An approach for simultaneous monitoring the content of insensitive agent in the double-base oblate spherical propellant by application of near-infrared spectroscope and partial least squares

The content of insensitive agent is an important parameter that has been shown correlated with the combustion characteristic of double-base oblate spherical propellant (DOSP). This work focused on the feasibility of simultaneous monitoring the content of insensitive agent (dibutyl phthalate (DBP) and N, N'-dimethyl-N, N'-diphenylurea (C₂)) in DOSP by using near-infrared (NIR) spectroscope coupled with partial least squares (PLS). The optimal spectral intervals for creating models of DBP and C₂ corresponded to 5964 cm^-1-4212 cm^-1 and 6240 cm^-1-4380 cm^-1, respectively. It had been demonstrated that derivative tools were more suitable for spectral preprocessing as which had the lowest root mean squares error of cross-validation (RMSECV). The best-performance models of DBP and C₂ were built under 4 and 7 PLS factors, respectively. The results showed that the determination coefficients of calibration (R_c²) and the root mean squares error of calibration (RMSEC) were 0.9771 and 0.0173 for DBP; 0.984 and 0.0072 for C₂, respectively. Besides, the developed models exhibited excellent ability in prediction with the determination coefficients in prediction (R_P²) and the root mean squares error in prediction (RMSEP) of 0.9681 and 0.0275 for DBP, and of 0.9554 and 0.0107 for C₂, respectively. The residual predictive deviation (RPD) of prediction set were 5.68 and 5.12 for DBP and C₂, respectively. The average relative errors of the proposed and reference methods were 0.652% for DBP, and 0.429% for C₂, revealing a good correlation between the reference values and predicted values. Therefore, it concluded that the proposed plan has shown to be an attractive means since its efficient and highly accurate which could provide a better option for quality control in the large-scale production of DOSP.