Fire performance of closed-cell charring insulation materials in plasterboard-insulation assemblies

Abstract

This paper presents an experimental study on the fire performance of two types of plastic charring insulation materials when covered by a plasterboard lining. The specific insulation materials correspond to rigid closed-cell plastic foams, a type of polyisocyanurate (foam A) and a type of phenolic foam (foam B), whose thermal decomposition and flammability were characterised in previous studies. The assemblies were instrumented with thermocouples. The plasterboard facing was subjected to constant levels of irradiation of 15, 25, and 65 kW m using the heat-transfer rate inducing system. These experiments serve as (1) an assessment of the fire behaviour of these materials studied at the assembly scale and (2) an identification of the fire hazards that these systems pose in building construction. The manifestation of the hazards occurred via initial pyrolysis reactions and release of volatiles followed by various complex behaviours including char oxidation (smouldering), cracking, and expansion of the foam. Gas-phase conditions may support ignition of the volatiles, sustained burning, and ultimately spread of the flame through the unexposed insulation face. The results presented herein are used to validate the insulation “critical temperature” concept used for a performance-based methodology focused on the selection of suitable thermal barriers for flammable insulation.