Thermal response characteristics of fire blanket materials

摘要

The thermal response characteristics of over 50 relatively thin (0.15-3.7 mm) fire blanket materials from four different fiber groups (aramid, fiberglass, amorphous silica, and pre-oxidized carbon) and their composites have been investigated. A plain or coated fabric sample was subjected to a predominantly convective or radiant heat flux (up to 84kW/m~2) using a Meker burner and a cone heater, respectively. In addition to conventional thermal protective performance ratings for protective clothing, two transient thermal response times (for the fabric back-side temperature to reach 300 ℃ and for the through-the-fabric heat flux to reach 13kW/m~2) and a steady-state heat-blocking efficiency (HBE) were introduced for both convective and radiant heat sources. For most woven fabrics, the HBE values were approximately 70±10% for both convection and radiation and only mildly increased with the fabric thickness or the incident heat flux. Nonwoven (felt) fabrics with low thermal conductivity exhibited significantly better insulation (up to 87%) against convective heat. Highly reflective aluminized materials exhibited exceptionally high HBE values (up to 98%) for radiation, whereas carbon and charred aramid fabrics showed lower HBEs (down to 50%) because of efficient radiation absorption. A relatively thin fire blanket operating at high temperatures can efficiently block heat from a convective source by radiative emission (enhanced by its T~4-dependence and high surface emissivity) coupled with thermal insulation and from a radiant heat source by surface reflection while the aluminum surface layer remains.