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.     

Flame retardancy of ceramic-based rigid polyurethane foam composites

In this work, ceramic fillers zirconia and alumina powder were incorporated in the rigid polyurethane foams derived from modified castor oil and their impact on the mechanical, thermal, and fire performances of composite foams have been analyzed. It was observed that the addition of ceramic filler showed improved mechanical and thermal properties and best properties were shown by 6% zirconia with compressive strength of 6.61 MPa and flexural strength of 5.72 MPa. Zirconia also demonstrated an increase in T_5% up to 260 °C. Cone calorimetry shows a decrease in peak of heat release from 118 to 84 kW m⁻² and 94 kW m⁻² by the incorporation of alumina and zirconia powder, respectively. Furthermore, total heat release (THR), smoke production rate (SPR), and total smoke release (TSR) were also found to decrease remarkably on the incorporation of ceramic fillers. So, these fillers have a great potential as an additive to incorporate good mechanical, thermal, and fire properties in bio-based rigid PU foams. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 48250.     

Flame retardancy working mechanism of methyl‐DOPO and MPPP in flexible polyurethane foam

The chemical nature of flexible polyurethane (flex PU) foams, the low density, the high air permeability and the open cell structure cause this material to be highly flammable. The new phosphorus flame‐retardant (FR) methyl‐DOPO (9, 10‐dihydro‐9‐oxa‐methylphosphaphenanthrene‐10‐oxide) is known to show an excellent flame retarding behavior in flex PU foam by acting mainly in the gas phase. In this study, the FR working mechanism of methyl‐DOPO and its ring‐opened analogue MPPP (methylphenoxyphenyl‐phosphinate) is investigated by TGA, TG–MS, FMVSS 302 and Cone Calorimeter measurements. Under TG–MS conditions comparable concentrations of low molecular weight species such as HPO, mathrmCH₃PO or PO₂ are released. These species are able to scavenge the H‐ and OH‐radicals in the radical chain reactions of the flame leading to a significant increase in the CO/CO₂ ratio and the smoke density during cone calorimeter experiments. Finally, the flame retardancy of MPPP is determined to be less efficient in flex PU foam because of the higher vapor pressure compared with methyl‐DOPO. Here, the vaporization of methyl‐DOPO occurs in the same temperature region as the depolymerization of the urethane and the bisubstituted urea groups during pyrolysis of the foam leading to an optimal interaction. Copyright © 2010 John Wiley & Sons, Ltd.     

Effect of different size‐modified expandable graphite and ammonium polyphosphate on the flame retardancy,thermal stability,physical, and mechanical properties of rigid polyurethane foam

In this study, three different sizes of tripolyphosphate‐modified expandable graphite (EG_p) are prepared and incorporated into rigid polyurethane foam (RPUF) in order to obtain a flame retardant material with low density, good mechanical properties, and hydrophobicity. The influence of particle size on material combustibility, thermal stability, compression strength, pore cell structure, diathermancy, and hydrophobic property is investigated. Synergistic effect between the EG_p and ammonium polyphosphate (APP II) is also examined. Results show the limiting oxygen index value and residue yield increase as the EG_p size increases. On the contrary, the heat release rate and total heat release decrease as the EG_P size increases. In addition, the chemical char formation effect of APP on RPUF is more important than the char formation of the graphite intercalation compounds. EG_p and APP show synergistic effect in improving flame retardancy, thermal stability, and hydrophobicity. POLYM. ENG. SCI., 59:1381–1394 2019. © 2019 Society of Plastics Engineers     

高回弹聚氨酯软泡的无卤阻燃研究

随着人们环保意识的不断提高,卤系阻燃剂的毒性问题受到越来越多的关注,阻燃剂无卤化已经成为必然趋势。间苯二酚双(二苯基磷酸酯)齐聚物(RDP)阻燃剂是一种无卤添加型阻燃剂,因具有优异的热稳定性和低挥发性而得到广泛应用。实验中分别用它与膨胀石墨来阻燃高回弹聚氨酯软泡并进行了二者协同阻燃聚氨酯软泡的研究。用氧指数仪和民航飞机用垂直燃烧方法测试表征了制备的泡沫样品,并对其阻燃性能进行了研究。     

Preparation of microencapsulated aluminum hypophosphite and flame retardancy and mechanical properties of flame‐retardant ABS composites

Microencapsulated aluminum hypophosphite (MFAHP) with a shell of melamine–formaldehyde resin (MF) was prepared via in situ condensation polymerization. The presence of MFAHP increased the water resistance of flame‐retarded (FR) acrylonitrile–butadiene–styrene (ABS) composites after hot water treatment. The mechanical properties indicate that the tensile strength and flexural strength of the FR ABS/MFAHP composites is enhanced with the incorporation of MFAHP. Cone calorimeter test results demonstrated that the peak heat release rate, total heat release, and total smoke release values of the ABS/MFAHP composites were significantly decreased. Digital photos and scanning electron microscopy images of the residues of ABS/25 wt % MFAHP₂ composites exhibited compact char layer structures, with many cobweb‐like nanoparticle arrangements formed on the surface by the burning process. The investigation of flame‐retardant mechanisms of ABS/MFAHP composites using infrared spectroscopy and energy‐dispersive X‐ray spectroscopy indicated that both the formation of char residue in the condensed phase and the release of inert gases by the MF shell in the gas phase led to the formation of compact and stable char layers containing carbon/pyrophosphate and aluminum polyphosphate, consequently leading to the good flame‐retardant performance of MFAHP. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45008.     

Flame retardancy,mechanical, and thermal properties of waterborne polyurethane conjugated with a novel phosphorous‐nitrogen intumescent flame retardant

A novel phosphorous‐nitrogen intumescent flame retardant with reactive diamino groups, benzoguanamine spirocyclic pentaerythritol bisphosphonate (BSPB), was synthesized and used as a chain extender, and then a series of flame retardant waterborne polyurethanes (FRWPU) were prepared by covalently conjugating the BSPB into waterborne polyurethane (WPU) backbone. Their structures were characterized by Fourier transformed infrared spectrometry (FTIR), ¹H and ³¹P nuclear magnetic resonances (NMR), respectively. Simultaneously, the flame retardancy and the thermal stability of FRWPU were systematically investigated by limiting oxygen index (LOI) test, UL‐94 vertical burning test and thermogravimetric analysis (TGA). The results indicated that with the increase of BSPB content from 0 to 8 wt%, the LOI value of FRWPU increased from 18.6 to 27.3%, showing significant improvement by 8.7%. Compared with WPU, FRWPU showed decreased thermal stability but promoted char residue ratio. Conjugation of BSPB could obviously enhance the mechanical properties of FRWPU, the Young's modulus and tensile strength dramatically increased with the increase of BSPB. Investigation of char forming mechanism of BSPB through real time Fourier transform infrared spectra (RTFTIR) and scanning electronic microscopy (SEM) revealed that the polyphosphoric acid and phosphorus oxynitrides rich outer intumescent char layer could form protective shields to inhibit effectively internal polyurethane to heat and flame diffusion during contacting fire. POLYM. COMPOS., 38:452–462, 2017. © 2015 Society of Plastics Engineers     

Manufacturing and mechanical characterization of perforated hybrid composites based on flexible polyurethane foam

This study focused on the fabrication and mechanical evaluation of nonwoven reinforced flexible polyurethane foam composites. Effects of perforation ratio, aperture size, and perforation depth on bursting and low‐velocity impact responses of perforated composite panels were investigated. The nonwoven fabric used for cover sheet was composed of flame retardant polyester, low‐melting point polyester, and recycled Kevlar staple fibers. Blending ratio of Kevlar fiber was confirmed to have relation to mechanical mechanism of cushioning layer. The highest mechanical strength value was obtained at 5 wt % of Kevlar ratio because of the highest cohesive force among recycled Kevlar, flame retardant polyester, and low‐melting point polyester fibers was provided at the blending ratio. The perforated high‐density flexible polyurethane foam composites panel was adhered with intra‐ply hybrid laminates with various areal densities on each face to form sandwich structural composites. The results revealed that perforation ratio and aperture significantly influenced the bursting and low‐velocity impact resistance behaviors of the perforated composites panel. Perforated composites with 10% perforation ratio and 4 mm aperture lead to maximum bursting strength of 437 N. Additional hybrid laminates significantly promoted the maximum bursting strength of the semiperforated hybrid composites by 212%. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42288.     

TPS/EVA泡沫复合材料的制备及其阻燃与力学性能

以热塑性淀粉(TPS)为成炭剂与聚磷酸铵(APP)、可膨胀石墨(EG)复配组成膨胀型阻燃剂,通过熔融密炼、开炼塑化、硫化发泡制备了热塑性淀粉/乙烯-醋酸乙烯酯共聚物(TPS/EVA)泡沫复合材料,探讨了TPS用量对泡沫复合材料阻燃性能、力学性能的影响。结果表明,TPS的加入显著提高了TPS/EVA泡沫复合材料阻燃性能,可起到良好的成炭作用;TPS/EVA泡沫复合材料的拉伸强度、断裂伸长率以及撕裂强度随着TPS用量的增加呈现先增大后减小的趋势,相对密度则是小幅度上升。当TPS用量为6%时,TPS/EVA泡沫复合材料综合性能最好,其LOI可达26.5%且UL-94为V-0级,拉伸强度、断裂伸长率、撕裂强度以及相对密度可达2.395 MPa、177.48%、10.59 N·mm^-1、0.21452。     

Mechanical,thermal properties,and flame retardancy of PC/ultrafine octaphenyl‐POSS composites

Composites of ultrafine polyhedral oligomeric octaphenyl silsesquioxane (OPS) and polycarbonate (PC) were prepared by melt blending. The mechanical and thermal properties of the composites were characterized by tensile and flexural tests, impact test, differential scanning calorimeter (DSC), dynamic mechanical analysis (DMA), and thermal gravimetric analysis (TGA). Rheological properties of these melts were tested by torque rheometer. The flame retardancy of the composites was tested by limiting oxygen index (LOI), the vertical burning (UL‐94), and cone calorimeter test. The char residue was characterized by scanning electron microscope (SEM) and ATR‐FTIR spectrum. Furthermore, the dispersion of OPS particles in the PC matrix was evidenced by SEM. The results indicate that the glass transition temperatures (T_g) and torque of the composites decrease with increasing OPS loading. The onset decomposition temperatures of composites are lower than that of PC. The LOI value and UL‐94 rating of the PC/OPS composites increase with increasing loading of OPS. When OPS loading reaches 6 wt %, the LOI value is 33.8%, UL‐94 (1.6 mm) V‐0 rating is obtained, and peak heat release rate (PHRR) decreases from 570 to 292 kJ m^?2. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Influence of aging conditions on the mechanical properties and flame retardancy of HIPS composites

In this study, we evaluate the changes in physical properties and flame retardancy of HIPS composites after natural aging tests in Turpan (high sunlight radiation dose and dry) and Qionghai (high temperature and rainy) in China for 21 months. The HIPS composite aged in Turpan revealed a higher chromatic aberration than that in Qionghai due to the higher sunlight radiation dose. After aging tests for 21 months, the mechanical properties and the peak heat release of the HIPS composite aged in Qionghai decreased by more than 50% and increased by 39.7%, respectively, results that were worse than for the HIPS composite in aged Turpan. This was related to the combined effects of light, temperature, rain, and moisture in Qionghai leading to more severe degradation of HIPS composites, which results in breaking of the polymer chains and migration and erosion of the flame retardant. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46339.     

Improving the flame retardancy and mechanical properties of epoxy composites using flame retardants with red mud waste

In this study, a novel flame retardant ammonium tetrafluoroborate (ATFB) was successfully synthesized using boric acid (H₃BO₃) and ammonium hydrogen difluoride (NH₄HF₂) as the reactants. In addition to ATFB, aluminum hydroxide (Al(OH)₃) was used as a flame retardant and red mud (RM) waste was used as a filler to prepare epoxy composite materials with enhanced flammability properties. The appropriate ratio of RM:ATFB:Al(OH)₃ both in terms of combustion and mechanical properties was found to be 15:10:5 wt%. The tensile strength of the composite in this ratio was obtained as 112 MPa, while the neat ER was 46 MPa. The burnout of the composite with the appropriate RM:ATFB:Al(OH)₃ ratio decreased in the first 10 seconds, and extinguished in 32 seconds. Moreover, the burned area of this composite was the smallest among all the others. The experimental and estimated LOI values for this composite was found as 26 and 29, respectively.     

Thermal,mechanical properties,and low‐temperature performance of fibrous nanoclay‐reinforced epoxy asphalt composites and their concretes

Epoxy asphalt (EA) concretes have been widely used in the pavement of orthotropic steel bridge decks. The objective of this study was to figure out the enhanced effects of natural fibrous attapulgite (ATT) as a reinforced nanofiller in ATT/EA nanocomposites through a comparison of the properties of the composites with a series of various nanoclay loadings. The rheological properties, glass transition, thermal stability, mechanical properties, and morphology of the ATT/EA composites were characterized. Furthermore, the low‐temperature flexibility of the ATT/EA concretes was investigated. The test results show that the addition of ATT had no significant effect on the rotational viscosity of EA in the initial stage of the curing reaction. In addition, the ATT/EA composites showed better performance than the neat one in thermal stability with a higher glass‐transformation temperature. The tensile strength and elongation at break of the ATT/EA composites at a loading of 0.5 wt % ATT were 21 and 22% higher than those of the neat EA. The addition of ATTs also enhanced the low‐temperature flexibility of the EA concretes. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41694.     

Effect of expandable graphite particle size on the flame retardant,mechanical, and thermal properties of water‐blown semi‐rigid polyurethane foam

Different particle size of expandable graphite (EG) were incorporated into water‐blown semi‐rigid polyurethane foams (SPFs), which acted as the fire shield, in order to enhance the fire retardant properties. In this study, the particle size of EG was systematically varied from 70 µm to 960 µm. The effect of EG particle size on the density, mechanical properties, and thermal stability of SPFs was also investigated. Results showed that EG with smaller particle size showed almost no effect on the fire retardant properties of SPFs while the larger particle size of EG could effectively enhance it. It was observed that the flame retardancy of the composite improved with the increase of EG size which was attribute to the formation and densification of isolation layer with the increase in volume of expanded graphite. Limiting oxygen index (LOI) value of EG/SPF composites increased linearly by two steps with the increase in EG particle size. Horizontal burning test confirmed the above conclusion. Thermogravimetric analysis (TGA) indicated that EG particles and its size exhibited minor effect on the thermal stability of the SPF composites. Moreover, SPF filled with medium particle size of EG (about 400 µm) exhibited a poor compression performance compared with the others. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39885.     

Intumescent flame retardant polyurethane/starch composites: Thermal,mechanical, and rheological properties

Intumescent flame retardant polyurethane/starch (IFRPU/starch) composites were prepared by means of melt blending. Microencapsulated ammonium polyphosphate (MCAPP) was added to improve its compatibility with matrix, retardation of reaction between acid and carbon source, and its water resistancy. Fourier transform infrared spectroscopy (FTIR) confirmed the presence of hydrogen bonding and entangled network between IFR system and PU matrix. Further, scanning electron microscopy (SEM) illustrated homogeneity of starch in matrix. By addition of 10 wt % of starch and 20 wt % of IFR, limiting oxygen index (LOI) increased from 22.0 to 40.0 and UL94 V0 rating was achieved. Differential scanning calorimetry (DSC) detected three endothermic transitions and one glass transition (T_g). The temperature of transition III and T_g increased with starch due to crosslinking between PU and starch. The improved thermal stability in the presence of starch was confirmed by thermogravimetric analysis (TGA). Beside the fact that starch was used as a carbonization agent to improve flame retardancy, it also effectively led to enhanced mechanical and viscoelastic properties. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 41158.     

聚氨酯泡沫塑料的阻燃及热解性能

采用热重分析仪、傅里叶变换红外光谱仪和扫描电子显微镜研究了氨基树脂型高分子膨胀阻燃剂（AIFR）阻燃软质聚氨酯泡沫塑料（FPUF）的阻燃、热解性能。结果表明,w（AIFR）为15％以上时,阻燃FPUF的垂直燃烧性能达到美国联邦航空局颁布的条例FAR25．853的要求。AIFR阻燃FPUF热解首先发生脱磷酸、酸催化FPUF脱水和重排交联炭化反应,使其热解中间产物热稳定性增加,热失重速率降低0．144％／s,剩炭率提高10．6％,AIFR主要以凝聚相成炭作用模式起阻燃作用。残炭扫描电子显微镜照片显示,AIFR阻燃FPUF的炭层致密,空洞少;残炭的韧性好．强度较高,可阻挡燃烧过程中的热量和气体的交换,达到阻燃目的。     

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.     

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.     

Investigation of flame retardancy and physical–mechanical properties of zinc borate/boric acid polyester composites

The glass fiber reinforced polyester composite materials were prepared with varying contents of boric acid, zinc borate, and magnesium hydroxide as flame retardants to improve the flame retardancy of the composites. Experimental results showed that boric acid exhibited a good flame retardant effect on the polyester composite. When boric acid content is used as 15 wt %, the Limiting Oxygen Index (LOI) value of the composite reached upto 25.3. The increase in boric acid content from 15 to 30 wt %, the LOI values of composite were enhanced from 25.3 to 34.5 by 9.2 units. The LOI values of the composite samples increased with increasing boric acid content. The smoke density results showed that the addition of glass fiber and flame retardants decreased the smoke density of the unreinforced polyester resin. The mechanical properties of the composites have decreased by the addition of flame retardants. The scanning electron micrographs taken from fracture surfaces were examined. The flame retardants, such as boric acid, were well dispersed in the glass fiber reinforced polyester composites and obviously improved the interfacial interaction between glass fibers and polyester composites. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

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