GB/T 36526-2018Test methods of industrial nitrocellulose (English PDF)

3.1 Industrial nitrocellulose

Nitrocellulose used in coatings, inks, celluloids, daily chemical products, environmentally friendly products, biomedical products, etc.

3.2 Calibration model

A mathematical model of the relationship between the near-infrared spectrum of the sample and the corresponding reference value.

3.3 Prediction standard error

In the multivariate calibration, the prediction ability of the calibration model is evaluated, and the standard error calculated by verifying the sample standard value and the predicted value is used. press Equation (1) is calculated.

In the formula.

SEP---predicting standard error;

Ni --- the predicted value obtained from the ith verification sample;

Ni --- the standard value of the ith verification sample;

m ---Verify the number of samples.

3.4 Calibration standard error

In the multivariate calibration model, the prediction ability of the calibration model is evaluated, and the standard error calculated by correcting the sample standard value and the predicted value is used. Calculated according to formula (2).

In the formula.

SEC---corrected standard error;

Yi --- the predicted value obtained from the ith corrected sample;

Yi --- the standard value of the i-th calibration sample;

d --- The degree of freedom of the calibration model (d is equal to nk, where n is the number of calibration samples and k is the number of model variables).

3.5 Mahalanobis distance

The covariance of the similarity of two unknown sample sets.

Calculated according to formula (3).

In the formula.

Hi --- covariance of Markov distance data;

Ti --- calibration set sample i spectral score;

T --- correction set average score matrix of n sample spectra;

M --- Markov matrix of the calibration set sample;

n --- the number of samples;

T --- calibration set sample spectral score matrix.

3.6 Mahalanobis distance limitation value

Calculated according to formula (4).

In the formula.

HL --- Mahalanobis distance threshold;

H --- The average value of the Markov distance of the calibration set sample;

SDMD---The standard deviation of the Markov distance of the calibration set sample.

3.7 Abnormal sample

The Mahalanobis distance is greater than the Mahalanobis distance threshold and exceeds the sample that corrects the analytical capabilities of the model.

4.1 Divald alloy reduction method

4.1.1 Test principle

Nitrocellulose is saponified with sodium hydroxide in the presence of hydrogen peroxide to form nitrates, which are reduced to ammonia by Divald alloy.

Gas, condensed with water vapor, and absorbed by excess boric acid solution, using bromocresol green-methyl red as indicator, titration with hydrochloric acid standard solution Calculate the nitrogen content in the sample.

4.1.2 Reagents and materials

4.1.2.1 Water, Class III, GB/T 6682.

4.1.2.2 30% hydrogen peroxide, analytical grade, GB/T 6684.

4.1.2.3 Divald alloy (Cu. 50%, Al. 45%, Zn. 5%), HG/T 3438.

4.1.2.4 Ethanol, analytical grade, GB/T 679.

4.1.2.5 Boric acid solution. boric acid, analytically pure, GB/T 628, a solution with a mass fraction of 4%.

4.1.2.6 Sodium hydroxide solution. Sodium hydroxide, analytically pure, GB/T 629, a solution with a mass fraction of 20%.

4.1.2.7 Hydrochloric acid standard solution. hydrochloric acid, analytically pure, GB/T 622, concentration 0.2mol/L.

4.1.2.8 Bromocresol green, analytical grade, GB/T 15349.

4.1.2.9 Methyl red, analytically pure, HG/T 3449.

4.1.3 Equipment

4.1.3.1 Automatic tester for nitrogen content of nitrocellulose, mainly by microcomputer controller, steam generator, distillation system, boric acid system, dripping Composition system, waste disposal system and cleaning system, with automatic completion of reagent quantitative addition, distillation, absorption, titration and output test results Function, its schematic diagram is shown in Figure 1.

4.1.3.2 Porous saponification apparatus, the pore temperature should be adjustable from room temperature to 400 °C.

4.1.3.3 Analytical balance with an accuracy of 0.0001g.

4.1.3.4 The oven has a temperature control accuracy of ±2 °C.

4.1.3.5 Saponification tube, the specification is 250mL.

4.1.3.6 Dryer.

4.1.3.7 Weighing bottles.

4.1.3.8 Beakers, specifications are. 100mL, 1000mL.

4.1.3.9 Measuring cylinders, the specifications are. 5mL, 50mL.

4.1.3.10 Glass rods.

4.1.4 Test preparation

4.1.4.1 Preparation of equipment

4.1.4.1.1 Add the corresponding solution to each solution tank of the instrument so that the amount of the added solution meets the experimental requirements.

4.1.4.1.2 In order to ensure accurate test results, two or three blank tests are performed after each power-on, for instrument preheating and cleaning instruments. Pipeline.

4.1.4.2 Indicator preparation

4.1.4.2.1 Mixed indicator. bromocresol green is formulated into a 1g/L ethanol solution; methyl red is formulated to a concentration of 1g/L Ethanol solution; the bromocresol green ethanol solution and the methyl red ethanol solution were mixed at a volume ratio of 5.1.

4.1.4.2.2 Boric acid absorption solution. Add the mixed indicator (4.1.4.2.1) to the boric acid solution (4.1.2.5), mix, boric acid and mixed indicator The volume ratio is 100.1, placed in a cool place, and the storage period is one month.

4.1.4.3 Preparation of samples

Use a pair of tweezers to tear the sample, and then take 1.5 times the required mass into the aluminum box. If it is an aqueous sample, it should be placed in an oven at 108 °C~ Dry at 112 °C for 1 h, put it in a desiccator and cool to room temperature, then dry it again in an oven for 30 min, until the two samples are weighed twice.

The difference is no more than 0.0005g. If it is an alcohol-containing sample, it should be placed in an oven at 100~105 °C for 1 hour, and placed in a desiccator to cool to the room.

The temperature was then dried again in an oven for 30 minutes until the difference between the two sample samples did not exceed 0.0005 g. Known quality Weigh the bottle and weigh 0.40g~0.65g, accurate to 0.0001g.

4.1.5 Test procedure

4.1.5.1 Blank test

4.1.5.1.1 50 mL of distilled water was placed in a saponified tube pre-filled with 5 mL of ethanol.

4.1.5.1.2 Insert a funnel into the saponification tube, and add about 1.5mL~2mL of hydrogen peroxide solution and 50mL of sodium hydroxide solution. Shake well.

4.1.5.1.3 After 5min~10min, slowly heat on the graphite furnace saponifier, the heating temperature is about 150 °C, until the small bubble disappears Lose, cool the saponification tube to room temperature.

4.1.5.1.4 Quickly add 4g of Divald alloy to the saponification tube and immediately install the saponification tube on the instrument and seal it. hit Turn on the instrument steam switch, so that a small amount of steam flow is gradually heated, the recording time is about 30s, the steam switch is turned off, and the reaction is 10 minutes.

4.1.5.1.5 Start the instrument program, the instrument setting parameters should be. steam flow 80%, boric acid volume 35mL, distillation time 8min.

The instrument simultaneously performs the steps of distillation, absorption, and titration, and titrates with a hydrochloric acid standard solution to obtain a titration result.

4.1.5.1.6 Perform the parallel blank test according to the procedure of 4.1.5.1.1~4.1.5.1.5. The difference between the two values should not exceed 0.05mL, and the average value should be taken. As a blank volume V0 of hydrochloric acid.

4.1.5.2 Sample test

4.1.5.2.1 Prepare two samples and perform two tests in parallel.

4.1.5.2.2 Pour the constant weight sample in the weighing bottle into a saponification tube containing 5 mL of ethanol, and divide the weighing bottle with 50 mL of distilled water.

The washing was washed three to five times, and the washed distilled water was poured into a saponification tube.

4.1.5.2.3 Press 4.1.5.1.2.

4.1.5.2.4 After placing for 5min~10min, slowly heat the saponification on the graphite furnace saponifier. At this time, it should be shaken continuously until the sample solution changes.

To clarify, the solution is clarified and heating is continued to destroy excess hydrogen peroxide until the small bubbles disappear. After the saponification reaction is completed, the saponification tube is cooled. To room temperature.

4.1.5.2.5 Repeat the operation according to 4.1.5.1.4 and 4.1.5.1.5.

4.1.6 Treatment of test results

4.1.6.1 The nitrogen content of nitrocellulose is calculated according to formula (5).

In the formula.

wN --- mass fraction of nitrogen content of nitrocellulose, %;

c --- hydrochloric acid standard titration solution concentration value, the unit is mole per liter (mol/L);

V --- sample consumption of hydrochloric acid standard titration solution volume value in milliliters (mL);

V0 --- blank test consumption of the standard volume of hydrochloric acid titration solution, the unit is milliliter (mL);

0.0140---The value of the mass of nitrogen equivalent to 1.00mL hydrochloric acid standard titration solution (hydrochloric acid concentration 1.000mol/L), single The position is gram per millimol (g/mmol);

m --- The value of the sample mass in grams (g).

4.1.6.2 The difference between the two parallel test calculation results should be no more than 0.04%, and the average value should be taken as the nitrogen content of nitrocellulose.

Show to two decimal places. Retest when the calculated result difference is greater than 0.04%.

4.1.7 Test report

See Appendix A for the content and format of the test report.

4.2 Interferometer method

4.2.1 Test principle

The quantitative sample is taken in a special steel cylinder, and the sample is detonated by electric heating in the case of airtightness. Pass the blasted gas into the interferometer and measure it The number of interference fringes corresponding to the refractive index of the gas is determined from the reference curve, and the nitrogen content is calculated.

4.2.2 Reagents and materials

4.2.2.1 Copper sulfate pentahydrate, analytical grade, GB/T 665.

4.2.2.2 Color changing silica gel, HG/T 2765.4.

4.2.2.3 Soda lime. calcium hydroxide, HG/T 4120, 75%; water 20%; sodium hydroxide, GB/T 629, 3%; potassium hydroxide, GB/T 2306, 2% mixture.

4.2.3 Equipment

4.2.3.1 Interferometer, measuring tube length is 1000mm or 500mm, and its attached device, its structural schematic is shown in Figure 2.

4.2.3.2 Special steel cylinder (according to safety requirements), the material is stainless steel, the volume is about 300mL.

4.2.3.3 Nickel-chromium wire, diameter from about 0.1mm to 0.2mm.

4.2.3.4 Weighing shovel, made of aluminum or copper.

4.2.3.5 Dryer.

4.2.3.6 Aluminum box.

4.2.3.7 Thermometer, measuring range is 0 °C ~ 50 °C, the division value is 0.1 °C.

4.2.3.8 Barometer.

4.2.3.9 Ignition device, the working voltage range is 0V~20V, and the working current range is 0A~5A.

4.2.3.10 Water jet or vacuum pump.

4.2.3.11 Hair dryer.

4.2.4 Test preparation

4.2.4.1 Sample Preparation

Use a pair of tweezers to tear the sample, and then take 1.5 times the required mass into the aluminum box. If it is an aqueous sample, it should be placed in an oven at 108 °C ~ 112 °C.

Dry for 1h, put it in a desiccator and cool to room temperature for later use; if it is an alcohol-containing sample, it should be placed in an oven at 100 °C ~ 105 °C for 1 h, put Cool to room temperature in a desiccator and set aside.

4.2.4.2 Instrument preparation

4.2.4.2.1 Rinse the special cylinder cylinder with water, wipe off the water drops, blow dry with a hair dryer or dry in an oven, wipe the special steel cylinder cover and blow it.

Dry, set the rubber ring, and connect the resistance wire for use.

4.2.4.2.2 Disconnect the connecting hose between the insulation sleeve and the flowmeter, connect the insulation sleeve to the piston of the outlet of the standard pipe, and open the piston.

Disassemble the hose between the filter and the copper sulfate tube, connect the filter to the water flow tube, and pump with the water tube for at least 2 minutes. Filter The hose at one end is disconnected from the water flow cylinder and the piston is closed. Rotate the micrometer drum of the interferometer to make the upper and lower stripes coincide, and record the micro wheel drum at this time. The reading is n0, which is zero.

4.2.5 Test procedure

4.2.5.1 Prepare two samples and perform two tests in parallel.

4.2.5.2 Weigh 5g of dry sample with a sample shovel to the nearest 0.1g.

4.2.5.3 Carefully pour a sample into a cylinder that has been prepared and cooled to room temperature. The pier is placed twice, the lid is closed, the sink is placed, and the guide is connected. Line, power on and blast.

4.2.5.4 When the cylinder is cooled, remove it from the water tank, wipe the outside, open the needle valve to check for gas, and close it immediately.

4.2.5.5 Connect the top of the cylinder to the hose on the upper part of the copper sulfate tube, carefully open the needle valve carefully, and let the gas enter the interferometer measuring tube.

In the middle, observe the interferometer flow meter, operate the needle valve, and control the flow rate from 300mL/min to 600mL/min.

4.2.5.6 The first ventilation is 1min~3min, close the needle valve, turn the micro-drum to make the upper and lower stripes coincide, and record the reading on the micro-drum.

Number nc. After reading for half a minute for each ventilation, until the difference of the stripes or the three consecutive readings does not exceed 4, the average is taken.

Calculation. Simultaneously record temperature (accurate to 0.1 °C) and pressure (accurate to 0.1 kPa).

4.2.6 Treatment of test results

4.2.6.1 During the test, the value read from the interferometer at room temperature and atmospheric pressure shall be corrected to the reference condition as follows (20 °C standard large The reading under air pressure is calculated according to equation (6).

In the formula.

n --- reference status reading;

Nc---the interferometer measures the micro drum's reading when testing the sample;

N0---interferometer measures the reading of the micro drum at zero point;

Bt---temperature correction value;

Bp---pressure correction value.

Note: The temperature and pressure correction values are based on statistical data.

4.2.6.2 According to the reference condition reading n, use the arbitration method to draw the reference curve, and find the degree of nitrification of the test sample from the reference curve. (7) Calculate the nitrogen content.

In the formula.

wN --- mass fraction of nitrogen content of nitrocellulose, %;

WX---the value of nitrification in milliliters per gram (mL/g);

16 --- Conversion constant of nitrification and nitrogen content.

4.2.6.3 The difference between the two parallel test calculation results should be no more than 0.04%, take the arithmetic mean, and the result is expressed to two decimal places. When Retest when the difference between the results is greater than 0.04%.

4.2.7 Test report

See Appendix A for the content and format of the test report.

4.3 Near Infrared Spectroscopy

4.3.1 Test principle

Using the CH and OH bonds in the nitrocellulose molecule to generate frequency-doubling and frequency-doubling absorption characteristics in the near-infrared region, A calibration model for the correlation between the external spectrum and the nitrogen content, the absorption spectrum of the sample is tested, and the nitrogen content is calculated according to the calibration model.

4.3.2 Reagents and materials

4.3.2.1 Verification calibration model nitrocellulose comparison sample. Nitrogen-containing nitrocellulose samples were measured by arbitration.

4.3.2.2 Hibiscus, about 15mm in diameter and about 150mm in length.

4.3.3 Instruments and equipment

4.3.3.1 Near-infrared analyzer. A reliable calibration model for analyzing the nitrogen content of nitrocellulose; prediction standard error and calibration standard error should be Meet the requirements of Table 1.

Table 1 Standard error of the calibration model: SEP <=0.04%; SEC <=0.04%.

4.3.3.2 Sample cup. The bottom of the cup is made of low-hydroxy quartz with a diameter greater than 50mm.

4.3.4 Test preparation

4.3.4.1 Turn on the instrument, preheat it for 30 minutes, and perform self-test of the instrument. After the self-test passes, you can start the test.

4.3.4.2 Verify the calibration model according to the 4.3.5 test. Use the nitrocellulose to compare the nitrogen content of the sample to perform quality monitoring of the calibration model. Measurement The test result should be no more than 0.10% compared with the standard value of the comparison sample; if the difference is greater than 0.10%, it should be stopped.

4.3.4.3 Verification calibration model The nitrocellulose comparison sample should not be contaminated.

4.3.5 Test procedure

4.3.5.1 Prepare two samples and perform two tests in parallel.

4.3.5.2 Set the test conditions of the sample a […]