Effects of Specimen Holder Configurations on the Combustion Characteristics of PMMA in a Cone Calorimeter

This study compared the combustion characteristics of black poly (methyl methacrylate) (PMMA) for different specimen holder configurations using an ISO 5660-1-based cone calorimeter. Identical PMMA specimens were tested using a standard holder with a retainer frame and a modified holder without a retainer frame, in which the specimen was surrounded by a ceramic fiber board and its entire upper surface was exposed. The tests were conducted at an external heat flux of 20–50 kW/m2. The ignition times were similar for both holders; however, the burning duration of the modified holder decreased by approximately 55.7% and 56.5% at 20 and 50 kW/m2, respectively. The mass loss rate and heat release rate were higher for the modified holder, and the differences remained after normalization to the exposed area, as shown by the MLRPUA and HRRPUA. By contrast, the total heat release was similar for both holders, whereas the THRPUA of the modified holder was approximately 12.2% lower than that of the standard holder, primarily reflecting normalization by its larger exposed area. The effective heat of combustion was approximately 7.8% lower for the modified holder. These results indicate that cone calorimeter measurements should be compared and interpreted by considering the overall specimen holder configuration, including the exposed area, retainer frame, and surrounding thermal boundary conditions.