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The high flammability and generation of toxic volatiles during combustion are big obstacles for thermoplastic polyurethane (TPU). In this work, a 10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) derivate containing phosphorus and nitrogen was synthesized and then grafted onto the surface of graphene oxide (GO-DOPO) by using a silane agent [(...
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... proposed flame retardant mechanism for TPU/GO-DOPO nanocomposites is illustrated in Fig. 5. In the gas phase, the grafted DOPO-NH 2 on the surface of GO can generate phosphorous radicals during combustion, such as P⋅ and PO⋅ radicals, which can capture active radicals (such as OH and H radicals) to interrupt the free radical chain reaction in the flame zone, thereby it can suppress further combustion reaction [24,25]. In ...
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Halloysite nanotubes (HNTs) have been considered as a promising flame retardant fillers for polymers. In this work, the polyhedral oligomericsilsesquioxane (POSS) containing amino group was covalently grafted on the surface of HNTs with 3-(2,3-epoxypropoxy)propytrimethoxysilane as a chemical bridge. The POSS modified HNTs (HNTs-POSS) dispersed unif...
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... It is noted that T 5 of all the samples is higher than 517 • C. Moreover, the T 5 values of PI/H-PDA composites shift to higher temperatures compared to pure PI, which can be attributed to the benzene ring of H-PDA contributing to the generation of a carbonized char layer, thereby prolonging the thermal decomposition process of PI [36]. Furthermore, the incorporation of H-PDA in the PI composites offers an additional advantage as it acts as a free radical scavenger, thereby delaying the thermal decomposition process [37]. ...
Polydopamine (PDA) has been extensively investigated due to its excellent adhesion ability and versatile chemical potential for secondary reactions. However, the potential application of hollow polydopamine micro-spheres (H-PDA) in the field of low-dielectric electronic packaging remains an unexplored area. Here, H-PDA microspheres with adjustable size were synthesized by a template-assisted approach, and the influence of size and content of H-PDA on the comprehensive performance of PI/H-PDA composites was explored in detail. The morphology observation revealed that the presence of H-PDA could be homogeneously dispersed in the PI matrix, and the PI/H-PDA composite containing 2 wt% H-PDA-800 achieved the lowest dielectric constant of 1.96 with a dielectric loss of 0.0123 at 1 MHz. It was attributed to the synergistic effects of nano-sized air bubbles from H-PDA and the dielectric confinement effect. Meanwhile, PI/H-PDA composites maintained high thermal stability (T 5 > 517 • C). In addition, the incorporation of H-PDA had a strengthening and toughening effect on PI composites, which can be explained by the sliding theory of macromolecular chains. This work offers a feasible strategy to obtain ultra-low dielectric constant of porous PI composites while maintaining good mechanical properties and thermal stability.
... The nano-silica produced by the degradation of the Si−O−C/Si−O−Si bond could also migrate to the char surface during combustion, improving the integrity and quality of the char layer. 43 Consequently, the flame retardancy of Lig-K-DOPO-filled SBR samples was enhanced. ...
In this study, we present an innovative environmental silicon-, phosphorus-, and nitrogen-triple lignin-based flame retardant (Lig-K-DOPO). Lig-K-DOPO was successfully prepared by condensation of lignin with flame retardant intermediate DOPO-KH550 synthesized via Atherton-Todd reaction between 9, 10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) and γ-aminopropyl triethoxysilane (KH550A). The presence of silicon, phosphate, and nitrogen groups was characterized by FTIR, XPS, and 31P NMR spectroscopy. Lig-K-DOPO exhibited advanced thermal stability compared with pristine lignin supported by TGA analysis. The curing characteristic measurement showed that addition of Lig-K-DOPO promoted the curing rate and crosslink density to styrene butadiene rubber (SBR). Moreover, the cone calorimetry results indicated Lig-K-DOPO conferred impressive flame retardancy and smoke suppression. The addition of 20 phr Lig-K-DOPO reduced SBR blends 19.1% peak heat release rate (PHRR), 13.2% total heat release (THR), 53.2% smoke production rate (SPR), and 45.7% peak smoke production rate (PSPR). This strategy provides insights into multifunctional additives and greatly extends the comprehensive utilization of industrial lignin.
... The ratio of I D /I G can be utilized to visually evaluate the graphitization degree of carbon. [40,41] According to the data fitting, the I D /I G value of char residues in PLA/PA@CS and PLA/APBA@PA@CS is 2.81 and 2.78 lower than that of PLA/CS (I D /I G = 3.01), ...
The inherent shortcomings such as flammability, brittleness, and low crystallinity limit the broad applications of poly(lactic acid) (PLA). To improve the fire resistance and mechanical properties of PLA, a chitosan-based core-shell flame retardant additive (APBA@PA@CS) was prepared for PLA via the self-assembly of interionic interactions among chitosan (CS), phytic acid (PA), and 3-aminophenyl boronic acid (APBA). The peak heat release rate (pHRR) and total heat release rate (THR) of PLA composite containing 3 wt% APBA@PA@CS decreased from 460.1 kW/m2 and 75.8 MJ/m2 to 419.0 kW/m2 and 53.1 MJ/m2, respectively. The presence of APBA@PA@CS contributed to the formation of a high-quality char layer rich in phosphorus and boron in the condensed phase and released non-flammable gases in the gas phase to hinder the exchange of heat and O2, thereby having a synergistic flame retardant effect. Meanwhile, the tensile strength, elongation at break, impact strength, and crystallinity of PLA/APBA@PA@CS were increased by 3.7 %, 17.4 %, 5.3 %, and 55.2 %, respectively. This study provides a feasible route to construct a chitosan-based N/B/P tri-element hybrid to improve the fire safety performance and mechanical properties of PLA biocomposites.
... The morphology of the fracture surfaces of the TPU composites is presented in Fig. 2. In Fig. 2a, pure TPU exhibits a smooth fracture surface, which is characteristic of brittle fracture [35]. With the addition of ZIF-8-based particles, the TPU composites exhibit rougher crosssectional features. ...
... The tensile properties of pure TPU and its composites with various types of fillers are presented in Fig. 11. In Fig. 11a, the pure TPU has a tensile strength of 42.36 MPa and an elongation at break of 2138.1%, which exhibits high ductility as reported in other papers [35,45]. However, the mechanical properties of the TPU/ZIF-8 composite are severely deteriorated, with a tensile strength of 22.51 MPa and elongation at break of 1783.9%. ...
The addition of traditional flame retardant additives can usually significantly reduce the flammability of thermoplastic polyurethane (TPU) but has a limited contribution to suppressing smoke release during combustion. To overcome this obstacle, a double core-shell structured zeolite imidazole framework-8 (ZIF-8) in combination with negatively charged phytic acid and positively charged hyperbranched polysiloxane (NH2-HBPSi) was layer-by-layer self-assembled through the electrostatic method. The decorated NH2-HBPSi layer effectively improved the interfacial compatibility between the fillers and the TPU matrix. The peak heat release rate (PHRR), total heat release (THR), total smoke production (TSP), and total CO production (TCOP) of the TPU composite containing 2.0 wt% [email protected]@NH2-HBPSi were reduced by 35.2%, 25.2%, 65.5%, and 52.8%, respectively, as compared to those of pure TPU. The distinguished fire resistance and smoke suppression were ascribed to the flame retardant effects of Zn, N, P, and Si elements in the [email protected]@NH2-HBPSi hybrid. In addition, the TPU/[email protected]@NH2-HBPSi composite maintained a high elongation at break of 2178.2% and tensile strength of 46.87 MPa due to the steric effect of NH2-HBPSi. This work presents a feasible strategy for the design and development of flame retardant fillers to improve fire resistance and inhibit smoke emission while maintaining the high ductility of TPU.
... The integrated area ratio of D-band and G-band (I D /I G ) in Raman spectra is often used to reflect the graphitization degree of samples. The lower I D /I G means the higher graphitization degree and quality of the char layer [7,60]. In Figure 8, it is noteworthy that the values for I D /I G of pure TPU, TPU/BNNO, TPU/BNNO@Co 3 O 4 , and TPU/BNNO@Co 3 O 4 @PPZ are 3.06, 3.08, 2.98, and 2.85, respectively, which indicates the highest graphitization degree for the char residue of TPU/BNNO@Co 3 O 4 @PPZ. ...
... The integrated area ratio of D-band and G-band (ID/IG) in Raman spectra is often used to reflect the graphitization degree of samples. The lower ID/IG means the higher graphitization degree and quality of the char layer [7,60]. In Figure 8, it is noteworthy that the values for ID/IG of pure TPU, TPU/BNNO, TPU/BNNO@Co3O4, and TPU/BNNO@Co3O4@PPZ are 3.06, 3.08, 2.98, and 2.85, respectively, which indicates the highest graphitization degree for the char residue of TPU/BNNO@Co3O4@PPZ. ...
Thermoplastic polyurethane (TPU) is widely used in daily life due to its characteristics of light weight, high impact strength, and compression resistance. However, TPU products are extremely flammable and will generate toxic fumes under fire attack, threatening human life and safety. In this article, a nanohybrid flame retardant was designed for the fire safety of TPU. Herein, Co3O4 was anchored on the surface of exfoliated ultra-thin boron nitride nanosheets (BNNO@Co3O4) via coprecipitation and subsequent calcination. Then, a polyphosphazene (PPZ) layer was coated onto BNNO@Co3O4 by high temperature polymerization to generate a nanohybrid flame retardant named BNNO@Co3O4@PPZ. The cone calorimeter results exhibited that the heat release and smoke production during TPU combustion were remarkably restrained after the incorporation of the nanohybrid flame retardant. Compared with pure TPU, the peak heat release rate (PHRR) decreased by 44.1%, the peak smoke production rate (PSPR) decreased by 51.2%, and the peak CO production rate (PCOPR) decreased by 72.5%. Based on the analysis of carbon residues after combustion, the significant improvement in fire resistance of TPU by BNNO@Co3O4@PPZ was attributed to the combination of quenching effect, catalytic carbonization effect, and barrier effect. In addition, the intrinsic mechanical properties of TPU were well maintained due to the existence of the PPZ organic layer.
... Thermoplastic polyurethanes (TPU) are capable of adding great economic and social value to the production industry with excellent properties such as high strength, good toughness, cold resistance, aging resistance, and so on [1,2]. The TPU composites are usually applied in many fields, such as aerospace, automobile manufacturing, building, electronics and electrical appliances, etc., [3,4]. ...
... However, fluoride salts and milder acid etching MAX phases are a better choice due to the dangers of hydrofluoric acid [20]. The reaction formulas are [21,22]: Ti 3 AlC 2 + 3HF = AlF 3 + Ti 3 C 2 + 1.5H 2 (1) ...
In this work, a novel functionalization strategy for ZIF-67-modified layered MXene was proposed, aiming at improving the fire safety of thermoplastic polyurethanes (TPU). The ZIF-67@MXene was verified by microscopic morphology, elemental composition, functional group species and crystal structure, and then the successfully prepared ZIF-67@MXene was introduced into the TPU material. When ZIF-67@MXene content was only 0.5 wt%, the peak heat release rate, total heat release rate, peak smoke release rate, total smoke release rate, and CO yield of the TPU/ZIF-67@MXene composites were reduced by 26%, 9%, 50%, and 22%, respectively, compared with the pure TPU. The thermogravimetric tests showed that the residual char of TPU/ZIF-67@MXene composites was the most in all samples. In short, the high-quality carbon layer of TPU/ZIF-67@MXene composites acts as a physical barrier to the transfer of heat and toxic gases, greatly improving the flame retardant properties of the TPU polymer.
... This char barrier isolates underlying polymer pyrolysis zone from heat of fire zone [73][74][75][76][77]. Recently, graphene oxide (GO) was covalently modified with 10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) yielded GO-DOPO, which then dispersed in thermoplastic polyurethane (TPU). The developed flame retardant system achieved very good flame retardancy properties for the new nanocomposites, recording reduction by ~ 36 and 50% for PHRR (Table 1) and peak smoke production, respectively [78]. Additionally, the peak emission rate of CO and CO 2 was significantly reduced by 57 and 36%, respectively [78]. ...
... The developed flame retardant system achieved very good flame retardancy properties for the new nanocomposites, recording reduction by ~ 36 and 50% for PHRR (Table 1) and peak smoke production, respectively [78]. Additionally, the peak emission rate of CO and CO 2 was significantly reduced by 57 and 36%, respectively [78]. The flame retardancy mechanism was scrutinized and revealed that the developed GO-DOPO trigger the generation of compact and dense char layer which offer good shielding effect isolating thermoplastic polyurethane from degradation as shown in Fig. 8 [78]. ...
... Additionally, the peak emission rate of CO and CO 2 was significantly reduced by 57 and 36%, respectively [78]. The flame retardancy mechanism was scrutinized and revealed that the developed GO-DOPO trigger the generation of compact and dense char layer which offer good shielding effect isolating thermoplastic polyurethane from degradation as shown in Fig. 8 [78]. Kim et al, studied, the influence of dispersion of graphene oxide and sulfur-doped graphene oxide in polyacrylonitrile (PAN) flammability properties [79]. ...
Polymeric and textile based materials constitute the majority of market products, however, due to their low thermal stability and high flammability hazards, their uses are limited in some applications. Therefore, flame retardant materials have to be dispersed as fillers in polymer matrix and coated on textile fabrics to enhance their fire safety and thermal stability. Graphene is two-dimensional materials and considered as a promising carbon nanomaterials with sp 2-hybridization and with unique properties. In this review article conventional flame retardant and different methods of synthesis of graphene layers were summarized. Also, the possibility of use graphene sheets alone as flame retardant material for polymeric materials was reviewed and compared with other common nanofillers. Graphene sheets and their composite as flame retardant nanofillers for polymers and flame retardant coating for textiles are discussed in details. Synergistic flame retardant effect of use of nano-particles decorated graphene sheets as flame retardant for polymer nanocomposites are discussed.
... From this perspective, new nanomaterials including graphitic carbon nitride (GCN) [6], graphene oxide (GO) [7], black phosphorus (BP) [8] and transition metal carbides/nitrides (MXenes) [9], have received much scientific attention. Compared with the preparation method of GO, BP, and MXenes, GCN, which can be obtained by self-polymerization from an inexpensive nitrogen source [10], is promising as an FR for large-scale use. ...
Graphitic carbon nitride (GCN) has been recognized as a potential flame retardant (FR) due to its high thermal stability and nitrogen richness. Previous work has been limited to hybridization without involving covalent modification. Here, we developed a facile covalent modification approach to polycondensation that can chelate with metal ions (PCNOH–CuCo) from GCN. Structural and mechanical property characterization confirmed the ability of PCNOH–CuCo to be uniformly dispersed in the epoxy resin (EP). Fire tests showed excellent fire resistance of EP with 10 wt% PCNOH–CuCo (EP/10PCNOH–CuCo), including a limiting oxygen index of EP/10PCNOH–CuCo up to 31.5%, and the reduction in the peak heat release rate, total heat release, peak smoke production, total smoke production peak CO production, and peak CO2 production of 47.9%, 37.5%, 20%, 44.5%, 30.9%, and 42.5%, respectively. This work provides a solution for the fabrication of GCN-based FRs and their derived metal-doped FRs.
... In the gas phase, P-HBPSi flame retardants undergo pyrolysis to generate ⋅P and ⋅PO free radical scavengers, which can react with flammable free radicals (⋅O, ⋅H and ⋅OH) to cut off the combustion reaction and form more solid products [61,62]. In addition, the nonflammable gases (H 2 O, N 2 , NH 3 and CO 2 ) generated during combustion can dilute the concentration of combustible gases [63]. In the condensed phase, the heat conduction and barrier effect of GO nanosheets produce a labyrinth effect, in which the heat and combustible pyrolysis products must follow a flexural path to the fuel [64]. ...
In this work, a novel type of phosphorus containing hyperbranched polysiloxane (P-HBPSi) was synthesized by sol-gel method, and then utilized to functionalize graphene oxide (P-HBPSi@GO). The P-HBPSi@GO hybrids were mixed with TPU by melt compounding. The SEM observation revealed that the P-HBPSi@GO dispersed homogeneously in the TPU matrix with good compatibility. The TPU/P-HBPSi@GO-2.0 maintained high ductility with elongation at break of 1750.8%. The peak heat release rate and total heat release of TPU/P-HBPSi@GO-2.0 were reduced by 63.5% and 20.9%, respectively. In addition, the peak smoke production rate and total smoke production of TPU nanocomposites were also reduced dramatically by 58.3% and 36.4%, respectively. The production of phosphorus free radical scavengers in the gas phase and the barrier effects of GO nanosheets, catalytic charring and the unique Si-O-Si framework of P-HBPSi flame retardant in the condensed phase contributed to the outstanding flame retardancy and toxic gas suppression of TPU/P-HBPSi@GO nanocomposites.
