Impact of rendering cover on thermal behavior of graphite-enhanced expanded polystyrene exposed to external radiation

Abstract

This study explores the thermal behavior of graphite-enhanced expanded polystyrene (GEPS) both with and without a rendering cover during cone calorimeter testing. We designed a sample holder with inserted thermocouples to capture temperature variations at different levels. Without a cover, the sample remained unignited under radiant intensity of 25 kW m−2, experiencing a brief temperature rise followed by stabilization. At 50 kW m−2, ignition occurred after a period of steady temperature. However, at 75 kW m−2, the temperature soared rapidly without a stable phase, leading to swift ignition. With a cover, the temperatures for all tested scenarios ultimately stabilized without ignition, even though the recorded values exceeded the ignition point under high heat fluxes. This indicates that the protective mechanism of render lies mainly in isolating mass transfer. Increasing the render's thickness from 3 mm to 5 mm delayed and slowed the initial temperature rise but had little impact on the final steady temperatures. Based on the energy conservation principles, a steady temperature prediction model for liquified GEPS and rendering cover was established. Notably, the calculated outcomes closely align with the measured temperatures. These findings provide valuable insights into the fire safety characteristics of GEPS and the protective effects of rendering covers.