Flame-retardant Polyurethane Research Articles

Water-based hybrid coatings toward mechanically flexible, super-hydrophobic and flame-retardant polyurethane foam nanocomposites with high-efficiency and reliable fire alarm response

Flammability feature of combustible polymer foam materials often causes massive casualties and property loss, and it is therefore urgent to develop a green and high-efficiency strategy that can reduce or avoid the fire blaze disasters. Here, an extremely simple water-based coating approach is proposed to prepare mechanically flexible, super-hydrophobic and flame-retardant polyurethane (PU) foam nanocomposites with high-efficiency fire warning response. The hybrid ammonium polyphosphate (APP)/graphene oxide (GO) is decorated onto the PU foam surface via electrostatic interactions followed by surface silane functionalization. Interestingly, the silane and APP molecules present selective distributions on the GO and thus form micro-/nano- rough surface with low water affinity to achieve super-hydrophobicity (e.g. water contact angle of ~158.4°). Meanwhile, such hybrid APP/GO/silane coatings produce synergistic flame resistance for the PU foam materials, which is attributed to the formation of compact and uniform P-Si elements co-covered rGO layer on the foam surface. Further, the hybrid coatings can provide high-efficiency fire warning response under complicated conditions, e.g. flame detection response time of only ~2.0 s and excellent fire early warning time in pre-combustion (e.g. 11.2 s at 300 °C). Therefore, this work provides new perspectives to design and develop multi-functional coatings for fire safety and prevention applications.

Synthesis and flame retardant properties of new boron-containing polyurethane

A novel boron-containing chain extender of diglyceride borate was synthesized and used to improve flame retardancy of polyurethane (PU). Diglyceride borate derived from boric acid with glycerin was synthesized by esterification reaction. The boron-containing polyurethanes were synthesized from polyether polyol, 4,4-diphenylmethane diisocyanate (MDI) and diglyceride borate through one-step method. The structure of diglyceride borate was fully characterized by Fourier transform infrared spectroscopy (FTIR), 1H-NMR. The thermal stability and fire behaviors of boron-containing PU were investigated by thermogravimetric analysis (TGA), limiting oxygen index (LOI), UL-94 rating and cone calorimeter (CCT). The LOI increased from 23.8% to 30.0%, with the content of diglyceride borate in the polymer chains increased from 13.6% to 25.7%, meanwhile char formation was enhanced and heat release reduced. Scanning electron microscope (SEM) images, residue digital photos, FTIR, Raman spectroscopy and X-ray diffraction (XRD) analysis of the char residues suggested the formation continuous compact char layer. The results showed that the flame retardancy of polyurethane was positively correlated with boron content.

Synthesis and characterization of flame retardant polyurethane: Effect of castor oil polyurethane on its properties

A Flame retardant polyether ester urethane was produced using PPG, phosphorous, phthalic anhydride, and isophorone diisocyanate. For the formulation of polymer blend (PBs), bio-based polyurethane was procured from castor oil (CPU) and was blended with polyether ester urethane (PEEU). The different characterizations were done to determine the effect of bio based polyurethane on the properties of PEEU. The comparative studies show PBs have better properties compared to flame retardant PEEU. The thermal degradation study shows a 30–40% decrease in the rate of thermal degradation in PBs. LOI values of PBs have been decreased by 2–3%. The mechanical properties show that the breaking elongation of PBs has increased with 50–90%, but on the other hand, tensile strength has been decreased from 3 (MPa) to 5 (MPa). The gel content in PBs has increased with 10–20%. The hydrolytic stability and contact angle of PBs have been increased with an increase in the CPU ratio. Soil burial test results show that increasing the ratio of CPU in PBs lowers the rate of bacterial attack on the polymeric chain.

Flame-retardant polyurethane elastomer based on aluminum salt of monomethylphosphinate

The flame retardancy of polyurethane (PU) elastomer based on aluminum monomethylphosphinate (MeP-Al) was investigated. Thermal analysis, evolved gas analysis (TG-FTIR), flammability tests (LOI, UL 94), heat release rate (HRR) (microcombustion calorimeter), and chemical analysis of residues (SEM–EDX and FTIR) were used to investigate the flame-retardant performance and mechanism of the PU/MeP-Al. Results show that adding MeP-Al endows PU desired flame retardancy and anti-dripping property. The sample containing 20 mass% of MeP-Al passes the UL 94 V0 rating with LOI value of 29.6% and no dripping during combustion. Moreover, the heat release during combustion and the amount of organic volatile from PU decomposition are significantly reduced. The good flame retardancy, anti-dripping property, dramatically a reduction in release of heat and organic compounds are attributed to the efficient action of the MeP-Al in both the gas and condensed phase. In the gas phase, the MeP-Al decomposes into monomethylphosphinic acid to inhibit flame and reduces the heat release. In the condensed phase, MeP-Al turns into the tough aluminum pyrophosphonate and promotes PU to form stable carbonaceous char by interacting with PU.

A facile, environmentally and friendly flame-retardant: Synergistic flame retardant property of polyurethane rigid foam

In this work, aluminum diethylphosphite (ADPO2) and expandable graphite (EG) exhibited synergistic effect and were introduced into polyurethane to improve the flame retardancy and thermal behavior. The structures were confirmed more denser than when added into either of the two. Additionally, the thermal performance and combustion behaviors of flame-retardant polyurethane were evaluated that when the ratio of ADPO2 to EG was 1:2, the flame-retardant performance was better than that achieved at a ratio of 2:1; Finally, the thermodynamic properties could demonstrate that when the ADPO2-to-EG ratio was 1:2 (ADPO25g and EG10g), the heat release rate (HRR) was 125 kW/m2, the lowest of all values, and was nearly half of the value without adding flame retardants.

Flame retardancy and thermal properties of rigid polyurethane foam conjugated with a phosphorus–nitrogen halogen-free intumescent flame retardant

In this work, a halogen-free intumescent combining phosphorus and nitrogen, flame-retardant 2-((2-hydroxyphenyl)(phenylamino)methyl5,5-dimethyl-1,3,2-dioxaphosphinane 2-oxide (HAPO) was successfully synthesized. It had been synthesized by reaction of 5,5-dimethyl-1,3, 2-dioxphosphinane 2-oxide with Schiff base. Its chemical structure was characterized in detail by Fourier transform infrared spectroscopy, 1H NMR, and 31P NMR spectrum. The flame-retardant polyurethanes were prepared with different loadings of HAPO. The thermal properties, flame retardancy and combustion behavior of the pure polyurethane foam thermosets were investigated by a series of measurements involving thermogravimetric analysis, limited oxygen index measurement, UL-94 vertical burning test, and cone calorimeter test. The results of the aforementioned tests indicated that HAPO can significantly improve the flame retardancy as well as smoke inhibition performance of polyurethane foam. Compared with the PU-Neat, the limited oxygen index of flame-retardant polyurethanes (15%) thermoset was increased from 19.5% to 23.8% and its UL-94 reached V-0 rating. In addition, the cone test results showed that the heat release rate, total heat release, rate of smoke release, and total smoke production of flame-retardant polyurethanes (10%) were decreased obvious sly. The apparent morphology of carbon residue was characterized by scanning electron microscopy, and results revealed that the modified polyurethane foam can form dense carbon layer after combustion. Thermogravimetric analysis results also indicated that the char amount of flame-retardant polyurethanes was obviously increased compared with PU-Neat. Based on the above analysis, we can draw the conclusions which in the condensed phase, phosphorus-based acids from the degradation of HAPO, this could promote the formation of continuous and dense phosphorus-rich carbon layer. In the gas phase, the flame-retardant mechanism was ascribed to the quenching effect of phosphorus-based radicals and diluting effect by non-flammable gases.

Mechanically robust self-healing and recyclable flame-retarded polyurethane elastomer based on thermoreversible crosslinking network and multiple hydrogen bonds

Self-healing polymers have drawn significant attention because of their great potential for applications in many fields. It is highly desirable to prepare materials capable of self-healing and with excellent mechanical properties. Additionally, the flammability of polymers make them unsafe during use. A novel strategy is proposed to manufacture a multifunctional polyurethane elastomer with high tensile strength (37.11 ± 1.89 MPa) and excellent self-healing efficiency (91.8%), containing a thermo-reversible crosslinking network and multiple hydrogen interactions. The furan-terminated phosphorus-based monomer, tri(2-furyl) phosphoramide (TFP), was successfully synthesized and then conjugated into a maleimide-terminated linear segmented polyurethane (MPU) backbone to prepare self-healing, recyclable, and flame-retarded polyurethane (MPUF). Due to its synergetic dual reversible bonds, the multifunctional polyurethane elastomer possessed ultrahigh strength, and excellent self-healing, shape recovery, and reprocessing properties. The phosphorus containing polyurethane elastomer exhibited improved thermal stability a limiting oxygen index value of 28.5%, and a 12.3% decrease in the peak heat release rate (pHRR) relative to those of unmodified polyurethane. This work demonstrates an effective strategy to prepare multifunctional polyurethane elastomer with both high self-healing efficiency and excellent mechanical properties allowing application for this material in the fields of fire-control coatings and building materials.

Layer-by-layer assembled nanocoating containing MoS2 nanosheets and C60 for enhancing flame retardancy properties of flexible polyurethane foam

A novel three bilayers nanocoating containing MoS2 nanosheets and C60 was constructed on the surface of flexible polyurethane (FPU) foam by a layer-by-layer assembly method. MoS2 nanosheets were prepared by ultrasonic-assistant exfoliation method in a mixed solvent of N-Methyl-2-pyrrolidinone (NMP) and aqueous hydrogen peroxide (30% H2O2). MoS2-C60/FPU foam was prepared by alternately submerging the FPU foam into C60/guargum and MoS2/sodium alginate suspensions. Scanning electron microscopy (SEM) characterization showed that MoS2 nanosheets and C60 nanoparticles were uniformly distributed on the surface of FPU foam matrix. Thermogravimetric analysis demonstrated that MoS2-C60/FPU foam exhibited better thermal stability than the control FPU foam. Cone calorimeter test results revealed that MoS2-C60/FPU foam with the incorporation of 5.24 wt% MoS2-C60 nanocoating had a remarkable reduction in peak heat release rate (pHRR, 47.5% reduction), total heat released (THR, 51.1% reduction) and total smoke production (TSP, 33.1% reduction) compared with those of the control FPU foam. Furthermore, the morphology and structure of char residue after cone calorimeter test were investigated by SEM and Raman spectroscopy. The possible flame-retardant mechanism of MoS2-C60/FPU foam was proposed, and this significant improvement in flame retardancy could be ascribed to the insulating barrier and adsorption effect of MoS2 nanosheets, free radicals-trapping ability of C60 in condensed phase, and the catalytic carbonization effect of the MoS2-C60 nanocoating. This work provides a new approach for producing high quality flame retardant polyurethane foam materials.

Large-scale production of simultaneously exfoliated and Functionalized Mxenes as promising flame retardant for polyurethane

The low yield of MXenes nanosheets and its poor interfacial compatibility with polymer matrix have been an unavoidable obstruction for the fabrication of related polymer nanocomposites. Here, we reported a facile and large-scale route for the simultaneous organic modification and exfoliation of MXene by utilizing the wet ball milling process. Due to the electrostatic attraction effect, positively charged poly(diallyldimethylammonium chloride) (PDDA) long chains would attach to negatively charged MXene, which prevented the newly peeled-off MXene sheets from agglomerating and reduced the collision from the steel balls. Also, the attached PDDA molecule may act as protective shield for MXene nanosheets, leading to the delay of oxidation on the surface of MXene nanosheets in atmosphere. Notably, with the incorporation of 3 wt% PDDA modified MXene in thermoplastic polyurethane (TPU) matrix, the peak heat-release rate (decreased by 50%) and total smoke production (decreased by 47%) were significantly decreased. Moreover, mechanical performance (tensile strength at break was raised by 31.2%) and thermal conductivities (increased by 88.6%) of TPU nanocomposites were evidently enhanced. This novel strategy provide a simple and effective way to obtain exfoliated and functionalized MXenes nanosheets, enriching the application of MXenes in polymeric material field.

Two in One: Modified Polyurethane Foams by Dip‐Coating of Halloysite Nanotubes with Acceptable Flame Retardancy and Absorbency

Front Cover: The work in article number 1900213 by Mingxian Liu and co-workers, reports the facial preparation of flame-retardant polyurethane foam by dip-coating of halloysite nanotubes. The surfaces of foam change from hydrophobic to super-hydrophilic after nanotube coating, which leads to the increase in dye adsorption capacity of the foam. Moreover, the halloysite coating improves fire retardation properties of polyurethane foam with self-extinguish properties.

Synthesis and properties of flame-retardant reactive hot melt polyurethane adhesive

A novel liquid polyphosphonate polyol (DMDP) was synthesized from dimethyl methylphosphonate and 1,6-hexanediol. Reactive hot melt polyurethane adhesives with high flame retardancy (HMPURs) were prepared from poly(tetramethylene ether glycol) (PTMG-2000), two kinds of poly(1,4-butylene adipate) (PBA-2000 and PBA-3000) and DMDP or dimethyl methylphosphonate as well as tetrahydrofuran acrylate. Five specimens of flame-retardant HMPURs with different weight percent of DMDP (0, 2, 4 and 6 wt%) and dimethyl methylphosphonate (4 wt%) were obtained. The mechanical properties, thermal stability, flammability, and bonding strength of the specimens were investigated. The results show that with the increase of DMDP content, the elongation at break and tensile strength decrease slightly, and the flame retardancy of HMPURs is significantly improved with the limiting oxygen index (LOI) value increasing from 17.2 to 28.2. The incorporation of DMDP leads to a higher thermal stability of HMPURs at high temperature and more char yield at 650 °C. With the increase of DMDP content, the final bond strength of HMPURs on the same substrate changes little, but the green strength of HMPUR-6 on the same substrate is observably less than other samples. The performance of HMPUR with the reactive flame retardant is superior to that of HMPUR with the additive flame retardant. In addition, the corresponding flame-retardant mechanism of DMDP-containing HMPURs was investigated by pyrolysis-gas chromatography coupled to mass spectrometry (Py-GC/MS). The results indicate that the pyrolysis of the HMPURs releases phosphorus-containing fragments to play a flame retardant role.

Gamma-irradiation-induced micro-structural variations in flame-retardant polyurethane foam using synchrotron X-ray micro-tomography.

Flame-retardant polyurethane foams are potential packing materials for the transport casks of highly active nuclear materials for shock absorption and insulation purposes. Exposure of high doses of gamma radiation causes cross-linking and chain sectioning of macromolecules in this polymer foam, which leads to reorganization of their cellular microstructure and thereby variations in physico-mechanical properties. In this study, in-house-developed flame-retardant rigid polyurethane foam samples were exposed to gamma irradiation doses in the 0-20 kGy range and synchrotron radiation X-ray micro-computed tomography (SR-µCT) imaging was employed for the analysis of radiation-induced morphological variations in their cellular microstructure. Qualitative and quantitative analysis of SR-µCT images has revealed significant variations in the average cell size, shape, wall thickness, orientations and spatial anisotropy of the cellular microstructure in polyurethane foam.

Effect carbon black microencapsulated ammonium polyphosphate on the flame retardancy and mechanical properties of polyurethane composites

ABSTRACTCarbon black microencapsulated ammonium polyphosphate (APP@CB) was synthesized to enhance the interfacial compatibility, mechanical property and flame retardancy of polyurethane (TPU). The chemical structure of APP@CB hybrids were characterized by Raman spectra and scanning electron microscope. Compared with APP flame retardant TPU composite, the tensile strength of TPU composite containing APP@2CB increased by 23%, and the smoke density approximately decreased by 46%. This is owing to the strong interaction between the CB and TPU in TPU4 (flame retardant by APP@2CB) composite. Furthermore, the TPU4 composite restrained the smoke and toxic volatiles evolved, indicating suppressed toxicity of the TPU composites.

Preparation and Characteristics of an Environmentally Friendly Hyperbranched Flame-Retardant Polyurethane Hybrid Containing Nitrogen, Phosphorus, and Silicon.

The NCO functional group of 3-isocyanatoproplytriethoxysilane (IPTS) and the OH functional group of 10-(2,5-dihydroxyphenyl)-10H-9-oxa-10-phospha-phenantbrene-10-oxide (DOPO-BQ) were used to conduct an addition reaction. Following completion of the reaction, triglycidyl isocyanurate (TGIC) was introduced to conduct a ring-opening reaction. Subsequently, a sol–gel method was used to initiate a hydrolysis–condensation reaction on TGIC–IPTS–DOPO-BQ to form a hyperbranched nitrogen–phosphorous–silicon (HBNPSi) flame retardant. This flame retardant was incorporated into a polyurethane (PU) matrix to prepare a hybrid material. Fourier-transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), limiting oxygen index (LOI), UV-VIS spectrophotometry, and Raman analysis were conducted to characterize the structure and analyze the transparency, thermal stability, flame retardancy, and residual char to understand the flame retardant mechanism of the prepared hybrid material. After the flame retardant was added, the maximum degradation rate decreased from −36 to −17 wt.%/min, the integral procedural decomposition temperature (IPDT) increased from 348 to 488 °C, and the char yield increased from 0.7 to 8.1 wt.%. The aforementioned results verified that the thermal stability of PU can be improved after adding HBNPSi. The LOI analysis indicated that the pristine PU was flammable because the LOI of pristine PU was only 19. When the content of added HBNPSi was 40%, the LOI value was 26; thus the PU hybrid became nonflammable.

Novel Biobased Polyol Using Corn Oil for Highly Flame-Retardant Polyurethane Foams

A novel bio-based polyol was synthesized using corn oil and 2-mercaptoethanol via thiol-ene reaction as an alternative to petroleum-based polyol for the synthesis of polyurethane foams. The polyol was analyzed using wet chemical techniques to obtain hydroxyl number and viscosity. Infrared spectroscopy and gel permeation chromatography were used to confirm the structural properties of the foams. Flame-retardant polyurethane foams were prepared by the addition of different concentrations of dimethyl methyl phosphonate (DMMP) in final foam composition. The effect of DMMP on the thermo-mechanical properties of the polyurethane foams was analyzed. The TGA analysis showed improved stability of the final char with addition of DMMP in the foams. All the foams maintained a well-defined cellular structure and over 95% of closed cell content. The horizontal burning test showed reduced burning time and weight loss from 115 s and 38 wt.% for the neat foams, to 3.5 s and 5.5 wt.% for DMMP-containing foams (1.94 wt.% P). The combustion test using cone calorimeter showed a considerable reduction in heat release rate and total heat release. Thus, our study shows that corn-oil based polyol can be used to produce renewable polyol for industrially producible rigid polyurethane foams. The addition of a small amount of DMMP could result in a significant reduction in the flame-retardant properties of the polyurethane foams.

Novel Oligo-Ester-Ether-Diol Prepared by Waste Poly(ethylene terephthalate) Glycolysis and Its Use in Preparing Thermally Stable and Flame Retardant Polyurethane Foam.

Rigid polyurethane foam (PUF) was successfully prepared from a novel oligo-ester-ether-diol obtained from the glycolysis of waste poly(ethylene terephthalate) (PET) bottles via reaction with diethylene glycol (DEG) in the presence of ZnSO4·7H2O. The LC-MS analysis of the oligodiol enabled us to identify 67 chemical homologous structures that were composed of zero to four terephthalate (T) ester units and two to twelve monoethylene glycol (M) ether units. The flame retardant, morphological, compression, and thermal properties of rigid PUFs with and without triphenyl phosphate (TPP) were determined. The Tg values showed that TPP played a role of not only being a flame retardant, but also a plasticizer. PUF with a rather low TPP loading had an excellent flame retardancy and high thermal stability. A loading of 10 wt % TPP not only achieved a UL-94 V-0 rating, but also obtained an LOI value of 21%. Meanwhile, the PUF without a flame retardant did not achieve a UL-94 HB rating; the sample completely burned to the holder clamp and yielded a low LOI value (17%). The fire properties measured with the cone calorimeter were also discussed, and the results further proved that the flame retardancy of the PUF with the addition of TPP was improved significantly. The polymeric material meets the demands of density and compression strength for commercial PUF, as well as the needs of environmental development. The current study may help overcome the drawback of intrinsic high flammability and enlarge the fire safety applications of materials with a high percentage of recycled PET.

Preparation, characterization, and properties of novel ultraviolet-curable and flame-retardant polyurethane acrylate

A series of flame-retardant polyurethane acrylate oligomer (FRPUA)–nhexa- phenoxy-cyclotriphosphazene (HPCP) (n = 0, 10, 15, and 20, where n is the amount of HPCP added to a 100 g mixture of FRPUA and other additives) ultraviolet (UV)-cured samples have been prepared. FRPUA was synthesized by the reaction of poly(glycidyl methacrylate) (an unsaturated polyether), a derivative of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) (2DOPO–4,4′- dihydroxy-benzophenone (DHBP)), and isophorone diisocyanate. As a control sample, the polyurethane acrylate (PUA) oligomer and cured PUA sample were also prepared. Surface drying of the PUA and FRPUA–nHPCP curable mixtures required a few seconds under UV irradiation (400 W lamp). The effects of 2DOPO–DHBP and HPCP on the flame retardancy and thermal stability of the PUA system were also investigated. For the FRPUA–nHPCP series, as n increases from 0 to 20, the limiting oxygen index (LOI) increases from 21.1% to 23.3% and the total heat release (THR) slowly decreases from 32.4 to 26.4 kJ/g, while the PUA cured sample possesses the LOI and THR values of 19.0% and 29.2 kJ/g, respectively. Besides, the PUA system can achieve better flame retardant properties when using both 2DOPO-DHBP and HPCP. Thermogravimetric analysis indicates that the amount of char residue of the FRPUA–nHPCP (n = 0, 10, 15, and 20) cured samples ranges from 15.1 to 21.9 wt.%, which are much are higher than 10.5 wt.% for the PUA cured sample. Improving the flame retardancy of the PUA system will expand its applications, such as for paper manufacturing and architectural coatings, while simultaneously retaining the feature of fast surface drying.

The effects of N,N-(pyromellitoyl)-bis-l-phenylalanine diacid ester glycol on the flame retardancy and physical–mechanical properties of rigid polyurethane foams

Flame-retardant rigid polyurethane foams incorporating N,N-(pyromellitoyl)-bis-l-phenylalanine diacid ester glycol have been prepared. After adding N,N-(pyromellitoyl)-bis-l-phenylalanine diacid ester glycol, the density and compressive strength of the polyurethane foams were seen to decrease. The flame retardancy of the polyurethane foams has been characterized by limiting oxygen index, upper limit–94, and cone calorimeter tests. The polyurethane foam with 2.27 wt% N,N-(pyromellitoyl)-bis-l-phenylalanine diacid ester glycol gave a highest limiting oxygen index of 33.4%, and the peak heat release rate of polyurethane foam reduced to 19.5 kW/m2 from 47.6 kW/m2 of PU-0 without N,N-(pyromellitoyl)-bis-l-phenylalanine diacid ester glycol. Upper limit–94 revealed N,N-(pyromellitoyl)-bis-l-phenylalanine diacid ester glycol did not change the burning rating, and all polyurethane foams had passed V-0 rating. The thermal stability of polyurethane foams has been investigated by thermogravimetric analyzer. N,N-(pyromellitoyl)-bis-l-phenylalanine diacid ester glycol significantly increased the initial decomposition temperature of polyurethane foams and their residues. In addition, the morphology of residual char from the flame-retarded polyurethane foams after cone calorimeter tests has also been characterized by digital photographs. The results indicated that N,N-(pyromellitoyl)-bis-l-phenylalanine diacid ester glycol significantly enhanced the strength and compatibility of the char layer formed by the polyurethane foams. These results indicate that N,N-(pyromellitoyl)-bis-l-phenylalanine diacid ester glycol can improve both the quality and quantity of the char, which has a significant effect on the flame-retardant properties of the foam.

A flame retardant rigid polyurethane foam system including functionalized graphene oxide

A functionalized graphene oxide (fGO) was prepared by graphene oxide (GO), boric acid and 3‐aminopropyltriethoxysilane in an ethanol aqueous solution using ultrasonic agitation. Its structure was characterized by the Fourier transform infrared (FTIR), X‐ray diffraction (XRD), thermogravimetric analysis (TG), and elemental analysis. Subsequently, the fGO was incorporated into the flame‐retardant‐polyurethane (FRPU) system, in which fGO as a synergist and reinforcing agent, expandable graphite (EG), and dimethyl methylphosphonate (DMMP) as flame retardants, to improve its the flame‐retardancy and mechanical properties, evidenced by the limiting oxygen index (LOI), vertical burning test (UL‐94) test and the cone calorimeter test (CONE). The LOI value of FRPU/fGO composites reached 28.1% by addition of 0.25 phr fGO and 10 phr EG/DMMP, and its UL‐94 test reached V‐0 rating. The CONE results revealed that fGO could significantly enhance flame retardant properties of FRPU composites, and the peak heat release rate (PHRR) values value of FRPU/fGO remarkably reduced by 32.9%. Moreover, fGO indeed enhanced the mechanical properties of rigid polyurethane foam (RPUF). POLYM. COMPOS., 40:E1274–E1282, 2019. © 2018 Society of Plastics Engineers

Sustainable flame-retardant polyurethanes using renewable resources

Renewable bio resources such as soybean, orange peel, and castor along with a novel phosphorous based polyol were used to prepare highly flame-retardant polyurethane foams. Diethyl allyl phosphonate (DEAP) and thioglycerol (TG) were used to synthesize phosphorous (P) based flame retardant polyol (DEAP-TG). Polyurethane (PU) foams having a various weight percentage of phosphorous were prepared using a varying amount of DEAP-TG (as a phosphorous source) and other bio-based polyols. Use of DEAP-TG polyol in polyurethane foams showed improved compressive strength without affecting closed cell content and morphology of the foams. The horizontal burning test showed a drastic reduction in self-extinguishing time and weight loss for the PU foams containing DEAP-TG polyol. For example, castor oil and DEAP-TG based PU foam which contains 1.5 wt% P showed significant reduction in self-extinguishing time (from 94s to 1.7s) and weight loss (from 48.5% to 3%) compared to neat castor oil based foams. Cone calorimeter data also showed a significant reduction in peak heat release rate, total heat release, total smoke release, and overall smoke production rate for the foam containing 1.5 wt% P compared to 0 wt% P in the foam. The improved flame retardancy was due to the formation of a protective char layer over the surface of the foam due to decomposition of a phosphorus compound. Our research provides a green alternative to prepare industrial grade flame-retardant polyurethane foams.