Characterising fundamental fire protection performance of intumescent coating under realistic fire conditions

Over 70% of commercial buildings in the UK are steel framed and intumescent coating now accounts for more than 50% of the steel structure fire protection market. However, the fire protection properties of intumescent coating under realistic fire conditions are not known because assessment of their fire protection performance is based on the so-called standard fire resistance tests in which the fire exposure bears no relation to realistic fire conditions. Intumescent coating is a reactive material and its properties are highly dependent on the fire exposure type so using the standard fire resistance test to assess its performance is not valid. This problem has become acute because fire safety design is now moving away from prescriptive design under the standard fire condition to performance based design which allows for realistic fire conditions. In addition, under performance based design, much of the redundancy in fire protection to steel structures is now being removed to reduce construction cost. It is therefore important that the critical fire protection materials perform as intended under realistic fire conditions. Performance based fire safety design is a technology advance. In order to help the construction industry to safetly exploit advances in this new technology, the proposed research will develop a rational method of characterising the fire protection performance of intumescent coating under realistic fire conditions. The proposed research will involve extensive testing of a number of intumescent coating products exposed to a range of heating conditions under a cone calorimeter and in furnace and will be carried out with substantial contributions from the UK's two largest intumescent coating manufacturers who will provide relevant industrial advice, free test samples and TGA test results. Analysis will be performed to establish a procedure to extract the following key fire protection properties of intumescent coating: chemical reaction kinetics constants (from TGA data), maximum rate of expansion (from an understanding of the duration of time available for intumescing), void volume and equivalent void size (from mass loss, rate of expansion and heat transfer analysis). This proposed research aims to validate the hypothesis that the above key properties extracted from a small set of fire tests can be applied to other fire conditions. Some preliminary work has already been done in a PhD project supervised by the proposers to demonstrate the feasibility of the proposed methodology. The proposed research will investigate wide applicability of the method, by investigating different intumescent coating products under different fire conditions and will develop a robust protocol to reliably extract the key fire protection performance properties of intumescent coating under realistic fire conditions.