Novel flame retardant flexible polyurethane foam: plasma induced graft-polymerization of phosphonates

Abstract

Flame retardancy of flexible polyurethane foams has become an issue due to very severe regulations. To overcome the challenge of incorporating flame retardant (FR) additives during the foaming process without altering the foam properties, a plasma surface treatment was used for the first time in this work: a cold plasma induced graft-polymerization of phosphonate containing precursors (diethylvinylphosphonate-DEVP) with or without a crosslinking agent (1,4 butanedioldiacrylate) was applied on open cell flexible polyurethane foams (PUF). The flame retardant properties of these foams,before and after further rinsing, were evaluated using horizontal UL-94 test for 10 s and 60 s. One of the tested systems (DEVP + crosslinker), even after sonication, completely stops the melt dripping of the foams when exposed to the flame of the butane torch and charring occurs. This efficient surface treatment was characterized before and after burning by Scanning Electron Microscopy (SEM), electron probe microanalysis (EPMA), 31 P solid state NMR and X-ray Photoelectron Spectroscopy (XPS). Its FR mechanism of action was then further investigated using microscale combustion calorimetry (MCC), thermogravimetric analyses coupled with infrared Fourier transform spectroscopy (TGA-FTIR), pyrolysis gas-chromatography coupled with mass spectrometry (GC-MS pyrolysis) and 31 P solid state NMR. The results obtained show that it is necessary (i) to use the crosslinking agent, as DEVP mainly reacts with this crosslinker and (ii) to activate the PU foam before graft-polymerization to promote further reaction with the crosslinker. The characterizations also proved that before sonication, non-reacted DEVP precursors mainly act in the gas phase, preventing ignition, whereas after sonication the covalently grafted phosphorus containing species mainly act in the condensed phase to form phosphonic acid which will promote charring and thus will limit dripping and flame spread.

Microintumescent mechanism of flame‐retardant water‐based chitosan–ammonium polyphosphate multilayer nanocoating on cotton fabric

“…Pyrolysis‐GC/MS is an accurate tool to identify the nature of gases released during the thermal decomposition of a material and its utility to elucidate FR mechanisms has been proven many times . The system used was purchased from Shimadzu (Tokyo, Japan) and has a Frontier Lab PY‐2020iD micro‐furnace pyrolyzer (Fukushima, Japan), a gas chromatograph (equipped with a capillary column), and a quadrupole mass spectrometer [equipped with an Electron‐Impact (EI) ionization source (Shimadzu GC/MS QP2010 SE)], all directly connected in series.…”

Activated carbons for applications in catalysis: the point of view of a physical-chemist

“…On the contrary, the resonance at 14.1 ppm is attributed to phosphonates, i.e. organo-phosphorous compounds containing one P-C bond, revealing that at least a fraction of phosphorous has functionalized the carbon (Benaddi et al 1998;Budinova et al 2006;Jimenez et al 2015;Puziy et al 2002;Puziy et al 2008;Sadykova et al 2015).…”

A flame‐retardant composite foam: foaming polyurethane in melamine formaldehyde foam skeleton

“…The former technology is simple and many commercial FRs can be selected, but this easily brings about deterioration of mechanical properties due to the poor compatibility of FRs with PU resin . The latter is free of such problems, but usually involves greater efforts to develop a new prepolymer containing flame‐retardant elements . For instance, Rao et al .…”