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(a) Heat release rate (HRR) curves and (b) total heat release (THR) curves of control and coated FPU foams during the cone calorimetry test.
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Polymer–clay membranes constructed via the layer-by-layer (LbL) assembly, with a nanobrick wall structure, are known to exhibit high flame retardancy. In this work, chitosan–montmorillonite nanosheet (CH–MMTNS) membranes with different thickness of MMTNS were constructed to suppress the flammability of flexible polyurethane (FPU) foam. It was found...
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Context 1
... cone calorimeter, simulating a developing fire scenario, was employed to more quantitatively investigate the improvement of flame retardancy for the FPU foam by MMTNS-1 and MMTNS-2 [22]. The heat release rate (HRR) curves of control and coated FPU foams during the cone calorimeter test are illustrated in Figure 6. All foam curves consisted of two peaks associated with the combustion of polyisocyanate and polyol [23]. ...
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... two peaks of the coated foams were both much lower than those 2019,11,213 8 of 13 A cone calorimeter, simulating a developing fire scenario, was employed to more quantitatively investigate the improvement of flame retardancy for the FPU foam by MMTNS-1 and MMTNS-2 [22]. The heat release rate (HRR) curves of control and coated FPU foams during the cone calorimeter test are illustrated in Figure 6. All foam curves consisted of two peaks associated with the combustion of polyisocyanate and polyol [23]. ...
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... both peaks of the MMTNS-1-coated foam were higher than those of the MMTNS-2-coated foam, revealing that MMTNS-2 was more efficient than MMTNS-1 in suppressing the flammability of the FPU foam. Similar results could also be obtained from the total heat release (THR) curves, because the THR decrement between control and MMTNS-2-coated foam was twice the THR decrement between control and MMTNS-1-coated foam (the table inserted in Figure 6b). Polymers 2018, 10, x FOR PEER REVIEW 9 of 13 foam was twice the THR decrement between control and MMTNS-1-coated foam (the table inserted in Figure 6b). ...
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... results could also be obtained from the total heat release (THR) curves, because the THR decrement between control and MMTNS-2-coated foam was twice the THR decrement between control and MMTNS-1-coated foam (the table inserted in Figure 6b). Polymers 2018, 10, x FOR PEER REVIEW 9 of 13 foam was twice the THR decrement between control and MMTNS-1-coated foam (the table inserted in Figure 6b). ...
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Citations
... Each positive-negative pairing layer is named a bilayer (BL) [10][11][12]. To date, various polyelectrolytes such as chitosan [13][14][15][16][17][18][19][20], alginate [20][21][22], poly(vinyl sulfonic acid) [11], lignosulfonate [19], poly (allylamine hydrochloride) [23], poly(sodium phosphate) [23], poly (allylamine diphosphonate) [10], and poly(phosphoric acid) [24]) and nanostructures including carbon fibers (CNFs) [12], graphene oxide (GO) [13,20,25], carbon nanotubes (CNTs) [26,27], titanate nanotubes [28], layered double hydroxides (LDHs) [29,30], and clays [14-18, 21, 31]) have been utilized to enhance the fire properties of polyurethane foams by the LbL assembly technique. ...
... 26 After the exfoliation process, the 2D clay nanosheets can not only completely retain the natural superior thermal/chemical stability properties of the precursor minerals but also fully expose the interlayer active sites and gain a higher specific surface area. 27 Rationally, various 2D clay nanosheet-based functional materials can be reassembled in a controlled manner after delamination for their application in the fields of safety science, 28 environmental remediation, 29 energy storage, 30 etc. For the nanofluidic devices, researchers have used the typical clays of montmorillonite and vermiculite, with which nanofluidic channel membranes of extraordinary thermal stability could be prepared. ...
... Song et al. observed that thinner MMT nanosheet membranes were more efficient in terms of the flame retardancy of PU foam. 131 Wei et al. also reported improvements in the thermal properties of highly flammable cellulose microcrystals (sisal fiber) after coating of chitosan and MMT layers. 132 Furthermore, the flame retardant properties of the MMT and rGO (MMT-rGO) membrane prepared by the vacuumassisted self-assembly process were reported by Liu et al. 133 As shown in Figure 20a, when the MMT-G was subjected to an open flame, it burned in a flash due to the presence of residual oxygen groups. ...
... e l s e v i e r . c o m / l o c a t e / a p a c o u s t molecular weight, and formulation [8,[14][15][16]. Despite their extensive applications, there are concerns regarding the disadvantages of PUFs, like low thermal stability, combustibility, and low mechanical strength. ...
The present study aimed to focus on improving acoustic and mechanical characteristics by embedding the polyurethane foam (PUF) with the rock wool fibers (RWF) of diverse values (0–3 wt%) that were synthesized using the polymerization process. In addition, the association between non-acoustical parameters and sound absorption characteristics of the porous polyurethane foams was investigated. Moreover, indicators of effective non-acoustic parameters, including air-flow resistance (AFR), porosity, volumetric density, and microstructure were determined. The results showed sound absorption properties were highly enhanced when polyurethane composite foam (PUF/RWF) (i.e. 1, 2, and 3 wt%) were used, as compared to the pristine PUF. Furthermore, the sound absorption coefficient (SAC) of PUF composite was highly enhanced in the frequency range of 400 to 1600 Hz when the foam was combined with an RWF amount of 2 wt%. Besides, the density and AFR increased with the addition of different contents of RWF. Open porosity composite foams strongly depended on AFR and volumetric density (i.e. a negative association with RWF content). The use of the excessive amount of the RWF (RWF > 2 wt%) caused intramolecular agglomeration, which resulted in reduced sound absorption efficiency. Finally, multiple regression analysis was used to investigate the association between SAC and non-acoustic parameters, including AFR, porosity, volumetric density, and RWF amount, which revealed a well proportion between experimental data and statistical analysis.
... When pH was increased to 6, conformations were more globular, thickening the layers and doubled the mass gain during coating. Moreover, it enabled better clay dispersion, which is very important for the performance of coating [201]. As a result, the coating created an almost complete gas barrier decreasing when 30 bilayers were assembled, which enhanced the flame retardancy effect. ...
Polyurethanes are a very important group of polymers with an extensive range of applications in different branches of industry. In the form of foams, they are mainly used in bedding, furniture, building, construction, and automotive sectors. Due to human safety reasons, these applications require an appropriate level of flame retardance, often required by various law regulations. Nevertheless, without the proper modifications, polyurethane foams are easily ignitable, highly flammable, and generate an enormous amount of smoke during combustion. Therefore, proper modifications or additives should be introduced to reduce their flammability. Except for the most popular phosphorus-, halogen-, or nitrogen-containing flame retardants, promising results were noted for the application of clays. Due to their small particle size and flake-like shape, they induce a "labyrinth effect" inside the foam, resulting in the delay of decomposition onset, reduction of smoke generation, and inhibition of heat, gas, and mass transfer. Moreover, clays can be easily modified with different organic compounds or used along with conventional flame retardants. Such an approach may often result in the synergy effect, which provides the exceptional reduction of foams' flammability. This paper summarizes the literature reports related to the applications of clays in the reduction of polyurethane foams' flammability, either by their incorporation as a nano-filler or by preparation of coatings.
... Chen et al. [76] prepared chitosan-montmorillonite membrane structures with different thicknesses on FPUF and tested their flame retardant properties. It was found that chitosan-montmorillonite coatings can significantly improve the flame retardancy of FPUF, and the thin chitosan-montmorillonite coatings have more montmorillonite and better flame retardancy. ...
... The thermal shielding membranes usually use montmorillonite (MMT) or vermiculite (VMT) as flameretardant material, which can be tightly attached to the surface of the foam, thus greatly limiting the translation of heat, oxygen and volatile gases. As displayed in Fig. 17, the dense CS/MMT membrane is formed on the surface of the FPUF [76]. The decrease in heat conduction and of oxygen permeation delay the pyrolysis of FPUF, thereby reducing the flammability of FPUF. ...
... The flame-retardant mechanism of two-dimensional nanosheet materials is basically the same, Figure 17 Schematic diagram of the flame-retardant mechanism of the CS/MMT coating. Reprinted with permission from Chen et al. [76]. ...
Flexible polyurethane foam (FPUF) has many advantages such as lightweight, low density and high specific strength and is widely used in furniture, automobile industry, construction and transportation. However, FPUF is extremely flammable in the air, and a large amount of toxic gas will be generated when it is burned. The fire protection technology of FPUF has attracted more and more attention. Generally, it is an effective method to improve fire protection of FPUF by introducing additive flame retardant. As a relatively new approach, layer-by-layer (LBL) self-assembly technology is widely used in research fields such as biology, materials and nanoscience. In this work, the research and application of LBL self-assembly technology in the field of flame-retardant FPUF were described, and zero-dimensional, one-dimensional, two-dimensional nanomaterials, one- and two-dimensional nanocomposites systems and other self-assembly systems in flame-retardant FPUF were introduced in detail. The flame-retardant mechanism of flame-retardant FPUF systems was also systematically analyzed, and finally, the development of LBL self-assembly technology in flame-retardant FPUF was prospected.
... ere are various methods that have been used to realize flame-retardant polymer/montmorillonite nanocomposites, including intercalation, synergy, organic modification, hybridization, layer-by-layer assembly, and self-assembly [134][135][136][137][138][139][140][141][142][143][144][145][146][147][148][149][150][151][152]. Inspired by nacre, Xie et al. [151] developed a super-efficient fire-safe nanocoating based on carboxymethyl chitosan and modified MMT via one-step self-assembly. ...
Polymer materials are ubiquitous in daily life. While polymers are often convenient and helpful, their properties often obscure the fire hazards they may pose. Therefore, it is of great significance in terms of safety to study the flame retardant properties of polymers while still maintaining their optimal performance. Current literature shows that although traditional flame retardants can satisfy the requirements of polymer flame retardancy, due to increases in product requirements in industry, including requirements for durability, mechanical properties, and environmental friendliness, it is imperative to develop a new generation of flame retardants. In recent years, the preparation of modified two-dimensional nanomaterials as flame retardants has attracted wide attention in the field. Due to their unique layered structures, two-dimensional nanomaterials can generally improve the mechanical properties of polymers via uniform dispersion, and they can form effective physical barriers in a matrix to improve the thermal stability of polymers. For polymer applications in specialized fields, different two-dimensional nanomaterials have potential conductivity, high thermal conductivity, catalytic activity, and antiultraviolet abilities, which can meet the flame retardant requirements of polymers and allow their use in specific applications. In this review, the current research status of two-dimensional nanomaterials as flame retardants is discussed, as well as a mechanism of how they can be applied for reducing the flammability of polymers.
... Compared with a rigid polyurethane foam, it has more diversied applications as a thermal barrier in the appliance industry and as a cushioning material; moreover, it can be used in mattresses, heat insulation pipes, automobile interiors, energy absorption, oil/heavy metal adsorption, vibration-proof packaging, construction, decoration, building roofs, and ltration. [1][2][3][4][5] The most potential hazard of FPUF is its ammability. Neat FPUF is combustible, and its LOI is lower than 19. ...
Compared with a rigid polyurethane foam, a flexible polyurethane foam (FPUF) has more diversified applications including filtration, sound absorption, vibration-proofing, decoration, packaging, and heat insulation. However, its most potential hazard is flammability. Therefore, in this study, we focused on improving its flame retardation and then tested its sound absorption with the addition of nitrogen/phosphorus synergistic flame retardants. The influence of phosphorus-based flame retardants (TCPP, TDCP, and V6) and a nitrogen/phosphorus synergistic flame retardant (melamine-TDCP) on its microstructure, compressive stress, sound absorption, thermal stability, and flame retardation was systematically explored. The presence of phosphorus flame retardants improved the sound absorption but considerably decreased the mechanical properties. The melamine-TDCP compound flame retardant delivered smaller cells and thus increased the compression property of the resulting foam. Moreover, with a higher content of melamine, the initial mass-loss temperature also increased. In particular, on using TDCP and 5 wt% of melamine as flame retardants, the compressive stress increased by 3.4 times, the average sound absorption coefficient was 0.45, and LOI reached 25.5, which met the requirements of industrial flame retardant/sound absorbent materials. This resultant flame retardant/sound absorbent flexible polyurethane foam can serve as a mattress and furniture pad material, vehicle seat cushion material, and liner for laminated composites in the future.
... Lu et al. [27] studied the influence of aspect ratio on barrier properties of polymer-clay nanocomposites, and the results showed that the barrier properties and mechanical properties would enhance more with the aspect ratio of nanosheets increasing. Recently, it was found that MMT nanosheets membrane with high aspect ratio could efficiently reduce flammability of flexible polyurethane (FPU) foam [28]. Besides, Chen et al. [29] successfully prepared the MMT nanosheets with different aspect ratios combined freezing/thawing with ultrasonic exfoliation method. ...
... All the measurements are performed with 10 −3 mol/L KCl background electrolyte. As can be seen, all zeta potentials of MMT nanosheets suspensions are negative, which is similar to former studies [28,30,34]. Fig. 5a showed that the zeta potential peak of MMT nanosheets with low aspect ratio was located at −24.6 mV. ...
... Wang et al. [22] have found that the negative zeta potential of MMT nanosheets plays an important part in fabricating steady hydrogel beads. Moreover, it has been reported that the surface electronegativity is very important for the layer-by layer (LBL) assembly, and the electrostatic attraction between the chitosan chain and MMT nanosheets would be greater with the negative zeta potential of MMT nanosheets increasing by Chen and co-workers [28]. Thus, MMT nanosheets will have better applications as the negative zeta potential increases. ...
Montmorillonite (MMT) is easily exfoliated to two-dimensional nanosheets for making multifunctional nanocomposite materials. In this work, exfoliated MMT nanosheets have been studied in order to understand the correlation of the aspect ratio with the colloidal properties. The nanosheets with various aspect ratios were prepared through controlling the number of the freezing thawing cycles and the power of the ultrasonic exfoliation, and the colloidal properties were determined through the measurements of atomic force microscope (AFM), zeta potential, acid-base back-titration, viscosity and turbidity. It has been shown that as the aspect ratio increased, the negative zeta potential of MMT nanosheets increased, and the active sites with H+ or OH− on the surfaces decreased, indicating that the MMT nanosheets with lower aspect ratio were easier to coagulate. Meanwhile, the viscosity of the MMT suspensions at high shear rate increased with increasing the aspect ratio. It suggests that the aspect ratio has a strong effect on the colloidal properties of MMT nanosheets, which might be helpful of the applications of MMT nanosheets in functional nanocomposite areas. Keywords: Montmorillonite nanosheets, Aspect ratio, Zeta potential distribution, Rheology
