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 polysiloxane and silane‐modified SiO2 on a novel intumescent flame retardant polypropylene system

The effects of polysiloxane and silane‐modified SiO₂ (M‐SiO₂) on properties of intumescent flame retardant polypropylene (IFR‐PP) have been studied. The results demonstrate that both polysiloxane and M‐SiO₂ could effectively enhance the flame retardancy of the IFR‐PP, despite only 20 wt% loading of IFRs. Remarkably, the polysiloxane can clearly improve the water resistance of IFR‐PP. It can obtain UL‐94 V‐0 rating, and its LOI remains over 34% after the water treatment. The surface tension data, XPS data, and SEM sufficiently prove that the some of polysiloxane transfers to the IFR‐PP surface during processing. The TGA data show that the polysiloxane more effectively enhances the thermal stability of the IFR‐PP at high temperature and increases the char residue. The CONE results reveal that the polysiloxane can clearly change the decomposition behavior of PP and markedly reduce flammability parameters. The homogenous and compact intumescent char layers further confirm that polysiloxane is a very effective silicon‐containing additive for the flame retardancy and water resistance of the IFR‐PP. 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.     

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.     

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.     

Synergistic effects of ferric pyrophosphate (FePP) in intumescent flame‐retardant polypropylene

Ferric pyrophosphate (FePP) was added to an ammonium polyphosphate (APP)—pentaerythritol (petol) intumescent flame retardant (IFR) system in polypropylene (PP) matrix, with subsequent investigation into the synergistic effect between FePP and the IFRs. Limited oxygen index (LOI), UL‐94 test and cone calorimeter test were employed to study the flame retardance of the synthesized flame retardant PP composites. Thermogravimetric analysis (TGA) and thermogravimetric analysis‐infrared spectrometry (TG‐IR) were used to study their thermal degradation characteristics and gas products. TG‐IR results demonstrate that there is no Fe (CO)₅ produced from PP/IFR/FePP system, which implies that the flame retardant mechanism of PP/IFR/FePP system is in the condensed phase rather than in the gas phase. Real time FTIR and X‐ray photoelectron spectroscopy (XPS) were used to monitor the thermal oxidative stability and the high temperature performance of the flame retardant PP composites. The real time FTIR spectra show that all peaks around 2900 cm^?1 almost disappear at 380°C for the PP/IFR system, meaning that PP decomposes completely at this temperature. But after the addition of 2 wt%wt% FePP, the peaks still exist till 400°C. XPS shows that the aliphatic carbon atom content in PP/23 wt%wt% IFR/2 wt%wt% FePP (63.8%) is much higher than the one without FePP, and the total oxygen atom content in PP/23 wt%wt% IFR/2 wt%wt% FePP is just 19.1%, while the one in PP/25 wt% IFR is as high as 35.7%. Copyright © 2009 John Wiley & Sons, Ltd.     

Supramolecular self‐assembly modification of ammonium polyphosphate and its flame retardant application in polypropylene

In order to improve its water resistance and compatibility with polymer matrix, ammonium polyphosphate (APP) is modified with melamine‐trimesic acid (MEL‐TA) aggregates by supramolecular self‐assembly technology. Chemical structure and morphology of APP@MEL‐TA are investigated by Fourier transform infrared spectroscopy and scanning electron microscopy (SEM), respectively. Intumescent flame retardant system of APP@MEL‐TA and charring‐foaming agent is introduced into polypropylene (PP) matrix. The flammability and combustion behavior of PP composites are investigated by limiting oxygen index (LOI), UL‐94 vertical burning, and cone calorimetry tests. In terms of LOI values and cone combustion results, APP@MEL‐TA performs better than pristine APP. Char residue of PP composites is investigated by SEM and Raman spectra. Flame retardant mechanisms are proposed based on thermal decomposition, combustion results, and analysis on char residue.     

Joint‐aggregation intumescent flame‐retardant effect of ammonium polyphosphate and charring agent in polypropylene

In order to explore the structure mode of intumescent flame retardants (IFRs) with higher efficiency, IFR particles with joint‐aggregation structure (@IFR) were obtained through the treatment of ammonium polyphosphate (APP) and a charring agent (PT‐Cluster) in their aqueous solution. Then, the joint‐aggregation IFR effect was researched using its application in polypropylene. In case of 20 wt% IFR loading, the limiting oxygen index (LOI) value of @IFR/PP was 1.1% higher than that of 15APP/5PT‐Cluster/PP mixture, and a 1.6 mm‐thick @IFR/PP composite passed the UL 94 V‐2 rating test, while 15APP/5PT‐Cluster/PP demonstrated no flame‐retardant rating in UL 94 vertical burning tests. In a cone calorimeter test, @IFR also had a better inhibition effect on heat release. The average heat release rate (av‐HRR) value during 0 to 120 seconds of @IFR/PP was only 41 kW m^?2, which was 33.9% lower than that of the 15APP/5PT‐Cluster/PP. Furthermore, the peak heat release rate (pk‐HRR) of @IFR/PP was 20.5% lower than that of 15APP/5PT‐Cluster/PP, and the time to pk‐HRR of @IFR/PP was 710 seconds, while that of 15APP/5PT‐Cluster/PP was 580 seconds. The better inhibition effect on HRR and the delay of time to pk‐HRR were caused by the joint‐aggregated structure of @IFR, which can rapidly react to form stable and efficient char layers. This kind of join‐aggregation IFR effect has great significance in suppressing the spread of fire in reality. In addition, @IFR also increased the mechanical properties of PP composites slightly compared with the APP/PT‐Cluster mixture.     

Synergistic effects of lanthanum oxide on a novel intumescent flame retardant polypropylene system

The effects of lanthanum oxide (La₂O₃) as a synergistic agent on the flame retardancy of intumescent flame retardant polypropylene composites (IFR-PP) were studied, and the new IFR system mainly consisted of the charring-foaming agent (CFA) and ammonium polyphosphate (APP). The limiting oxygen index (LOI), UL-94 test, thermogravimetric analysis (TGA), cone calorimeter (CONE) and scanning electron microscopy (SEM) were used to evaluate the synergistic effects of La₂O₃. It was found that when IFR was fixed at 20 wt% in IFR-PP composites, only a little amount of La₂O₃ could enhance LOI value and pass the UL-94 V0 rating test (1.6 mm). The TGA data showed that La₂O₃ could enhance the thermal stability of the IFR-PP systems at high temperature and effectively increase the char residue formation. The CONE results revealed that La₂O₃ and 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), ignition time (IT) and so on. The morphological structures observed by SEM demonstrated that La₂O₃ could promote to form the homogenous and compact intumescent char layer. Thus, a suitable amount of La₂O₃ plays a synergistic effect in the flame retardancy and smoke suppression of IFR composites.     

Synergistic effects of cerium phosphate and intumescent flame retardant on EPDM/PP composites

An intumescent flame retardant system composed of ammonium polyphosphate (APP) and pentaerythritol (PER) was used for flame retarding ethylene–propylene–diene‐modified elastomer (EPDM)/polypropylene (PP) blends. Cerium phosphate (CeP) was synthesized and the effect on flame retardancy and thermal stability of EPDM/PP composites based on intumescent flame retardant (IFR) were studied by limiting oxygen index (LOI), UL‐94, and thermogravimetic analysis (TGA), respectively. Scanning electron microscopy (SEM) and Fourier transform infrared spectrometry (FTIR) were used to analyze the morphological structure and the component of the residue chars formed from the EPDM/PP composites, and the mechanical properties of the materials were also studied. The addition of CeP to the EPDM/PP/APP/PER composites gives better flame retardancy than that of EPDM/PP/APP/PER composites. TGA and RT‐FTIR studies indicated that an interaction occurs among APP, PER, and EPDM/PP. The incorporation of CeP improved the mechanical properties of the materials. Copyright © 2010 John Wiley & Sons, Ltd.     

Synthesis of a novel hyperbranched and phosphorus‐containing charring‐foaming agent and its application in polypropylene

In this work, a novel hyperbranched and phosphorus‐containing triazine derivative (HPCFA) is synthesized. HPCFA is used as charring‐foaming agent and combined with ammonium polyphosphate (APP) as intumescent flame retardant to flame retard polypropylene (PP). PP/HPCFA/APP composite can achieve limited oxygen index value of 31% and pass UL 94V‐0 rating by addition of 20 wt% HPCFA/APP (1/2, w/w). Besides, HPCFA is compared with another hyperbranched charring‐foaming agent (HCFA). HPCFA and HCFA have similar chemical structure, and their only difference is that HPCFA has phosphorus‐containing unit in the main chain compared with HCFA. HPCFA/APP system exhibits superior flame retardancy compared with HCFA/APP system. Char residue analysis demonstrates that HPCFA/APP system can form denser and more compact char layer in comparison with that of HCFA/APP system.     

Effect of anion of polyoxometalate based organic–inorganic hybrid material on intumescent flame retardant polypropylene

In this work, 12‐tungestocobaltic acid based organic–inorganic hybrid material, [Bmim]₆CoW₁₂O₄₀ (CoW) was synthesized and applied as a synergist in polypropylene (PP)/intumescent flame retardant (IFR) composites. The flame retardant properties were investigated by the limiting oxygen index (LOI), UL‐94 vertical burning test, thermal gravimetric analyzer (TGA), cone calorimeter and scanning electron microscopy (SEM) etc. The results showed that the PP composites with 16 wt% IFR and 1 wt% CoW achieves the UL‐94 V‐0 rating and gets a LOI value 28.0. However, only add no less than 25 wt% single IFR, can the PP composites obtain the UL‐94 V‐0 rating, which suggests that CoW has good synergistic effects on flame retardancy of PP/IFR composites. In addition, the SEM and cone calorimeter tests indicated the CoW improves the quality of char layer. The rate of char formation has been enhanced also because of the existence of CoW. It is the combination of a better char quality and a high rate of char formation promoted by CoW that results in the excellent flame retardancy of PP/IFR composites. Copyright © 2016 John Wiley & Sons, Ltd.     

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.     

Effects of metal oxides on intumescent flame‐retardant polypropylene

Variable amounts of transition metal oxides (MO), such as MnO₂, ZnO, Ni₂O₃, etc., were incorporated into blends of polypropylene (PP)/ammonium polyphosphate (APP)/dipentaerythritol (DPER) with the aim of studying and comparing their effects with main‐group MO on intumescent flame retardance (IFR). The PP/IFR/MO composites were prepared using a twin‐screw extruder, and the IFR behavior was evaluated through oxygen index and vertical burning tests. The progressive enhancement of flame retardancy has proved to be strongly associated with the interaction between APP and MO. With the aid of thermogravimetry (TG) analysis, Fourier transform infrared (FTIR) spectra and scanning electron microscopy, Ni₂O₃ has been shown to be the most effective among the aforementioned three MO. The flame‐retardant mechanism of the IFR system is also discussed in terms of catalytic charring, which relates to complex formation through the d‐orbitals of the transition metal elements. It is considered that the melt viscosity of a PP/APP/DPER blend containing Ni₂O₃ corresponds well to the gas release with increasing temperature. Copyright © 2009 John Wiley & Sons, Ltd.     

Preparation of piperazine cyanurate by hydrogen‐bonding self‐assembly reaction and its application in intumescent flame‐retardant polypropylene composites

Piperazine cyanurate (PCA) is designed and synthesized via hydrogen‐bonding self‐assembly reactions between piperazine and cyanuric acid. Chemical structure and morphology of PCA are investigated by Fourier transform infrared spectroscopy and scanning electron microscopy, respectively. The prepared PCA is combined with ammonium polyphosphate (APP) to prepare flame‐retardant polypropylene (PP) composites. Thermostability, flammability, and combustion characteristics of PP composites are analyzed. The maximum thermal decomposition rate of flame‐retarded PP composites has an apparent reduction compared with that of pure PP, and obvious char is left for this intumescent flame retardant (IFR) system of APP and PCA. A high limiting oxygen index value and UL‐94 V‐0 rating are achieved with addition of APP and PCA. In cone calorimetry test, heat and smoke releases of PP are significantly decreased by this IFR system. Gaseous decomposition products during the thermal decomposition of flame‐retardant composites are studied. Chemical structure and morphology of char residues are analyzed. The results illustrate that APP and PCA have a superb synergistic action in the aspect of improvement in fire safety of PP. A possible flame‐retardant mechanism is concluded to reveal the synergism between APP and PCA.     

Synthesis and characterization of a novel organophosphorus flame retardant and its application in polypropylene

A novel organophosphorus containing spiro and caged bicyclic phosphate, 3,9‐Bis‐(1‐oxo‐2,6,7‐trioxa‐1‐phospha‐bicyclo[2.2.2]oct‐4‐ylmethoxy)‐2,4,8,10‐tetraoxa‐3,9‐diphospha‐spiro[5.5]undecane 3, 9‐dioxide (SBCPO), was synthesized and characterized by Fourier transform infrared (FTIR), hydrogen‐1 nuclear magnetic resonance (NMR) and phosphorus‐31 NMR. The flame retardancy of polypropylene (PP) containing the novel intumescent flame retardant (IFR) based on the combination between SBCPO and melamine (MA) was studied by limiting oxygen index (LOI), UL‐94 test and cone calorimeter test. Results indicated that this combination showed the excellent flame retardancy for PP at appropriate proportions (with the total loading of 30 wt. % and SBCPO: MA = 4:1). The value of LOI was as high as 31.6, and the rating in UL94 reached to V‐0. Moreover, the HRR and THR of IFR/PP decreased significantly in comparison with that of neat PP. The scanning electron microscopy results indicated that the incorporation of SBCPO could induce the formation of intumescent char layer, which retarded the degradation and combustion process of PP. The thermal oxidative degradation of the PP samples at different temperature was analyzed by FTIR. The thermal stabilities of the composites were further investigated by thermogravimetric analysis. It was found that the amount of residues was increased greatly with the addition of SBCPO that remained in the form of polyaromatic stacks and phosphoric or polyphosphoric acid at the residual chars. Copyright © 2013 John Wiley & Sons, Ltd.     

Synthesis of siloxane‐containing benzoxazine and its synergistic effect on flame retardancy of polyoxymethylene

A type of trialkoxysilane‐containing naphtholoxazine compound (Naph‐boz) was successfully synthesized and combined with ammonium polyphosphate/melamine (APP/ME) as an intumescent flame retardant (IFR) to improve the flame‐retardant efficiency of polyoxymethylene (POM). The Underwriters Laboratories 94 (UL94) vertical burning test, limiting oxygen index (LOI), cone calorimeter, thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and Raman spectral analysis were used to study the flame‐retardant properties and related mechanism. The results showed that the formulation with 20 wt.% of APP, 6 wt.% of ME, and 4 wt.% of Naph‐boz passed UL94 V‐1 rating, and the LOI value was improved to 40.3%. Compared with pure POM, the IFR with Naph‐boz had greater reduction in peak heat release rate (lower 74.9%) and total heat release (lower 40.2%). SEM images showed that compact and reinforcing charred layer was formed during the POM/IFR/4Naph‐boz samples combustion, which was beneficial at reducing and maintaining low combustion parameters throughout the cone calorimeter test. The synergistic flame‐retardant effect between Naph‐boz and APP/ME was considered as the reason for the improvement in flame retardancy POM. Furthermore, because of the Naph‐boz was conducive to the compatibility between the flame retardants and matrix, the notched Izod impact strength of POM/IFR/4Naph‐boz composite was higher than that of POM/IFR system.     

A new intumescent flame‐retardant: preparation,surface modification,and its application in polypropylene

Melamine salt of tripentaerythriol phosphate (MTP), as a new intumescent flame‐retardant, was prepared from tripentaerythritol (TPE), polyphosphoric acid, phosphoric pentoxide, and melamine, and then incorporated into polypropylene (PP) to obtain flame‐retarded PP‐MTP. FT‐IR analysis showed that MTP was in the form of cage structure. The flammability, combustion behavior, and thermal degradation and stability of flame‐retarded PP were characterized by using LOI, UL‐94 test, cone calorimetry, and TGA, respectively. By SEM, the char structure of PP‐MTP was analyzed. XRD diffraction tests showed that PP‐matrix of PP‐MTP presented better crystallized phases, when MTP was modified by methyl hydrogen siloxane. The relations of the dispersion of MTP in PP matrix to the compatibility between PP and MTP, and to the flame retardancy were discussed. Copyright © 2008 John Wiley & Sons, Ltd.     

Synergistic effect of cocondensed nanosilica in intumescent flame‐retardant polypropylene

Amino‐functionalized nanosilica (SiO₂‐NH₂) was prepared through cocondensation method using aminopropyltriethoxysilane as comonomer to hydrolyze and cocondense with tetraethylorthosilicate. The synergistic effect of combination of ammonium polyphosphate and pentaerythritol with SiO₂‐NH₂ on the thermal and flame‐retardant properties of intumescent flame‐retardant (IFR) polypropylene (PP) has been investigated by thermogravimetric analysis (TGA), scanning electron microscopy, Raman spectra, X‐ray diffraction (XRD), limiting oxygen index (LOI), and UL 94 tests. When 1.0 wt.% SiO₂‐NH₂ was added, the LOI value of the PP/IFR composite with 25 wt.% of IFR increased from 26.6% to 31.7%, while the UL 94 rating raised from not classified to V‐0. The TGA data demonstrated that the SiO₂‐NH₂ nanoparticles increased the charred residue of the PP/IFR composites. The morphological structures and the orderliness of the charred residue proved that SiO₂‐NH₂ promoted the formation of compact intumescent charred layer, which effectively protected the underlying polymer from burning. The XRD patterns of the charred residue indicated that nanosilica reacted with APP to form SiP₂O₇ crystal structure during combustion, which was beneficial to the formation of compact charred layers. In comparison with the inorganic SiO₂‐cal nanoparticles, the amino‐functionalized nanosilica revealed much more efficient synergistic flame‐retardant effect due to the difference of surface properties.     

新型单组份磷-氮膨胀型阻燃剂的热分解动力学

利用热重分析法研究了在不同升温速率下新型单组份磷-氮膨胀型阻燃剂六(4-(9,10-二氢-9-氧杂-10-磷杂菲-10-氧化物)-羟甲基苯氧基)环三磷腈(DOPOMPC)在氮气气氛和空气气氛中的热分解动力学.采用Kissinger和Flynn-Wall-Ozawa(FWO)法分别计算出DOPOMPC在相应气氛下的活化能和指前因子.