Fast assay of ethyl acetate content of double-base oblate spherical propellant after balling process by near-infrared spectroscope

Abstract

Ethyl acetate (EAC) is commonly used as a solvent in the balling process of double-base oblate spherical propellant (DOSP) because of its excellent performance in swelling. However, the residual content of EAC in the DOSP has an adverse effect on combustion performance of DOSP. Therefore, it is necessary to fast assay the EAC content of DOSP in the production process for avoiding economic loss caused by unqualified products. This work is to investigate the feasibility of using a Fourier transform near-infrared (NIR) spectroscope coupled with partial least squares (PLS) algorithm to construct a quantitative model, which can rapidly monitor the EAC content of DOSP after balling process. In the NIR spectra, two characteristic peaks were observed in the range of 6096–5464 cm−1 and 4824–4524 cm−1, which were employed as modeling intervals for analyzing the content of EAC in DOSP intermediate samples. According to the minimum value of the root mean square error of cross-validation (RMSECV), first derivative and standard normal variate (SNV) were chosen as original spectral preprocessing method, and the optimum number of PLS factors for EAC calibration model was 6. The quantitative EAC model was developed based on PLS algorithm. The determination coefficients of the calibration (RC2) and prediction (RP2) for the developed model were equal to 0.9786 and 0.9883, respectively. The root means square error of calibration and prediction (RMSEC and RMSEP) were 0.0536 and 0.0412, respectively. The residual predictive deviation (RPD) values of calibration and prediction were 6.83 and 10.7, respectively. Using independent samples as prediction set to test robustness of the developed model, and the average deviation between traditional measured values and NIR predicted values was 0.017%. Therefore, the experimental results indicated that the NIR spectroscope can give a fast and accurate analysis the EAC content of DOSP after the balling process.