Effects of organopalygorskite on intumescent flame‐retarded polypropylene

The effect of organopalygorskite (OPGS) on an intumescent flame retardant (IFR) low‐density polypropylene (PP) has been investigated using the limited oxygen index (LOI), vertical burning test (UL‐94) and thermogravimetric analysis (TGA). The results of the LOI and UL‐94 tests indicate that the addition of OPGS substantially increases the LOI value for PP/IFR at a OPGS to IRF mass ratio of 2/28 with 30 wt% of total flame retardant. In addition, the samples pass the V‐0 rating in the UL‐94 tests. The results indicate that the addition of 2.0 wt% of OPGS simultaneously increases the tensile strength and bending strength of PP/IFR. J. VINYL ADDIT. TECHNOL., 24:281–287, 2018. © 2016 Society of Plastics Engineers     

Flame‐retardant properties and mechanisms of epoxy thermosets modified with two phosphorus‐containing phenolic amines

Two phosphorus‐containing phenolic amines, a 9,10‐dihydro‐9‐oxa‐10‐phosphaphenanthrene‐10‐oxide (DOPO)‐based derivative (DAP) by covalently bonding DOPO and imine (SB) obtained from the condensation of p‐phenylenediamine with salicylaldehyde, and its analog (AP) via the addition reaction between diethyl phosphite and SB, were used to prepare flame‐retardant epoxy resins. The burning behaviors and dynamic mechanical properties of epoxy thermosets were studied by limited oxygen index (LOI) measurement, UL‐94 test, and dynamic mechanical analysis. The flame‐retardant mechanisms of modified thermosets were investigated by thermogravimetric analysis, Py‐GC/MS, Fourier transform infrared, SEM, elemental analysis, and laser Raman spectroscopy. The results revealed that epoxy thermoset modified with DAP displayed the blowing‐out effect during UL‐94 test. With the incorporation of 10 wt % DAP, the modified thermoset showed an LOI value of 36.1% and V‐0 rating in UL‐94 test. The flame‐retardant mechanism was ascribed to the quenching and diluting effect in the gas phase and the formation of phosphorus‐rich char layers in the condensed phase. However, the thermoset modified with 10 wt % AP only showed an LOI value of 25.7% and no rating in UL‐94 test, which was possibly ascribed to the mismatching of charring process with gas emission process during combustion. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43953.     

Synergistic effects of 4A zeolite on the flame‐retardant properties and thermal stability of an efficient halogen‐free flame‐retardant EVA composite

The synergistic effects of 4A zeolite (4A) on the thermal degradation, flame retardancy, and char formation of an efficient halogen‐free flame‐retardant ethylene‐vinyl acetate copolymer composite (EVA/IFR) were investigated by limited oxygen index (LOI), vertical burning test (UL‐94), cone calorimeter test (CCT), digital photography, scanning electron microscopy (SEM), energy dispersive spectrometry (EDS), laser Raman spectroscopy (LRS) and thermogravimetric analytical (TGA) methods. It was found that a small amount of 4A clearly improved the LOI value of the EVA/IFR composite and reinforced the fire retardant performance with a great reduction in the combustion parameters of the EVA/IFR system from the CCT test. The entire composites passed the UL‐94 V‐0 rating test. The TGA and integral procedure decomposition temperature (IDPT) results showed that 4A enhanced the thermal stability of the EVA/IFR system and increased the char residue content effectively. The morphological structures observed by digital and SEM imaging revealed that 4A could promote EVA/IFR to form a more continuous and compact intumescent char layer. The LRS and EDS results demonstrated that by introduction of 4A into the EVA/IFR system, a more graphite structure was formed with increase phosphorus content in the char residue. POLYM. ENG. SCI., 56:380–387, 2016. © 2016 Society of Plastics Engineers     

Synergistic effects of fumed silica on intumescent flame‐retardant polypropylene

The synergistic effects of fumed silica on the thermal and flame‐retardant properties of intumescent flame retardant (IFR) polypropylene based on the NP phosphorus‐nitrogen compound have been studied by 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 LOI and UL‐94 data show that when ≤1 wt % fumed silica substituted for the IFR additive NP can increase 2 to 4% LOI values of the PP blends and keep the V‐0 rating. The data obtained from the CCT tests indicate the heat release rates (HRR) reduce by about 23% for the PP/NP sample with 0.5 wt % fumed silica, whereas the mass loss rates (MLR) and total heat release (THR) values are much lower than those of the PP/NP samples without fume silica. The TGA data demonstrate that a suitable amount of fumed silica can increase the thermal stability and charred residue of the PP/IFR/SiO₂ blends after 500°C. The morphological structures of charred residues observed by SEM give positive evidence that a suitable amount of fumed silica can promote the formation of compact intumescent charred layers and prevent the charred layers from cracking, which effectively protects the underlying polymer from burning. The dynamic FTIR spectra reveal that the synergistic flame‐retardant mechanism of a suitable amount of fumed silica with IFR additive is due to its physical process in the condensed phases. However, a high loading of fumed silica restricts the formation of charred layers with P? O? P and P? O? C complexes formed from burning of polymer materials and destroys the swelling behavior of intumescent charred layers, which deteriorates the flame retardant and thermal properties of the PP/IFR blends. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Combustion characteristics and synergistic effects of red phosphorus masterbatch with expandable graphite in the flame retardant HDPE/EVA composites

In this work, the flammability behaviors and synergistic effects of red phosphorus masterbatch (RPM) with expandable graphite (EG) in flame‐retardant high‐density polyethylene/ethylene vinyl‐acetate copolymer (HDPE/EVA) composites have been investigated by limiting oxygen index (LOI), UL‐94 test, cone calorimeter test (CCT), thermogravimetric analysis (TGA), Fourier‐transform infrared (FTIR) and scanning electron microscopy (SEM). The data obtained from LOI, UL‐94 test and CCT showed that suitable amount of RPM had synergistic effects with EG in the HDPE/EVA/EG/RPM composites. The addition of RPM greatly increased the LOI values by 3.4%, obtained UL‐94 V‐0 rating, decreased the heat release rates and total heat release, and prolongated the ignition time when 6.7 phr RPM substituted for EG in the HDPE/EVA/EG/RPM composites. The data from TGA and FTIR spectra also indicated the synergistic effects of RPM with EG considerably enhanced the thermal degradation temperatures. The morphological observations after UL‐94, CCT, and SEM images presented positive evidences that the synergistic effects took place for RPM with EG, and the flame‐retardant mechanism has been changed in flame‐retardant HDPE/EVA/EG/RPM composites. The formation of stable and compact charred residues promoted by RPM acted as effective heat barriers and thermal insulations, which improved the flame‐retardant performances and prevented the underlying polymer materials from burning. POLYM. ENG. SCI., 55:2884–2892, 2015. © 2015 Society of Plastics Engineers     

Expandable graphite systems for halogen‐free flame‐retarding of polyolefins. I. Flammability characterization and synergistic effect

The use of some types of expandable graphite (EG) as an intumescent flame‐retardant additive in polyolefins was studied using the cone calorimeter test (CCT), thermogravimetric analysis (TGA), the limiting oxygen index (LOI), and the‐UL 94 test and through measurement of EG's mechanical and electrical properties. The present study has shown that some suitable EG systems combined with other organic and inorganic halogen‐free flame‐retardant (HFFR) additives apparently can improve the flame‐retardant capacity with good mechanical properties of polyolefin blends. For linear low‐density polyethylene and/or ethylene vinyl acetate/EG/HFFR blends the limiting oxygen index can reach a rating above 29, and the UL‐94 test can produce a value of V–0. The CCT and TGA data show that the EG and EG/HFFR additives not only promoted the formation of carbonaceous char but also greatly decreased the heat release rate and the effective heat of combustion and increased the residues after burning. The synergistic effect of EG with other HFFR additives, such as zinc borate, the phosphorus–nitrogen compound NP28, and microcapsulated red phosphorus is examined and discussed in detail in this article. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 1181–1189, 2001     

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

A 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     

Synthesis of a novel flame retardant containing phosphorus and sulfur and its application in polycarbonate

A novel flame retardant containing phosphorus and sulfur, bis(2‐tienyl)phenylphosphine (BTPP) was synthesized and characterized with Fourier transform infrared spectroscopy, ¹H, ¹³C, and ³¹P nuclear magnetic resonance. BTPP was used to impart flame retardancy to polycarbonate (PC). Combustion behaviors and thermal degradation properties of PC/BTPP system were assayed by limiting oxygen index (LOI), vertical burning test (UL‐94), cone calorimeter test, and thermogravimetric analysis. PC/3 wt% BTPP passed UL‐94 V‐0 rating with 3.0 mm samples and the LOI value was 36.5%. PC/6 wt% BTPP passed UL‐94 V‐0 rating with 1.6 mm samples and the LOI value was 38.5%. Scanning electron microscopy revealed that char properties had direct effects on the flame retardancy. Mechanical properties and water resistance of PC/BTPP system were also examined. After water resistance test, PC/3 wt% BTPP with 3.0 mm samples and PC/6 wt% BTPP with 1.6 mm samples kept V‐0 rating and mass loss were only 0.2%. POLYM. ENG. SCI., 2012. © 2012 Society of Plastics Engineers     

An easy‐to‐obtain silicone‐containing flame retardant and its effects on the combustion of polycarbonate

A novel silicone‐containing flame retardant (HSOBA) synthesized from hydrogen‐containing silicone oil and Bisphenol A via a simple approach has been incorporated into polycarbonate (PC) matrix to study its effects on the flame retardancy. The flame retardancy of PC/HSOBA composites is investigated by limiting oxygen index (LOI), vertical burning tests (UL‐94), and cone calorimeter measurement. The LOI value of the composites is 31.7 and the UL‐94 rating reaches V‐0, when the content of HSOBA is 3 wt %. Cone calorimeter data confirm that the HSOBA acts as an effective additive functioning both as flame retardants and as smoke suppressant. Evolution of the thermal behaviors of the composites tested by TGA, the morphological structures, and the constituent of char residue after LOI tests characterized by scanning electronic microscopy‐energy‐dispersive X‐ray analysis were used to explain the possible flame‐retardant mode. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

The effect of morphology on the flame‐retardant behaviors of melamine cyanurate in PA6 composites

Three types of melamine cyanurate (MCA) with micrometer‐size sphere‐like, micrometer‐scale rod‐like, and nanometer‐scale flake‐like morphologies were synthesized by changing the chemical circumstances of the reactions. The microcosmic morphologies of MCA were characterized via scanning electron microscopy and X‐ray diffraction. After the MCAs with different morphologies were incorporated into polyamide 6 (PA6), the flame‐retardant properties of the MCA/PA6 composites were investigated using the limited oxygen index (LOI), UL94, and cone calorimeter tests. The MCA/PA6 composites with nanometer‐scale flake‐like MCA obtained an LOI value of 29.5% and a UL94 V‐0 rating, which were higher than those with micrometer‐size sphere‐like and rod‐like MCAs. However, the different morphologies did not affect the heat release rate, total smoke release, average carbon monoxide yield, and average carbon dioxide yield based on the cone calorimeter. The flame‐retardant mechanism of MCAs with different morphologies was investigated via thermal gravimetric analysis (TGA) and TGA‐Fourier transform infrared spectra. The results show that the different morphologies of MCA resulted in different dispersed evenness of MCA. Further, the nanometer‐scale flake‐like morphology of MCA brought more interactions of hydrogen bond between MCA and PA6, which resulted in the delay of MCA decomposition and the enhancement of MCA flame‐retardant effect. The nanometer‐scale flake‐like MCA had a better performance compared with the other samples because of the delaying and even release of flame‐retardant effect by the decomposition of evenly dispersed MCA. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40558.     

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     

Preparation of a novel phosphorus‐ and nitrogen‐containing flame retardant and its synergistic effect in the intumescent flame‐retarding polypropylene system

A novel phosphorus‐ and nitrogen‐containing flame retardant (melamine phytate) was synthesized via the reaction between melamine and phytic acid. The chemical structure of melamine phytate (MPA) was confirmed by Fourier transform‐infrared spectra (FT‐IR) and elemental analysis. And the thermal behavior of MPA investigated by thermogravimetric analysis (TGA) demonstrates that MPA possesses a good char‐forming ability at high temperature. Besides, limiting oxygen index (LOI) and vertical burning tests (UL‐94) illustrate that polypropylene/melamine phytate/dipentaerythritol (PP/MPA/DPER) (70/22.5/7.5) can reach the LOI value of 28.5% and achieve V‐0 rating at the flame retardant loading of 30 wt%. Except that, the thermal weight loss of MPA and DPER in PP composites was investigated by TGA in detail. Moreover, the char residue of PP composite after combustion was systematically analyzed by FT‐IR, scanning electron microscope (SEM) and X‐ray photoelectron spectroscopy (XPS), which can further propose and confirm the flame retardant mechanism. POLYM. COMPOS., 36:1606–1619, 2015. © 2014 Society of Plastics Engineers     

Investigation of the influence of red phosphorus,expansible graphite and zinc borate on flame retardancy and wear performance of glass fiber reinforced PA6 composites

The flame retarded materials were prepared which used wear‐resistant PA6 composite (PA6/GF/PTFE/UHMWPE/CG, 85/15/5/5/5 by weight) as matrix, red phosphorus (RP), expansible graphite (EG), and zinc borate (ZB) as fire retardant. The flame retarded properties were characterized by LOI and UL‐94 testing. PA6 composite with 15 wt% RP reached V0 rating and had a high LOI value (27.3 vol%). When a combination of 7 wt% ZB and 8 wt% RP was added, increases in LOI (27.9 vol%) and UL‐94 rating(V0) were both observed. Thermogravimetric analysis (TGA) and char residue characterization showed that the combination of RP and ZB can promote the formation of char barrier, reduce the mass loss rate, and thus improve the flame retardancy of PA6 composites. The wear test showed that, the composite filled by 15 wt% RP or a combination of 7 wt% ZB and 8 wt% RP both possessed a low wear rate and a much stable friction coefficient. The presence of EG could also improve the flame retardance but was harmful to the mechanical property as well as wear performance. The results indicated that ZB and RP had synergy effect on improving both flame retardance and wear performance of PA6 composites. POLYM. COMPOS., 38:2090–2097, 2017. © 2015 Society of Plastics Engineers     

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

The 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     

Synthesis of a phenylene phenyl phosphine oligomer and its flame retardancy for polycarbonate

A novel flame retardant, phenylene phenyl phosphine oligomer (PPPO) was synthesized and its chemical structure was characterized using Fourier transform infrared spectroscopy, ¹H, ¹³C, ³¹P nuclear magnetic resonance spectroscopy and mass spectrometer. PPPO was used to impart flame retardancy to polycarbonate (PC). Combustion behaviors and thermal degradation properties of PC/PPPO system were assayed by limiting oxygen index (LOI), vertical burning test (UL‐94), cone calorimeter test, and thermogravimetric analysis. PC/6 wt % PPPO passed UL‐94 V‐0 rating with 3.0 mm samples and the LOI value was 34.1%, and PC/8 wt % PPPO also passed UL‐94 V‐0 rating with 1.6 mm samples and the LOI value was 36.3%. Scanning electron microscopy reveals that the char properties had crucial effects on the flame retardancy of PC. Mechanical properties and water resistance of PC/PPPO system were also measured. After water resistance test, PC/6 wt % PPPO with 3.0 mm samples and PC/8 wt % PPPO with 1.6 mm samples kept V‐0 rating and mass loss was only 0.2%. The results revealed that PPPO was an efficient flame retardant for PC. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Influence of the pentaerythritol phosphate melamine salt content on the combustion and thermal decomposition process of intumescent flame‐retardant ethylene–vinyl acetate copolymer composites

Pentaerythritol phosphate melamine salt (PPMS) as a single‐molecule intumescent fire retardant was synthesized and characterized. The influence of the PPMS content on the combustion and thermal decomposition processes of intumescent‐flame‐retardant (IFR) ethylene–vinyl acetate copolymer (EVA) composites was studied by limiting oxygen index (LOI) measurement, UL 94 rating testing, cone calorimetry, thermogravimetric analysis, and scanning electron microscopy. The LOI and UL 94 rating results illustrate that PPMS used in EVA improved the flame retardancy of the EVA composites. The cone calorimetry test results show that the addition of PPMS significantly decreased the heat‐release rate, total heat release, and smoke‐production rate and enhanced the residual char fire performance of the EVA composites. The IFR–EVA3 composite showed the lowest heat‐release and smoke‐production rates and the highest char residue; this means that the IFR–EVA3 composite had the best flame retardancy. The thermogravimetry results show that the IFR–EVA composites had more residual char than pure EVA; the char residue yield increased with increasing PPMS content. The analysis results for the char residue structures also illustrated that the addition of PPMS into the EVA resin helped to enhance the fire properties of the char layer and improve the flame retardancy of the EVA composites. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42148.     

Preparation and investigation of flame‐retardant epoxy resin modified with a novel halogen‐free flame retardant containing phosphaphenanthrene,triazine‐trione,and organoboron units

In this article, a novel flame retardant (coded as BNP) was successfully synthesized through the addition reaction between triglycidyl isocyanurate, 9,10‐dihydro‐9‐oxa‐10‐phosphaphenanthrene‐10‐oxide and phenylboronic acid. BNP was blended with diglycidyl ether of bisphenol‐A to prepare flame‐retardant epoxy resin (EP). Thermal properties, flame retardancy, and combustion behavior of the cured EP were studied by thermogravimetric analysis, limited oxygen index (LOI) measurement, UL94 vertical burning test, and cone calorimeter test. The results indicated that the flame retardancy and smoke suppressing properties of EP/BNP thermosets were significantly enhanced. The LOI value of EP/BNP‐3 thermoset was increased to 32.5% and the sample achieved UL94 V‐0 rating. Compared with the neat EP sample, the peak of heat release rate, average of heat release rate, total heat release, and total smoke production of EP/BNP thermosets were decreased by 58.2%–66.9%, 27.1%–37.9%, 25.8%–41.8%, and 21.3%–41.7%, respectively. The char yields of EP/BNP thermosets were increased by 46.8%–88.4%. The BNP decomposed to produce free radicals with quenching effect and enhanced the charring ability of EP matrix. The multifunctional groups of BNP with flame retardant effects in both gaseous and condensed phases were responsible for the excellent flame retardancy of the EP/BNP thermosets. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45291.     

酚醛树脂基新戊二醇磷酸酯阻燃剂的合成及其性能研究

通过用新戊二醇磷酰氯对线型酚醛树脂(PF)酚羟基实行磷酰化封端处理,制备了线型PF基新戊二醇磷酸酯(NDMPP)阻燃剂,将其应用于阻燃PA6。采用核磁共振氢谱(1H NMR)、核磁共振磷谱(31P NMR)和傅立叶变换红外光谱(FTIR)表征了NDMPP的结构,采用热重(TG)分析研究其热分解行为,采用极限氧指数(LOI)和UL 94测试其阻燃PA6材料的阻燃性能,采用万能材料试验机和冲击试验机测试阻燃材料的力学性能。1H NMR,31P NMR和FTIR结果表明,线型PF中大约82%的羟基被磷酰化,NDMPP中的磷含量约为11.9%。TG分析结果表明,NDMPP阻燃剂在氮气气氛下起始分解温度超过250℃,600℃的残炭率达到43.5%,显示出良好的热稳定性。当NDMPP质量分数为25%时,其阻燃的PA6达到UL 94 V–0等级,LOI达到33.4%,而拉伸强度、缺口冲击强度、弯曲强度和弯曲弹性模量分别为纯PA6的76%,41%,72%和71%。     

The flame‐retardant effect of calcium hypophosphite in various thermoplastic polymers

The flame‐retardant behavior of calcium hypophosphite (CaHP) was investigated in different thermoplastic polymers including polyamide 6 (PA), poly (lactic acid) (PLA), thermoplastic polyurethane (TPU), and poly methyl metacrylate (PMMA). CaHP was used at three different amounts of 10, 20, and 30 wt%. The characterization of the composites was performed using limiting oxygen index (LOI), vertical burning test (UL 94), thermogravimetric analysis (TGA), and mass loss calorimeter test. According to the test results, CaHP enhances the fire‐retardant properties in different levels depending on the polymer type. The CaHP exhibits its flame‐retardant effect via the formation of foamed char structure in the condensed phase and via the dilution and radical scavenging effect in the gas phase.     

Application of a novel halogen‐free intumescent flame retardant for acrylonitrile‐butadiene‐styrene

A novel intumescent flame retardant (IFR), containing ammonium polyphosphate (APP) and poly(tetramethylene terephthalamide) (PA4T), was prepared to flame‐retard acrylonitrile‐butadiene‐styrene (ABS). The flame retardation of the IFR/ABS composite was characterized by limiting oxygen index (LOI) and UL‐94 test. Thermogravimetric analysis (TGA) and TGA coupled with Fourier transform infrared spectroscopy (TG‐FTIR) were carried out to study the thermal degradation behavior of the composite and look for the mechanism of the flame‐retarded action. The morphology of the char obtained after combustion of the composite was studied by scanning electron microscopy (SEM). It has been found the intumescent flame retardant showed good flame retardancy, with the LOI value of the PA4T/APP/ABS (7.5/22.5/70) system increasing from 18.5 to 30% and passing UL‐94 V‐1 rating. Meanwhile, the TGA and TG‐FTIR work indicated that PA4T could be effective as a carbonization agent and there was some reaction between PA4T and APP, leading to some crosslinked and high temperature stable material formed, which probably effectively promoted the flame retardancy of ABS. Moreover, it was revealed that uniform and compact intumescent char layer was formed after combustion of the intumescent flame‐retarded ABS composite. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012