Cone calorimeter: Initial experiences of calibration and use

Abstract

The primary objectives after taking delivery of a cone calorimeter were to develop operator skills and to establish the reliability, accuracy and repeatability of the instrument. Since the instrument would be used with a wide range of plastics and rubber materials, for research and development of materials and additives, and also for routine tests, it was necessary to establish the effect of instrument variables on test data and of possible instrument/material interactions. Cast, thick, black polymethyl methacrylate (PMMA) sheet is an ideal calibration material. Attempts to obtain this type of material in usable quantities were unsuccessful and tests were carried out using various adhesives to construct a thermally thick speciment. Alternative systems based on thin black PMMA and transparent PMMA sheets were also evaluated. The cone calorimeter has shown itself to be an extremely useful instrument capable of determining basic fire parameters under present heat flux conditions. Test repeatability can be extremely good depending on the material and test regime. Considerable care is required to interpret data since relatively few materials show pseudo-steady-state burning and data may depend on the selected test end point, sample preparation and size. Difficulties arise with the testing of certain types of materials and products which swell, shrink or melt. These can be accommodated from the research point of view but may present difficulties for the simple comparison or possible specification of end-use products comprising materials of dissimilar behaviour.