Study on the Downward and Upward Flame Spread Characteristics of Thermoplastic Thermal Insulation Materials After Light Aging

ABSTRACT Thermoplastic thermal insulation materials (TTIMs) in high‐rise buildings are often exposed to ultraviolet radiation, different temperatures, and humidity environments, leading to light aging. Their performances, such as surface color and morphology, have changed, whereas their fire risk has not been reported. Especially, the fire hazard of TTIMs is always an essential issue for high‐rise building fires. Therefore, it is necessary to study the fire risk of aging TTIMs. An accelerated aging experiment of expanded polystyrene (EPS) was performed. Subsequently, downward and upward flame spread experiments were conducted to analyze the appearance properties of EPS, flame temperature, mass loss rate, and flame spread rate at different light aging stages. Finally, based on the laws of energy conservation and mass conservation, two models were established to characterize the flame spread rates of downward and upward flame spread. The results showed that light aging led to morphology changes in EPS, such as yellowing of color and structural damage. Aging increased the values of multiple parameters such as flame temperatures, mass loss, and flame spread rate, indicating that light aging increased the fire risk. Especially, the models indicated that the flame spread rate had a nonlinear relationship with flame temperature and pyrolysis temperature.