Monitoring of the Curing Process for Lining Materials Based on Terahertz Time-Domain Reflective Spectroscopy

As a bonding material for bonding the shell and propellant in the combustion chamber of solid rocket motor, the liner plays a protective role for the engine. Only when the liner is in a “semi-solidified state” can the charge quality be guaranteed, and it is easy to cause the phenomenon of unstable bonding interface if the charge is loaded too early or too late. Therefore, noncontact monitoring of the gradual solidification process of the material from liquid state can prevent the problems of unstable bonding interface and significantly improve the safety of solid rocket motors. In this paper, the reflective terahertz time-domain spectroscopy technology is used to monitor the curing process of lining materials, extract the refractive index spectra of samples with different curing degrees, establish the relationship between refractive index and curing reaction time, and compare it with the material loss factor obtained by rheometer to establish the correlation between refractive index and material loss factor. The experimental results show that the refractive index decreases gradually during the curing process, and the correlation coefficient between the refractive index and material loss factor is higher than 0.9. With the curing reaction, the refractive index can accurately reflect the curing process of polyurethane materials. This study provides an effective means for monitoring the curing process of lining materials.