Intumescent Flame Retardant Loading Research Articles

Preparation of DOPO‐derived magnesium phosphate whisker and its synergistic effect with ammonium polyphosphate on the flame retardancy and mechanical property of epoxy resin

AbstractIn this study, a magnesium phosphate whisker (DPM‐H) was synthesized by the acid–base neutralization reaction between magnesium hydroxide and 10‐hydroxy‐9,10‐dihydro‐9‐oxa‐10‐phosphaphenanthrene‐10‐oxide (DOPO‐OH) at 120°C. A new synergistic intumescent flame retardant (IFR) for epoxy resin (EP), which was composed of DPM‐H and ammonium polyphosphate (APP) was thoroughly studied. When the IFR loading was 8%, with the DPM‐H to APP weight ratio at 1:7, the prepared flame‐retardant EP (EPDA‐2) passed the vertical burning tests (UL‐94) V‐0 rating and obtained the limiting oxygen index (LOI) value of 29.3%. Microscale combustion calorimetry (MCC) results showed that the total heat release (THR) of EPDA‐2 reduced by 32.1% compared with pure EP. Meanwhile, the addition of DPM‐H can partially solve the problem of the decrease of the EP mechanical property caused by the addition of APP. Compared with the flame‐retardant EP with the 8% loading of APP, the impact strength of EPDA‐2 increased 152.3%.

Halogen‐free intumescent flame retardancy and mechanical properties of the microcellular polypropylene with low expansion ratio via continuous extrusion assisted by subcritical CO2

AbstractContinuous preparation of the intumescent flame retardant (IFR) and polypropylene (PP) composite (IFR‐PP) foams with excellent flame retardancy and mechanical properties via the extrusion assisted by subcritical CO2 was presented. The effects of die structure, die temperature/pressure and CO2 injection ratios on expansion ratio, cell diameter, and cell density of the IFR‐PP foams were investigated. A uniform cell structure without obvious defects was prepared by the die with better pressure holding capacity. With the increase of die temperature, die pressure decreased accordingly, the expansion ratio of the obtained IFR‐PP foams decreased, the cell diameter increased, and the cell density decreased. With an appropriate increase in the CO2 injection ratio, the expansion ratio of the resulting IFR‐PP foams increased, the cell diameter decreased, and the cell density increased. Cell wall thickness played an important role in mechanical properties. When the expansion ratio was maintained near 3 or cell diameter was maintained near 92 μm, as the cell wall thickness increased, the tensile modulus and tensile strength increased. A cell structure without defects possessed better mechanical properties and flame retardancy than a deformed cell. Moreover, the IFR‐PP foams exhibiting excellent flame retardancy including the 30% of limiting oxygen index (LOI) values and UL‐94 V0 rating without dripping were achieved at only 22.5 wt% of IFR loading.

Synthesis, Characterization of sym-2,4,6-trisubstituted-s-Triazine Derivatives and Their Effects on Flame Retardancy of Polypropylene Composites

Polypropylene (PP) is flammable material, which brings latent danger to the environment and human society. Therefore, developing new environmentally friendly and effective flame-retardant is one of the most important ways to improve the flame retardancy of PP and improve safety during its lifetime. Herein, we describe the synthesis of five sym-2,4,6-trisubstituted-s-triazine derivatives, namely, N2,N4,N6-triphenyl-1,3,5-triazine-2,4,6-triamine (TAT), N2,N4,N6-tris(4-bromophenyl)-1,3,5-triazine-2,4,6-triamine (TBAT), N2,N4,N6-tris(4-chlorophenyl)-1,3,5-triazine-2,4,6-triamine (TCAT), 4,4′,4″-((1,3,5-triazine-2,4,6-triyl) tris(azanediyl)) triphenol (THAT), and N2,N4,N6-tris(4-methoxyphenyl)-1,3,5-triazine-2,4,6-triamine (TMAT), from the reaction of cyanuric chloride and p-substituted aniline employing conventional heating or microwave irradiation. The prepared compounds characterized by different techniques, such as Fourier-transform infrared (FTIR), Ultra-Violet and Visible (UV-Vis), Nuclear Magnetic Resonance spectroscopy (1H-NMR and 13C-NMR), Thermogravimetric Analysis (TGA), and differential scanning calorimetry (DSC). The effect of substituent on the aniline moiety has great impact on its thermal stability, as observed from the TGA and DSC data. Based on the TGA and DSC results, three triazine derivatives TAT, TBAT, and TMAT were used as charring agents in the presence of different proportions of ammonium polyphosphate (APP) to form an intumescent flame-retardant (IFR) system, to improve the flame retardancy of PP. The flammability property of PP was investigated by a vertical burning test (UL94). The results of UL94 revealed that the TXAT/APP (IFR) system influence the PP and could improve the flame retardancy of PP. Best results were obtained with the mass ratio of APP and TXAT 2:1. When the IFR loading was 25 wt%, it displayed great influence and passed V-0 with TMAT, and V-1 with both TAT and TBAT in the UL94 test.

Ultrastrong, flexible and lightweight anisotropic polypropylene foams with superior flame retardancy

Novel polypropylene (PP) foams with both greatly enhanced mechanical properties and superior flame-retardant performance are urgently needed in the area of automobiles, packaging, electrics and military. In this work, ultrastrong, flexible and lightweight anisotropic PP foams with superior flame retardancy have been fabricated by foaming of PP and intumescent flame retardant (IFR) composites through the drawing-assisted supercritical carbon dioxide (scCO2) continuous extrusion-foaming technique. The as-prepared PP/IFR foams with only 25 wt% IFR loading and an ultralow density of ∼0.08 g cm−3 could reach the HF-1 level in the standard horizonal burning tests due to the uniform IFR dispersion resulting from the plasticization effect of scCO2 coupled with the in-situ bubble stretching during foaming, and also exhibited greatly enhanced mechanical properties mainly owing to their anisotropic cellular structure and oriented molecular chains, reaching a record specific stiffness as high as ∼1813 MPa/(g cm−3). More importantly, this technique is environment-friendly without the use of any volatile organic solvents, and can go into practical mass production with a speed up to ∼0.56 m s−1.

High-performance flame retarded paraffin/epoxy resin form-stable phase change material

In this study, a novel halogen-free flame retarded form-stable phase change material (PCM) was designed and prepared, selecting paraffin as the thermal-energy storage material and epoxy resin (EP) as the supporting material; furthermore, a novel flame retardant curing agent PEPA–TMA (2,6,7-trioxa-1-phosphabicyclo-[2.2.2]-octane-4-methanol reacted with trimellitic anhydride) and melamine cyanurate were combined into the energy-storing material to obtain the flame retarded PCM. Thermal performances of the PCM were investigated through differential scanning calorimeter, the data suggested that the PCM had relatively high latent heat, and values normalized to the amount of paraffin were lower than the theoretical values. The thermogravimetric analysis displayed that the intumescent flame retardant (IFR) could improve the charring of the PCM, and the PCM had passed a UL 94 V-0 test when the IFR loading reached 24 wt%. The cone calorimeter results further proved that the PCM had better flame retardancy. The morphology of the composites was observed by scanning electron microscopy, and the images showed that the paraffin could be dispersed uniformly in the materials, which formed a three-dimensional network by EP.

Synthesis of amino trimethylene phosphonic acid melamine salt and its application in flame‐retarded polypropylene

ABSTRACTAmino trimethylene phosphonic acid melamine salt (MATMP) was synthesized and used as acid source and blowing agent in intumescent flame‐retarded polypropylene (PP); its compositions were characterized by Fourier transform infrared spectroscopy and X‐ray powder diffraction. An intumescent flame retardant (IFR) system composed of MATMP, pentaerythritol (PER), and PP was tested by limiting oxygen index (LOI), UL‐94, cone calorimeter tests, and thermogravimetric analysis and compared with an ammonium polyphosphate (APP)/PER system. The results showed that MATMP had better water resistance than APP, the LOI value of PP/MATMP/PER composite can reach 30.3%, and a UL‐94 V‐0 rating can be reached at 25 wt % IFR loading. The amount of residual char of IFR MATMP/PER was 20.3 and 9.5 wt % at 400 and 600 °C, respectively. A thermooxidative degradation route and a possible flame‐retardant mechanism of IFR were proposed according to the analysis of evolved gases and residual chars. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46274.

Utilization of MHSH as Synergistic Agent in Flame‐retarded PBS Composites

Basic magnesium hydroxide sulfate whisker (MHSH) was used as flame‐retarded synergistic agent of intumescent flame retardant (IFR) system, and to prepare flame‐retarded PBS composites. Furthermore, the mechanics performance, the limiting oxygen index (LOI) analysis and the flame retardant properties of the composites were investigated. Experimental data show that with the incorporation of MHSH, the LOI values and the UL‐94 levels of composites improved in comparison with those of the composites without MHSH addition, indicating the synergistic effect of MHSH in composites. Furthermore, when the IFR and MHSH loading were 23% and 2 wt%, respectively, the UL‐94 level achieved V0 rate. Simultaneously, as indicated by mechanical properties, illustrating that MHSH played a reinforcement effect in composites.

Preparation and characterization of oligomeric char forming agent and its effect on the thermal degradation and flame retardant properties of LDPE with ammonium polyphosphate**

An efficient oligomeric charring agent (CNCA-DA) containing a triazine and benzene rings was synthesized and characterized by the nuclear magnetic resonance spectroscopy (13C solid-state NMR), elemental analysis (EA) and thermal gravimetric analysis (TGA). The synergistic effects between Ammonium polyphosphate (APP) and CNCA-DA on the flame retardancy, thermal degradation and flame retardant mechanism of low density polyethylene (LDPE) were investigated. The 13C NMR and elemental analysis (EA) results indicated that the structure of CNCA-DA coincided with the expected design. The thermogravimetric analysis (TGA) analysis showed that CNCA-DA had a good char forming ability with a high initial temperature of thermal degradation. APP improved the char residue of the APP/CNCA-DA system with char residue reached 41.0% and 18.2at 600 and 700°C under air. The results from limited oxygen index (LOI) and vertical burning test (UL-94) showed that the intumescent flame retardant (IFR) was very effective in the flame retardancy of LDPE. When the mass ratio of APP and CNCA-DA was 2:1 with IFR loading at 30%, the LOI value of LDPE/IFR composite reached 30.9%. It was also found that when the IFR loading was only 25%, the flame retardancy of LDPE/IFR still passed V-0 rating in UL-94 tests with LOI value of 26.8%. The thermogravimetric analysis (TGA) and Thermogravimetric analyzer coupled to a mass spectrometer (TGA/MS) results indicated that IFR could reduce the thermal degradation rate at main stage of degradation and side chain fragmentation was probably the dominant mechanism of thermal degradation. The cone calorimeter teat test (CCT) results demonstrated that IFR clearly changed the decomposition behavior of LDPE and formed an intumescent char layer on the surface of the composites, subsequently resulting in the efficient reduction of the flammability parameters, such as the heat release rate (HRR), total heat release (THR), smoke production rate (SPR), total smoke production (TSP), mass loss (ML), CO production (COP) and CO2 production (CO2P). The morphological structures observed by digital photos and scanning electron microscopy (SEM) demonstrated that IFR promoted to form the continuous and compact intumescent char layer. The Fourier Transform infrared spectroscopy (FTIR), Laser Raman spectroscopy analysis (LRS) analysis results revealed that an appropriate graphitization degree and network structure of the residue char were formed to improve the strength and shield properties of the char layer to obtain better flame retardant properties of the composite.

Flame retardant properties and mechanism of an efficient intumescent flame retardant PLA composites

The charring agent (CNCA-DA) containing triazine and benzene rings was combined with ammonium polyphosphate (APP) to form intumescent flame retardant (IFR), and it was occupied to modify polylactide (PLA). The flame retardant properties and mechanism of flame retardant PLA composites were investigated by the limited oxygen index (LOI), vertical burning test (UL-94), thermogravimetric analysis, microscale combustion calorimetry, scanning electron microscopy, laser Raman spectroscopy analysis and X-ray photoelectron spectroscopy. The analysis from LOI and UL-94 presented that the IFR was very effective in flame retardancy of PLA. When the weight ratio of APP to CNCA-DA was 3:1, and the IFR loading was 30%, the IFR showed the best effect, and the LOI value reached 45.6%. It was found that when 20 wt% IFR was loaded, the flame retardancy of PLA/IFR still passed UL-94 V-0 rating, and its LOI value reached 32.8%. The microscale combustion calorimetry results showed that PLA/IFR had lower heat release rate, total heat release, and heat release capacity than other composites, and there was an obvious synergistic effect between APP and CNCA-DA for PLA. IFR containing APP/CNCA-DA had good thermal stability and char-forming ability with the char residue 29.3% at 800°C under N2 atmosphere. Scanning electron microscopy observation further indicated that IFR could promote forming continuous and compact intumescent char layer. The laser Raman spectroscopy analysis and X-ray photoelectron spectroscopy analysis results indicated that an appropriate graphitization degree of the residue char was formed, and more O and N were remained to form more cross-linking structure. Copyright © 2016 John Wiley & Sons, Ltd.

Synergistic effect of ammonium polyphosphate and triazine-based charring agent on the flame retardancy and combustion behavior of ethylene-vinyl acetate copolymer

Triazine-based charring agent poly(4,6-dichloro-N-hydroxyethyl-1,3,5-triazin-2-amine-1,6-diaminohexane) (CNCO-HA) with ammonium polyphosphate (APP) was chosen to prepare intumescent flame retardant ethylene-vinyl acetate copolymer (EVA) composites by melting blending. The synergistic effect of APP and CNCO-HA on the flame retardancy, combustion behavior and flame retardant mechanism of EVA are investigated. The flame retardant properties from limited oxygen index (LOI) and vertical burning test (UL-94) show that the intumescent flame retardant (IFR) shows the best effect when the mass ratio of APP to CNCO-HA is 3:2; and the LOI value of EVA/IFR composite reaches maximum value 30.9% with 30% IFR loading. When the IFR loading is only 20%, the flame retardancy of EVA/IFR still passes UL-94 V-0 rating with LOI value of 28.2%. The cone calorimeter test (CCT) results reveal that IFR clearly changes the combustion behavior of EVA and forms a char layer on the surface of the composites, consequently resulting in obvious reduction of the flammability and smoke production of EVA. The thermogravimetric analysis (TGA) and thermogravimetric analyzer coupled to a mass spectrometer (TGA/MS) results indicate that IFR improves char residue and side chain fragmentation is probably the dominant mechanism of thermal degradation. The morphology observed by digital photos and SEM demonstrate that IFR promotes to form the compact intumescent char layer. The LRS and FTIR results indicate that EVA/IFR forms more connected structures containing POP and POC bonds and polyaromatic structure.

Flame retardancy and thermal degradation of intumescent flame retardant EVA composite with efficient charring agent

Intumescent flame retardant ethylene-vinyl acetate (EVA) composites with ammonium polyphosphate (APP) and efficient charring agent (CNCA-DA) were prepared through melt blending. The effect of APP and CNCA-DA on the flame retardant properties and thermal degradation of EVA were investigated by the means of limited oxygen index (LOI), vertical burning test (UL-94), thermogravimetric analysis (TGA), cone calorimeter test (CCT), scanning electron microscopy (SEM), laser Raman spectroscopy (LRS), and Fourier transform infrared (FTIR). The results from LOI and UL-94 showed that the intumescent flame retardant (IFR) containing CNCA-DA and APP was very effective in flame retardancy of EVA. When the mass ratio of APP and CNCA-DA was 3:1, the IFR showed the best effect, and when the IFR loading held 30%, the LOI value reached 32.1%. It was also found that when the IFR loading held only 20%, the flame retardancy of EVAP/IFR can still pass V-0 rating in UL-94 tests, meanwhile, its LOI value reached 27.0%. As for CCT results, IFR could clearly change the decomposition behavior of EVA and formed an intumescent char layer on the surface of the composites, consequently resulting in efficient reduction of the flammability parameters, such as heat release rate (HRR), total heat release (THR), smoke production rate (SPR), and mass loss (ML). In addition, the morphological structures which were observed by digital photos and SEM manifested that IFR could promote to form the continuous and compact intumescent char layer. The analysis of LRS and FTIR indicated that EVA/IFR could form POP and POC connected structures as well as polyaromatic structure. When APP and CNCA-DA were combined together, the suitable strength of char layer was obtained to improve the flame retardant properties.

Preparation and characterization of a novel oligomeric charring agent and its application in halogen-free flame retardant polypropylene

A novel charring agent (CNCO-HA) containing triazine rings was synthesized by a series of polycondensation reactions, and characterized by Fourier transform infrared (FTIR), nuclear magnetic resonance spectroscopy (13C solid-state NMR), and thermal gravimetric analysis (TGA). The synergistic effects between APP and CNCO-HA on flame retardancy, thermal degradation, flammability properties and mechanism of polypropylene (PP) were investigated by the limited oxygen index (LOI), vertical burning test (UL-94), thermogravimetric analysis (TGA), cone calorimeter teat test (CCT), Laser Raman spectroscopy analysis (LRS) and Scanning electron microscopy (SEM). The TGA results showed that CNCO-HA had a good char forming ability, and a high initial temperature of thermal degradation; the char residue of CNCO-HA reached 36.2% and 6.2% at 600°C and 700°C under air; ammonium polyphosphate (APP) could improve the char residue of the APP/CNCO-HA system, the char residue reached 39.8% and 25.5% at 600°C and 700°C under air. The results from LOI and UL-94 showed that the intumescent flame retardant (IFR) containing CNCO-HA and APP was very effective in flame retardancy of PP. When the mass ratio of APP and CNCO-HA was 4:1, and the IFR loading was 30%, the IFR showed the best effect, and the LOI value reached 40.2%. It was also found that when the IFR loading was only 25%, the flame retardancy of PP/IFR could still pass V-0 rating in UL-94 tests, and its LOI value reached 34.3%. The CCT results demonstrated that IFR could clearly change the decomposition behavior of PP and form a char layer on the surface of the composites, consequently resulting in the efficient reduction of the flammability parameters, such as heat release rate (HRR), total heat release (THR), smoke production rate (SPR), total smoke production (TSP) and mass loss (ML). The morphological structures observed by digital photos and SEM demonstrated that IFR could be promoted to form the continuous and compact intumescent char layer. The LRS analysis results indicated that an appropriate graphitization degree of the residue char was formed to improve strength and shield properties of the char layer to obtain better flame retardant properties of the composite.

Investigations of Flame-Retarded Thermoplastic Poly(imide–urethane)s with Intumescent Flame Retardants

A series of flame-retarded thermoplastic poly(imide–urethane)s (TPIUs) with either ammonium polyphosphate (APP) alone or APP and dipentaerythritol (DPER) have been prepared. The fracture strength and strain of TPIU composites decrease with increasing amount of intumescent flame retardant (IFR), as shown by tensile tests. Thermogravimetric analysis shows that the initial decomposition temperature (T5%) of TPIU composites decreases with increasing IFR loading. The flame retardancies of these TPIU composites have also been tested according to the limiting oxygen index (LOI) and UL-94 standards. The results have indicated that the LOI value of TPIU/APP is a little higher than that of TPIU/(APP + DPER) with the same loading. Furthermore, 50% APP alone or APP + DPER incorporation into TPIU allowed attainment of the UL-94 V-0 standard. Details of fire behavior, such as time to ignition, heat release rate, peak of the heat release rate, total smoke release, and total heat release, have been tested by means of a c...

Enhancement of a hyperbranched charring and foaming agent on flame retardancy of polyamide 6

AbstractA hyperbranched polyamine was prepared using an A2 + B3 approach. It acted as a hyperbranched charring and foaming agent (HCFA) in combination with ammonium polyphosphate (APP) to form a new intumescent flame retardant (IFR) system for polyamide 6 (PA6). Effect of HCFA on flame retardant and thermal degradation properties of IFR‐PA6 was investigated by limiting oxygen index (LOI), UL‐94 vertical burning, cone calorimeter, and thermogravimetric analysis (TGA) tests. The IFR system presented the most effective flame retardancy in PA6 when the weight ratio of APP to HCFA was 2:1. The LOI value of IFR‐PA6 could reach 36.5 with V‐0 rating when the IFR loading was 30 wt%. Even if the loading decreased to 25 wt%, IFR‐PA6 could still maintain V‐0 rating with an LOI value of 31. TGA curves indicated that APP would interact with both PA6 and HCFA in PA6/APP/HCFA composite under heating. The interaction between APP and HCFA improved the char formation ability of IFR system and then much more char was formed for PA6/APP/HCFA composite than for PA6/APP. Therefore, better flame retardancy was achieved. Moreover, the structure and morphology of char residue were studied by Fourier transform infrared (FTIR), X‐ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM). The results indicated that compact and foaming char layer containing P‐O‐C structure was formed for PA6/APP/HCFA system during combustion. Copyright © 2010 John Wiley & Sons, Ltd.

Synthesis of novel triazine charring agent and its effect in intumescent flame‐retardant polypropylene

AbstractA novel charring agent (CNCA‐DA) containing triazine and benzene ring, using cyanuric chloride, aniline, and ethylenediamine as raw materials, was synthesized and characterized. The effects of CNCA‐DA on flame retardancy, thermal degradation, and flammability properties of polypropylene (PP) were investigated by limited oxygen index (LOI), vertical burning test (UL‐94), thermogravimetric analysis (TGA), and cone calorimeter test (CCT). The TGA results showed that CNCA‐DA had a good char forming ability, and a high initial temperature of thermal degradation; the char residue of CNCA‐DA reached 18.5% at 800°C; Ammonium polyphosphate (APP) could improve the char residue of APP/CNCA‐DA system, the char residue reached 31.6% at 800°C. The results from LOI and UL‐94 showed that the intumescent flame retardant (IFR) containing CNCA‐DA and APP was very effective in flame retardancy of PP. When the mass ratio of APP and CNCA‐DA was 2 : 1, and the IFR loading was 30%, the IFR showed the best effect; the LOI value reached 35.6%. It was also found that when the IFR loading was only 20%, the flame retardancy of PP/IFR can still pass V‐0 rating in UL‐94 tests, and its LOI value reached 27.1%. The CCT results demonstrated that IFR could clearly change the decomposition behavior of PP and form a char layer on the surface of the composites, consequently resulting in efficient reduction of the flammability parameters, such as heat release rate (HRR), total heat release (THR), smoke production rate (SPR), total smoke production (TSP), and mass loss (ML). © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Synergistic effect of metal oxides on the flame retardancy and thermal degradation of novel intumescent flame‐retardant thermoplastic polyurethanes

AbstractThe synergistic effects of some metal oxides on novel intumescent flame retardant (IFR)–thermoplastic polyurethane (TPU) composites were evaluated by limiting oxygen index (LOI), vertical burning test (UL‐94), thermogravimetric analysis (TGA), cone calorimetry, and scanning electron microscopy. The experimental data indicated that the metal oxides enhanced the LOI value and restricted the dropping of the composites. The IFR–TPU composites passed the UL‐94 V‐0 rating test (1.6 mm) in the presence of magnesium oxide (MgO) and ferric oxide (Fe2O3) at 35 wt % IFR loading, whereas only the MgO‐containing IFR–TPU composite reached a UL‐94 V‐0 rating at 30 wt % IFR loading. The TGA results show that the metal oxides had different effects on the process of thermal degradation of the IFR–TPU compositions. MgO easily reacted with polyphosphoric acid generated by the decomposition of ammonium polyphosphate (APP) to produce magnesium phosphate. MgO and Fe2O3 showed low flammability and smoke emission due to peak heat release rate, peak smoke production rate, total heat release, and total smoke production (TSP). However, zinc oxide brought an increase in the smoke production rate and TSP values. Among the metal oxides, MgO provided an impressive promotion on the LOI value. The alkaline metal oxide MgO more easily reacted with APP in IFRs. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Effects of Reactive Compatibilization on the Morphological, Thermal, Mechanical, and Rheological Properties of Intumescent Flame-Retardant Polypropylene

Flame-retardant polypropylene (PP) samples were in situ compatibilized with maleic anhydride grafted PP. Compatibilization reaction was verified by an IR spectrum and gel content measurements. Electron microscopy images showed that compatibilization could considerably reduce the size of the flame-retardant domains, control the phase morphology, and improve the interfacial adhesion between PP and intumescent flame retardant (IFR) with different IFR loading levels. The limiting oxygen index (LOI) of flame-retardant PP increased to different extents after compatibilization, indicating an improvement in the flame retardancy. Compatibilization enhanced the thermal stability to some extent and remarkably delayed thermal oxidative degradation of flame-retardant PP. For PP containing 20 wt % flame retardant, the temperature at which the maximum weight loss rate occurred was enhanced by about 99 degrees C after compatibilization. The storage modulus and glass transition temperatures were elevated to different extents. Tensile strengths of samples reduced in the presence of flame retardant alone but in the additional presence of compatibilizer were restored to levels similar to those of pure PP. Elongation-at-break values, however, showed IFR concentration-dependent reductions that were less for compatibilized samples. Furthermore, the complex viscosity of a compatibilized PP melt turned slightly smaller, which is favorable to melt processing.

A novel intumescent flame-retardant system containing metal chelates for polyvinyl alcohol

A novel flame retardant containing phosphorous–nitrogen structure, the ammonium salt of 2-hydroxyl-5,5-dimethyl-2,2-oxo-1,3,2-dioxapho sphorinane (PNOH), was synthesized and its structure was characterized by 1H NMR and FTIR spectra. PNOH was used together with ammonium polyphosphate (APP) to prepare a novel intumescent flame retardant (IFR) for polyvinyl alcohol (PVA). When a few amounts (0.5%) of metal chelates were added, the flame retardancy of the IFR–PVA systems was significantly improved, having a high LOI value of 34.2 in a total IFR loading of 15 wt.%. In order to have an understanding of the resulting flame retardant effects, the thermal degradation behaviors of IFR–PVA systems were investigated by thermogravimetric analysis (TGA), and the morphology and structures of residues generated in different conditions were investigated by scanning electronic microscopy (SEM) and FTIR spectra. The results show that NiSAO can promote the thermal stability of the IFR–PVA; the residual char containing polyphosphoric or phosphoric acid is formed during the combustion; the formation of a continuous and dense char layer could inhibit the transmission of heat during contacting with flame and shows good flame retardancy.

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.

Performance of an intumescent‐flame‐retardant master batch synthesized by twin‐screw reactive extrusion: effect of the polypropylene carrier resin

AbstractA novel way of preparing an intumescent flame retardant (IFR) and its master batch by the reactive extrusion of melamine phosphate and pentaerythritol, together with a polypropylene (PP) carrier, in a twin‐screw extruder has been established. The effect of the PP carrier resin on the flame retardancy and water resistance of the intumescent‐flame‐retarding PP materials was investigated by using the limited oxygen index (LOI), UL94 test, elemental analysis (EA), thermogravimetric analysis (TGA) and water solubility testing, respectively. In addition, the mechanism of the carrier effect was analysed by melt flow index (MFI), scanning electron microscopy (SEM), and TGA. The experimental results show that with increasing content of carrier resin (PP) in the IFR master batch from 0 to 15 wt%, the flame retardancy LOI of the PP/IFR (25 wt% loading) blend increased from 29.5 to 32, and the UL94 level at 1.6 mm thickness was improved from failure to a V‐0 rating. In addition, the water resistance of a flame‐retarded composite at 25 wt% IFR loading was greatly improved, i.e. after treatment with hot water at 70 °C for 168 h, the reducing rate of element N in the IFR/PP blend decreased from 18.3% with 5 wt% carrier resin to 12.9% with 15 wt% carrier resin, and the LOI reduction rate decreased from 15.3% without any carrier resin to 10.9% with 15 wt% carrier resin, while the flame‐retarded PP with an IFR master batch containing 10–15 wt% carrier resin maintained its UL94 V‐0 rating at 3.2 mm thickness. The improvement in flame retardancy was attributed to the improved flame‐retardant (FR) dispersion due to the carrier resin, while the improved water resistance was explained by the lowered water solubility of the IFR, the improved FR dispersion and the improved compatibility of the FR with the matrix resin due to the carrier resin. Reactive extrusion is a novel way to obtain pelletissed IFRs without powder pollution and their corresponding flame‐retarding materials with a number of desired properties. Copyright © 2004 Society of Chemical Industry