Flame Retardancy and Thermal Performance of Polypropylene Treated With the Intumescent Flame Retardant,Piperazine Spirocyclic Phosphoramidate

Piperazine spirocyclic phosphoramidate (PSP), a novel halogen‐free intumescent flame retardant, was synthesized and used to improve the flame retardancy and dripping resistance of polypropylene (PP) combined with ammonium polyphosphate (APP) and a triazine polymer charring‐foaming agent (CFA). The optimum flame‐retardant formulation was PSP:APP:CFA = 3:6:2 (weight ratio). The flammability and thermal behavior of the (intumescent flame‐retardant)‐PP (IFR‐PP) were investigated via limiting oxygen index (LOI), vertical burning tests (UL‐94), thermogravimetric analysis, and cone calorimetry (CONE). The results indicated that the IFR‐PP had both excellent flame retardancy and anti‐dripping ability. The optimum flame‐retardant formulation gave an LOI value of 39.8 and a UL‐94 V‐0 rating to PP. Moreover, both the heat release rate and the total heat release of the IFR‐PP with the optimum formulation decreased significantly relative to those of pure PP, according to the cone calorimeter analyses. The residues of IFR‐PP obtained after CONE tests were observed by scanning electron microscopy, and it was found that the char yield was directly related to the flame retardancy and anti‐dripping behavior of the treated PP. J. VINYL ADDIT. TECHNOL., 20:10–15, 2014. © 2014 Society of Plastics Engineers     

Effect of Phosphorus-Based Flame Retardants and PA6 on the Flame Retardancy and Thermal Degradation of Polypropylene

The investigation mainly focuses on the effect of polyamide 6 (PA6) and phosphorus based flame retardants (FRs) on improving the flame retardancy of polypropylene (PP). The flame retardant properties have been studied by limiting oxygen index, vertical burning test tests and cone calorimeter testing. The results demonstrate that PA6 and FRs can greatly improve the flame-retardant and thermal properties of PP. It’s found that the addition of PA6/APP/FRs can promote the formation of stable intumescent char layers. Those indicate that the flame retardancy of PA6/APP/FRs/PP composites is improved by the condensed-phase action of PA6/APP/FRs.     

Flame retardation and thermal degradation of intumescent flame‐retarded polypropylene composites containing spirophosphoryldicyandiamide and ammonium polyphosphate

A novel halogen‐free intumescent flame retardant, spirophosphoryldicyandiamide (SPDC), was synthesized and combined with ammonium polyphosphate (APP) to produce a compound intumescent flame retardant (IFR). This material was used in polypropylene (PP) to obtain IFR‐PP systems whose flammability and thermal behavior were studied by the limiting oxygen index (LOI) test, UL‐94, thermogravimetric analysis, and cone calorimetry. In addition, the mechanical properties of the systems were investigated. The results indicated that the compound intumescent flame retardant showed both excellent flame retardancy and antidripping ability for PP when the two main components of the IFR coexisted in appropriate proportions. The optimum flame retardant formulation was SPDC:APP = 3:1, which gave an LOI value of 38.5 and a UL‐94 V‐0 rating. Moreover, the heat release rate, production of CO, smoke production rate, and mass loss rate of the IFR‐PP with the optimum formulation decreased significantly relative to those of pure PP, according to the cone calorimeter analysis. The char residues from the cone calorimetry experiments were observed by scanning electron microscopy, which showed that a homogeneous and compact intumescent char layer was formed. J. VINYL ADDIT. TECHNOL., 2010. © 2010 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     

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     

氧化锌对膨胀阻燃聚丙烯的影响

研究了协效剂氧化锌（ZnO）对聚磷酸铵（APP）、季戊四醇（PER）、氰尿酸三聚氰胺（MCA）膨胀阻燃聚丙烯（PP）体系的阻燃协效作用。采用氧指数（LOI）、热失重法（TG）、锥形量热仪（Cone）、红外光谱（FTIR）等手段分析了ZnO对膨胀阻燃PP的影响。结果表明，氧化锌可提高该体系的LOI和阻燃性能，还可促进阻燃体系形成炭层，且可提高其炭层的强度，该体系氧化锌最佳用量应为1．0份。     

Synergistic flame‐retarded effect between carbon nanotubes and ammonium polyphosphate in Nylon6 and Nylon6/polystyrene blends

The association of carbon nanotubes (CNTs) and ammonium polyphosphate (APP) as flame retardants was utilized for improving the flame retardancy of nylon6 (PA6) and blends of PA6/Polystyrene (PS). A remarkable synergistic effect between APP and CNTs was observed in PA6 at 1‐wt% CNTs loading. Rheological tests showed that 1‐wt% CNTs formed a network structure. Morphology of residue char indicated that a network enhanced synergistic effect. A synergy between APP and CNTs in blends of PA6/PS (56/24) was also investigated. APP and CNTs exhibited a remarkable synergistic effect at 0.25‐wt% CNTs loading, but the antagonistic effect on flame retardancy of blends was observed at 1‐wt% CNTs loading. Transmission electron microscopy showed that CNTs were exclusively dispersed in the PA6 phase of blends. The selective dispersion of CNTs caused the formation of a network at 0.25‐wt% CNTs loading. Morphology of residue char indicated that 0.25‐wt% CNTs were benefited by the formation of a continuous and well‐swollen residue char that enhanced the synergistic effect in blends. However, the aggregation of 1‐wt% CNTs in PA6 phase caused high viscosity of PA6 phase, resulting in a poor expansion of the residue char. Consequently, the antagonism was exhibited.     

硅锡协同阻燃尼龙6

采用氯化亚锡(SnCl2)/聚氨丙基苯基倍半硅氧烷(PAPSQ)复合阻燃剂阻燃改性尼龙6(PA6)。测定了阻燃PA6的氧指数(LOI),利用锥形量热仪测定了阻燃PA6的释热速率、总释热量、有效燃烧热等多种阻燃参数,并用扫描电镜(SEM)观察了阻燃PA6残炭的形貌。实验表明,当SnCl2用量为4%,PAPSQ用量为1%时,PA6的LOI为31%,PA6的释热速率、总释热量和有效燃烧热均明显下降,PAPSQ对SnCl2有协同阻燃效果。     

Preparation and characterization of microcapsulated red phosphorus and its flame‐retardant mechanism in halogen‐free flame retardant polyolefins

Microcapsulated red phosphorus (MRP), with a melamine–formaldehyde resin coating layer, was prepared by two‐step coating processes. The physical and chemical properties of MRP were characterized by Fourier‐transform infrared spectroscopy (FTIR), X‐ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM) and other measurements. The flame retardant action and mechanism of MRP in the halogen‐free flame retardant (HFFR) polyolefins (PO) blends have been studied using cone calorimeter, limiting oxygen index (LOI), thermogravimetric analysis (TGA) and dynamic FTIR spectroscopy. The results show that the MRP, which is coated with melamine–formaldehyde resin, has a higher ignition point, a considerably lower amount of phosphine evolution and of water absorption compared with red phosphorus (RP) itself. The data observed by cone calorimeter, LOI and TGA measurements from the PO/HFFR blends demonstrated that the MRP can decrease the heat release rate and effective heat of combustion, and increase the thermostability and LOI values of PO materials. The dynamic FTIR results revealed the flame‐retardant mechanism that RP can promote the formation of charred layers with the P–O and P–C complexes in the condensed phase during burning of polymer materials. Copyright © 2003 Society of Chemical Industry     

Effect of charring agent THEIC on flame retardant properties of polypropylene

Tris(2‐hydroxyethyl) isocyanurate (THEIC) was used as charring agent and combined with ammonium polyphosphate (APP) to form an intumescent flame retardant (IFR) for polypropylene (PP). The flame retardancy and combustion performance of PP/IFR composite was tested by limiting oxygen index (LOI), UL‐94 vertical burning test and cone calorimeter. The results showed that PP/IFR composite had highest LOI of 34.8 and obtained V‐0 rating when 30 wt % IFR was loaded and mass ratio APP/THEIC was 2 : 1. The peak heat release (PHRR) and total heat release (THR) values of PP composite containing FRs were remarkably reduced compared with that of pure PP. However, water resistant test demonstrated the PP/IFR composite had poor flame retardant durability, both the LOI value and UL‐94 V‐rating decreased when PP/IFR composite was soaked in water at 70°C after 36 h. The degradation process and the char morphology of IFR and PP/IFR composite were investigated by TGA and SEM images. The possible reaction path between APP and THEIC in the swollen process was proposed. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41214.     

Synergistic effects of ammonium polyphosphate/melamine intumescent system with macromolecular char former in flame-retarding polyoxymethylene

The improvement of the flame retardancy of polyoxymethylene (POM) is a world-wide difficult problem due to its zippered decomposition property. This paper reported the preparation of the flame-retarding (FR) POM with the synergistic combination of ammonium polyphosphate (APP)/melamine (ME) intumescent flame retardant system and macromolecular char former (MC). The UL94 testing, mechanical properties testing, thermogravimetric analysis (TGA), cone calorimetry and scanning electron microscopy (SEM) were used to investigate the corresponding structure, performance and synergistic flame retardant mechanism. The experimental results showed that, in the used macromolecular char formers (novolac, PA6 and TPU), the combination of novolac with APP/ME intumescent system has the best synergism in flame-retarding POM, greatly enhancing the quality of the formed condensed charred layer and hence the corresponding flame retardancy. The obtained FR POM composite could achieve flame retardancy of UL94 3.2 mm V-0 level and remarkably decreased heat release rate relative to pure POM. The synergistic effect of novolac was shown to be the char formed cross-linking reaction of it with APP. Due to the thermodynamic compatibility of novolac and POM, the prepared FR POM composite also has fairly good mechanical performance, having tensile strength of 49.1 MPa and Izod notched impact strength of 2.60 kJ/m².     

Synergistic effects of hydroxy silicone oil on intumescent flame retardant polypropylene system

The effects of hydroxy silicone oil as a synergistic agent on the flame retardancy of intumescent flame retardant polypropylene composites (IFR-PP) were studied, and the IFR system mainly consisted of the ammonium polyphosphate (APP), melamine (MEL) and pentaerythritol (PER). The UL 94 rating, thermogravimetric analysis (TGA), cone calorimeter (CONE) and digital photograph were used to evaluate the synergistic effects of hydroxy silicone oil (HSO). It has been found that the PP composite containing only APP, MEL and PER does not show good flame retardancy at 30% additive level. The cone calorimeter results show that the heat release rate, mass loss rate, mass, total heat release, carbon monoxide and carbon dioxide of PP/APP/MEL/PER/HSO composites decrease in comparison with the PP/APP/MEL/PER composite. The digital photographs demonstrated that HSO could promote to form the homogenous and compact intumescent char layer. Thus, a suitable amount of HSO plays a synergistic effect in the flame retardancy.     

Flame retarded epoxy resins by adding layered silicate in combination with the conventional protection‐layer‐building flame retardants melamine borate and ammonium polyphosphate

The pyrolysis and flammability of phosphonium‐modified layered silicate epoxy resin nanocomposites (EP/LS) were evaluated when LS was combined with two flame retardants, melamine borate (MB) and ammonium polyphosphate (APP), that also act via a surface protection layer. Thermogravimetry (TG), TG coupled with Fourier Transform Spectroscopy (TG‐FTIR), oxygen index (LOI), UL 94 burning chamber (UL 94) and cone calorimeter were used. The glassy coating because of 10 wt % MB during combustion showed effects in the cone calorimeter test similar to nanodispersed LS, and somewhat better flame retardancy in flammability tests, such as LOI and UL 94. Adding APP to EP resulted in intumescent systems. The fire retardancy was particularly convincing when 15 wt % APP was used, especially for low external heat flux, and thus, also in flammability tests like LOI and UL 94. V0 classification is achieved when 15 wt % APP is used in EP. The flame retardancy efficiency of the protection layers formed does not increase linearly with the MB and APP concentrations used. The combination of LS with MB or APP shows antagonism; thus the performance of the combination of LS with MB or APP, respectively, was disappointing. No optimization of the carbonaceous‐inorganic surface layer occurred for LS‐MB. Combining LS with APP inhibited the intumescence, most probably through an increase in viscosity clearly above the value needed for intumescent behavior. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Synergist flame retarding effect of ultrafine zinc borate on LDPE/IFR system

The flame retardancy of low‐density polyethylene (LDPE) treated with complex flame retardant composed of ultrafine zinc borate (UZB) and intumescent flame retardant (IFR) have been investigated by limited oxygen index (LOI), UL‐94 test, thermogravimetric analysis (TGA), cone calorimeter test, scanning electron micrograph (SEM), energy‐dispersive spectrometer (EDS), and X‐ray diffraction (XRD). The results of LOI and UL‐94 test indicate the desired flame retardancy of LDPE is obtained when the mass ratio of UZB to IFR is 4.2 : 25.8 and the complex flame retardant mass content is 30% (based on LDPE). The results of cone calorimeter show that heat release rate (HRR) peak, total heat release (THR), and mass loss of LDPE/IFR/UZB decrease substantially when compared with those of LDPE/IFR. TGA results show that the residue of LDPE/IFR/UZB increases obviously than that of LDPE/IFR when the temperature is above 600°C. SEM indicates the quality of char forming of LDPE/IFR/UZB is superior to that of LDPE/IFR. The results of EDS and XRD indicate that boron orthophosphate (BPO₄) and zinc‐contained compounds are formed in the residual char and these substances may play an important role in stabilizing the intumescent char structure and decrease the degradation speed substantially when subjected to high temperature. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 3667–3674, 2007     

有机-金属杂化化合物阻燃聚丙烯的研究

将有机-金属杂化三嗪化合物（SCTCFA-ZnO）与聚磷酸铵（APP）复配制备了膨胀型阻燃剂（IFR）,通过极限氧指数测试、垂直燃烧测试、锥形量热分析、热失重分析和扫描电子显微镜分析等表征方法研究了SCTCFA-ZnO/APP的协同作用对PP复合材料阻燃性能的影响。结果表明,APP与SCTCFA-ZnO复配可以有提高PP材料的阻燃性能,当IFR的添加量为25 %（质量分数,下同）,且APP/SCTCFA-ZnO的质量比为2/1时,复合材料的极限氧指数最高,达到31.1 %,达到UL 94 V-0级;IFR可提高复合体系的温热稳定性,阻燃复合材料燃烧后会形成一层致密、连续的炭层,从而起到良好的阻燃效果。     

Butyltriphenylphosphine-based chelate borates influenced on flame retardancy of polystyrene composite containing self-expanded intumescent flame retardants

The polystyrene (PS) composite containing self-expanded intumescent flame retardant (polyphosphate ammonium and expandable graphite) was blended with three butyltriphenylphosphine-based chelate borates, respectively, to evaluate their effect on flame retardancy. The chemical structure of as-prepared three chelate borates was confirmed by nuclear magnetic resonance (NMR) and Fourier transform infrared spectrum (FTIR). The flame retardancy of various PS composites was evaluated by vertical burning test (UL-94), limited oxygen index (LOI), and cone calorimeter (CC). Flammability and combustion results suggested that one of chelate borates, named [BTP][BMB], made PS composite (PS4) obtain V-0 rating, 27.0 ± 0.3% LOI value, and reduction on heat release and smoke production with 17 wt% total flame retardants loading. The combustion residue was analyzed by scanning electron microscope and FTIR, and the pyrolysis gaseous products were investigated by TG-FTIR technique. Besides, complex viscosity of PS composites composed of various chelate borates from a rheology instrument indicated that the improvements of flame retardancy of PS composites depended on the temperature of construction of crosslinked network by expandable graphite, which the chelate borates showed distinctive influence. Accordingly, the flame-retarding mechanism about fast response to flame has been proposed.     

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     

Intumescent flame retardant TPO composites: Flame retardant properties and morphology of the charred layer

Intumescent flame retardant thermoplastic polyolefin (TPO) composites were prepared to study the relationships between their structure of charred layer (including of the multicellular intumescent layer and the charry layer) and flame retardant properties. They were characterized using the LOI and UL‐94 test, which indicated that the best fire retardant behavior (V‐0 rating and LOI reach to 28.1%) was obtained at the formulation of TPO/ammonium dihydrogen phosphate/starch (100/60/20). Thermal gravimetric analysis demonstrated that the presence of ammonium dihydrogen phosphate/starch promoted the esterification and carbonization process in lower temperature range while enhancing the thermal stability of intumescent flame retardant TPO in high‐temperature range. Scanning electron microscope and optical microscope were shown that, with combustion time prolonged, the intumescent layers obtained greater number of cells, and the charry layer became more compact while the size of the carbon granules became smaller on the surface. Introduction of starch had an obvious effect on the structure of the intumescent and charry layers. The charry layer of the composites with the content of 20 phr starch was more compact and uniform than that of the composites with 50 phr. The weight ratio of ammonium dihydrogen phosphate to starch in the intumescent flame retardant was fixed as 3 : 1 which cooperated with each other well to promote a compact charry layer and to obtain the better flame retardancy performance. Therefore, the better the charred layers produced, and the better flame retardant properties they obtained. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Component ratio effects of hyperbranched triazine compound and ammonium polyphosphate in flame‐retardant polypropylene composites

A hyperbranched derivative of triazine group (EA) was synthesized by elimination reaction between ethylenediamine and cyanuric chloride. The different‐mass‐ratio EA and ammonium polyphosphate (APP) were mixed and blended with polypropylene (PP) in a constant amount (25%) to prepare a series of EA/APP/PP composites. The component ratio effect of EA/APP on the flame‐retardant property of the EA/APP/PP composites was investigated using the limiting oxygen index (LOI), vertical burning (UL‐94), and cone calorimetry tests. Results indicated that the EA/APP/PP (7.50/17.50/75.00) composite with the appropriate EA/APP mass ratio had the highest LOI, UL94 V‐0 rating, lowest heat release rate, and highest residue yield. These results implied that the appropriate EA/APP mass ratio formed a better intumescent flame‐retardant system and adequately exerted their synergistic effects. Furthermore, average effective combustion heat values revealed that EA/APP flame retardant possessed the gaseous‐phase flame‐retardant effect on PP. Residues of the EA/APP/PP composites were also investigated by scanning electron microscopy, Fourier‐transform infrared, and X‐ray photoelectron spectroscopy. Results demonstrated that the appropriate EA/APP mass ratio can fully interact and lock more chemical constituents containing carbon and nitrogen in the residue, thereby resulting in the formation of a dense, compact, and intumescent char layer. This char layer exerted a condensed‐phase flame‐retardant effect on EA/APP/PP composites. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 41006.     

Synthesis of a novel intumescent flame retardant and its flame retardancy in polypropylene

Microencapsulated ammonium polyphosphate (GMFAPP) is prepared by in situ polymerization method with a shell of poly(ethylene glycol) modified melamine-formaldehyde resin. Due to the presence of shell, GMFAPP shows less size, higher water resistance and flame retardancy in polypropylene (PP) compared with ammonium polyphosphate (APP). The flame retardant action of GMFAPP and APP in PP are studied using LOI, UL-94 and cone calorimeter, and their thermal stability is evaluated by thermogravimetric apparatus. The limiting oxygen index (LOI) value of the PP/GMFAPP at the same loading is higher than the value of PP/APP. UL-94 ratings of PP/GMFAPP can reach V-0 at 30 wt% loading. The water resistant properties of the PP composites are studied, and the results of the composites containing with APP and GMFAPP are compared. The cone results put forward that GMFAPP is an effective flame retardant in PP compared with APP. Moreover, the thermal oxidative behavior of GMFAPP is evaluated by dynamic FTIR to study its flame retardant mechanism in PP.