Preparation of a novel synergistic flame retardant and its application in silicone rubber composites

Dehydration condensation product (DHCP) was prepared by addition and dehydration condensation reactions of 9,10-dihydro-9-oxa-10-phenanthrene-10-oxide (DOPO), vinyl trimethoxysilane, and (3-aminopropyl) triethoxysilane. DHCP-PA with high phosphorus content was prepared by reaction between DHCP and phytic acid (PA). It was then compounded with oxidized multi-walled carbon nanotubes (OMWCNTs) to prepare silicone rubber (SR) flame retardant composites. The results showed that the SR with a small amount of DHCP-PA owned good flame retardant effect. The heat release rate (HRR) was decreased from 436 kW/m² for pure SR to 288 kW/m² for the SR with 5 phr DHCP-PA, and the decreasing degree was 33.9%. After mixing 5 phr DHCP-PA with 1 phr OMWCNTs, the HRR of SR composite was decreased from 436 to 251 kW/m², the smoke production rate was decreased from 0.161 to 0.087 m²/s, the limited oxygen index value was increased from 20.4% to 28.4%, and the flame retardant grade can reach UL94 V-0. In addition, the synergistic flame retardant mechanism was researched and analyzed.     

碱式碳酸镁基复合阻燃剂的制备及其阻燃性能研究

采用硅烷表面处理的碱式碳酸镁纳米片和氢氧化镁以及氢氧化铝为复合阻燃剂,通过密炼模压法制备了一系列复配阻燃剂协效阻燃EVA的复合材料。利用拉伸性能测试仪、熔融指数仪、垂直燃烧测试仪和锥形量热仪分别测试了复合材料的力学性能、加工流动性能和阻燃性能,利用热重分析仪测试了复配阻燃剂的热分解行为。结果表明,复配阻燃剂以适当比例协效阻燃EVA在更宽的燃烧温度范围内发生分解,能够起到更好的阻燃效果。并且复配阻燃剂/EVA复合材料的热释放速率和烟释放率大幅度降低,分别为181.06 kW/m²和0.032 m²/s。另外,复配阻燃剂/EVA复合材料的拉伸强度达到9.73 MPa,断裂伸长率为155.07%,每10 min熔融指数为1.00 g,符合电线电缆行业标准。     

Lightweight and flame retardant fluorosilicone rubber composited foam prepared by supercritical nitrogen

Improving the flame retardancy and lightweight of fluorosilicone rubber (FSR) foam is important for its application in aerospace, rail transportation, petrochemical equipment, etc. In this work, ammonium polyphosphate (APP) and expandable graphite (EG) were used as synergistic flame retardants, and the lightweight FSR composite foam with flame retardancy was prepared by supercritical N₂ foaming. When there were 12.5 phr APP and 7.5 phr EG, the composite foam with density of 0.254 g/cm³ showed superiority in foaming performance and flame retardancy, and the limit oxygen index was 36.4%, the UL-94 grade reached V-0, the ignition time was 12 s and the fire performance index was 0.071 s·m²/kW. In addition, the aging, oil and solvent resistance of FSR foam was not affected. This work provided data support for the production and application of the flame retardant FSR foam.     

Synergistic flame retardant effects of activated carbon and molybdenum oxide in poly(vinyl chloride)

The synergistic effects of activated carbon (AC) and molybdenum oxide (MoO₃) in improving the flame retardancy of poly(vinyl chloride) (PVC) were investigated. The effects of AC, MoO₃ and their mixture with a mass ratio of 1:1 on the flame retardancy and smoke suppression properties of PVC were studied using the limiting oxygen index and cone calorimeter tests. It was found that the flame retardancy of the relatively cheaper AC was slightly weaker than that of MoO₃. In addition, the incorporation of AC and MoO₃ greatly reduced the total heat release and improved smoke suppressant property of PVC composites. When the total content of AC and MoO₃ was 10 phr, PVC/AC/MoO₃ had the lowest peak heat release rate and peak smoke production rate values of 173.80 kW m^?2 and 0.1472 m² s^?1, which represented reductions of 47.3 and 59.9%, respectively, compared with those of PVC. Furthermore, thermogravimetric analysis and gel content tests were used to analyze the flame retardant mechanism of AC and MoO₃, with results showing that AC could promote early crosslinking in PVC. Char residue left after heating at 500 °C was analyzed using scanning electron microscopy and Raman spectroscopy, and the results showed that MoO₃ produced the most compact char, with the smallest and most organized carbonaceous microstructures. © 2017 Society of Chemical Industry     

Low‐melting sulfate glasses as additives to semirigid PVC and their flame retardant and smoke suppressant properties

The role of low‐melting sulfate glasses (LMSG) as additives on the flame retardant and smoke suppressant properties of semirigid poly(vinyl chloride) (PVC), as well as the mechanism for flame retardancy and smoke suppression, were studied through the Limiting Oxygen Index (LOI) test. Smoke Density Rating (SDR) test, DTA‐TG, and SEM. The results show that the LMSG have good smoke suppressant properties. When the PVC compound contains 40 parts of LMSG, the SDR value will be reduced by about 45%. The Cu²⁺, Zn²⁺, Mn²⁺, and Ni²⁺ sulfates, as well as MoO₃, cause PVC to crosslink and form char, and the melt can protect not only the char formed during combustion and thermal degradation, but also undecomposed polymer. That is the main mechanism for flame retardation and smoke suppression when the additives melt. The mechanical properties of the PVC compounds containing different levels of LMSG were also studied.     

A novel phytic acid based flame retardant to improve flame retardancy,hydrophobicity and mechanical properties of linear low-density polyethylene

Exploiting high phosphorus content of phytic acid, it was grafted onto magnesium hydroxide (MH) by neutralization reaction to obtain MGPA, a flame retardant. A current study investigated the effect of MGPA on hydrophobicity, flame retardancy, and mechanical properties of MGPA-linear low-density polyethylene (LLDPE) composites. The LLDPE composite with 50 parts of MGPA has the better flame retardancy and thermal stability with a limiting oxygen index of 23.3%, which is higher than that of neat LLDPE (17%). In addition, MGPA could effectively promoted LLDPE to form a continuous and compact char residue during combustion, which reduce the peak of heat release rate and total smoke production value of LLDPE composite by 70% and 36%, respectively, and the char residue rate increase to 67.5%. Furthermore, the maximum of loss-rate showed by LLDPE composite with MGPA reduce to 1.25%/min while the value of LLDPE composite with MH is 1.8%/min. Meanwhile, the LLDPE composite with MGPA show remarkable elongation at break and hydrophobicity, which are 398% and 99°, respectively. In addition, this study presents a substantial flame retardancy and interfacial compatibility of MGPA for extending the applications of flame-retardant LLDPE composites.     

Preparation and properties of modified aluminum diethylphosphinate flame retardant for low-density polyethylene

To improve the flame retardancy of low-density polyethylene (LDPE) and mechanical properties of LDPE composites, phenol-formaldehyde aluminum diethylphosphinate microcapsules (PF@ADP) was prepared by in-situ polymerization with phenol-formaldehyde (PF) resin as the wall material and halogen-free flame-retardant aluminum diethylphosphinate (ADP) as the core material. The effects of PF@ADP on flame retardancy and mechanical properties of LDPE were investigated by methods of combustion experiments, mechanical analysis, thermogravimetric analysis (TGA), and smoke density analysis. The results indicated that, compared with ADP/LDPE composites, the flame retardancy and mechanical properties of PF@ADP/LDPE were obviously improved. With the addition of 20 wt% PF@ADP (PF:ADP = 3:7), the limit oxygen index (LOI) of LDPE composites increased to 30.7% and UL-94 reached V-1 grade. The tensile strength and elongation at break reached 12.5 MPa and 431.2%, which was 20.2% and 23.1% higher than that of ADP/LDPE with the same addition. The addition of PF@ADP was beneficial to the smoke suppression of LDPE.     

Epoxy resin/phosphorus‐based microcapsules: Their synergistic effect on flame retardation properties of high‐density polyethylene/graphene nanoplatelets composites

Two types of microcapsule flame retardants are prepared by coating ammonium polyphosphate (APP) and aluminum diethylphosphinate (ADP) with epoxy resin (EP) as the shell via in situ polymerization, and blended with high density polyethylene (HDPE)/graphene nanoplatelets (GNPs) composites to obtain flame‐retardant HDPE materials. Fourier transform infrared spectroscopy, scanning electron microscopy (SEM), and water contact angle results confirm the formation of core–shell structures of EP@APP and EP@ADP. The limiting oxygen index (LOI), vertical burning test (UL‐94), cone calorimetry, and Raman spectroscopy are employed to characterize the HDPE/GNPs composites filled with EP@APP and EP@ADP core–shell materials. A UL94 V‐0 level and LOI of 34% is achieved, and the two flame retardants incorporated in the HDPE/GNPs composite at 20 wt % in total play a synergistic effect in the flame retardancy of the composite at a mass ratio of EP@ADP:EP@APP = 2:1. According to the cone‐calorimetric data, the compounding composites present much lower peak heat release rate (300 kW/m²) and total heat release (99.4 MJ/m²) than those of pure HDPE. Raman spectroscopic analysis of the composites after combustion reveals that the degree of graphitization of the residual char can reach 2.31, indicating the remarkable flame retarding property of the composites. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46662.     

An efficient approach to improving fire retardancy and smoke suppression for intumescent flame‐retardant polypropylene composites via incorporating organo‐modified sepiolite

In this work, an efficient approach to improving the fire retardancy and smoke suppression for intumescent flame‐retardant polypropylene (PP) composites is developed via incorporating functionalized sepiolite (organo‐modified sepiolite [ONSep]). The PP composites with different amounts of intumescent flame retardants and ONSep were prepared by melt compounding. The morphology, thermal behavior, fire retardancy, smoke suppression, and mechanical property of flame‐retardant PP composites were studied. The results indicate an appropriate amount of ONSep in the flame‐retardant PP composites can increase thermal degradation temperature and char formation as well as a reduction of the peak heat release rate and total heat release; moreover, the addition of ONSep significantly decreases the CO production, total smoke production, smoke production rate, and smoke temperature. Simultaneously, the impact strength of intumescent flame‐retardant PP composite is also maintained by introducing an appropriate amount of ONSep as compared with that without ONSep.     

Self-emulsification synthesis of epoxy phosphate ester and its flame-retardant mechanism in flexible poly(vinyl chloride)/magnesium hydroxide composites

A trade-off dilemma exists for simultaneously improving the mechanical properties and flame resistance of flexible polyvinyl chloride (fPVC)/magnesium hydroxide (MH) composites. In this study, epoxy phosphate ester (EPE), a hydrophobic surface modifier of MH, was synthesized using a self-emulsification method. After modification, EPE was bonded to the surface of MH (MHEPE) without altering its morphology. The results of limiting oxygen index and cone calorimetry tests indicated that fPVC/MHEPE exhibited better flame retardancy and smoke suppression effects than did fPVC/MH. The peak of the heat release rate, total heat release, peak of the smoke production rate, and total smoke production of the fPVC/MHEPE composite were 206.0 kJ m⁻², 45.90 MJ m⁻², 0.0729 m² s⁻¹, and 9.88 m², which were 8.64%, 14.00%, 27.61%, and 9.02% lower than those of the fPVC/MH composite, respectively. For the fPVC/MHEPE composite, a compact and continuous char residue formed, which could inhibit heat and flammable volatile migration between the matrix and burning zones. In the gas phase, the dilution effect of H₂O vapor reduced the concentrations of O₂ and flammable volatiles. The free-radical quenching effect of ·PO and ·PO₂ also played a vital role in extinguishing flame and terminating combustion. Further, the introduction of EPE improved the tensile and impact strengths of the fPVC/MH composites because of the excellent interfacial compatibility between MHEPE and the fPVC matrix. This study provides a simple and workable solution for the trade-off dilemma, and the remarkable flame retardancy and mechanical properties of the fPVC/MHEPE composite render it a promising cable material.     

用锥形量热仪研究无卤阻燃HDPE体系的燃烧性

在35kW／m^2热辐照条件下,利用锥形量热仪研究了膨胀型阻燃剂／Mg(OH)2阻燃高密度聚乙烯(HDPE)体系的燃烧性。结果表明：膨胀型阻燃剂／Mg(OH)2能明显降低HDPE的热释放速率、总热释放量、最大生烟速率及总烟释放量。与膨胀型阻燃剂单独使用相比,Mg(OH)2与膨胀型阻燃剂复合使用的阻燃效果明显,总烟释放量减少了38％,总热释放量减少了10％,达到了低发炯、高效阻燃的目的。     

Synergistic flame retardant effect of piperazine salt and ammonium polyphosphate as intumescent flame retardant system for polypropylene

Amino trimethylene phosphonic acid piperazine (ATPIP) salt, as a novel charring agent, is prepared via a simple ionic reaction in distilled water using amino trimethylene phosphate (ATMP) and piperazine as raw materials. The synergistic flame retardant effect of ATPIP and ammonium polyphosphate (APP) as an intumescent flame retardant (IFR) is investigated by various characterization and testing methods. The results show that the polypropylene (PP)/modified APP with piperazine (MAPP)/ATPIP ternary blend passes UL-94 V-0 rating and achieve a limiting oxygen index (LOI) of 30% at a loading level of 25 wt% IFR (MAPP:ATPIP = 3:1). Meanwhile, the total smoke production (TSP) value of IFR-PP samples is 3.3 m², which decreases by 93.2% compared with that of pure PP, exhibiting excellent smoke suppression performance. Besides, the analysis of gaseous pyrolysis products and char residue indicates that the IFR-PP samples show a synergistic flame-retardant mechanism including the gas phase and the condensed phase.     

Rigid polyurethane foams with halogen-free flame retardants: Thermal insulation,mechanical, and flame retardant properties

Rigid polyurethane foam (RPUF) composites with triphenyl phosphate (TPhP), aluminum trihydrate (ATH), and zinc borate (ZnB) alone, as well as their binary blends, were prepared via a one-shot process. The amount of flame retardant (FR) or FR blend was varied from 10 to 50% by polyol weight percentage, and the weight fraction of the blends was also fixed at 40%. The effects of additives on thermal insulation, mechanical, and flame retardancy properties of the composites were investigated. Thermal conductivity of the neat foam (RPUF) decreased from 22.53 to 21.04–21.58 mW m⁻¹ K⁻¹. The compressive strength of foams displayed an increase with increasing the amount of TPhP, ATH, and ZnB till 40% by weight. The limited oxygen index values of all foams increased and the flame spread rates of all foams significantly decreased. It was also observed that the flame was self-extinguished in some cases. The cone calorimeter test results indicated that the FR additives improved the flame retardancy of the RPUF. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 47611.     

Enhancement of organoclay on thermal and flame retardant properties of polystyrene/magnesium hydroxide composite

Organoclay (organically modified montmorillonite, OMMT) was introduced to the composite of polystyrene/magnesium hydroxide (PS/MH) by melt compounding. The structure of the obtained PS/MH/OMMT composite was characterized by X‐ray diffraction and transmission electron microscopy. Thermal degradation behavior and flame retardancy of the composite were investigated by various means. It is shown that the PS/MH/OMMT composite has an intercalated nanostructure with the PS chains intercalated between the OMMT layers and the MH particles dispersed evenly in the PS matrix. Compared with the PS/MH composite containing identical amount of flame retardant, the introduction of OMMT has increased the thermal degradation temperature and lowered the mass loss rate at high temperatures. The PS/MH/OMMT nanocomposite can produce a more continuous and compact charred residue layer upon degradation both in air and burnt in flame than the PS/MH composite. Because of formation of this highly thermally stable and insulating charred residue layer, the nanocomposite exhibits much improved thermal endurance, flame retardancy, smoke suppression, and dripping resistance. Moreover, the combination of MH and OMMT makes the composite more difficult to ignite and decreases the release of toxic gas. The advantage of the PS/MH/OMMT nanocomposite is more pronounced in the early stage of combustion. POLYM. COMPOS., 37:746–755, 2016. © 2014 Society of Plastics Engineers     

Synergistic effects between red phosphorus and alumina trihydrate in flame retardant silicone rubber composites

Abstract

The synergistic flame retardant effects between red phosphorus (RP) and alumina trihydrate (ATH) in silicone rubber (SR) composites were evaluated using limiting oxygen index, UL 94 rating, cone calorimeter, thermogravimetric analysis and digital photographs. It has been found that the SR composite containing only ATH does not show good flame retardancy at 39·0 wt-% loading. The cone calorimeter results showed that the heat release rate, mass loss rate, mass and total heat release of SR/ATH/RP composites decrease greatly in comparison with the SR/ATH composites. The digital photographs demonstrated that 1·0 wt-%RP could promote the formation of the homogenous and compact char layer. Thus, a suitable amount of RP has a synergistic effect with ATH in the flame retardant SR composite system.     

A P/N-containing flame retardant constructed by phosphaphenanthrene,phosphonate, and triazole and its flame retardant mechanism in reducing fire hazards of epoxy resin

A P/N-containing flame retardant (PPT) constructed by phosphaphenanthrene, phosphonate, and triazole groups was successfully synthesized and used as a reactive co-curing agent for epoxy resin (EP). The curing behavior, thermal property, combustion behavior, and flame retardant mechanism of EP thermosets were comprehensively investigated. According to the analysis of DSC and TGA, PPT accelerated the crosslinking reaction and enhanced the charring ability for EP thermosets at high temperature. The results of combustion test indicated that PPT endowed epoxy thermoset with outstanding flame retardancy. When the phosphorus content was 0.71 wt%, EP/DDS/PPT-2 achieved a LOI value of 33.2% and passed V-0 rating in UL-94 test, and its peak heat release rate and total heat release were decreased by 63.7 and 30.5%, respectively, relative to EP/DDS. Moreover, the FIGRA of EP/DDS/PPT-2 was reduced from 9.7 to 3.5 kW m⁻² s⁻¹, manifesting the significantly improved fire safety of EP thermoset. The flame retardant mechanism was summarized as two parts: (a) the barrier effect of continuous phosphorus-rich char layers in condensed phase, (b) the quenching effect of phosphorous radicals and diluting effect of nonflammable gases in gaseous phase.     

The synthesis and characterization of a novel phosphorus–nitrogen containing flame retardant and its application in epoxy resins

A novel, halogen‐free, phosphorus–nitrogen containing flame retardant 2[4‐(2,4,6‐Tris{4‐[(5,5‐dimethyl‐2‐oxo‐2λ⁵‐[1,3,2]dioxaphosphinan‐2‐yl)hydroxymethyl]phenoxy}‐(1,3,5)‐triazine (TNTP) was successfully synthesized in a three‐step process, and characterized by FTIR, NMR spectroscopy, mass spectra, and elemental analysis. A series of modified DGEBA epoxy resin with different loadings of TNTP were prepared and cured by 4,4‐diaminodiphenylsulfone (DDS). Thermal gravimetric analysis and vertical burning test (UL‐94) were used to evaluate the flame retardancy of TNTP on DGEBA epoxy resin. The results showed that TNTP had a great impact on flame retardancy. All modified thermosets by using TNTP exhibited higher T_g than pure DGEBA/DDS. The loading of TNTP at only 5.0 wt % could result in satisfied flame retardancy (UL‐94, V‐0) together with high char residue (27.3%) at 700°C. The addition of TNTP could dramatically enhance the flame retardancy of DGEBA epoxy resins, which was further confirmed by the analysis of the char residues by scanning electron microscopy and FTIR. Furthermore, no obviously negative effect was found on the Izod impact strength and flexural property of DGEBA epoxy resins when TNTP loading limited in 5.0 wt %. DGEBA/DDS containing 2.5 wt % TNTP could enhance Izod impact strength from 10.47 to 10.94 kJ m^?2, and showed no appreciable effect on the flexural property (85.20 MPa) comparing with pure DGEBA/DDS (87.03 MPa). Results indicated that TNTP as a phosphorus–nitrogen synergistic intumescent flame retardant could be used for DGEBA epoxy resin. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 41079.     

纳米阻燃抑烟PVC的研究进展

PVC是一种应用广泛的高分子材料,但因其具有热稳定性差、易燃烧、发烟量大的缺点而限制了发展,因此PVC的阻燃与抑烟成为阻燃科学研究领域的关键问题之一。纳米型阻燃抑烟剂克服了传统型阻燃抑烟剂添加量大、阻燃抑烟效果不明显的缺点,为研究和解决PVC阻燃抑烟提供了一个新途径。本文介绍了PVC纳米阻燃抑烟剂的制备方法、表征手段及其在PVC中的应用以及PVC降解、阻燃与抑烟的表征,最后简要论述PVC阻燃抑烟的发展趋势。     

Synergistic effect between zeolitic imidazolate framework-8 and expandable graphite to improve the flame retardancy and smoke suppression of polyurethane elastomer

Zeolitic imidazolate framework-8 (ZIF-8) was synthesized at room temperature, and then added with expandable graphite (EG) to polyurethane elastomer (PUE) to study their flame retardancy and smoke suppression of PUE. The results showed that when the total flame retardant was 3 wt % and the ratio of ZIF-8 and EG was 1:3, it had the best effect on the flame retardancy and smoke suppression of PUE. Compared with pure PUE, the peak heat release rate, the total heat release, and the maximum smoke density values of Z1E3 decreased by 83.4, 42.6, and 22.4%, respectively. Moreover, the limited oxygen index value of Z1E3 increased to 30.2% and its UL-94 vertical burning test reached V-1 rating. This was because ZIF-8 synergized with EG to make the intumescent char layer compact, resulting in improved flame retardancy and smoke suppression of PUE. The specific mechanism of flame retardancy and smoke suppression is also discussed in this article. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48048.     

A facile approach to prepare anhydrous MgCO3 and its effect on the mechanical and flame retardant properties of PVC composites

Anhydrous MgCO₃ is considered a promising inorganic filler because of its many outstanding properties. In this study, a facile approach was developed to prepare anhydrous MgCO₃ using urea as CO₂ source. MgCO₃ with cube-like morphology (MC-cube) was prepared and then modified with β-cyclodextrin (CD) (CD@MC-cube) in order to improve its interfacial adhesion with PVC matrix. The results indicate that the incorporation of MgCO₃ can not only reinforce and toughen PVC composites, but it can also enhance their thermal stability and flame retardancy. Specifically, the impact strength of CD@MC-cube/PVC composite with 4 wt% of CD@MC-cube is increased by 92.5%, and the total smoke production and the total heat release of CD@MC-cube/PVC composite with 12 wt% of CD@MC-cube are decreased by 38.8% and 51.3% compared with that of PVC matrix, respectively.