Physical Approach to the Combustion Process of Polymer Fibre-Based Insulation Materials: An Initial Experimental Study

The flammability of building materials and products is expressed by the reaction to fire class according to the European standard EN 13501-1. However, the procedures described in this technical standard and in the related test standards do not fully reflect the physical and chemical principles of combustion. Especially in the area of lower classes B–F, the methodology is based on empirical principles, which makes it relatively very complicated to use the test results in the development of new insulation materials and predict their behaviour. This paper presents the initial phase of research that approaches combustion from a building-physics perspective at the scale of the fibre microstructure. In the case of insulation materials based on polymer fibres (very often based on recycled textile fibres), the situation is very complicated because, in most cases, the reaction to fire is given by combination of physical and chemical processes under contact of material with the flame. Rather than proposing a complete predictive model, this study formulates the basic governing relationships and reports the first experimental results, which will serve as the basis for a comprehensive model developed within the follow-up research. Single-flame-source tests (EN ISO 11925-2), combined with microstructural, calorimetric and airflow-resistivity measurements, established basic relationships between the observed flame behaviour and parameters such as fibre type, thickness and bulk density. The main observation is a clear ignition/no-ignition dichotomy between primary fibres (which melted and withdrew from the flame without igniting) and recycled fibres (which ignited), showing that neither the heat of combustion alone nor a purely physical description is sufficient—both physical and chemical aspects must be considered.