Sub‐micrometre coatings as an infrared mirror: A new route to flame retardancy

Abstract

SUMMARY Most of the polymeric materials used are easy to ignite and show extensive flame spread along their surfaces. Apart from extensive heat release rates, their short time to ignition (tig), in particular, is a key fire hazard. Preventing ignition eliminates fire hazards completely. Protection layers that shift tig by more than an order of magnitude are powerful flame retardancy approaches presenting an alternative to the usual flame retardancy concepts. Coatings are proposed that consist of a three‐layer system to ensure adhesion to the substrate, acting as an infrared (IR) mirror and protecting against oxidation. The IR‐mirror layer stack is realised by physical vapour deposition in the sub‐micrometre (<1 µm) range, reducing heat absorption by up to an order of magnitude. Not only is the ease of ignition diminished (tig is increased by several minutes), the flame spread and fire growth indices are also remarkably reduced to as little as 1/10 of the values of the uncoated polymers open for further optimization. Sub‐micrometre thin IR‐mirror coatings yielding surface absorptivity <0.1 are proposed as a novel and innovative flame retardancy approach. Copyright © 2011 John Wiley & Sons, Ltd.

Influence of multiwall carbon nanotube (MWCNT) dispersion on ignition of poly(dimethylsiloxane)–MWCNT composites

“…Schartel et al have shown that a coating acting as an infrared mirror can be a powerful strategy to delay ignition. [11] Flame retardancy of an epoxy resin nanocomposite was assigned to higher reradiation due to high emissivity of the thermally stable barrier layer. [12] High reflectance of SWNT and poly(acrylonitrile-co-methacrylate)-SWNT films was measured by Bellayer et al [13] This result is somewhat surprising because it should lead to higher time-to-ignition, in contradiction with many results.…”

Electronic structure and photoluminescence properties of Zn-ion implanted silica glass before and after thermal annealing

“…Si 24 (3) where the first step is an insertion of the interstitial impurity that is over 5 eV energetically favorable with respect to the substitutional defect (Fig. 5).…”

“…Technological application of SiO 2 (both in crystalline and amorphous phases) actually is not limited with the use of only stoichiometric forms of silicon dioxide -also doped SiO x (where x < 2) polymorphs are employed for passivation coatings and interlayers in microelectronics [1][2], low-index mid-infrared protecting coatings for mirrors [3], etc.…”

“…It is not surprising, because the understanding of Zn-ion incorporation process is the point for controlled modification of key electronic properties for SiO 2 :Zn system that might be employed in the fields of photovoltaics, light-emitting/laser applications, optoelectronics, etc. An accumulated data reported previously [2][3][4][5][6][7][8] allow to conclude that most of technologists are using thermal annealing in the range of temperatures from 600 o C up to 700 o C after Zn-ion embedding process in order to obtain the defect-free high-quality Zn-doped SiO 2 . But these recent results seem far away from being perfect -i.e.…”

Spectrally selective and adaptive surfaces for protection against radiative heating: ITO and VO2

“…Another approach, to increase the reflection of radiative heat from a surface, is to apply a thin coating to the surface. In a recent publication by Schartel et al [8], polycarbonate and polyamide specimens are coated with thin layers whereof the middle is a 0.5-mm thick highly IR-reflecting bulk Cu layer. Theoretical calculations show that the effective absorptivity for radiation from a blackbody at 1300 K is as low as 3%, which is extraordinarily good from a fire safety point of view.…”