Critical burning conditions for planar layers of PMMA on substrates differing in thickness and conductivity

Abstract

This paper studies the critical conditions for the burning of PMMA planar layers on substrates differing in thickness and thermal conductivity. The experiments were performed by igniting by an electrical spiral horizontal specimens in air at atmospheric pressure and room temperature. Burning completeness and critical layer thickness are determined. The physical meaning of the dependence of delta /SUB cr/ on the thermal conductivity of the PMMA layer and that of the substrate is studied. The data can be summarized by saying that delta /SUB cr/ varies by a factor 6.2, wcr by a factor 12, ucr by a factor 14.7, and A only by a factor two when the density of the PMMA layer varies and also the thermal conductivity and thickness of the substrate vary.