Effects of Irradiance, Pressure, and Temperature on the Photodegradation of Fast Pressure-Sensitive Paints

Photodegradation limits the accuracy of fast pressure-sensitive paints (PSPs), but its dependences on irradiance and operating conditions remain insufficiently researched. Here, the photodegradation kinetics of a polymer-ceramic PSP (PC-PSP) and a mesoporous-particle PSP (MP-PSP) were investigated under independently varied irradiance (50-122 mW/cm²), pressure (0.5-100 kPa), and temperature (20-100 °C). Normalized intensity histories acquired during 900 s of continuous irradiation were fitted with a bi-exponential model, whose composite degradation rate was correlated to the studied parameters using physical relations. PC-PSP exhibited greater absolute degradation and an approximately linear irradiance dependence (m = 1.28), whereas MP-PSP showed a nonlinear dependence (m = 2.13), consistent with a greater relative contribution from photooxidative processes. The degradation rate of PC-PSP decreased predominantly with increasing pressure because oxygen quenching reduced the excited-state luminophore population. MP-PSP exhibited a non-monotonic pressure dependence: decreasing pressure initially accelerated degradation by weakening oxygen quenching, whereas further pressure reduction below the half-saturation region suppressed oxygen-limited photooxidation. Increasing temperature generally accelerated degradation in both formulations; the fitted apparent activation energies were 12.99 kJ mol^-1 for PC-PSP and 33.12 kJ mol^-1 for MP-PSP, reflecticng the stronger overall temperature dependence of MP-PSP. These findings provide a basis for quantitatively evaluating PSP photostability and assessing photodegradation-induced measurement errors.