Effects of expandable graphite and ammonium polyphosphate on the flame‐retardant and mechanical properties of rigid polyurethane foams

In this work, the effect of expandable graphite (EG) and ammonium polyphosphate (APP) on the flame retardancy and mechanical properties of the rigid polyurethane foam (RPUF) was studied. The results indicated that both EG and APP could effectively improve the flame retardancy of RPUF, while the retardancy of EG was better than APP. When the flame‐retardant loading was 15 wt %, the limited oxygen index (LOI) values of APP‐ and EG‐filled RPUF were 24.5 and 32 vol %, respectively. According to the LOI test, the optimal ratio of APP to EG in RPUF composites was 1 : 1 by weight, at which the LOI value of 15 wt % (APP + EG)/RPUF was 30.5 vol %. Thermal degradation test of RPUF composites by thermogravimetric analysis indicated that the addition of APP and EG to RPUF could lead to an increase in the amount of high‐temperature residue. Under the same conditions, the residue amount of EG/RPUF was less than that of APP/RPUF at the same temperature. Compression test and dynamic thermal mechanical analysis indicated that both the compressive strength and modulus decreased at a certain extent with the EG‐ or APP‐filled into RPUF, respectively, but with the mixture of EG and APP added into RPUF, the mechanical properties of these materials increased. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Synergistic effect of expandable graphite and α‐type zirconium phosphate on flame retardancy of polyurethane elastomer

Organically modified zirconium phosphate (OZrP) was prepared by cation exchange of natural counterions with hexadecyltri‐n‐butylphosphonium bromide. Subsequently, OZrP and expandable graphite (EG) were incorporated into polyurethane elastomer (PUE), and the thermal stability and flame retardancy of PUE composites were investigated. The thermogravimetric analysis indicated that partial substitution of EG with OZrP could improve both the thermal stability and char yield of PUE composites. The cone calorimetry and limiting oxygen index test showed that partial substitution of EG with OZrP could further enhance the flame retardancy of PUE composites and presented an excellent synergistic effect. Moreover, the char residue of PUE composites was analyzed by X‐ray photoelectron spectroscopy and laser Raman spectroscopy. Their results indicated that the synergistic effect of the physical barrier to prevent transmission of heat and mass between condensed and gas phases. Therefore, the further combustion of the nether material could be inhibited, which created better flame retardancy. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45188.     

Effect of the particle size of expandable graphite on the thermal stability,flammability, and mechanical properties of high‐density polyethylene/ethylene vinyl‐acetate/expandable graphite composites

In this article, high‐density polyethylene/ethylene vinyl‐acetate copolymer (HDPE/EVA) composites filled with two different particle sizes (45 and 150 µm) of expandable graphite (EG) were prepared by using a twin‐screw extruder. The thermal stability, flammability, and mechanical properties of HDPE/EVA/EG composites were investigated by thermogravimetric analysis (TGA), cone calorimeter test (CCT), tensile test, and scanning electron microscopy (SEM). The results from TGA and CCT indicated that EG significantly enhanced the thermal stability and fire resistance of HDPE/EVA blend. The thermal stability and flame retardancy of HDPE/EVA/EG composites were improved with decreasing particle size of EG. Although the onset of weight loss of the flame‐retardant composites occurred at a lower temperature than that of HDPE/EVA blend, the flame‐retardant composites produced a large amount of char residue at a high temperature. The consolidated char layer formed a barrier, which could reduce heat, low‐molecular transfer, and air incursion, and thus enhanced the flame retardancy. The data from the tensile test showed that the addition of EG deteriorated the mechanical properties; however, the tensile stress and strain of HDPE/EVA/EG composites increased with decreasing the particle size of EG owing to the strong interface adhesion between polymer matrix and inorganic particles. POLYM. ENG. SCI., 54:1162–1169, 2014. © 2013 Society of Plastics Engineers     

可膨胀石墨与含磷阻燃剂在聚氨酯硬泡材料中的应用

通过氧指数仪与锥形量热仪研究了可膨胀石墨（EG）与低聚磷酸酯多元醇（OP550）、二乙基N,N二(2羟乙基)胺基甲基膦酸酯（WSFR 6）2种反应型含磷阻燃剂对聚氨酯硬泡材料（RPUF）阻燃性能的影响。结果表明,在OP550与WSFR 6的存在下,RPUF具有较好的成炭性,且炭层较为致密;添加EG后,体系的阻燃性能进一步提高,当其含量为14 %（质量分数,下同）时,RPUF体系的极限氧指数达到33.6 %,热释放速率峰值降低到106.93 kW/m2。     

阻燃硬质聚氨酯泡沫塑料垂直火蔓延特性研究

通过一步合成法制备了阻燃硬质聚氨酯泡沫,自主搭建保温材料火蔓延实验台,采用中小尺寸实验对比研究了阻燃及非阻燃硬质聚氨酯的垂直火蔓延特性,分析了火焰结构特性、火蔓延速度、火焰温度、质量损失速率等参数的变化规律。结果表明,火蔓延过程中,材料表面均出现了炭化现象,垂直双面燃烧过程中聚氨酯纯样RPUF燃烧最剧烈,阻燃剂膨胀石墨(EG)、次磷酸铝(AHP)和二乙基次膦酸铝(ADP)的加入,抑制了材料的燃烧和蔓延,使材料燃烧的火蔓延速度、质量损失速率及温度等参数都相应降低。RPUF/AHP5垂直双面火蔓延过程中,火焰稳定性差,在20 s后出现熄灭现象,原因是阻燃剂次磷酸铝(RPUF/AHP5)受热挥发出难燃气体。AHP降解后形成的含磷化合物可促进聚氨酯分子链成炭,导致产生熄灭现象。而RPUF/ADP5火蔓延过程中,同样出现了熄灭现象,其熄灭的程度低于阻燃剂次磷酸铝(RPUF/AHP5)试样。RPUF/EG5火蔓延过程中试样表面温度存在两个峰值,由于RPUF/EG5燃烧生成的炭层不稳定所致。当温度高于400℃时炭层被迅速氧化,热量穿透炭层使内部未燃样品热解,生成温度的第二个峰值。     

The flame retardant behaviors and synergistic effect of expandable graphite and dimethyl methylphosphonate in rigid polyurethane foams

A series of flame‐retardant rigid polyurethane foams (RPUFs) containing dimethyl methylphosphonate (DMMP) and expandable graphite (EG) were prepared by box‐foaming. The RPUFs were characterized by thermogravimetric analysis (TGA), the limiting oxygen index (LOI), cone calorimeter, and scanning electron microscope (SEM). The decomposition process of DMMP was investigated by Pyrolysis‐Gas Chromatography/Mass Spectroscopy (Py‐GC/MS). Accordingly, their flame retardant behaviors and mechanism were also discussed. The results show that the DMMP/EG system can linearly enhance the LOI value from 19.2% of the pure RPUF to 33.0% of RPUFs containing 16 wt% flame retardant. In addition, the DMMP/EG system also remarkably increases yields of the residual char and drastically decreases the peak value of heat release rate (PHRR), heat release rate (HRR), total heat release (THR), total smoke release (TSR), and the yields of CO (COY). In the flame retardant RPUFs, when the matrix is ignited, the flame retardant DMMP should be decomposed to gaseous PO₂ fragments, which can inhibit free radical chain reaction of flammable alkyl free radical from the decomposed matrix; whereas the flame retardant EG can rapidly expand and form loose and worm‐like expanding graphite char layer accordingly, which can hinder the heat transmission to the inner matrix and reduce decomposing velocity of matrix. After the combination of the two flame retardant effects, the DMMP/EG flame retardant system provides the matrix with better flame retardant effects than one of them does. Namely, it shows excellent gas‐condensed bi‐phase synergistic effect. POLYM. COMPOS., 35:301–309, 2014. © 2013 Society of Plastics Engineers     

Flame‐retardant and mechanical properties of high‐density rigid polyurethane foams filled with decabrominated dipheny ethane and expandable graphite

The article reported the flame‐retardant and the mechanical properties of expandable graphite (EG), an intumescent type, and decabrominated dipheny ethane (DBDPE), a gas‐phase type of flame‐retardant‐containing high‐density rigid polyurethane foams (RPUF) with a constant density of 0.5g/cm³. The results indicated that both EG and DBDPE could effectively interdict the burning of RPUF, besides, the EG exhibited more effective flame retardancy than the DBDPE. When the flame‐retardant loadings were 20 wt %, the LOI value of DBDPE‐filled RPUF increased to 33 vol %, while, surprisingly, the EG‐filled RPUF reached 41 vol %. Unfortunately, when they were both simultaneously added into RPUF, there was not any flame‐retardant synergistic effect. Although EG had outstanding flame retardancy, the compressive strength and modulus of 20 wt % EG‐filled RPUF dropped to only 9.1MPa and 229.7MPa respectively, which were lower than those of DBDPE (12.4 MPa and 246.8 MPa). The phenomena were ascribed to the different flame‐retardant mechanisms of EG and DBDPE, which were verified by scanning electronic microscope (SEM) observation of the burned surfaces. Besides, the dynamical mechanical analysis (DMA) demonstrated that the additions of EG and DBDPE made the glass transition temperature shift to the high temperatures, and the EG‐filled RPUF had the higher storage modulus. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Influence of polyamide 6 as a charring agent on the flame retardancy,thermal, and mechanical properties of polypropylene composites

In this work, polyamide 6 (PA6) as a charring agent has been used in combination with thermoplastic polyurethane (TPU)‐microencapsulated ammonium polyphosphate (MTAPP) forming intumescent flame retardants (IFRs) which applies in polypropylene (PP). The effects of the IFRs on the flame retardancy, morphology of char layers, water resistance, thermal properties and mechanical properties of flame‐retardant PP composites are investigated by limiting oxygen index (LOI), UL‐94 test, scanning electron microscopy (SEM), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and mechanical properties test. The results show that the PP/MTAPP/PA6 composites exhibit much better flame‐retardant performances than the PP/MTAPP composites. The higher LOI values and UL‐94 V‐2 of the PP/MTAPP composites with suitable amount of PA6 are obtained, which is attributed to the thick and compact char layer structure evidenced by SEM. The results from TGA and DSC demonstrate that the introduction of PA6 into PP/MTAPP composites has a great effect on the thermal stability and crystallization behaviors of the composites. Furthermore, the mechanical properties of PP/MTAPP/PA6 composites are also improved greatly due to the presence of PA6 as a charring agent. POLYM. ENG. SCI., 55:1355–1360, 2015. © 2015 Society of Plastics Engineers     

Flame retardation and thermal stability of novel phosphoramide/expandable graphite in rigid polyurethane foam

A novel flame retardant named diethylene N,N',N''‐tri (diethoxy)phosphoramide (DTP) was synthesized using diethyl phosphate and diethylenetriamine via Atherton–Todd reaction. Then, series of flame‐retardant water‐blown rigid polyurethane foams (RPUFs) with expandable graphite (EG) and DTP were prepared through box‐foaming. The results of thermogravimetric analysis showed that DTP/EG changed thermal degradation process of RPUF and promoted enhancing char residues. The complex flame‐retardant system (EG/DTP) endowed RPUF higher limiting oxygen index (LOI) values (29.1%–30.2%) and lower heat release rate peak (PHRR) values according to LOI and microscale combustion calorimeter tests. More importantly, the synergistic flame‐retardant effect between EG and DTP in RPUF was proved by the analysis of synergistic effectivity values. Based on the analysis of cone calorimetric tests, EG/DTP revealed remarkable effects to inhibit the fire intensity and smoke release of RPUF with decreased PHRR and total smoke production due to good char‐forming action. To further investigate the char‐residues of the foams after combustion, scanning electron microscope and energy dispersive X‐ray spectroscopy analyses were conducted. The results suggested that EG/DTP flame‐retardant system promoted RPUF forming a compact, continuous and phosphorus‐rich char layer as a good fire barrier in combustion. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46434.     

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     

Intumescent char structures and flame‐retardant mechanism of expandable graphite‐based halogen‐free flame‐retardant linear low density polyethylene blends

The structures of the intumescent charred layers formed from expandable graphite (EG)‐based intumescent halogen‐free flame retardant (HFFR) linear low‐density polyethylene (LLDPE) blends and their flame‐retardant mechanism in the condensed phase have been studied by dynamic Fourier transform infrared (FTIR), X‐ray photoelectron spectroscopy (XPS), laser Raman spectroscopy (LRS), scanning electron microscopy (SEM), differential thermal analysis (DTA) and thermal conductivity (TC) measurements. The dynamic FTIR, XPS and LRS data show that the carbonaceous structures of intumescent charred layers consist of EG and various numbers of condensed benzene rings and/or phosphocarbonaceous complexes attached by the P? O? C and P? N bonds or quaternary nitrogen products. The addition of EG can hasten the formation of these phosphocarbonaceous structures. The above results show that the flame‐retardant mechanism in the condensed phase is that the compact char structures, as observed by SEM, slow down heat and mass transfer between the gas and condensed phase and prevent the underlying polymeric substrate from further attack by heat flux in a flame. The DTA and TC data show that carbonaceous charred layers are good heat‐insulating materials, the TC value of which is only about one‐tenth of that of the corresponding blend and that they increase the oxidization temperature and decrease thermal oxidization heat of the LLDPE/EG/HFFR systems. © 2003 Society of Chemical Industry     

四元复合体系在硬质聚氨酯泡沫材料中的逐级释放阻燃行为研究

以甲基膦酸二甲酯（DMMP）、10-（2,5-二羟基甲苯）-10-氢-9-氧杂-10-磷酰杂菲-10-氧化物（DOPO-HQ）、可膨胀石墨（EG）和氢氧化铝（ATH）构建了四元阻燃复合体系,并通过热失重分析仪（TG）、锥形量热仪、极限氧指数分析仪等研究了其在硬质聚氨酯泡沫（RPUF）中的阻燃行为。结果表明,四元阻燃体系能够在较宽温度区间内发挥逐级释放的协同阻燃效应;DOPO-HQ能够与EG/DMMP/ATH三元阻燃体系形成加合阻燃效应,使得RPUF复合材料的极限氧指数（LOI）提升至30.8%;与采用EG/DMMP/ATH三元阻燃体系的RPUF复合材料相比,采用加入DOPO-HQ的四元阻燃体系的RPUF复合材料的热释放速率峰值（PHRR）、总热释放量（THR）、总烟释放量（TSR）均有所下降,残炭率得到了进一步提升,说明DOPO-HQ与EG/DMMP/ATH所构建的四元阻燃体系在成炭性方面具有协同效应;此外,通过扫描电子显微镜（SEM）对残炭进行表征,验证了四元阻燃体系在凝聚相中能够发挥优异的成炭阻隔效应,并能够在燃烧的初期、中期和末期发挥逐级释放阻燃效应。     

Flame‐retardant and thermal degradation mechanism of low‐density polyethylene modified with aluminum hypophosphite and microencapsulated red phosphorus

Aluminum hypophosphite (AHP), a novel flame retardant, was used to improve the flame retardancy of low‐density polyethylene (LDPE) with microencapsulated red phosphorus (MRP). The synergistic effect between MRP and AHP was investigated by the limiting oxygen index (LOI), vertical burning test (UL‐94), and thermogravimetric analysis. When the contents of MRP and AHP were 10 and 30 phr, the LOI of LDPE/10MRP/30AHP composite was 25.5%, and it passed the UL‐94 V‐0 rating (the number before “MRP” and “AHP” is the loading of MRP and AHP, In LDPE/10MRP/30AHP, the content of the LDPE, MRP and AHP is 100phr, 10phr and 30phr, where phr refers to parts per hundreds of resin). The results of cone calorimetry testing show that the heat release rate of the composites was significantly reduced, and the strength of the char layer improved when the loading of AHP increased. The thermal stability of the LDPE/10MRP/30AHP composite was enhanced. The structure of the char was investigated by Fourier transform infrared spectrometry and scanning electron microscopy/energy‐dispersive spectrometry. The results indicate that AHP promoted the formation of stable char. This research provided a good way to prepare flame‐retardant materials with a halogen‐free flame retardant and contributed to environmental protection. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43225.     

Study of using aluminum hypophosphite as a flame retardant for low‐density polyethylene

Aluminum hypophosphite (AHP) was first used to improve the flame retardance of low‐density polyethylene (LDPE). The flame‐retardant properties of LDPE composites were investigated by the limiting oxygen index, vertical burning test (UL‐94), microscale combustion calorimetry, and cone calorimeter tests. The results showed that the incorporation of AHP could improve the flame retardancy of LDPE dramatically, the limiting oxygen index of LDPE containing 50 phr AHP reached 27.5%, and the UL‐94 could pass V‐0 rating. The cone calorimeter test results indicated that PP/AHP composite exhibited superior performance, and the heat release rate and the total heat release of composites were significantly reduced. In addition, the strength of the char was improved with the load of AHP increased. The structure of the char was researched by Fourier transform infrared spectrometry (FTIR) and scanning electron microscope‐energy dispersive spectrometer, and the results revealed that AHP promoted the formation of compact char layer. The TG‐FTIR analyses proved that AHP could react with LDPE to reduce the production of olefin in gas phase. Moreover, the structure of P–O–C was found, and the effective mechanism of AHP in LDPE composites was also hypothesized in this work.     

Flame retardancy of different‐sized expandable graphite particles for high‐density rigid polyurethane foams

The effects of expandable graphite (EG) of different particle sizes, on the fire‐retardant properties of high‐density rigid polyurethane foam (RPUF) (0.45 g cm^?3) were studied. Samples of EG with different particle sizes were obtained by pulverization in an ultra‐high‐speed mixer for 4 and 13 min, respectively. It was shown that as received (EG0) and 4 min pulverized EG (EG4) efficiently improved the fire‐retardant properties of RPUF composites, while 13 min pulverized EG (EG13) did not. The char of the burned composites filled with EG0 and EG4 covered the whole surface of the samples and formed a complete physical barrier. This barrier material prevented combustible gases from feeding the flame and also isolated oxygen efficiently from the burning material. EG13 did not produce enough char to cover the whole surface of the burning sample, resulting in poor fire‐retardant property of the RPUF composites. Thermal degradation tests of the foams by thermogravimetric analysis indicated that EG showed negligible effects on the thermal stability of the RPUFs. Copyright © 2006 Society of Chemical Industry     

Effects of inorganic fillers on the flame‐retardant and mechanical properties of rigid polyurethane foams

Rigid polyurethane foam (RPUF) composites filled with expandable graphite (EG), hollow glass microspheres (HGM), and glass fibers (GF) have been synthesized and characterized by limiting oxygen index, radiation ignition, compressing and torsion testing, and scanning electron microscopy. The results indicate HGM and GF benefit to the mechanical properties, while EG is good for flame retardancy. Proper ingredient of additive can lead to good flame retardancy and mechanical properties of the RPUF. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40253.     

Synergistic effects of aluminium hypophosphite on the flame retardancy and thermal degradation behaviours of a novel intumescent flame retardant thermoplastic vulcanisate composite

ABSTRACT

The synergistic effects of aluminum hypophosphite (AHP) on the flame retardancy, thermal degradation behaviors of a novel intumescent flame retardant thermoplastic vulcanizate (TPV/IFR) composite were investigated. The results showed that the combination of AHP with IFR showed evident synergistic effects on the increase in the LOI value and reduction of the combustion parameters for the TPV/IFR/AHP composites at the optimum weight ratio of IFR/AHP (6/1) as evidenced by LOI, UL-94 and CCT. The TGA data revealed that AHP could change the degradation behavior of TPV/IFR composites and enhance the thermal stability of the TPV/IFR composites at high temperature. The results of FTIR, EDXS, LRS and SEM demonstrated that TPV/IFR/AHP composites could form more continuous, dense and stable char layer on the materials surface, and consequently improving the flame retardancy. Based on these results, the possible condensed flame retardant mechanism of TPV/IFR/AHP composites was concluded in detail.     

Thermoplastic polyurethane/polytetrafluoroethylene/bridged dopo derivative composites: Flammability,thermal stability,and mechanical properties

A phenethyl‐bridged DOPO derivative (DiDOPO) is combined with polytetrafluoroethylene (PTFE) in thermoplastic polyurethane (TPU). The flame retardancy and thermal stability of TPU/PTFE/DiDOPO composites with different weight percentages of DiDOPO are investigated by using limiting oxygen index (LOI), UL‐94 test, cone calorimetry test (CCT), scanning electronic microscopy (SEM), energy‐dispersive spectrometry, and thermogravimetric analysis (TGA). With the incorporation of 8 wt% DiDOPO, the LOI value of TPU/PTFE/DiDOPO composites increases to 34.0% from 25.4% of TPU, and the V‐0 rating level is achieved. The CCT results indicate that the peak heat release rate and total heat release of TPU/PTFE/DiDOPO composites decrease due to the addition of DiDOPO and PTFE. The thermal decomposition process of TPU is changed due to the present of DiDOPO and PTFE. Based on this, the Flynn–Wall–Ozawa method for the determination of characteristic degradation kinetics parameters is evaluated. SEM results and residues from TGA curves show that the addition of DiDOPO promotes the increase in the char layer and a crosslinked char coating exists after burning. The flame‐retardant mechanism is flame inhibition. Overall, these findings indicate that the combination of DiDOPO with PTFE in TPU is an effective way in developing high‐performance resins with attractive flame retardancy. POLYM. ENG. SCI., 59:1593–1602 2019. © 2019 Society of Plastics Engineers     

Percolation and catalysis effect of bamboo‐based active carbon on the thermal and flame retardancy properties of ethylene vinyl‐acetate rubber

The effect of percolation and catalysis of bamboo‐based active carbon (BAC) on the thermal degradation and flame retardancy of ethylene vinyl‐acetate rubber (EVM) composites with intumescent flame retardants (IFR) consisting of ammonium polyphosphate (APP) and dipentaerythritol (DPER) has been investigated. The vulcanization characteristics were analyzed by a moving die rheometer. Thermogravimetric analysis (TGA) and fire behavior tests such as limiting oxygen index (LOI), vertical burning (UL 94), and cone calorimetry were used to evaluate the thermal properties and flame retardancy of EVM composites. Scanning electron microscopy (SEM) was used to study the morphology of residues of EVM composites. The addition of BAC significantly increased the maximum torque (M_H) of EVM composites and EVM matrices. The combination of IFR with BAC can improve the thermal stability of EVM composites. Moreover, BAC can enhance char residue and promote the formation of a network for IFR. The current EVM/37IFR/3BAC composite achieved an LOI of 33.6% and a UL 94 V‐0 rating. The PHRR, total heat release (THR), and total smoke release (TSR) for EVM/IFR/BAC were greatly reduced as compared to EVM/40IFR. Also, the mechanical properties of the EVMIFR/BAC composites increased with increasing BAC contents. The physical percolation effect between BAC and EVM before and after thermal degradation, and the chemical catalysis effect between BAC and IFR during thermal degradation are responsible for the improved flame retardancy of EVM composites. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42414.     

Effect of a novel phosphorus‐containing compound on the flame retardancy and thermal degradation of intumescent flame retardant polypropylene

A novel flame retardant, tetra(5,5‐dimethyl‐1,3‐ dioxaphosphorinanyl‐2‐oxy) neopentane (DOPNP), was synthesized successfully, and its structure was characterized by FT‐IR, ¹H NMR, and ³¹P NMR. The thermogravimetric analysis (TGA) results demonstrate that DOPNP showed a good char‐forming ability. Its initial decomposition temperature was 236.4°C based on 1% mass loss, and its char residue was 41.2 wt % at 600°C, and 22.9 wt % at 800°C, respectively. The flame retardancy and thermal degradation behavior of novel intumescent flame‐retardant polypropylene (IFR‐PP) composites containing DOPNP were investigated using limiting oxygen index (LOI), UL‐94 test, TGA, cone calorimeter (CONE) test, and scanning electron microscopy (SEM). The results demonstrate that DOPNP effectively raised LOI value of IFR‐PP. When the loading of IFR was 30 wt %, LOI of IFR‐PP reached 31.3%, and it passed UL‐94 V‐0. TGA results show that DOPNP made the thermal decomposition of IFR‐PP take place in advance; reduced the thermal decomposition rate and raised the residual char amount. CONE results show that DOPNP could effectively decrease the heat release rate peak of IFR‐PP. A continuous and compact char layer observed from the SEM further proved the flame retardance. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011.