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Untreated polyurethane flexible foams (PUFs) are prone to rapid fire growth due to their low density and low thermal conductivity. Furthermore, the low viscosity of the decomposition products generates severe dripping that increases the fire hazard related to the combustion of PUFs. In fact, this downward flow of flaming liquid often results in a pool‐fire that promotes flame propagation and boosts the rate of heat release (HRR) due to a significant increase in the burning area and to feed‐back between the flame on the pool‐fire and the residual foam. In this work the effect of nanoparticles, i.e., clays and carbon nanofibers (CNFs), on the HRR is investigated with special attention given to melt dripping. A modified cone calorimeter test has been developed for this purpose. It is shown that CNFs form an entangled fiber network which eliminates melt dripping and decreases the HRR. Published in 2008 by John Wiley & Sons, Ltd.

Electrospinning of uniform biohybrid fibers with concealed cellulose microfibrils (CMF) is reported as a promising and environmentally sound concept for reinforcement of polymer nonwoven fiber systems of fine dimensions. The extraction and refinement of the high-strength crystalline microfibril bundles (15−20 nm thick) from bacterial cellulose networks is presented, as well as their morphology prior to and post electrospinning, Nanofibers composed of a poly(methyl methacrylate) (PMMA) matrix with cellulose contents reaching 20 wt % were repeatedly obtained. A high degree of dispersion of the microfibrils was obtained for a variety of CMF contents and the aggregation of the CMF was greatly suppressed as the microfibrils were aligned and rapidly sealed inside the acrylate matrix during the continuous formation of the fibers. The limited CMF aggregation up to 7 wt % was related to a suppressed phase separation caused by the rapid solidification of the polymer solutions during spinning. The fibers’ diameters decreased significantly from ∼1.8 μm (1 wt %) to ∼100 nm (20 wt %) with increasing cellulose contents, resulting in CMF agglomerations and percolating architectures within the acrylate host, which was consistent with microscopy, thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC) evaluations. The nominal content of cellulose in the fibers was assessed by Lorentzian profile fit assignment of the crystalline vs amorphous fractions of the fibers’ X-ray diffractograms. TGA of fibers with low CMF content revealed that both CMF and PMMA showed a significantly improved thermal stability in the composite material. The biohybrid fibers were continuously aligned into an anisotropic nanocomposite yarns from a liquid support during spinning. The strategy described herein may allow for new mechanically robust nonwoven fiber systems, or be used as implemented on existing electrospun formulations that are lacking mechanical integrity. It is envisioned that the cellulose microfibrils may be of importance in biomedical applications where biocompatibility is a requirement.

Phosphorus-containing compounds are added to polymers as fire retardants and they are believed to act in both the gas and solid phase. In gaseous flame studies, they have been shown to be very effective gas-phase flame inhibitors; however, their performance varies with flame type. In particular, their effectiveness in co-flow diffusion flames is much lower than in other flames. To understand this behavior, co-flow diffusion flame experiments have been performed using dimethyl methylphosphonate (DMMP) added to the fuel stream. CO 2 flame extinguishing tests show that phosphorus (via DMMP addition) is much more effective (~4 times) than bromine (Br 2) at low concentrations. At higher concentrations (above ~5000 μL/L), the efficiency ranking is reversed due to saturation of the DMMP inhibition effect, which is not observed in the case of Br 2 addition. The role of particle formation (via condensation of active phosphorus-containing species) in the loss of effectiveness of DMMP is investigated using Rayleigh scattering measurements. In order to understand the behavior of the flame stabilization region that is disrupted during flame extinguishment, premixed burning velocity simulations with detailed kinetics are performed for DMMP or Br 2 addition to the flames.

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