Synthesis and thermal stability of a novel phosphorus-nitrogen containing intumescent flame retardant

A novel phosphorus-nitrogen containing intumescent flame retardant （P-N IFR） was prepared via the reaction of dichlor-opentate with N-methylaniline. The structure of the product was confirmed by ^1H NMR, ^31p NMR, MS and IR. TGA analysis showed it has effective thermal stability.     

A novel halogen-free flame retardant for glass-fiber-reinforced poly(ethylene terephthalate)

In order to prepare halogen-free flame-retardant glass-fiber-reinforced poly(ethylene terephthalate) (FR-GF-PET), a novel flame retardant containing three flame-retardant elements, P, N and S, was synthesized by melt condensation reaction. Its chemical structure was characterized by FT-IR and ¹H NMR spectra. FR-GF-PET was prepared by melt-mixing the flame retardant with GF-PET. The effects of the flame retardant on the flammability and thermally decomposing behaviors of GF-PET were studied via LOI, UL-94 and TGA tests. The results showed that despite a negative effect on the thermal stability of GF-PET, the incorporation of the flame retardant improved the flame retardancy of GF-PET largely. The LOI values of GF-PET increase linearly with the increase of flame retardant content. The GF-PET passed the V-0 rating in UL-94 tests when 15 wt% of the flame retardant was added to GF-PET. An interesting phenomenon was found, that is, with the increase of flame retardant content, the flame retardancy of the system increased but the char yield decreased, which was explained according to the evidences of XPS tests and the kinetics of thermally decomposing reaction.     

An efficient halogen-free flame retardant for glass-fibre-reinforced poly(butylene terephthalate)

Compared with poly(butylene terephthalate) (PBT), glass-fibre-reinforced poly(butylene terephthalate) (GF-PBT) is difficult to flame retard with halogen-free flame retardants. In the present study, the aluminium salt of hypophosphorous acid (AP) was used as a flame retardant for GF-PBT. A series of flame-retardant GF-PBT composites was prepared via melt compounding. The flame retardance and combustion behaviour of the composites were studied by limiting oxygen index (LOI), vertical burning test (UL-94) and cone calorimetric test. Thermal behaviours and thermal decomposition kinetics were investigated by thermogravimetric analysis (TGA) under N₂ atmosphere. The addition of AP to the composites could result in an increased LOI value, a UL-94 V-0 (1.6 mm) classification and a better fire performance in cone calorimetric tests. The char morphology observation after flame-retardant tests, calculation of decomposition kinetics, X-ray photoelectron spectroscopy (XPS) and infra-red spectral analysis of the char residue confirmed the condensed-phase flame-retardant mechanism. Furthermore, the mechanical properties of the flame-retardant composites were not deteriorated, retaining an acceptable level.     

Flame retardancy and thermal degradation of intumescent flame retardant polypropylene material

The flame retardancy and thermal degradation properties of polypropylene (PP) containing intumescent flame retardant additives, i.e. melamine pyrophosphate (MPyP) and charring‐foaming agent (CFA) were characterized by limiting oxygen index (LOI), UL 94, cone calorimeter, microscale combustion calorimetry, and thermogravimetric analysis (TGA). It has been found that the PP material containing only MPyP does not show good flame retardancy even at 30% additive level. Compared with the PP/MPyP binary system, the LOI values of the PP/MPyP/CFA ternary materials at the same additive loading are all increased, and UL 94 rating is raised to V‐0 from no rating (PP/MPyP). The cone calorimeter results show that the heat release rate and mass loss rate of some ternary materials decrease in comparison with the binary material. The microscale combustion calorimetry results indicate that the sample containing 22.5 wt% MPyP and 7.5 wt% CFA has the lowest heat release rate among all samples. The TGA results show that the thermal stability of the materials increases with the addition of MPyP, while decreases with the addition of CFA. Copyright © 2009 John Wiley & Sons, Ltd.     

Effect of a novel charring-foaming agent on flame retardancy and thermal degradation of intumescent flame retardant polypropylene

A new triazine polymer was synthesized by using cyanuric chloride, ethanolamine and ethylenediamine as raw materials. It is used both as a charring agent and as a foaming agent in intumescent flame retardants, designated as charring-foaming agent (CFA). Effect of CFA on flame retardancy, thermal degradation and mechanical properties of intumescent flame retardant polypropylene (PP) system (IFR-PP system) has been investigated. The results demonstrated that the intumescent flame retardant (IFR) consisting of CFA, APP and Zeolite 4A is very effective in flame retardancy of PP. It was found that when the weight ratio of CFA to APP is 1:2, that is, the components of the IFR are 64 wt% APP, 32 wt% CFA and 4 wt% Zeolite 4A, the IFR presents the most effective flame retardancy in PP systems. LOI value of IFR-PP reaches 37.0, when the IFR loading is 25 wt% in PP. It was also found that when the IFR loading is only 18 wt% in PP, the flame retardancy of IFR-PP can still pass V-0 rating, and its LOI value reaches 30.2. TGA data obtained in pure nitrogen demonstrated that CFA has a good ability of char formation itself, and CFA shows a high initial temperature of the thermal degradation. The char residue of CFA can reach 35.7 wt% at 700 °C. APP could effectively promote the char formation of the APP-CFA system. The char residue reaches 39.7 wt% at 700 °C, while it is 19.5% based on calculation. The IFR can change the thermal degradation behaviour of PP, enhance T_max of the decomposition peak of PP, and promote PP to form char, based upon the results of the calculation and the experiment. This is attributed to the fact that endothermic reactions took place in IFR charring process and the char layer formed by IFR prevented heat from transferring into inside of IFR-PP system. TGA results further explained the effective flame retardancy of the IFR containing CFA.     

Flame retardancy and thermal degradation of intumescent flame retardant polypropylene with MP/TPMP

The performances of the novel intumescent flame retardant (IFR) polypropylene (PP) composites containing melamine phosphate (MP) and tris(1‐oxo‐2,6,7‐trioxa‐1‐phosphabicyclo[2,2,2]methylene‐4)phosphate (TPMP) were investigated. The flame retardancy of IFR‐PP system was characterized by limiting oxygen index (LOI) and UL 94 and cone calorimeter. The morphology of the char obtained after cone calorimeter testing was studied by scanning electron microscopy (SEM). The thermal oxidative degradation (TOD) of the composites was investigated by using thermogravimetric analysis (TGA) and real‐time Fourier transform infrared spectroscopy (RT‐FTIR). Compared with the PP/ TPMP or PP/ MP binary composite, at the same addition level, the LOI values of the PP/MP/TPMP ternary composites increase and reach V‐0 at the suitable MP/TPMP ratio. The results of TGA and RT‐FTIR showed the existence of the interaction between IFR and PP. Copyright © 2008 John Wiley & Sons, Ltd.     

Flame‐retardancy and anti‐dripping effects of intumescent flame retardant incorporating montmorillonite on poly(lactic acid)

In the present study, the effects of intumescent flame retardant (IFR) incorporating organically modified montmorillonite (O‐MMT) on the flame retardancy and melt stability of PLA were investigated. The flame‐retardant PLA was prepared using a twin‐screw extruder and a two roll mill. Then, the influence of IFR and MMT on flame retardancy and melt stability was thoroughly investigated by means of limiting oxygen index (LOI), vertical burning test, thermogravimetric analysis, scanning electronic microscopy, melt flow index (MFI), and parallel plate rheological experiments. The experimental results show that the IFR system in combination with MMT has excellent fire retardancy, i.e. the sample could achieve a UL94 V‐0 rating and LOI value increases from 20.1 for pristine PLA to 27.5 for the flame‐retarded PLA. MFI and rheological measurement indicate that O‐MMT significantly enhances the melt stability and suppresses the melt dripping. Copyright © 2009 John Wiley & Sons, Ltd.     

Effect of a polyetheramine additive on the melt-flowability of poly(butylene terephthalate)

A polyetheramine (PEA) was added to poly(butylene terephthalate) (PBT) to improve its melt-flowability. Fourier transform infrared (FTIR) and solution proton nuclear magnetic resonance spectroscopy (¹H-NMR) were employed to check the change in chemical structure after compounding, while differential scanning calorimetry (DSC), wide angel X-ray diffraction (WAXD), capillary rheometer and a universal testing machine were used to investigate the thermal properties, crystal structure, rheological behavior and mechanical properties of PBT/PEA blends. The results revealed that a loading of 1.0wt% PEA in PBT drastically improved its melt-flowability without the loss of thermal properties and tensile strength. As comparisons, blends of PBT with polyols such as pentaerythritol and di(trimethylolpropane) were also prepared and the properties were evaluated. It was found that the melt-flowability improvement from these polyols was much lower than that from PEA.     

干法制备磷-氮膨胀型阻燃剂的研究

以磷酸、五氧化二磷、季戊四醇和三聚氰胺为原料,采用干法(不添加任何溶剂)合成了一种磷-氮膨胀型阻燃剂。IR分析发现合成阻燃剂具有与磷酸酯三聚氰胺盐类似的P=O和P-O-C双环结构。反应温度、时间和原料配比对酯化反应有明显的影响。酯化反应温度宜控制在120-130℃之间,反应时间2.5小时,加入五氧化二磷可以提高酯化反应的转化率,磷酸与五氧化二磷的摩尔比控制在2:1为宜。热重分析表明,该阻燃剂的起始分解温度为190℃左右,700℃时的成炭率约为30%。该阻燃剂受热后膨胀倍数约为30-50倍,SEM分析发现,阻燃剂膨胀炭层外表面连续、平滑、颗粒之间连结紧密,炭层为内部为多孔结构,空隙大小分布均匀,孔径约为150-200μm之间,这样的泡层结构能更好的起到隔热的效果。     

A novel intumescent flame retardant: Synthesis and application in ABS copolymer

A novel phosphorous-nitrogen structure containing intumescent flame retardant, poly(4,4-diaminodiphenyl methane spirocyclic pentaerythritol bisphosphonate) (PDSPB) was synthesized and characterized. Thermal stability and flammability properties of ABS/PDSPB composites were investigated by thermogravimetric analysis (TGA) and cone calorimeter test, respectively. The results showed that the addition of PDSPB enhanced the thermal stability and flame retardancy of ABS significantly. The weight of residues improved greatly with the addition of PDSPB. FTIR and SEM investigations revealed that the residual chars contain polyphosphoric or phosphoric acid, which plays an important role in the process of carbonization. The intumescent chars formed from PDSPB and ABS/PDSPB composites were intact, multicellular and strong. It is confirmed that the char structure was a critical factor for flame retardancy of ABS resin.     

Properties of sulfonated poly(butylene terephthalate)

The synthesis, morphology, and mechanical properties of sulfonated poly(butylene terephthalate) (PBT) and its unsulfonated analogs were studied. The morphology of these copolymers crystallized from the melt were examined by a combination of wide-angle x-ray scattering (WAXS), polarized light microscopy, and small-angle light scattering (SALS). Stress-strain measurements are correlated with the morphological results. Spherulitic morphology, with a maltese cross at 45°C with respect to the crossed polars, is formed at low sulfonate levels (≤ 5.0 mol %). At a higher ion content, the maltese cross rotates 45° to form a cross pattern. At still higher sulfonate contents, typically 13 mol %, the light scattering pattern disappears completely. Microscopic and WAXS examination of these functionalized PBT copolymers confirms that the crystallinity level decreases with increasing ion content and is eliminated completely at the higher sulfonation level. The spherulite radius, however, remains invariant until the highest functionalization level. On the contrary, the morphology and properties of the unsulfonated isophthalate copolymer analogs remain relatively constant over the entire composition range examined. In several compositions clearly inferior properties are noted compared with the ion-containing copolymers.     

Study on rheological behaviour of poly(butylene terephthalate)/montmorillonite nanocomposites

Poly(butylene terephthalate)/montmorillonite composites (PBT/MMT) were prepared by melt intercalation and then investigated using X-ray diffractometer (XRD) and transmission electron microscope (TEM) as well as parallel plate rheometer. It was found that the composites had various phase morphologies with nanoscales and distinct behaviours of a percolation network structure under certain conditions. The linear viscoelastic region of the composites is much narrower than that for PBT matrix, the percolation threshold of the composites is near 3 wt.%, and the percolation network structure is not stable under a shear as well as in a quiescent annealing process. Moreover, PBT/MMT presents the nature of temperature independence of G′ versus G″ whether the internal percolated tactoids network formed or not. The magnitudes of the stress overshoots observed in the reverse flow experiments were strongly dependent on the rest time, which could be inferred that the ruptured network is reorganized under the quiescent annealing process. Furthermore, PBT/MMT shows a strain-scaling stress response to the startup of steady shear, indicating that the formation of the liquid crystalline-like phase structure in the nanocomposites may be the major drive force for the reorganization of the internal network.     

Flame retardancy mechanisms of poly(1,4‐butylene terephthalate) containing microencapsulated ammonium polyphosphate and melamine cyanurate

The flame retardancy mechanisms of poly(1,4‐butylene terephthalate) (PBT) containing microencapsulated ammonium polyphosphate (MAPP) and melamine cyanurate (MC) were investigated via pyrolysis analysis (thermogravimetric analysis (TGA), real‐time Fourier transform infrared (FTIR), TG‐IR), cone calorimeter test, combustion tests (limited oxygen index (LOI), UL‐94), and residue analysis (scanning electron microscopy (SEM)). A loading of 20 wt% MC to PBT gave the PBT composites an LOI of 26%, V‐2 classification in UL‐94 test and a high peak heat release rate (HRR) in cone calorimeter test. Adding APP to PBT/MC composites did not improve their flame retardancy. In comparison with the addition of ammonium polyphosphate (APP) to PBT, MAPP with silica gel shell and MAPP with polyurethane shell both promoted the intumescent char‐forming and improved the flame retardancy of PBT through different mechanisms in the presence of MC. These two halogen‐free PBT composites with V‐0 classification according to UL‐94 test were obtained; their LOI were 32 and 33%, respectively. Copyright © 2010 John Wiley & Sons, Ltd.     

Manufacturing,thermal stability,and flammability properties of polypropylene containing new single molecule intumescent flame retardant

Melamine salt of pentaerythritol phosphate kaolin (MPPK) was synthesized by the reaction of pentaerythritol phosphate with kaolin (K) and melamine. The structure of MPPK was confirmed by EDXS, ¹H NMR, FTIR, and XRD. MPPK was blended with polypropylene (PP) at different loading levels. Thermogravimetric analysis (TGA) results showed that MPPK improved the thermal stability of PP at high temperatures in all PP composites. Vertical burning rate test manifested that PP composites can achieve V0 at 20% and 25% MPPK loading levels. Cone calorimeter data exhibited that addition of 25% MPPK to PP reduced peak of heat release rate (pHRR) and total heat release (THR) by 86% and 76% and increased the char residue after test to 67%. The results of PP/25% MPPK composite were compared with the data obtained from PP containing 25% K and 25% of traditional intumescent flame retardant composed of melamine phosphate (MP), pentaerythritol (PE), and K. The outcomes indicated that MPPK was more efficient in flame retardancy than the other systems. The digital photographs and SEM images for char residue demonstrated that MPPK succeeded in forming cellular and coherent char layer on the PP surface. The main advantage of adding 25% MPPK to PP was its ability to preserve nearly the inner half of the sample without burning after cone calorimeter test.     

Phosphorus polyester versus aluminium phosphinate in poly(butylene terephthalate) (PBT): Flame retardancy performance and mechanisms

Pyrolysis and fire behaviour of a phosphorus polyester (PET-P-DOPO) have been investigated. The glycol ether of the hydroquinone derivative of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide was used as a reactive halogen-free flame retardant in PET-P-DOPO. PET-P-DOPO is proposed as an alternative to poly(butylene terephthalate) (PBT) with established halogen-free additives. It exhibits a high LOI (39.3%) and achieves V-0 classification in the UL 94 test. Three different mechanisms (flame inhibition, charring and a protection effect by the intumescent char) contribute to the flame retardancy in PET-P-DOPO and were quantified with respect to different fire risks. The fire load was reduced by 66% of the PBT characteristic. The reduction is the superposition of the relative reduction due to flame inhibition (factor 0.625) and charring (factor 0.545). The peak of heat release rate (pHRR) was reduced by 83% due to flame inhibition, charring and the protection properties of the char (factor 0.486). The strength of all three mechanisms is in the same order of magnitude. The intumescent multicellular structure enables the char to act as an efficient protection layer. PBT flame-retarded with aluminium diethylphosphinate was used as a benchmark to assess the performance of PET-P-DOPO absolutely, as well as versus the phosphorus content. PET-P-DOPO exhibits superior fire retardancy, in particular due to the additional prolongation of the time to ignition and increase in char yield. PET-P-DOPO is a promising alternative material for creating halogen-free flame-retarded polyesters.     

Effect of nanoscale fully vulcanized acrylic rubber powders on crystallization of poly(butylene terephthalate): Isothermal crystallization

Poly(butylene terephthalate) (PBT) was blended with nanoscale fully vulcanized acrylic rubber (FVAR) powders in a twin extruder, and the FVAR powders were dispersed well in PBT from scanning electron microscopy (SEM) and transmission electron microscope (TEM) investigation. The isothermal crystallization kinetics of PBT/FVAR blends were investigated by differential scanning calorimeter (DSC) and simulated by Avrami model. Equilibrium melting temperature was estimated by the nonlinear Hoffman-Weeks relation. The active energy (ΔE) and nucleation parameters (K_g) increased with the addition of FVAR, suggesting that FVAR particles hindered the crystallization; however more content FVAR had a lower ΔE and K_g because FVAR powders acted as heterogeneous nuclei in the nucleation of crystallization and facilitated the crystallization of PBT. The crystallization ability followed the order: PBT > PBT/FVAR6 > PBT/FVAR3 > PBT/FVAR1 when undercooling was considered.     

Fire hazard suppression of intumescent flame retardant polypropylene based on a novel Ni‐containing char‐forming agent

Reducing the fire hazard of polypropylene (PP) is an important research direction in the fields of fire safety materials. In this article, a novel Ni‐containing char‐forming agent (TTPN) was successfully synthesized, using tris(2‐hydroxyethyl) isocyanurate (THEIC), terephthalic acid, and nickel dihydrogen phosphate. Then, TTPN was combined with the silica‐gel microencapsulated ammonium polyphosphate (OS‐MCAPP) to prepare intumescent flame retardant PP composites. From the results of the limiting oxygen index (LOI) test and cone calorimeter, the composite containing 30% IFR (OS‐MCAPP: TTPN = 3:2) shows the highest LOI value of 33.5%, and its peak heat release rate is 275.5 kWm^?2, decreased by 79.0% and 37.4% than those of pure PP and the composite containing the char‐forming agent without Ni. Meanwhile, the composite containing TTPN present the best smoke and CO₂/CO suppression. The results indicate that TTPN has an excellent ability to dramatically reduce the fire hazard of PP.     

Thermal stability and flame retardant effects of halloysite nanotubes on poly(propylene)

Naturally occurred halloysite nanotubes (HNTs) with hollow nanotubular structures were used as a new type filler for poly(propylene) (PP). Nanocomposites based on PP and HNTs were prepared by melt blending. Scanning electronic microscopy (SEM) results suggested HNTs were dispersed in PP matrix evenly at nanoscale after facile modification. Thermal stability of the nanocomposites was found remarkably enhanced by the incorporation of HNTs. Cone calorimetric data also showed the decrease of flammability of the nanocomposites. Entrapment mechanism of the decomposition products in HNTs was proposed to explain the enhancement of thermal stability of the nanocomposites. The barriers for heat and mass transport, the presence of iron in HNTs, are all responsible for the improvement in thermal stability and decrease in flammability. Those results suggested potential promising flame retardant application of HNTs in PP.     

Nanocomposite of montmorillonite with telechelic sulfonated poly(butylene terephthalate): Effect of ionic groups on clay dispersion, mechanical and thermal properties

Telechelic ionomeric poly(butylene terephthalate) nanocomposites with organically modified clays have been prepared by the melt intercalation technique both in Brabender mixer and in twin screw-extruder. The presence of ionic groups tethered at the end of the polymer chains permits electrostatic interaction between the polymer and the surface of an organically modified clays providing a thermodynamic driving force for the dispersion of the clay platelets in the polymer matrix. The improved dispersion has been verified by TEM and XRD analyses. Nanocomposites with telechelic polymers present therefore consistently higher thermo-mechanical properties and improved thermal and hydrolytic stability respect to nanocomposites with standard PBT. Nanocomposite obtained using PBT with 3% telechelic ionic groups and with 5% of clay present a heat deflection temperature that is 48 °C higher compared to that of the commercial material. The presence of the clay also slightly increases the thermal and hydrolytic stability respect to standard PBT.     

Synthesis of a novel ionic liquid containing phosphorus and its application in intumescent flame retardant polypropylene system

A novel ionic liquid containing phosphorus ([PCMIM]Cl) was synthesized and characterized by FTIR, ¹H NMR, ¹³C NMR and ³¹P NMR. Moreover, a new intumescent flame retardant (IFR) system, which was composed of [PCMIM]Cl and ammonium polyphosphate (APP), was used to impart flame retardancy and dripping resistance to polypropylene (PP). The flammability and thermal behaviors of intumescent flame‐retarded PP (PP/IFR) composites were evaluated by limiting oxygen index (LOI), UL‐94 test, thermogravimetric analysis (TGA) and cone calorimeter test. It was found that there was an obvious synergistic effect between [PCMIM]Cl and APP. When the weight ratio of [PCMIM]Cl and APP was 1:5 and the total amount of IFR was kept at 30 wt%, LOI value of PP/IFR composite reached 31.8, and V‐0 rating was obtained. Moreover, both the peak heat release rate and the peak mass loss rate of PP/IFR composites decreased significantly relative to PP and PP/APP composite from cone calorimeter analysis. The TGA curves suggested that [PCMIM]Cl had good ability of char formation, and when combined with APP, it could greatly promote the char formation of PP/IFR composites, hence improved the flame retardancy. Additionally, the rheological behaviors and mechanical properties of PP/IFR composites were also investigated, and it was found that [PCMIM]Cl could also serve as an efficient lubricant and compatibilizer between APP and PP, endowing the materials with satisfying processability and mechanical properties. Copyright © 2013 John Wiley & Sons, Ltd.