Thermal Stability and Flame Retardancy of Rigid Polyurethane Foams/Organoclay Nanocomposites

The thermal stability and flame retardancy of a new kind of rigid polyurethane (PU) foams/organoclay nanocomposites developed by our research group were investigated by using thermogravimetry analysis (TGA) and cone calorimeter test. Results indicate that compared with pure PU foams, rigid PU foams/organoclay composites show significantly enhanced thermal stability and flame retardancy. The reasons leading to the results were discussed in detail by relating with the morphology of the composites. The discussion suggests that the enhancement degree of thermal stability and flame retardancy of composites compared with that of PU foams coincides well with the sequences of gallery spacing of organoclay in the PU matrix.     

Inorganic–organic hybrid coating‐encapsulated ammonium polyphosphate and its flame retardancy and water resistance in epoxy resin

A novel encapsulated ammonium polyphosphate (APP) with an inorganic–organic hybrid coating (MAPP) was prepared by a sol–gel method using tetraethoxysilane and octyltriethoxysilane as precursors. The properties of MAPP were investigated by water solubility, hydrophobicity, and morphological determination. The structure of MAPP was characterized by X‐ray photoelectron spectroscopy. The flame retardancy of epoxy resin composite with MAPP was evaluated by limiting oxygen index, UL‐94 test, and cone calorimetry test. The results showed that both tetraethoxysilane and octyltriethoxysilane hydrolyze and condense to form a dense polysiloxane layer structure on the surface of APP. The water solubility of MAPP was reduced from 0.64 to 0.13 g/100 mL of water, and the water resistance of epoxy resin composites filled with MAPP was also greatly improved. The limiting oxygen index, UL‐94 test, and cone calorimeter results showed that the epoxy resin composites filled with MAPP had better flame retardancy, probably because of a synergistic effect between polysiloxane and APP. Copyright © 2013 John Wiley & Sons, Ltd.     

Reactive flame retardant with core‐shell structure and its flame retardancy in rigid polyurethane foam

With a shell of poly (methyl methacrylate‐co‐hydroxyl ethyl acrylate) (PMMA‐HA), microencapsulated ammonium polyphosphate (MHAPP) is prepared by in situ polymerization. The core‐shell structure of the reactive flame retardant (FR) is characterized by Fourier transform infrared (FTIR) and scanning electron microscopy/energy dispersive spectroscopy (SEM/EDS). The results of water leaching rate and water contact angle measurements show that ammonium polyphosphate (APP) is well coated by a hydrophobic shell. Due to the presence of active groups (–OH) and hydrophobic groups (–CH₃) in shell, MHAPP exhibits better compatibility, flame retardancy, and water resistance compared with neat ammonium polyphosphate (APP) in rigid polyurethane foam (PU). Compression strength of PU/MHAPP with suitable loading is higher than that of PU/APP and PU, the reason is that the active groups in shell can improve the compatibility of MHAPP in PU composite. From thermal stability and residue analysis, it can be seen that the presence of reactive flame retardant shows positive effect on thermal stability of PU composite at high temperature, results also indicate that MHAPP can promote the carbonization formation efficiency of PU composite during combustion process compared with APP. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42800.     

Phosphorus‐containing silica gel‐coated ammonium polyphosphate: Preparation,characterization, and its effect on the flame retardancy of rigid polyurethane foam

A phosphorus‐containing silica gel was synthesized via a reaction between phenyl dichlorophosphate, poly(ether polyol), and γ‐aminopropyltriethoxysilane. Ammonium polyphosphate (APP) was modified by the synthesized phosphorus‐containing silica gel (MAPP) and then incorporated into the rigid polyurethane foam (PU). Results showed that APP had a smaller particle size, lower initial decomposition temperature, better heat resistance at high temperature, and better compatibility with PU matrix after the modification. The cone calorimeter test results showed that the incorporation of MAPP obviously reduced the values including peak of heat release rate, total heat release, average effective heat of combustion, and total smoke release, and increased the char yield of PU composite comparing with APP. The improved flame retardancy of PU/MAPP composite was attributed to the quenching effect of PO· and PO₂· free radicals released by MAPP in the early stage and the improved thermal stability of phosphorus‐ and silicon‐containing char layer formed in the later stage. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46334.     

Bi-phase flame-retardant effect of hexa-phenoxy-cyclotriphosphazene on rigid polyurethane foams containing expandable graphite

The flame-retardant rigid polyurethane (PU) foams with hexa-phenoxy-cyclotriphosphazene/expandable graphite (HPCP/EG) were prepared through box-foaming in our laboratory. The flame retardancy of PU foams was characterized using the limiting oxygen index and cone calorimeter. The results show that the incorporation of HPCP into the PU foams containing EG enhanced flame retardancy. The main degradation process of HPCP in PU foams was investigated by pyrolysis gas chromatography/mass spectroscopy. HPCP during combustion generated phenoxyl and PO₂ free radicals, which could quench the flammable free radicals produced by the matrix and hamper the free radical chain reaction of combustion. This observation shows that HPCP produced a gas-phase flame-retardant effect in this specimen. Additionally, micro-morphology, elemental composition and content of residual char of the flame-retardant PU foams after the cone calorimeter test were also characterized using scanning electron microscope and energy dispersive X-ray microanalyser. The results exhibit that the partial phosphorus from HPCP remained in the residual char, and HPCP significantly enhanced the strength and compatibility of the char layer formed by the PU foams containing EG. These results indicate the important function of HPCP in condensed phase. Thus, HPCP exhibited gas-phase and condensed-phase flame-retardant effects on the PU/EG foams.     

The effects of intumescent flame retardant including ammonium polyphosphate/pentaerythritol and fly ash fillers on the physicomechanical properties of rigid polyurethane foams

In this study, rigid polyurethane foams that contain up to 5.0 wt % fly ash (FA) being a by‐product of thermal power stations and being cheap source were successfully produced using a polyurethane injection machine. The effects of FA content on the thermal conductivity, compressive strength, and flammability were investigated. The morphology of the cell was observed under a special microscope. The incorporation of FA in rigid polyurethane foams may dramatically decrease production costs and reduce environmental pollution. In addition, the effects of intumescent flame retardant composed of ammonium polyphosphate and pentaerythritol were examined in pure rigid polyurethane foams and FA‐rigid polyurethane foams. It was found that 5.0 and 7.5 wt % intumescent flame retardant loadings enhanced the thermal stability and improved the flammability resistance of the foams. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Synthesis of a green reactive flame-retardant polyether polyol and its application

The low-flame retardancy properties of pure rigid polyurethane (PU) foams hindered its practical application in many cases for the safety and environmental concern. Although rigid PU foams with flame retardants can achieve standard of fire resistance, addition of flame retardants in PU can worsen its mechanical properties, enlarge production cost, and induce safety problems. Therefore, green reactive flame-retardant polyether polyols (GPP) have been considered as one of the best solutions. In this work, the GPP by the ring-opening polymerization of the self-made environmentally friendly melamine resin (EFMR) with propylene oxide are synthesized with their hydroxyl number of 390 ~ 420 mg KOH/g, and the structure of GPP product was identified by Fourier transform infrared spectroscopy and nuclear magnetic resonance. The flame-retardant rigid polyurethane foams (RPUFs) were successfully prepared with GPP as the polyol, the results showed that the addition of GPP can greatly improve the thermal stability and flame retardancy of the RPUFs prepared. The RPUF were prepared by fully GPP with 30.4% of limiting oxygen index and 350 kpa of compressive strength. These properties are qualified for commercial utilization. Therefore, this GPP provides great prospect in the development of specified flame-retardant PU materials.     

Vinyl polysiloxane microencapsulated ammonium polyphosphate and its application in flame retardant polypropylene

Vinyl polysiloxane microencapsulated ammonium polyphosphate (MAPP) was prepared by a sol-gel method using vinyltrimethoxysilane as a precursor to improve its thermal stability and hydrophobicity. The MAPP was characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), energy dispersive spectrometer (EDS) and thermogravimetric analyzer (TGA). The results showed that ammonium polyphosphate (APP) was successfully coated with vinyl polysiloxane. MAPP and pentaerythritol (PER) were used together to improve the flame retardancy of polypropylene (PP). The flame retardant properties of PP composites were investigated by limiting oxygen index (LOI), UL-94 test, TGA and SEM. When the MAPP was added as a flame retardant, with PER as a char forming agent, the LOI of PP/MAPP/PER composites was 33.1%, and it reached the UL-94 V-0 level. The results also demonstrated that the flame retardant properties of PP/MAPP/PER composites were better than those of PP/APP/PER composites at the same loading. Moreover, the addition of flame retardant and carbon forming agent could promote the crystallization behavior of PP.     

Investigation of fire behavior of rigid polyurethane foams containing fly ash and intumescent flame retardant by using a cone calorimeter

Cone calorimeter is one of the most useful bench‐scale equipment which can simulate real‐world fire conditions. Therefore, cone calorimeter tests have been the most important and widely used tests for research and development of fire behavior of polymeric materials. In this study, fire behavior of rigid polyurethane foams containing fly ash (up to 5 wt %) and intumescent flame retardant (up to 5 wt %) composed of ammonium polyphosphate/pentaerythritol was investigated by using a cone calorimeter. In addition, thermogravimetric analysis of the additives and the foams were also carried out to explain the effects of fly ash and intumescent flame retardant on fire behavior of the foams. Experimental results indicated that rigid polyurethane foam containing fly ash and the intumescent flame retardant in comparison with pure rigid polyurethane foam shows significantly enhanced fire resistance and thermal stability. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

苯基聚硅氧烷微胶囊化聚磷酸铵的制备及其在PP中阻燃性能研究

采用苯基三甲氧基硅烷为前驱体,通过溶胶凝胶法制备出苯基聚硅氧烷微胶囊化聚磷酸铵（MAPP）。将MAPP作为阻燃剂,季戊四醇（PER）作为成炭剂,制备阻燃聚丙烯（PP）。用傅里叶红外光谱、扫描电子显微镜、能谱仪及热重分析仪对MAPP进行表征。结果表明,聚磷酸铵（APP）被苯基聚硅氧烷成功包覆;较之APP,MAPP的热稳定性和疏水性显著提高;MAPP的阻燃性能优于APP,PP/MAPP/PER复合材料达到V-0级别;阻燃剂及成炭剂的加入对PP的结晶行为有促进作用。     

Mechanical Properties and Flame Retardancy of Rigid Polyurethane Foams Containing SiO2 Nanospheres/Graphene Oxide Hybrid and Dimethyl Methylphosphonate

Halogen-free flame-retardant rigid polyurethane foams were prepared using the combination of SiO₂ nanospheres/graphene oxide hybrid and a phosphorus-containing flame retardant, dimethyl methylphosphonate. The flame retardancy, mechanical, and thermal properties of flame-retardant rigid polyurethane foams containing dimethyl methylphosphonate and SiO₂ nanospheres/graphene oxide were investigated. The results demonstrated that the combination of dimethyl methylphosphonate and SiO₂ nanospheres/graphene oxide enhanced flame retardant and mechanical properties of rigid polyurethane foam greatly compared with pure rigid polyurethane foam and dimethyl methylphosphonate-modified foam. Morphological study indicated that the partial substitution of dimethyl methylphosphonate with SiO₂ nanospheres/graphene oxide led to smaller cell sizes and more uniform cell sizes of dimethyl methylphosphonate-modified rigid polyurethane foams.     

典型聚磷酸盐对RPUF材料阻燃性能的提效

以可膨胀石墨/甲基膦酸二甲酯体系为基础,引入3种典型的聚磷酸盐阻燃剂:聚磷酸铵(APP)、焦磷酸哌嗪(PAPP)和三聚氰胺聚磷酸盐(MPP),制备了聚磷酸盐/磷酸酯/可膨胀石墨三元阻燃硬质聚氨酯泡沫(RPUF)材料。探究了典型聚磷酸盐对阻燃硬质聚氨酯泡沫材料阻燃性能的提效作用,对燃烧性能和物理力学性能进行了分析。在3种聚磷酸盐提高极限氧指数和降低热释放作用的比较中,APP相似文献   

铝/磷/氮三元体系阻燃PU硬泡的制备与性能研究

以氢氧化铝、三聚氰胺和聚磷酸铵为阻燃剂制备了阻燃聚氨酯硬质泡沫,研究了添加氢氧化铝前后阻燃剂用量对聚氨酯(PU)硬泡的阻燃性能和力学性能的影响。结果表明,铝/磷/氮复配阻燃体系的阻燃效果优于磷/氮阻燃体系,阻燃剂总添加量达30份时,PU硬泡同时具备较好的阻燃性能和力学性能,氧指数为32,烟密度为74,平均燃烧时间为31 s,其压缩强度和拉伸强度分别为6.52 MPa和6.16 MPa。     

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     

A novel intumescent flame retardant with nanocellulose as charring agent and its flame retardancy in polyurethane foam

Ammonium polyphosphate (APP) is microencapsulated with nanocellulose and dicyandiamide‐formaldehyde using in situ polymerization and flocculation method. The presence of nanocellulose and dicyandiamide‐formaldehyde significantly affects the thermal behavior and flame retardancy of microencapsulated ammonium polyphosphate (DFNAPP). DFNAPP is much more stable from 524 to 637°C than that of APP because of the charred formation. Rigid polyurethane foam (PU) composites added DFNAPP obtain higher limiting oxygen index (LOI) values than that with the same loading of APP. Due to the presence of shell, experimental results indicate that DFNAPP obtains better compatibility and water resistance in PU matrix, resulting in the improved mechanical properties of the PU composites and the water durability. LOI value of PU/APP composite added 16.7 wt% additives has a decrement of 3.0% after water treatment. By comparison, that of PU/DFNAPP composite with the same loading of DFNAPP is only 0.3%. Compression strength of PU composite is increased from 195 kPa to 213 kPa when the DFNAPP (16.7 wt%) additive substitutes for APP (16.7 wt%). POLYM. COMPOS., 38:2762–2770, 2017. © 2015 Society of Plastics Engineers     

Preparation and characterization of surface‐modified ammonium polyphosphate and its effect on the flame retardancy of rigid polyurethane foam

A functional surface‐modification agent was synthesized via a reaction between hexachlorocyclotriphosphazene and γ‐aminopropyl triethoxysilane. Ammonium polyphosphate (APP) was modified with this agent and then incorporated into a rigid polyurethane foam (RPUF). Fourier transform infrared spectroscopy, ¹H‐NMR, and X‐ray photoelectron spectroscopy were used to characterize the modified ammonium polyphosphate (M‐APP). The results show that the dispersibility was improved and the particle size decreased after the modification. The limiting oxygen index and cone calorimetry test results show that M‐APP enhanced the flame‐retardant properties of RPUF. The peak heat‐release rate of polyurethane (PU)/20% M‐APP decreased by 51.18% compared with that of PU–APP. The scanning electron microscopy results illustrate that M‐APP facilitated the formation of intumescent and compact char. The excellent flame‐retardant performance of M‐APP resulted from the flame‐inhibition and barrier effects, which were attributed to the phosphazene group and the intumescent char, respectively. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45369.     

聚磷酸铵微胶囊化及其在聚氨酯密封胶中的阻燃应用

以环氧树脂E-44为包裹材料．聚磷酸铵为芯材制备了微胶囊化聚磷酸铵。通过TG、水溶性测试等研究了微胶囊化聚磷酸铵耐热温度、强重、溶解度等性能,并将其添加到聚氨酯密封胶中,通过氧指数、垂直燃烧等研究了其阻燃性能,结果表明：聚磷酸铵微胶囊化后,初始分解温度为262℃,700℃时的残重为42．16％;水中粘度及溶解度分别为32．1MPa．s和0．18％,与未包覆聚磷酸铵相比,分别下降了64.2％和61．7％;当添加量为32％时,氧指数32．1,垂直燃烧V-O。     

环境友好型阻燃高回弹聚氨酯软泡性能

开发环境友好型聚氨酯是目前聚氨酯（polyurethane,PU）泡沫塑料领域的热点课题。在PU中引入大豆分离蛋白质（soy protein isolate,SPI）,采用阻燃聚醚制备了环境友好型阻燃高回弹聚氨酯软泡。研究了SPI的不同添加方式及用量对聚氨酯软泡物理、力学、阻燃和生物降解性能的影响。结果表明,SPI以添加的方式而不是替代聚醚的方式加入软泡性能更好;少量添加SPI可以提高PU软泡的开孔率、密度、压陷硬度、舒适因子、回弹率和断裂伸长率,对压缩永久变形率、拉伸强度和极限氧指数影响不大。SPI改变了PU的硬段结构,可以有效促进聚氨酯泡沫的生物降解。     

制备工艺对聚氨酯酰亚胺泡沫性能的影响

以均苯四甲酸二酐(PMDA)、多苯基多亚甲基多异氰酸酯(PAPI)、聚醚多元醇为主要原料,分别采用聚酰亚胺(PI)预聚法、聚氨酯(PU)预聚法和一步法制备聚氨酯酰亚胺泡沫,从微观形貌、力学性能、热稳定性能以及阻燃性能方面对上述3种制备工艺进行对比和评估。实验结果表明,采用一步法制备PUI泡沫时,PU链段和PI链段同时增长,容易造成泡孔缺陷,导致泡沫的力学性能较差;在采用PU预聚法制备的PUI泡沫中,PU链段含量较高,因此,泡孔孔径分布较宽且平均泡孔直径较大,对应的热稳定性和阻燃性能较差;采用PI预聚法制备的PUI泡沫的泡孔孔径分布窄且平均泡孔直径较小,对应的压缩性能、热稳定性以及阻燃性能均达到最佳。     

Preparation and characterization of cyclodextrin microencapsulated ammonium polyphosphate and its application in flame retardant polypropylene

A novel microencapsulated ammonium polyphosphate (MAPP) with shell of crosslinked β-cyclodextrin (HDI-CD) was prepared. The HDI-CD shell had a fibrous structure and covered with good completeness on the APP core, and a solid chemical bonding was found between the APP core and HDI-CD shell. The microcapsules were more hydrophobic than the pristine APP. When compounded within polypropylene (PP), the MAPP exhibited good compatibility and dispersibility. The combustion testing results showed that the novel all-in-one intumescent flame retardant had efficient flame retardancy for PP materials.