Influence of the Expandable Graphite on the Thermal properties of a Rigid Polyurethane Foam for construction

Abstract

In this paper, low-combustible composites were made by adding 0.8-25 wt% of expandable graphite to rigid polyurethane foams (PUF) to ensure effective and safe usage of building materials made of PUFs. Thermal gravimetric analysis (TGA) was used to study thermal properties and effectiveness of the resulting low-combustible composites in construction. The analysis of TGA curves of the studied composites can be interpreted as a two-stage process: acid-catalyzed degradation of PUF and formation of an intumescent char layer. A dense intumescent layer can provide an effective prevention of heat transfer. The paper showed that the addition of 25 wt% of expandable graphite to PUF composite improved the thermal stability by 8°C, as compared to starting PUF, while the residue was 36.2 wt% at 600°C, which was higher by approximately 16 wt% than the residue of starting PUF. So, the sample with 25 % loading of expandable graphite in rigid PUF composite showed the best thermal characteristics.