Thermal Protection Studies of Plastic Films and Fibrous Materials

An experimental method of radiant heating was used to study the thermal protection properties of certain film and woven materials. Samples of these, placed in front of fiberglass batting containing a phenolic resin, were exposed to a radiant heat flux of 5 W/cm² and the resin mass loss as a function of time indicated the thermal protective effectiveness of the film or woven material for the bare fiberglass insulation. The materials tested included aluminized and unaluminized synthetic plastic films and fibrous materials like silicon carbide and phenolic novolac. The yield strength of selected aluminized plastics at tem peratures ranging from room temperature to 260°C was also measured.

Aluminized polyimide (KAPTON®) was shown to be an effective light weight heat shield exhibiting the lowest weight loss in the assembly and most favorable stress-strain properties. Polyetheretherketone (PEEK) and poly etherimide (ULTEM®) were somewhat less satisfactory than KAPTON®, mainly for reasons of mechanical failure at high temperatures. Aluminized polyester (MYLAR®) and polyvinylfluoride (TEDLAR®) were severely ther mally damaged by the radiant energy and the observed weight loss came from both the film and the phenolic resin contained in the fiberglass. Poly benzimidazole (PBI) film, while not thermally damaged, also lost weight when exposed to the same radiant heat source, but we attribute this to bound water released upon heating. For the fibrous materials, aluminized woven silicon car bide (NICALON®) was better than an aluminized phenolic novolac (KYNOL®) in reducing the resin weight loss of the fiberglass insulation.