Preparation and characterization of microencapsulated ammonium polyphosphate and its synergistic flame‐retarded polyurethane rigid foams with expandable graphite

A facile and effective method for the preparation of microencapsulated ammonium polyphosphate (MAPP) by in situ surface polymerization was introduced. The ‘polyurethane‐like’ shell structure on the surface of MAPP was characterized by using Fourier transform infrared spectroscopy. The hydrophobicity and thermal behavior of MAPP were studied by using water contact angle tests and thermogravimetric analysis. The foam density and mechanical properties of polyurethane (PU) rigid foams were investigated. The flame retardancy of PU rigid foams formulated with MAPP was evaluated by using limiting oxygen index and cone calorimetry. The results show that MAPP can greatly increase the flame retardancy of PU materials. Also, there is a synergistic effect between MAPP and expandable graphite in flame retarding PU rigid foams. Moreover, the water resistance property of PU/MAPP composites is better than that of PU/ammonium polyphosphate. The morphology and chemical structure of PU/MAPP rigid foams after burning were systematically investigated. © 2013 Society of Chemical Industry     

Processing‐structure‐property relationship in rigid polyurethane foams

Rigid polyurethane (PU) foam is used as a thermal insulating and supporting material in domestic refrigerator/freezers and it is produced by reaction injection molding (RIM) process. There is a need to improve the thermal property of rigid PU foam but this is still a challenging problem. Accordingly, this work investigates the RIM process parameters to evaluate their effects on rigid PU foam's structure and hence property. It has been found that mold temperature is a key parameter whereas curing time has negligible effect on structure of PU foam. Cell size, strut thickness, and foam density have been found very critical in controlling the thermal and mechanical properties. Upper and lower values of 30 to 32 kg/m³ density are critical to observe contribution of radiation and solid conductivity separately. Finally, PU foam with 160 µm average cell size, 16 µm strut thickness, below 10% open cell content, and 30 to 32 kg/m³ density allow obtaining better thermal insulation without significant reducing in the compressive strength. The presented work provides a better understanding of processing‐structure‐property relationship to gain knowledge on producing high‐quality rigid PU foams with improved properties. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44870.     

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     

Preparation of sound‐insulating material based on discarded cow hair

In this article, we report a study on new functional materials based on the structural features of hair. In this study, discarded cow hair was treated with acid and hydrogen peroxide, dried, and pulverized to obtain a hair powder (HP). A sound‐insulating film (SIF) was prepared via the mixing of HP with acrylic resin [poly(acrylic acid) (PAA)]. On the basis of the function for the SIF, the formation conditions, including the HP weight percentage, film‐forming temperature, and solvent, were investigated. The sound‐insulating properties were studied and compared with commercially available sound‐insulating materials. The SIF had an equivalent sound‐insulating power to that of an asphalt‐based or a rubber‐based board but a better power than that of a polyurethane (PU)‐foam‐based board with identical thicknesses in the 20–20,000 Hz sound wave. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46332.     

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.     

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。     

Preparation of aluminum hydroxide/aluminum phosphinate flame‐retardant poly(vinyl alcohol) foam through thermal processing

A novel flame‐retardant poly (vinyl alcohol) (PVA) composite foam was prepared successfully through thermal processing, which was filled with high content of flame retardant, based on aluminum hydroxide (ATH) and aluminum phosphinate (AlPi) and using water as plasticizer and blowing agent. The flame‐retardant property and mechanism of the prepared foam matrix were studied by vertical burning test, limiting oxygen index (LOI), cone calorimeter, scanning electronic microscopy (SEM) and X‐ray photoelectron spectroscopy (XPS). The experimental results showed that the PVA/ATH/AlPi (1/1.2/0.05) composite achieved LOI value of 41% and UL94 V‐0 (3.2 mm) rate. The addition of ATH and AlPi into PVA matrix significantly decreased flammability of the composites, because a more compact and continuous char layer of the PVA/ATH/AlPi composite could be formed, due to the involvement of AlPi in the char‐forming reaction. Compared with the pure PVA sample, the peak heat release rate (PHRR) and total heat release (THR) of PVA/ATH/AlPi (1/1.2/0.05) composite were reduced by 76.5% and 58.2%, respectively. Built upon this PVA‐based foam matrix with good flame retardancy, the flame‐retardant PVA‐based foam was successfully prepared through thermal extrusion. In addition, the influence of water content on melt viscosity, foam structure and mechanical strength was also analyzed. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42020.     

Highly flame‐retardant bio‐based polyurethanes using novel reactive polyols

Poor flame retardancy of polyurethanes (PU) is a global issue as it limits their applications particularly in construction, automobile, and household appliances industries. The global challenge of high flammability of PU can be addressed by incorporating flame‐retardant materials. However, additive flame‐retardants are non‐compatible and depreciate the properties of PU. Hence, reactive flame‐retardants (RFR) based on aliphatic (Ali‐1 and Ali‐2) and aromatic (Ar‐1 and Ar‐2) structured bromine compounds were synthesized and used to prepare bio‐based PU using limonene dimercaptan. The aromatic bromine containing foams showed higher close cell content (average 97 and 100%) and compressive strength (230 and 325 kPa) to that of aliphatic bromine containing foams. Similar behavior was observed for a horizontal burning test where with a low concentration of bromine (5 wt %) in the foams for Ar‐1 and Ar‐2 displayed a burning time of 12.5 and 11.8 s while, Ali‐1 and Ali‐2 displayed burning time of 25.7 and 37 s, respectively. Neat foam showed a burning time of 74 s. The percentage weight loss for neat PU foam was 26.5%, while foams containing 5 wt % bromine in Ali‐1, Ali‐2, Ar‐1, and Ar‐2 foams displayed weight loss of 11.3, 14, 7.9, and 14%, respectively. Our results suggest that flame retardant PU foams could be prepared effectively by using RFR materials. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46027.     

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.     

Fabrication of Multifunctional Filters via Online Incorporating Nano‐TiO2 into Spun‐Bonded/Melt‐Blown Nonwovens for Air Filtration and Toluene Degradation

Multifunctional air filters with high filtration efficiency for aerosol and good degradation for toluene and bacteria are fabricated via online incorporation of TiO₂/Ag nanoparticles into the composite nonwovens with spun‐bonded/melt‐blown (SM) hierarchical structure. Today, severe environmental pollution attributed to atmospheric pollutants, mainly including particulate materials, and gaseous volatile organic compounds, as well as bacterial and viral contaminants, has drawn worldwide attention. In this work, a novel online incorporation technique to fabricate a multifunctional air filter with hierarchical structure of SM nonwovens and TiO₂ based nanoparticles is proposed. The in situ incorporation technique not only enables the SM nonwovens filters with four orders increment on toluene degradation rate, but also increases filtration quality factor Q_f of the SM filters to 0.2251 Pa^?1. This research shows promising applications of the multifunctional TiO₂/SM nonwoven filters for indoor air remediation. In addition, this scale‐up fabrication method of fiber‐based filters will potentially promote engineering of macromolecular fiber materials.     

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.     

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.     

Polyurethane–solid wood composites. II. Flammability parameters

Polyurethane (PU)–solid wood composites with good mechanical properties and dimensional stability have been prepared in the presence of four amine catalysts. Cone calorimetry and scanning electron microscopy (SEM) have been employed to characterize and evaluate the effects of the catalyst species on the flammability of the PU–wood composites. The results indicated that the PU–wood composites prepared in the presence of various catalysts had somewhat better flame resistance than the untreated wood control, as manifested in various flammability parameters (longer time to sustained ignition and time to peak heart rate release, larger mass and fire performance index (FPI), and lower mean HRR, mass loss rate, and peak HRR). The variations in the flame resistances of the PU–wood composites can be attributed to the various morphologies of the PU resin and the wood that resulted from the use of the various catalysts, as indicated by SEM micrographs. The PU–wood composite prepared in the presence of N‐methylmorpholine (NMM) as catalyst showed the best flame resistance, since the PU resin formed abundant PU foam that extended throughout the wood. This foam was effective in retarding the transfers of heat and combustible substances as well as the pyrogenation. In terms of FPI values, the flame resistances of these PU–wood composites decreased according to the catalyst used in the order NMM, triethanolamine, diethylenetriamine, and triethylenediamine. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

A commercial phosphorous–nitrogen containing intumescent flame retardant for thermoplastic polyurethane

The aim of this work is to develop a halogen‐free thermoplastic polyurethane (TPU) composite with significantly improved fire performance by using a highly commercial phosphorous–nitrogen containing intumescent flame retardant (P–N IFR). Based on the characterizations of thermogravimetric analysis and in situ Fourier transform infrared spectra, P–N IFR powder was proved a desired flame retardant for TPU in theory and the thermal degradation property of PU/PNIFR composites at elevated temperatures was investigated as well. Fire performance was evaluated by limiting oxygen index, underwriters laboratories 94 testing and char residue morphologies. Results showed that the addition of P–N IFR promotes the formation of char residues which were covered on the surface of polymer composites resulting in the improvement of thermal stability and flame retardancy. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39772.     

提高聚氨酯硬泡材料绝热性能的途径

本文从理论上分析了影响聚氨酯硬泡材料初期Ｋ值，老化后Ｋ值的各因素及其相互关系，评价了实践中可采用技术措施，对硬泡聚氨酯材料生产中，取代发泡剂ＣＦＣ－１１的同时仍维持产品较高的绝热性能有一定指导作用。     

Structure and thermal property of intumescent char produced by flame‐retardant high‐impact polystyrene/expandable graphite/microencapsulated red phosphorus composite

This paper is aimed to illustrate the structure and thermal property of intumescent char produced by flame‐retardant polymers containing expandable graphite (EG). For this purpose, high‐impact polystyrene (HIPS) flame retarded by EG individually or in combination with microencapsulated red phosphorus (MRP) was prepared. The results indicate that the intumescent char from HIPS/EG/MRP composite, which contains a small amount of phosphorus element and more oxygen element, is much more compact and continuous than that from HIPS/EG composite with identical loading of flame retardant due to binding effect of phosphoric acid and its derivatives. The intumescent char produced by HIPS/EG/MRP composite exhibits much enhanced thermal and thermo‐oxidative stability as well as thermal‐insulating effect, which can withstand destruction of heat and oxygen effectively and thus provide a good fire‐proof barrier. The temperature beneath this intumescent char is decreased significantly in case of action by flame. By comparison, the porous and loose intumescent char generated by HIPS/EG composite has poor thermo‐oxidative endurance, and most of it can be consumed in air at high temperature without effective protection for the polymer. This has resulted in remarkable increase in flame retardancy of the HIPS/EG/MRP composite.     

Flame‐retardant olefin block copolymer composites with novel halogen‐free intumescent flame retardants based on the composition of melamine phosphate and pentaerythritol

A series of halogen‐free intumescent flame retardants (IFR) based on home‐made melamine phosphate and pentaerythritol system (MPPER) including polyamid 12, basic nickel carbonate (NiCO₃·2Ni(OH)₂·4H₂O), lanthanum oxide (La₂O₃), and expandable graphite compounding with MPPER, were adopted for flame retarding olefin block copolymers (OBC). Flame‐retardant effects and thermal stabilities of OBC‐IFR composites were investigated by limiting oxygen index, vertical burning test (UL‐94), and thermogravimetry analysis along with the analysis of morphological structures of the char residue by scanning electron microscopy. The mechanical properties and the flame‐retardant mechanism of the final composited materials have been also discussed. The loading of suitable amount of IFR can improve effectively the flame retardancy of the OBC with tolerable decrease in mechanical properties. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40066.     

Wetting behavior of electrospun poly(L‐lactic acid)/poly(vinyl alcohol) composite nonwovens

Poly(L ‐lactic acid) (PLLA) fibers have been extensively studied for various applications. In this work, PLLA and poly(vinyl alcohol) (PVA) were prepared by coelectrospinning to form composite nonwoven materials. The structures and diameter distribution of the electrospun PLLA/PVA composite nonwovens were examined by atomic force microscopy (AFM) and scanning electronic microscope (SEM). The wetting behavior of the electrospun PLLA/PVA composite nonwovens was also investigated using static contact angles and dynamic water adsorption measurements. It was observed that the addition of PVA in the electrospun PLLA/PVA composite nonwovens significantly alerted the contact angles and water adsorption of the composite materials. It was also found that the increase in the content of PLLA led to the increase in the surface contact angle and decrease in water adsorption of the electrospun PLLA/PVA nonwoven materials. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Enhanced Thermo‐Mechanical Stiffness,Thermal Stability,and Fire Retardant Performance of Surface‐Modified 2D MoS2 Nanosheet‐Reinforced Polyurethane Composites

This article reports new‐generation 2D‐MoS₂ nanosheet‐containing polyurethane (PU) composite materials with improved thermo‐mechanical stiffness, thermal stability, and fire retardation properties. The surface of 2D‐MoS₂ nanosheets is modified with melamine (M‐MoS₂), and then PU composites with varying M‐MoS₂ loadings are synthesized using an in situ polymerization method. During polymerization, 3‐amino‐propyl‐trimethoxy silane is introduced to create silicate functionality on the PU chains, which further improves the compatibility between PU and M‐MoS₂. Microscopy studies confirm the distribution of highly intercalated and agglomerated M‐MoS₂ nanosheets in the PU matrix. The PU composite containing 5 wt% M‐MoS₂ shows a 65% higher storage modulus (at 30 °C) than that of pure PU. The thermal stability of pure PU is significantly improved (62 °C) after composite formation. Thermogravimetric analysis in combination with FTIR spectroscopy shows that the PU/M‐MoS₂ composites release less toxic gases during thermal degradation compared to pure PU. Moreover, the composite containing 5 wt% M‐MoS₂ shows improved fire retardation properties, with 45% and 67.5% decrease in the peak heat and total heat release rates, respectively, as compared with those of pure PU. In summary, 2D‐MoS₂ is shown to have potential as an advanced nano‐filler to obtain stiffer PU composite with improved fire retardant property for structural application.     

Synthetic Ni‐talc as filler for producing polyurethane nanocomposites

New synthetic Ni‐talc was used as filler in the synthesis of polyurethane (PU) nanocomposites by in situ polymerization and to emphasize the contribution of the new material compared with natural talc. Good dispersion of Ni‐talc was supported by homogeneous green coloration observed in the polymer matrix. X‐ray diffraction (XRD) analyses indicate the intercalation of polymeric matrix into the filler layers by the increase in d₀₀₁‐spacing value of the Ni‐talc for the nanocomposites when compared to the pristine filler. The nanocomposites obtained with synthetic talc showed an improvement in the crystallization temperature and in thermal stability when compared to pure PU and the composite obtained with natural talc. The young modulus of PU/talc materials containing both Ni‐talc and natural talc were slight higher than pure PU. As shown by scanning electron microscope (SEM), Ni‐talc fillers were well dispersed into the polymeric matrix probably due to the good compatibility of both phases filler/polymer mainly achieved by the filler OH interaction with the urethane group of the polymeric chain. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41854.