A flame‐retardant composite foam: foaming polyurethane in melamine formaldehyde foam skeleton

A composite foam, polyurethane–melamine formaldehyde (PU/MF) foam, was prepared through foaming PU resins in the three‐dimensional netlike skeleton of MF foam. The chemical structure, morphology, cell size and distribution, flame retardancy, thermal properties and mechanical properties of such composite foam were systematically investigated. It was found that the PU/MF foam possessed better fire retardancy than pristine PU foam and achieved self‐extinguishment. Moreover, no melt dripping occurred due to the contribution of the carbonized MF skeleton network. In order to further improve the flame retardancy of the composite foam, a small amount of a phosphorus flame retardant (ammonium polyphosphate) and a char‐forming agent (pentaerythritol) were incorporated into the foam, together with the nitrogen‐rich MF, thus constituting an intumescent flame‐retardant (IFR) system. Owing to the IFR system, the flame‐retardant PU/MF foam can generate a large bulk of expanded char acting as an efficient shielding layer to hold back the diffusion of heat and oxygen. As a result, the flame‐retardant PU/MF foam achieved a higher limiting oxygen index of 31.2% and exhibited immediate self‐extinguishment. It exhibited significantly reduced peak heat release rate and total heat release, as well as higher char residual ratio compared to PU foam. Furthermore, the composite foam also showed obviously improved mechanical performance in comparison with PU foam. Overall, the present investigation provided a new approach for fabricating a polymer composite foam with satisfactory flame retardancy and good comprehensive properties. © 2018 Society of Chemical Industry     

Loading the polyol carbonization agent into clay nanotubes for the preparation of environmentally stable UV‐cured epoxy materials

The halloysite nanotubes (HNTs) were loaded with pentaerythritol (PER). The as‐prepared composite (HNT‐P) and ammonium polyphosphate (APP) was subsequently added to the UV‐curable epoxy resins, giving a new flame‐resistant system. Loading of the hydrophilic PER into HNT can reduce the moisture absorption in the UV‐curable epoxy resins. The flame retardancy was evaluated by means of the cone calorimeter and limit oxygen index test. The results showed that the flame retardancy of the modified epoxy resin was greatly improved with an obvious decrease in both the heat release and smoke release. Moreover, it was revealed that HNT could catalyze the reaction of APP and PER, and the burning surface of the epoxy resin should be covered by the polyphosphoric‐HNT intumescent char layer. We have measured the moisture sorption and dynamic mechanical properties of the UV‐cured epoxy resins. As compared to the use of the simple mixture of PER and HNT, the use of the HNT‐P nearly kept the storage modulus at about 1809 Mpa and reduced the moisture absorption by 58.2 wt % at 40 °C. The results proved that the addition of the HNT‐P obtained lower moisture absorption and higher stability of the mechanical properties than adding the simple mixture. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45045.     

Newly emerging applications of halloysite nanotubes: a review

Halloysite nanotubes (HNTs) are types of naturally occurring 1:1 clays with nanotubular structures and similar chemical composition to kaolin. Due to various characteristics such as nanoscale lumens, high length‐to‐diameter ratio, relatively low hydroxyl group density on the surface, etc., numerous exciting applications have been discovered for this unique, cheap and abundantly deposited clay. After briefly summarizing applications in controlled release, nanotemplating and sorption, we emphasize the applications of HNTs in the fabrication of polymer nanocomposites. The unique structures and performance of HNT‐incorporated polymer nanocomposites processed by various routes are described. The results suggest that these nanocomposites exhibit remarkable performance such as reinforcing effects, enhanced flame retardancy and reduced thermal expansion. Accordingly, HNTs should be of interest in the area of polymer nanocomposites for structural and functional applications. Copyright © 2010 Society of Chemical Industry     

Bio-based rigid polyurethane foam composites reinforced with flame retardants: From synthesis to performance evaluation

The building and construction industry is under increasing pressure to make insulation materials greener, more sustainable, and less flammable. In this study, sugar beet pulp was liquified under the optimized liquefaction conditions and used as the source of bio-polyol (SBpol) in the production of bio-based rigid polyurethane foam (sPUF). In order to improve the flame retardancy, sPUF composites were prepared with the addition of flame retardants; expandable graphite (EG) and/or dimethyl methyl phosphonate (DMMP). The bio-polyol was used at a fixed ratio of 50 php in sPUF composites whereas the total ratio of flame retardants was fixed at 20 php. The effects of the ratio of EG and/or DMMP on the morphological, physicomechanical, thermal, and flame retardant properties of sPUF composites were evaluated. Although the thermal conductivity values of flame retardant added sPUF composites were increased in comparison to the petroleum-based foam, the compressive strength values were decreased as the amount of DMMP increased in the flame retardant formulation. Thermogravimetric analysis showed that the onset of decomposition of 20 php DMMP-containing sPUF composite decreased to 168.3°C. Although the limiting oxygen index (LOI) value of the petroleum-based PUF was as low as 19.7%, the LOI value of the sPUF/10E/10D foam increased to 24.9% (by about 26%). According to the cone calorimeter results, the peak heat release rate (pHRR) of sPUF was much higher than the petroleum-based foam. The incorporation of both DMMP and EG could further improve the flame retardant properties. The pHRR value of sPUF/10E/10D was 28.1% lower than that of sPUF. The results have shown that flame retardancy of sPUF composites could be improved by the addition of EG which acts in the condensed phase and DMMP, which acts mainly in the gas phase during burning. Flame retardant incorporated sPUF composites are considered as promising materials for use in insulation applications.     

Flame‐retardant cyanate ester resin with suppressed toxic volatiles based on environmentally friendly halloysite nanotube/graphene oxide hybrid

Development of high‐performance thermosetting resins by adding environmentally friendly flame retardant to heat‐resistant resins without deteriorating their outstanding thermal stability is an important research direction. Here, a unique hybrid (GHNT) consisting of graphene oxide (GO) and halloysite nanotubes (HNT) was synthesized, and then a series of composites based on cyanate ester (CE) resin were fabricated. The effects of GHNT on the heat resistance, flame retardancy, and smoke suppression of GHNT/CE composites were intensively investigated. The GHNT/CE composite with 5.0 wt % GHNT not only has about 15.1 °C higher initial degradation temperature, but also shows 54.6% or 37.9% lower peak heat release rate or maximum smoke density than CE resin. These results clearly demonstrate that GHNT is not the simple combination of GO and HNT; instead, it obviously shows positive synergistic effects in simultaneously improving the flame retardancy and thermal resistance of CE resin. The improved flame retardancy could be attributed to condensed‐phase mechanisms, including increasing char yield, building a dense char layer, and free radical scavenging. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46587.     

聚氨酯泡沫的阻燃方法研究进展

聚氨酯作为一种性能稳定的材料,广泛应用于社会生产生活的各个领域.聚氨酯泡沫的阻燃方法可分为反应型阻燃法、非反应型阻燃剂法、协同阻燃法、浸渍阻燃法、引入阻燃结构法.作者主要介绍了各种阻燃方法的研究进展,概述了阻燃方法研究新领域,并对今后阻燃聚氨酯泡沫研究开发提出了展望.     

Flame retardancy and mechanical properties of ferrum ammonium phosphate–halloysite/epoxy polymer nanocomposites

To recycle the nitrogen (N) and phosphorus (P) from wastewater, ferrum ammonium phosphate (FAP)–halloysite nanotubes (HNTs) were synthesized with simulated wastewater containing N, P, and Fe pollutants as raw materials. The adsorption–chemical precipitation in situ method was used to synthesize the target products, and the optimal conditions for the synthesis of the FAP–HNTs were obtained. Fourier transform Infrared (FTIR) spectroscopy, energy‐dispersive spectroscopy (EDS), scanning electron microscopy, transmission electron microscopy, and thermogravimetric analysis were conducted to characterize the samples. The FAP particle size was 20–30 nm in the FAP–HNTs. The FTIR spectra demonstrated that a small amount of water in the FAP–HNTs promoted the curing reaction. The FAP–HNTs and Exolit OP 1230 (OP) were introduced into epoxy (EP) to prepare the polymer nanocomposites. The heat release rate (HRR) and flammability of the EP composites were tested by microscale combustion calorimetry and UL‐94 instruments. The mechanical properties of the EP composites also were tested by a tension testing system. The results indicate that the flame retardancy and mechanical properties of the EP composites were improved by FAP–HNT. The addition of FAP–HNT and OP gave rise to an evident reduction of HRR and a prolonged burning time for the EP. EP/FAP–HNT/OP (20) (where 20 is the loading weight percentage) passed the UL 94 V‐0 rating. The analysis of the char revealed the synergy of the FAP–HNTs and OP in reducing the flammability of the polymers. We concluded that these polymers show potential for applications in wastewater treatment and N/P recycling. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41681.     

Properties of poly(vinyl chloride) incorporated with a novel soybean oil based secondary plasticizer containing a flame retardant group

A novel bio‐based plasticizer containing flame retardant groups based on soybean oil (SOPE) was synthesized from epoxidized soybean oil (ESO) and diethyl phosphate through a ring‐opening reaction. PVC blends plasticized with ESO and SOPE were prepared, respectively. Properties including rheological behavior, thermal stability, flame retardant performance, mechanical properties of PVC plasticized with ESO and SOPE were carefully studied. The results showed that the plasticized PVC blends indicated better compatibility, thermal, and mechanical properties. As a novel bio‐based plasticizer containing flame retardant groups, the TGA data indicated that the thermal degradation temperature of PVC blends plasticized with SOPE could reach to 275.5°C. LOI tests and SEM indicated that the LOI value of PVC blends could increase from 24.2 to 33.6%, the flame retardant performance of SOPE was put into effect by promoting polymer carbonization and forming a consolidated and thick flame retardant coating quickly, which is effective to prohibit the heat flux and air incursion. The enhancement in flame retardancy will expand the application range of PVC materials plasticized with SOPE. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42111.     

低密度及阻燃低密度高回弹聚氨酯泡沫研制

采用聚醚多元醇和阻燃聚合物多元醇为主要原料,制备了低密度及阻燃低密度高回弹聚氨酯泡沫,讨论了低密度高回弹聚氨酯泡沫性能及阻燃聚合物多元醇TM-300用量对聚氨酯泡沫性能的影响。结果表明,低密度高回弹泡沫密度可低至35kg/m3,性能与一般密度聚氨酯泡沫相当。随着TM-300用量增加,阻燃低密度高回弹聚氨酯泡沫的硬度和拉伸强度增加,撕裂强度和伸长率下降;TM-300可有效提高聚氨酯泡沫的阻燃性能,氧指数可达到32,各项性能均较优异。     

Preparation of microencapsulated red phosphorus through melamine cyanurate self‐assembly and its performance in flame retardant polyamide 6

A novel technology was developed to prepare microencapsulated red phosphorus (RP) with a coating of melamine cyanurate (MCA) serving as both a nitrogen‐containing flame retardant and as a solid lubrication agent. We took advantage of the self‐thickening effects during the MCA self‐assembly process to realize effective encapsulation on the surface of predispersed RP powder. The technology described in this article can overcome several drawbacks of current microencapsulation processes including (1) relatively complicated preparation processes, (2) use of formaldehyde or other noxious modifiers, and (3) poor compatibility with flame retardant fillers and polymer matrix resulting in poor physical properties. Additionally, this novel technology can also modify various properties of RP with regard to lubrication performance, ignition point, moisture absorption ratio, and color. As a composite system of flame retardant phosphorus encapsulated by a nitrogen‐containing flame retardant, the microencapsulated RP showed nitrogen‐phosphorus (N‐P) synergism with further improved flame retardancy. The action and mechanisms of the microencapsulated RP flame retardant polyamide 6 (PA6) were investigated by limiting oxygen index, vertical burning experiment (UL94), thermogravimetric analysis, and scanning electron microscope observations. The results indicated that the flame retardant PA6 possessed desired flame retardancy because of effective char‐formation of the condensed phase and it also showed satisfactory mechanical properties as the result of the good compatibility between flame retardant and PA6 resin. POLYM. ENG. SCI., 46:1548–1553, 2006. © 2006 Society of Plastics Engineers     

Effect of expandable graphite on the properties of intumescent flame‐retardant polyurethane foam

Water‐blown rigid polyurethane foam (PUF) with two different particle sizes (180 and 300 μm) of expandable graphite (EG) as a flame‐retardant additive were prepared, and the effects on the mechanical, morphological, water absorption, thermal conductivity, thermal, and flame‐retardant properties were studied. In this investigation, EG content was varied from 5 to 50 php by weight. The mechanical properties of PUF decreased with increasing EG loading in both cases. The water absorption of the PUF increased with an increase in the EG loading mainly because of the collapse of foam cells, as evidenced from the scanning electron microscopy pictures. The thermal conductivity of the EG‐filled PUF showed that the insulation properties decreased with EG loading. The flame‐retardant properties (limiting oxygen index and char yield measurement) of the PUF improved with increasing EG loading. PUF filled with the higher particle size EG showed better mechanical properties and fire‐retardant properties than the PUF filled with the lower particle size EG. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Thermoplastic Polyurethane-Encapsulated Melamine Phosphate Flame Retardant Polyoxymethylene

Due to its “unzipping” degradation mode and poor compatibility with most other flame retardants, polyoxymethylene (POM) is the most difficult flame-retarded polymer among macromolecular materials. In this project, we took advantage of thermoplastic polyurethane (TPU) resin, which possesses good compatibility with POM, serving as an encapsulation layer, and the carrier resin of the nitrogen-phosphorus composite flame retardant melamine phosphate to achieve even and fine dispersion of the flame retardant particles in the POM matrix. The improved morphology of the dispersion phase can markedly modify the flame retardancy and good mechanical performance. Additionally, the encapsulation of TPU avoids direct contact of the flame retardant with POM, thus also advantageous to the enhancement of its material performance. Moreover, as an efficient formaldehyde absorbent and toughening agent, TPU itself can greatly improve the flame retardancy, thermal stability, and toughness of the flame retardant POM. Therefore, this method provides a simple and effective method to prepare flame retardant POM with good comprehensive performance.     

次磷酸铝添加量对碱木质素基聚氨酯 泡沫阻燃性能的影响

利用精制后的碱木质素部分代替聚醚多元醇制备碱木质素基聚氨酯泡沫材料(PUF/木质素)。将次磷酸铝(AHP)作为阻燃剂添加到材料中制备PUF/木质素/AHP材料。通过极限氧指数(LOI)测试PUF/木质素/AHP材料的阻燃性能,通过热重分析(TG)研究了材料的热降解行为和成炭性能,通过锥形量热(CONE)测试和扫描电子显微镜(SEM)分别研究了PUF/木质素/AHP材料的燃烧行为和残炭的表面形貌。结果表明：当碱木质素添加量为聚醚多元醇的5%、AHP的添加量为30%时,PUF/5%木质素/30%AHP材料的LOI值达到了25.6%,同时降低了材料的热分解速率和热释放量,促进了材料的成炭。当AHP受热分解时,产生的PO自由基会捕捉材料燃烧时产生的氢氧自由基,从而抑制燃烧反应,同时产生磷酸铝和焦磷酸铝,形成致密的炭层阻隔物质和能量的传递,阻止材料进一步燃烧,从而提高材料的阻燃性能。     

Preparation of thermally stable and flame-retardant sugarcane bagasse-ammonium dihydrogen phosphate/epoxy composites and their performance

Epoxy resin was often applied in fiber-reinforced composite materials, adhesives, and encapsulation materials. However, epoxy was easily flammable and limited its usage in certain applications. The study recycled and reused agricultural waste sugarcane bagasse to prepare a halogen-free bio-based intumescent flame retardant and then mixed with epoxy resin to prepare a composite containing polymer with improved thermal properties and flame retardancy of the materials. The work followed the concept of circular economy and sustainability. Bagasse-ammonium dihydrogen phosphate (ADP) flame retardant was added to an epoxy resin to prepare epoxy/bagasse-ADP composites, an effective flame-retarding composite material through hydrothermal method. Adding bagasse-ADP increased the thermal stability and flame retardancy of the composite materials compared with that of pure epoxy. For the material with 30 wt% added bagasse-ADP, the char yield was 32.3 wt%, which was 18.2 wt% higher than that of pure epoxy (14.1 wt%) through thermogravimetric analysis. In addition, the limiting oxygen index increased from 21% to 30%, and the UL-94 classification improved from “Fail” to “V-0.” This performance was attributed to the nitrogen, phosphorus, and silicon content of the flame retardant.     

Synergistic flame‐retardant effect of halloysite nanotubes on intumescent flame retardant in LDPE

Synergistic flame‐retardant effect of halloysite nanotubes (HNTs) on an intumescent flame retardant (IFR) in low‐density polyethylene (LDPE) was investigated by limited oxygen index (LOI), vertical burning test (UL‐94), thermogravimetric analysis (TGA), cone calorimeter (CC) test, and scanning electronic microscopy (SEM). The results of LOI and UL‐94 tests indicated that the addition of HNTs could dramatically increase the LOI value of LDPE/IFR in the case that the mass ratio of HNTs to IFR was 2/28 at 30 wt % of total flame retardant. Moreover, in this case the prepared samples could pass the V‐0 rating in UL‐94 tests. CC tests results showed that, for LDPE/IFR, both the heat release rate and the total heat release significantly decreased because of the incorporation of 2 wt % of HNTs. SEM observations directly approved that HNTs could promote the formation of more continuous and compact intumescent char layer in LDPE/IFR. TGA results demonstrated that the residue of LDPE/IFR containing 2 wt % of HNTs was obviously more than that of LDPE/IFR at the same total flame retardant of 30 wt % at 700°C under an air atmosphere, and its maximum decomposing rate was also lower than that of LDPE/IFR, suggesting that HNTs facilitated the charring of LDPE/IFR and its thermal stability at high temperature in this case. Both TGA and SEM results interpreted the mechanism on the synergistic effect of HNTs on IFR in LDPE, which is that the migration of HNTs to the surface during the combustion process led to the formation of a more compact barrier, resulting in the promotion of flame retardancy of LDPE/IFR. In addition, the mechanical properties of LDPE/IFR/HNTs systems were studied, the results showed that the addition of 0.5–2 wt % of HNTs could increase the tensile strength and the elongation at break of LDPE/IFR simultaneously. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40065.     

DAM-DOPO的合成及其阻燃性能

以9,10-二氢-9-氧杂-10-膦酰杂菲-10-氧化物（DOPO）、甲醛和二乙醇胺为原料,强酸性阳离子交换树脂作催化剂,分两步合成了新型反应型阻燃剂9,10-二氢-9氧杂-10-\[N,N-二(羟乙基)氨甲基\]-10-膦杂菲-10-氧化物（DAM-DOPO）,并制备了DAM-DOPO阻燃剂阻燃聚氨酯泡沫（PUF）,采用红外光谱、核磁共振等分析手段对DAM-DOPO进行了表征,同时通过极限氧指数值测定、水平燃烧试验和CAL 117D实验评估了阻燃PUF的阻燃性能。结果表明,合成的DAM-DOPO阻燃剂熔点为165~167 ℃;添加12 份（质量份,下同）DAM-DOPO阻燃的PUF的极限氧指数为26.5 %,阻燃性能通过GB 8410—2006标准和CAL TB 117D实验。     

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.     

低烟阻燃ABS体系的研究

对ＡＢＳ聚合物阻燃、抑烟性,与其它性能的关系进行了研究和探讨。实验结果表明,综合采用与阻燃树脂共混、添加复合阻燃剂和抑烟剂的方法可以有效地获得阻燃、低烟及其它综合性能皆优的ＡＢＳ聚合物体系。     

Reinforcing and Flame-Retardant Effects of Halloysite Nanotubes on LLDPE

Halloysite nanotubes (HNTs) were used to compound with linear low density polyethylene (LLDPE) to prepare composites with better mechanical properties and higher flame retardancy. The PE graft was used as interfacial modifier in the LLDPE/HNTs composites. HNTs were showed to be a promising reinforcing and flame retardant nano-filler for LLDPE. The mechanical properties and flame retardancy as well as thermal stability of the composites can be further enhanced by the addition of the graft copolymer. Morphological observation revealed that the graft copolymer could facilitate the dispersion of HNTs in LLDPE matrix and enhance the interfacial bonding.     

树脂改性对玻璃纤维增强聚合物筋材物理力学性能的影响

在基体树脂中加入阻燃剂和抗静电剂可以改善复合材料的阻燃和抗静电性能,同时也会影响复合材料的力学性能。本文通过在不饱和聚酯树脂中加入阻燃剂和抗静电剂,研究了树脂改性对玻璃纤维增强聚合物（GFRP）筋材拉伸性能、压缩性能、剪切性能、抗静电性能和阻燃性能的影响,分析了改性树脂的阻燃和抗静电机理。试验发现,树脂改性对GFRP筋阻燃和抗静电性能有明显提高,压缩强度有所增加,但GFRP筋拉伸性能和剪切性能有不同程度的降低。