Development of Fast-Responding Pressure-Sensitive Paint for Cryogenic Conditions

A fast-responding pressure-sensitive paint (PSP) has been developed for the global measurement of pressure fluctuations on models under cryogenic conditions. In previous studies, poly(1-trimethylsilyl-1-propyne) (PTMSP), a highly oxygen-permeable polymer, was used as a binder in PSP for cryogenic testing (cryoPSP) in combination with PtTFPP. However, the response time of PtTFPP/PTMSP remained approximately 800 µs, even in air at room temperature. In this study, hydrophobically treated colloidal silica nanoparticles were incorporated into PTMSP to increase the effective porosity of the binder layer and thereby improve the response time of cryoPSP. The colloidal silica showed a strong affinity for PTMSP and good adhesion to the model surface. As a result, the response time of cryoPSP was reduced to 104 μs and 86 μs for a particle diameter of 400 nm at particle mass fractions of 95 and 98 wt%, respectively, representing a significant improvement compared to the approximately 800 µs response of particle-free PtTFPP/PTMSP. Furthermore, the time-dependent changes in the pressure- and temperature-sensitivity of cryoPSP were investigated up to 119 h post-coating, and only minor variations in sensitivity were observed. These findings indicate that the proposed fast-responding cryoPSP exhibits sufficient stability in both pressure and temperature sensitivity for practical cryogenic wind-tunnel experiments.