Flammability reduction of flexible polyurethane foams via carbon nanofiber network formation

Zammarano, Mauro; Krämer, Roland H.; Harris, Richard H.; Ohlemiller, Thomas J.; Shields, John R.; Rahatekar, Sameer S.; Lacerda, Silvia H. De Paoli; Gilman, Jeffrey W.

doi:10.1002/pat.1111

Cited by 97 publications

(71 citation statements)

References 21 publications

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“…This simply indicates that the oxygen on the nanofiber surface does not positively or negatively affect nanofiller dispersion in epoxy, something which has been confirmed by TEM and SEM of the base resin system in this paper [19]. When considering the network structure needed to reduce mass loss rate and subsequently peak HRR reported by Kashiwagi and others [20,21], it is clear that the nanofibers in the composites discussed here have not set up enough of a network structure, even if it was well dispersed, to reduce flammability further and therefore, the nanofiber has minimal effects on reducing the flammability of these composites.…”

Section: Bisphenol F Epoxy Composites: Effects Of Carbon Nanofiber (Nsupporting

confidence: 74%

Cone calorimeter testing of S2 glass reinforced polymer composites

et al. 2009

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SUMMARYWith the ever increasing demand for fuel savings on vehicles, there is a strong push to replace metal with polymeric + fiber (carbon/glass) composites. However, the replacement of metal with polymeric composites can lead to additional fire risk. Our study focused on glass fiber reinforced polymer composites meant for vehicular structural applications, and flammability performance of these composites was studied by cone calorimetery. The effects of fiberglass loading, nanocomposite use (clay, carbon nanofiber) and polymer type (epoxy, phenolic) were studied under a heat flux of 50 kW/m 2 to better understand the potential effects that these variables would have on material flammability. It was found that as fiberglass loading increased, flammability decreased, but at a cost to structural integrity of the residual polymer + fiber char. The use of nanocomposites has little effect on reducing flammability in this set of samples, but the use of phenolic resins in comparison with epoxy resins was found to yield the greatest improvements in flammability performance. Further, the phenolic system yielded a higher level of structural integrity to the final polymer + fiberglass char when compared with the other polymer systems of low heat release.

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Section: Bisphenol F Epoxy Composites: Effects Of Carbon Nanofiber (Nsupporting

confidence: 74%

Cone calorimeter testing of S2 glass reinforced polymer composites

et al. 2009

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“…Our results will have relevance to any application that requires efficient and rapid flow processing of CNT fluids or melt composites, such as effectively designing processing conditions for achieving electrically conductive networks of CNTs in a polymer matrix, [33] as well as any application that requires microscale confinement of CNTnetworks, such as flame-resistant polymer foams. [34] The overall conclusions will also be relevant in CNTs with chemical surface treatment or surfactant coatings, provided the effective interparticle potential is attractive in the short range.…”

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confidence: 98%

Length‐Dependent Mechanics of Carbon‐Nanotube Networks

et al. 2009

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Fibrous networks comprise a range of materials, from F-actin and tubulin, in eukaryotic cells, [1][2][3] to cellulose, in paper. [4] In the last decade, carbon nanotubes (CNTs) have emerged as a technologically important class of fibers, with nanoscale dimensions of width but micro-to macroscopic dimensions of length. CNT networks enhance the strength, [5,6] conductivity, [7][8][9] and flame resistance [10] of polymer composites, and have a spectacular effect on the rheology of CNT suspensions. [11][12][13][14][15][16][17] With recent progress in the ability to control CNT length, aspect ratio, defined as the ratio L/d, where L is nanotube length and d is diameter, has emerged as a key parameter in determining CNT percolation, [6,7] optical response, [18] toxicity, [19,20] and flow alignment. [21,22] Although in most commercial applications the network forming attributes of CNTs are critical, the influence of aspect ratio on the mechanics of such networks has received only limited attention. Here, we measure the length-dependent mechanics of CNT networks, and demonstrate a cross-over from strain-induced deformation governed by aggregates of short rigid nanorods to that governed by individual long semi-flexible nanotubes. Our results are in agreement with simple scaling arguments, and suggest that short CNTs can provide the same network forming attributes as long CNTs at slightly higher concentrations, but with significantly improved flow processability due to a substantially lower network yield stress. Our results have important implications for the efficient flow processing of CNT fluids and composites. We use two distinct batches of multiwalled CNTs (MWNTs) grown under the same conditions in the same reactor, [23] with uniform diameter distribution, around 50 nm, and ''short'' (L ¼ 4 mm) and ''long'' (L ¼ 60 mm) lengths, where the former are obtained by sonicating the initially long MWNTs in solution for an extended period of time. The insets to Figure 1 show scanning electron microscopy (SEM) images of the as-grown MWNTs from two different perspectives prior to dispersion in the Newtonian epoxy solvent. No surfactant was used, as this reduces the electrical conductivity of the network by several orders of magnitude.[24] The suspensions prepared in this way have conductivities of 0.1 (V m) À1 at 0.1% CNT. Suspensions were prepared with 0.015% < f < 2% and 0.015% < f < 7% for the long and short MWNTs, respectively, where f is the nanotube mass fraction. These concentrations correspond to a wide range of semidilute to concentrated regimes, [25] implying significant overlap and mechanical entanglement. To measure the network morphology, we used small-angle neutron scattering (SANS) and ultrasmall-angle neutron scattering (USANS), as shown in Figure 1. Scaling the scattering intensity by f collapses each data set onto a single curve, suggesting that the nature of the nanotube structure is relatively independent of concentration. Both the short and long nanotubes show Q À4 behavior, at large scattered wave-vector (Q...

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“…The Cone heat release curves and data ( Figure 8 and The only other reported reduction of PUF using CNFs measured a 35% reduction in PHRR by incorporating 4 mass fraction % CNF into the PUF (CNFs were added to the foam recipe). [40] In comparison, the LBL fabricated CNF coated PUF specimen had a 20% greater reduction in PHRR using 57 mass fraction % less CNFs. In other words, incorporating CNF as a coating rather than into the polyurethane will have a significantly greater reduction in the PUF flammability.…”

Section: Cnf/puf Fire Performancementioning

confidence: 92%

“…Compared to carbon nanotubes (CNT), CNFs can be at least an order of magnitude larger with a diameter and length in the range of 5 nm to 300 nm and 0.1 µm to 1000 µm, respectively. Due to the intrinsic electrical, thermal, and mechanical properties of CNFs, the thermal and electrical conductivity, tensile and compressive strength, ablation resistance, damping properties, and flammability of polymers [40] have been significantly altered with incorporation of CNF [41].…”

Section: Introductionmentioning

confidence: 99%

“…Zammarano recently reported a reduction in PUF flammability by the incorporation of CNFs directly into the polyurethane matrix [40]. At a 4 mass fraction % CNFs loading, the CNFs formed a network structure that reduced the peak heat release rate (PHRR) by 35% and prevented melt dripping, which in a real fire scenario, could result in an additional 30% reduction in PHRR.…”

Section: Introductionmentioning

confidence: 99%

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Fabrication, characterization and flammability testing of carbon nanofiber layer-by-layer coated polyurethane foam

Davis¹,

Kim²

2010

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This is the first reported use of Layer-by-Layer (LBL) assembly to fabricate thin film coatings on polyurethane foam, of incorporating carbon nanofibers (CNF) into LBL fabricated coatings, and of using LBL fabricated coatings to reduce the flammability of polyurethane foam. The (359 ± 36) nm thick four bilayer coating of polyethyleneimine/CNF (cationic layer) and poly(acrylic acid) (anionic layer) contained (50.9 ± 0.1) mass fraction % CNF. This CNF coating covered the entire internal and external surfaces of the porous foam. The distribution of the CNFs was nonuniform on the microscale with regions of large CNF aggregation to regions with individual CNFs and isolated regions that appeared to contain no CNFs. Even though the microscopic CNF distribution was non-uniform, the macroscopic CNF network armor that was generated from this LBL process significantly reduced the flammability of the foam; i.e., 55% ± 6% reduction in total heat release and peak heat release rate. This reduction caused by the CNF coating is 50% better than previously reported by incorporating twice as much CNFs directly into the foam and 12% to 47% greater than other technologies currently used to reduce foam flammability.

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Flammability reduction of flexible polyurethane foams via carbon nanofiber network formation

Cited by 97 publications

References 21 publications

Cone calorimeter testing of S2 glass reinforced polymer composites

Cone calorimeter testing of S2 glass reinforced polymer composites

Length‐Dependent Mechanics of Carbon‐Nanotube Networks

Fabrication, characterization and flammability testing of carbon nanofiber layer-by-layer coated polyurethane foam

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