KR101423291B1 - Method of Analyzing Stabilizer Contained in Propellant Using Near-Infrared Spectroscopy - Google Patents

Abstract

The present invention relates to a method for analyzing contents of a stabilizing agent contained in a propelling charge using a near-infrared spectroscopy. When utilizing the present invention, a large quantity of the stabilizing agent can be analyzed, since a swift measurement and an easy carrying of a device are possible. Moreover, the present invention does not require an additional test reagent and a use of an additional apparatus, thus reducing costs thereof.

Description

Technical Field [0001] The present invention relates to a method for analyzing the content of propellant stabilizer using near-infrared spectroscopy (hereinafter referred to as "near-infrared spectroscopy"

The present invention relates to a method for measuring the content of propellant stabilizer using near-infrared spectroscopy.

A propulsion charge is a charge that explodes to propel the shell to launch. Nitrosellulose is the main raw material used for such propellant charge. Nitrocellulose is a nitrate ester compound and has the risk of spontaneous ignition due to accumulation of heat generated during spontaneous decomposition. Decomposition can be delayed by adding a stabilizer that can suppress the auto-catalytic reaction by decomposition products of the propellant to suppress spontaneous ignition. Stabilizers can be broadly divided into organic stabilizers and inorganic stabilizers. Organic stabilizers include diphenylamine and ethyl centralite, and inorganic stabilizers include Na ₂ CO ₃ , NaHCO ₃ , and CaCO ₃ . The stabilizer serves as an indicator of the oxidation and decomposition reactions occurring in the propellant, and is used as an indicator for determining the storage stability of the propellant through the measurement of the content. In the group, storage grade is given according to the stabilizer content as shown in Table 1 below, and measures are taken.

Storage rating Stabilizer content (%) Action room A 0.3% or more Keep saving C 0.2% to 0.29% Consumed within one year D Less than 0.2% Disposal within 60 days

(Storage Rating and Measures)

In the group, the stabilizer content is measured at the following cycle.

division Test cycle (0.3%) Test period Domestic production Soldier Domestic production Soldier Poplar About 15 years About 35 years 10 years 30 years Night foil About 30 years About 50 years 25 years 45 years

(Test period for stabilizer content analysis according to the year of manufacture)

division Stabilizer content 0.2 to 0.29% 0.3 to 0.49% 0.5% or more Test cycle 1 year 3 years 5 years

(Retest cycle by stabilizer content)

The test to measure the stabilizer content of the propellant charge uses ultraviolet visible light spectrophotometry by steam distillation method and it takes 6 hours long for the pretreatment such as grinding, heating, dilution of extract, etc., and it takes a long time to use the reagent and equipment It costs 26,000 won per call. As a result, there is an ever-increasing accumulation of test volume due to the acquisition of long-term storage ammunition and war reserve stock for allies. In addition, the use of dust, toxic and flammable caustic soda and ethanol due to crushing has a detrimental effect on the experimenter, and there is always a risk of fire due to heating of the propulsion charge. It is an object of the present invention to limit the use of harmful reagents in the human body, shorten the test time, and reduce the cost.

The stabilizer content was determined by ultraviolet visible spectrophotometry using a conventional steam distillation method, and a calibration curve using the relationship between the measured spectra and concentration was obtained by irradiating the target sample with near infrared rays. Estimate the value.

NIR spectroscopy can be used for non-destructive testing, which makes it possible to carry out rapid measurement and portability of equipment, thereby enabling a large amount of analysis to be carried out in the field and reducing the cost by eliminating the use of test reagents and equipment.

Fig. 1 is a schematic view showing a measuring apparatus configuration diagram and a measurement principle of a near-infrared ray spectroscope.
Fig. 2 is the initial near-infrared spectrum of the propellant charge.
Figure 3 is a pretreatment spectra of propellant charge.
4 is a calibration curve (actual value versus predicted value).
5 is a diagram of a steam distillation apparatus of ultraviolet visible ray spectroscopy.
6 is a diagram of a near infrared ray spectroscopy test procedure.

According to the present invention,

1) selecting standard pilot charges to be used for the calibration curve development;

2) measuring a near-infrared spectrum of the propulsion charge standard sample;

3) measuring the stabilizer content of the propellant charge standard sample using ultraviolet visible light analysis through steam analysis;

4) developing a calibration curve for the correlation between the near infrared spectrum of the propulsion charge standard sample and the stabilizer content;

5) verifying the validity of the calibration curve;

6) measuring the near-infrared spectrum of the unknown sample; And

7) measuring the stabilizer content of the propellant unknown sample using the calibration curve and the near-infrared spectrum of the propellant unknown sample; The method comprising the steps of:

Each step of the analysis method of the present invention will be described below.

1) Select 250 or more samples (50 to 100 g each) of cylindrical short-term propellant charges containing nitrocellulose as the main component in the pilot sample selection stage to be used for the calibration curve development. In order to develop an effective calibration curve, it is necessary to prepare at least 25 each of stabilizer content (0.2 to 0.39% / 0.4 to 0.69% / 0.7% or more) Do. The reason for preparing the same type of coal is that the type and pattern of change of the near-infrared spectrum are different because the constituents, contents, and granular forms are different. Therefore, each calibration curve should be developed and used, and the method is the same.

2) In the near-infrared spectrum measurement step of the propulsion charge standard sample, the spectrum is obtained by irradiating near-infrared rays to the propulsion charge standard sample. At this time, the spectrum by the reflection method can be obtained. Near infrared spectra and X-axis represents a wave number (reciprocal, and the unit is cm ^-1 in wavelength), and a Y-axis reflective capacitance (reflectance), the measurement frequency in the present invention is 4,000cm ^-1 to 10,000cm ^-1 (wavelength of 1,000nm to 2,500 nm).

3) In the step of measuring the stabilizer content of the propulsion charge standard sample, the stabilizer content value can be derived from the propulsion charge standard sample by ultraviolet visible spectral analysis by steam distillation. The measurement of the stabilizer content of the propulsion charge standard sample can be made differently depending on the type of stabilizer.

Type of stabilizer and the like can be diphenylamine (Diphenylamine), ethyl Central light _{(Ethylcentralite), Na 2 CO 3} , NaHCO 3, CaCO 3.

4) In the step of developing the calibration curve, the stabilizer content derived from the above method is input to the software that controls the near-infrared spectroscope, and the near infrared spectrum of the sample is matched with the stabilizer content. After the matching of the near infrared spectrum and the stabilizer content of the propulsion charge standard sample is completed, a calibration curve is developed. Partial least squares regression (PLS) algorithm and CV-Set- (Standard Normal Variate), Ncl (Normalization by Closure), dg1 (1st Derivative Saviltzky-Golay 9points) and Kmu (Kubelka Munk) to improve the quality of original Spetra information using the validation water treatment method. Use more than one to calibrate the baseline, amplify the information needed for analysis, and use the Pretreated Spectra to discard any unnecessary information. C-V-Set-Validation The water treatment method is a method to make the calibration and the validation lines arbitrarily match. The proper ratio of the number of calibration and validation data is 2: 1 and the data set should be uniformly distributed over the whole concentration range.

5) In the step of verifying the validity of the calibration curve, internal and external verification work shall be carried out to increase the accuracy of the calibration curve. Internal verification work is a numerical check for the validity of the calibration curve and is calculated through Chemometric software. SEC, SEP, Q-value, r-value, and Consistency. The validity criteria are shown in Table 4 below.

division Reference range Remarks SEC
(Standard Error of Calibration) 0.1 or less Valid at close to 0 SEP
(Standard Error of Prediction) 0.1 or less Valid at close to 0 Consistency 80-120 Valid at close to 100 r-value (regression coefficient) 0.9 or more Valid in close proximity to 1 Q-value (Quality value) 0.75 or more Valid in close proximity to 1

(Criteria for determining effective calibration curve)

If the above values are included in the reference range, it is judged to be usable calibration curve. If it is out of the range, go back to the development step and re-verify the Pretreatment type and the number of Primary PCs and Secondary PCs.

When the internal verification operation is completed, an external verification operation is performed. Approximately 10% of the above pilot charge standard sample is selected as the verification sample. Test the selected test sample with near infrared spectrometry and check the error between the resultant value and the actual value. If the difference between the results of near-infrared spectroscopy and ultraviolet visible spectroscopy is less than ± 0.10%, if it is more than ± 0.10%, it is judged to be not suitable. If 90% of the test sample is judged to be suitable, And internal / external verification work is completed. If the conformity is deteriorated, the external verification data is added to the calibration curve again, and the internal and external verification are repeated. Although the calibration curve developed through the above process can be used for validity, near infrared spectroscopy requires constant data input and calibration curve update in order to narrow the error by statistical chemical method and obtain accurate data.

6) In the step of measuring the near-infrared spectrum of unknown propellant charge, the near-infrared spectrum of the propellant charge, which does not know the stabilizer content, is measured.

7) The stabilizer content of unknown propellant can be calculated by using the near-infrared spectrum of the verified calibration line and the measured propellant unknown sample. If the stabilizer content of the unknown sample is 0.5% or more, the stabilizer content of the sample is determined as the result. If the content of the stabilizer is less than 0.5%, the stabilizer content of the sample is measured by ultraviolet visible light spectrometry using steam distillation.

Hereinafter, preferred embodiments of the present invention will be described in order to facilitate understanding of the present invention. However, the following examples are provided only for the purpose of easier understanding of the present invention, and the present invention is not limited by the examples.

Example 1. Measurement of Stabilizer Contents in a 155 millisecond Excavation Charge by Near Infrared Spectroscopy

(1) Standard preparation of propulsion charge standard

From 2008 to 2012, we collected a total of 402 155-mile-eight propulsion charges (100g per piece) stored in various environments and conditions, including ground-type, IGU, and underground ammunition.

(2) Acquisition of near-infrared spectrum

Each sample was irradiated with near infrared rays in a Petri dish containing 50 ~ 100g of the original sample. Measuring wave number was 4,000cm ^-1 to 10,000cm ^-1 (wavelength of 1,000nm to 2,500nm). Three near infrared rays were set to one set and three near infrared spectra were obtained per sample. Here, the near infrared ray spectrometer uses Buchi FT-NIRFlex N-500 model, and the software used in this device is NIRWare Management Console, NIRWare Operator, and NIRCal.

(3) Ultraviolet visible light spectroscopy test of propulsion charge standard sample

Ultraviolet ray visible spectroscopy analysis of the samples obtained near infrared spectra revealed the stabilizer content.

A standard solution (1.5 / 3.0 / 4.5 / 6.0 ppm) was prepared according to the concentration of the stabilizer and the absorbance was measured to prepare the extinction coefficient and linear regression equation.

As shown in FIG. 5, 50 ml of caustic soda (50% -NaOH) and 100 ml of ethyl alcohol (95%) were placed in a distillation flask, and a cooling tube was assembled and heated on the mantle for 30 minutes. The alcohol was added and the distillation apparatus was assembled. One end of the 5L steam generating flask was immersed in the contents of the distillation flask, and one end of the distillation flask was immersed in an ethyl alcohol solution of a beaker to receive the distillate.

The distillate was distilled by steam until the distillate of the beaker containing ethyl alcohol became ± 25 ml. Here, the distillation rate was adjusted to 7 to 9 ml / min, and the temperature of the distillate received in the beaker was maintained at room temperature.

After distillation, the adapter and condenser were washed with ethyl alcohol and collected in a beaker. The beaker solution was transferred to a 1 L volumetric flask and diluted with ethyl alcohol to the indicated line. 20 ml of the solution was pipetted into a 100 ml volumetric flask and diluted to the mark with ethyl alcohol. The absorbance of this solution was measured at 285 nm using an ultraviolet visible light spectrophotometer, and the stabilizer content was calculated by the following equation.

D: Stabilizer extinction coefficient, C: Concentration of standard solution

A: absorbance of standard solution, A ': concentration of extract solution

Sample weight: mg unit of sample when taken with 20mL pipette

(4) Calibration curve development

After obtaining the near infrared spectrum and the stabilizer content, NIRWare Management Console in the near infrared spectroscopy control computer entered the stabilizer content into the spectrum and matched. After the matching of the prepared samples was completed, calibration curves were prepared by NIRCal using the data processing method shown in the table below.

division A B



Data processing Partial Least Squares Regression (PLS) Partial Least Squares Regression (PLS) C-V-Set-Validation (C: V = 2: 1) C-V-Set-Validation (C: V = 2: 1)

Pretreatment Ncl
(Normalization by closure)

SNV (Standard Normal Variate) dg1 (1st Derivative Saviltzky-Golay 9points)
Set
Condition Wavelengths 4000 to 10,000 4000 to 10,000 Primary PCs 10 13 Secondary PCs 1 to 8 1 to 12 range (%) 0.25 to 1.06 0.25 to 1.06

(Data processing and setting conditions of the developed calibration curve (A, B))

(5) Calibration curve internal / external verification

Calibration curves A and B with different data processing and setting conditions were prepared and internal / external verification was performed. First, verification based on internal calculation values is shown in the following table.

division SEC SEP Consistency R R ² Q-value Slope Bias A 0.0635 0.0625 101.78 0.9361 0.8763 0.8197 0.8763 B 0.0682 0.0577 118.22 0.9316 0.8679 0.8152 0.8679

(Internal verification data)

According to the above table, it is judged that the internal verification results can be used for both the calibration curves A and B. When the internal verification is completed, some of the pilot samples are selected for external verification. The following table shows the external verification results.

division Stabilizer content A B Result value Error (absolute value) Judgment Result value Error (absolute value) Judgment NO. One 0.3 0.27 0.03 Suitable 0.29 0.01 Suitable NO. 2 0.32 0.27 0.05 Suitable 0.39 0.07 Suitable NO. 3 0.33 0.29 0.04 Suitable 0.28 0.05 Suitable NO. 4 0.38 0.41 0.03 Suitable 0.42 0.04 Suitable NO. 5 0.39 0.38 0.01 Suitable 0.44 0.05 Suitable NO. 6 0.40 0.39 0.01 Suitable 0.35 0.05 Suitable NO. 7 0.40 0.44 0.04 Suitable 0.48 0.08 Suitable NO. 8 0.41 0.43 0.02 Suitable 0.44 0.03 Suitable NO. 9 0.42 0.42 0 Suitable 0.39 0.03 Suitable NO. 10 0.42 0.37 0.05 Suitable 0.47 0.05 Suitable NO. 11 0.43 0.47 0.04 Suitable 0.50 0.07 Suitable NO. 12 0.43 0.39 0.04 Suitable 0.39 0.04 Suitable NO. 13 0.44 0.36 0.08 Suitable 0.36 0.08 Suitable NO. 14 0.45 0.36 0.09 Suitable 0.40 0.05 Suitable NO. 15 0.46 0.40 0.06 Suitable 0.45 0.01 Suitable NO. 16 0.47 0.50 0.03 Suitable 0.49 0.02 Suitable NO. 17 0.48 0.45 0.03 Suitable 0.44 0.04 Suitable NO. 18 0.49 0.54 0.05 Suitable 0.54 0.05 Suitable NO. 19 0.49 0.41 0.08 Suitable 0.40 0.09 Suitable NO. 20 0.51 0.43 0.08 Suitable 0.46 0.05 Suitable NO. 21 0.51 0.57 0.06 Suitable 0.56 0.05 Suitable NO. 22 0.53 0.50 0.03 Suitable 0.51 0.02 Suitable NO. 23 0.53 0.58 0.05 Suitable 0.58 0.05 Suitable NO. 24 0.55 0.54 0.01 Suitable 0.54 0.01 Suitable NO. 25 0.55 0.54 0.01 Suitable 0.58 0.03 Suitable NO. 26 0.56 0.52 0.04 Suitable 0.55 0.01 Suitable NO. 27 0.63 0.61 0.02 Suitable 0.63 0 Suitable NO. 28 0.63 0.60 0.03 Suitable 0.61 0.02 Suitable NO. 29 0.97 0.99 0.02 Suitable 0.94 0.03 Suitable NO. 30 0.99 0.99 0 Suitable 0.94 0.05 Suitable

(Verification data through external sample)

As a result of the external verification, the validity of the calibration curve was confirmed within 30 ± 30% of all samples with an error of ± 0.10%.

(6) Analysis of stabilizer content of unknown

It is proved that the accuracy and reliability of the calibration curve can be verified through internal and external verification of the calibration curve, and it is found that there is no problem in using it as a substitute for ultraviolet visible spectral analysis. NIR spectroscopy was performed on site during the sampling period of the 12-year propellant stabilizer analysis test sample, since the extraction step using an organic solvent and the time-consuming pulverization step were unnecessary.

The near infrared spectrum was measured in the wavelength range of 1000 nm to 2500 nm. When the stabilizer content of the sample was less than 0.5%, the storage stability of the propellant charge was further enhanced by ultraviolet visible spectrophotometry by steam distillation method. The target of the test was 178 samples of 155mm 8 guns. The test results were applied to more than 0.5% of 63 samples, and 113 samples were less than 0.5%, and ultraviolet visible spectrophotometry was used to confirm the stabilizer content.

S100: Preparatory pilot sample preparation stage for calibration curve development
S200: Measurement step of near-infrared spectrum of propulsion charge standard sample
S300: Stabilizer content measurement step of pilot charge standard sample
S400: Calibration curve development step
S500: Calibration curve verification step
S600: Stabilizer content measurement step of unknown sample

Claims (4)

1) selecting standard pilot charges to be used for the calibration curve development;
2) measuring a near-infrared spectrum of the propulsion charge standard sample;
3) measuring the stabilizer content of the propellant charge standard sample using ultraviolet visible light analysis through steam analysis;
4) developing a calibration curve for the correlation between the near infrared spectrum of the propulsion charge standard sample and the stabilizer content;
5) verifying the validity of the calibration curve;
6) measuring the near-infrared spectrum of the unknown sample; And
7) measuring the stabilizer content of the unknown propellant using the calibration curve and the near-infrared spectrum of the propellant unknown sample; Wherein the stabilizer of the propellant charge is diphenylamine and is measured by a reflection method in a wavelength band of 1000 nm or more and 2500 nm or less.
The method according to claim 1,
Wherein the step 4) is performed by a partial least squares regression algorithm.
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