containing 10 wt% DOPO could be reduced by 25.2% and 23.6%, respectively, as compared with those of pure PLA. The presence of rich phosphorus element and aromatic groups in DOPO contributed to obtain continuous compact char layer and increase the graphitization level of char residues, thereby, resulting in improving the flame retardancy of PLA together with g‐C₃N₄. In addition, the incorporation of DOPO can serve as a plasticizer to reduce the complex viscosity, improving the processability of PLA composites.     

Flammability characteristics and flame retardant mechanism of phosphate-intercalated hydrotalcite in halogen-free flame retardant EVA blends

The flammability characteristics and flame retardant mechanism of phosphate-intercalated hydrotalcite (MgAl-PO₄) in the halogen-free flame retardant ethylene vinyl acetate (EVA) blends have been studied by X-ray diffraction (XRD), Fourier transfer infrared (FTIR) spectroscopy, cone calorimeter test (CCT), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), limiting oxygen index (LOI) and UL-94 tests. The results show that the hydrotalcite MgAl-PO₄ intercalated by phosphate possesses the enhanced thermal stability and flame retardant properties compared with ordinary carbonate-intercalated hydrotalcite MgAl-CO₃ in the EVA blends. The CCT tests indicate that the heat release rate (HRR) and mass loss rate (MLR) values of the EVA/MgAl-PO₄ samples are much lower than those of the EVA/MgAl-CO₃ samples. The TGA data show that the thermal degradation rates of MgAl-PO₄ and EVA/MgAl-PO₄ samples are much slower and leave more charred residues than those of MgAl-CO₃ and its corresponding EVA blends. The LOI values of EVA/MgAl-PO₄ samples are 2% higher than those of the corresponding EVA/MgAl-CO₃ samples at the range of 40–60 wt% loadings, while the EVA sample with 55 wt% MgAl-PO₄ can reach the UL-94 V-1 rating. The dynamic FTIR spectra reveal that the flame retardant mechanism of MgAl-PO₄ can be ascribed to its catalysis degradation of the EVA resin, which promotes the formation of charred layers with the P–O–P and P–O–C complexes in the condensed phase. The SEM observations give further evidence of this mechanism that the compact charred layers formed from the EVA/MgAl-PO₄ sample effectively protect the underlying polymer from burning.     

Thermal and flame retardant properties of novel intumescent flame retardant low-density polyethylene (LDPE) composites

A char-forming agent (CFA) and silica-gel-microencapsulated ammonium polyphosphate (MCAPP) were selected to form novel intumescent flame retardant system (IFRs), and then the influence of this novel IFRs on the thermal and flame retardant properties of low-density polyethylene (LDPE) were studied. The results of cone calorimetry show that the flame retardant properties of LDPE with 30?wt% novel IFR (CFA/MCAPP?=?1:3) improve remarkably. The heat release rate peak, total heat release (THR) decreases, respectively, from 1479.6 to 273.5?kW?m^?2 and from 108.0 to 80.5?MJ?m^?2. The LDPE composite with CFA/MCAPP?=?1:3 has the excellent water resistance, and it can still obtain a UL-94?V-0 rating after treated with water at 70?°C for 168?h.     

The effect of hBN on the flame retardancy and thermal stability of P-N flame retardant PA6

A novel thermally conductive Polyamide 6 (PA6) with good fire resistance was prepared by introducing a phosphorous-nitrogen flame retardant (FR) and platelet-shaped hexagonal boron nitride (hBN) into the matrix. With high thermal conductivity and good flame retardancy, the material is suitable for applications in electronic and electrical devices. The limiting oxygen index (LOI) changes for various loadings content of FR. However this formulation still does not show an ideal fire resistance, due to the appearance of melt dripping behavior during the UL 94 test. With the extra introduction of 3 vol% and 5 vol% hBN, the melt dripping behavior during the burning process completely disappeared. The hBN also increased the thermal conductivity. Furthermore PA6 compounded with FR and hBN showed a better thermal stability than neat PA6. The morphology of the char residues was investigated by scanning electron microscopy (SEM). The flaky hBN acted as the framework in the char structure and the rigid hBN could effectively break the bubble-shaped char on the surface of the residues which resulted in the enhancement of the strength and compactness of the char.     

Aromatic polysulfones for flame retardancy

A poly(ether sulfone) and a copoly(ester sulfone) were synthesized and characterized using elemental analyses, IR, ¹H-NMR spectrometry, GPC, thermogravimetric analyses. These polysulfones which show good thermal stability and flame retardancy were applied on textile materials and measurements for the evaluation of the flame retardant effect were carried out.     

Thermal degradation and flame retardancy of rigid polyurethane foams containing a novel intumescent flame retardant

A novel cheap macromolecular intumescent flame retardants (MIFR) was synthesized, and its structure was a macromolecule containing phosphorus characterized by IR. Rigid polyurethane foam (PUF) filled with MIFR as fire retardant additive was prepared. The effects of MIFR on properties such as density, compressive strength, flame-retardant behavior, thermal stability, and morphology of char were studied. The compressive strength of the MIFR-filled PUF increased initially and then decreased with further increase of MIFR content while its density straightly increased. Its flammability and burning behavior were characterized by UL 94 and limiting oxygen index (LOI). Twenty five percent of MIFR was doped into PUF to get 24.5 of LOI and UL 94 V-0. Activation energy for the decomposition of samples was obtained using Kissinger equation. The resultant data show that for PUF containing MIFR, compared with PUF, the mass loss, thermal stability, and the decomposition activation energy decreased, the char yield increased, which shows that MIFR can catalyze decomposition and carbonization of PUF to form an effective charring layer to protect the underlying substrate.     

Halogen-free flame retardant PUF: Effect of melamine compounds on mechanical, thermal and flame retardant properties

Water blown rigid polyurethane foam (PUF) was prepared with melamine polyphosphate (MPP) and melamine cyanurate (MC) as fire retardant (FR) additives. The effect of these additives on the properties of rigid PUF such as physico-mechanical, morphological, thermo-oxidative stability, flame retardancy and smoke density properties were studied. The mechanical and thermo-oxidative stability of PUF filled with MC was found to be better than those of MPP filled PUF. The insulation property of both MPP and MC filled PUF was improved with respect to the neat PUF. The FR properties of these filled PUF were evaluated by cone calorimeter, limiting oxygen index (LOI), smoke density, rate of burning and char residue estimation. The FR property of MPP filled PUF was better than that of the MC filled PUF.     

An experimental and theoretical evaluation of the nitrous oxide-acetylene flame as an atomization cell for flame spectroscopy

The formation of free atoms from aerosols of metal-containing solutions introduced into nitrous oxide-acetylene flames is examined by: (a) inference from well identified reactions and equilibria prevailing in cooler flames; (b) calculations employing a thermodynamic flame model; and (c) experimental observation of relative free-atom number densities in the flames as a function of stoichiometry. The calculated partial pressures of the major natural flame species and some of the spectroscopically observed minor species are presented as a function of the flow ratio of nitrous oxide to acetylene (p). Predicted relative number densities of Na, Mg, Cu, Fe, Li, Be, Al, W, Ti and Si as a function of p are compared with measured free-atom absorbances in an argon-shielded flame. These comparisons were completed for various heights above the burner tip. The data reported show that: (a) the degree of metal atomization in the nitrous oxide-acetylene flame can be adequately described by the equilibrium state; (b) in general, when solute vaporization is complete, there exists a value of ρ at which atomization is complete for metals that form monoxides with dissociation energies less than ~ 6.5 eV; and (c) certain metals may form carbon-containing compounds in the interconal zone.     

Digital image-based flame emission spectrometry

A digital image-based flame emission spectrometric (DIB-FES) method for the quantitative chemical analysis is proposed here for the first time. The DIB-FES method employs a webcam to capture the digital images which are associated to a radiation emitted by the analyte into an air-butane flame. Since the detection by webcam is based on the RGB (red-green-blue) colour system, a novel mathematical model was developed in order to build DIB-FES analytical curves and estimate figures of merit for the proposed method. In this approach, each image is retrieved in the three R, G and B individual components and their values were used to define a position vector in RGB three-dimensional space. The norm of this vector is then adopted as the RGB-based value (analytical response) and it has revealed to be linearly related to the analyte concentration. The feasibility of the DIB-FES method is illustrated in three applications involving the determination of lithium, sodium and calcium in anti-depressive drug, physiological serum and water, respectively. In comparison with the traditional flame emission spectrometry (trad-FES), no statistic difference has been observed between the results by applying the paired t-test at the 95% confidence level. However, the DIB-FES method has offered the largest sensitivities and precision, as well as the smallest limits of detection and quantification for the three analytes. These advantageous characteristics are attributed to the trivariate nature of the detection by webcam.     

Synthesis of a novel synergistic flame retardant based on cyclopolysiloxane and its flame retardant coating on cotton fabric

A synergistic flame retardant (silicon, phosphorus and nitrogen) based on cyclic polysiloxane, ammonium salt of tetramethylcyclosiloxyl-piperazin-phosphinic acid (APCTSi) was successfully prepared and firmly bonded to cotton fabric through a chemical grafting method. The chemical structure of APCTSi was characterized by Fourier transform infrared (FTIR) spectroscopy, ¹H and ³¹P nuclear magnetic resonance (¹H NMR and ³¹P NMR). The scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (SEM–EDX) proved that APCTSi successfully adhered to the surface of cotton fabric and the elements on the surface of cotton fabric were evenly distributed. The flame retardant properties were characterized by limiting oxygen index (LOI), vertical burning test, thermogravimetric (TG) analysis and TG-FTIR. The limiting oxygen index (LOI) can reach 30.9% with a char length of 8.7 cm for the weight gain of APCTSi was 16.2%. The combustion behavior was characterized by cone calorimetry test. The peak heat release rate (pHRR) and total heat release (THR) values of treated cotton fabric decreased by 30% and 48% respectively compared to that of pure cotton fabric. All the results proved that the cotton fabric treated by APCTSi had the flame retardant effect of condensed phase (forming stable char layer) and gas phase (releasing nonflammable gases).

Graphic abstract

     

A vanillin-derived flame retardant based on 2-aminopyrimidine for enhanced flame retardancy and mechanical properties of epoxy resin

In order to give epoxy resin good flame retardance, a novel bio-based flame retardant based on 2-aminopyrimidine (referred to as VAD) was synthesized from renewable vanillin as one of the starting materials. Its structure was confirmed by NMR and mass spectra. The epoxy resins containing VAD were prepared by utilizing 4,4-diaminodiphenylmethane (DDM) as a co-curing agent, and their flame-retardant, mechanical and thermal properties and corresponding mechanisms were studied. VAD accelerated the cross-linking reaction of DDM and E51 (diglycidyl ether of bisphenol A). 12.5 wt% VAD made the epoxy resin achieve UL-94 V-0 rating and its limited oxygen index (LOI) value increase from 22.4% to 32.3%. The cone calorimetric testing results revealed the decline in the values of total heat release (THR) and peak of heat release rate (pk-HRR) and the obvious enhancement of residue yield. A certain amount of VAD enhanced the flame inhibition, charring and barrier effects, resulting in good flame retardance of the epoxy resin. Furthermore, the tensile strength, flexural strength and flexural modulus of the epoxy resin with 12.5 wt% loading of VAD were 6.5%, 14.9%, 15.2% higher than those of EP, indicating the strengthening effect of VAD. This work guarantees VAD to be a promising flame retardant for enhancing the fire retardancy of epoxy resin without compromising its mechanical properties.