Preparation method of sample for testing mechanical properties of nitrocotton

Abstract

The invention discloses a preparation method, particularly discloses a preparation method of a sample for testing mechanical properties of nitrocotton, and belongs to the technical field of design and manufacturing processes of nitrocotton test articles. The invention provides the preparation method of the sample for testing the mechanical property of the nitrocotton, which can obviously shorten the preparation time and improve the preparation efficiency. The preparation method comprises the following steps: firstly, adding a solvent into nitrocotton for melting, then putting into a kneading machine for stirring and kneading to form a dough-shaped nitrocotton blank, and then putting the blank into a vacuum hot press for pressing into the mechanical property test standard sample strip. And finally, putting the mechanical property test standard sample strip into a supercritical reaction kettle, and removing the solvent in the mechanical property test standard sample strip under the cooperation of carbon dioxide gas to obtain the nitrocotton mechanical property test sample strip.

Description

Technical Field

[0001] The invention relates to a preparation method, in particular to a preparation method for a nitrocellulose mechanical property test sample, belonging to the technical field of nitrocellulose test product design and manufacturing process. Background Art

[0002] Nitrocellulose (also called nitrocellulose, English Nitrocellulose, abbreviated as NC) is the main component of single-base propellants, double-base propellants, triple-base propellants, modified double-base propellants, cross-linked modified double-base propellants and composite modified double-base propellants. As an energetic adhesive, its mechanical properties determine the strength of the above-mentioned propellants and propellants. Since nitrocellulose cannot be melt-formed, solvents such as acetone and ethyl acetate are required to prepare nitrocellulose mechanical property test samples. The solvents used in the preparation process need to be completely removed to ensure the reliability of the test results. However, the complete removal of the above solvents takes a week or even several weeks, which seriously affects the timeliness of the nitrocellulose mechanical property test. Summary of the invention

[0003] The technical problem to be solved by the present invention is to provide a method for preparing a sample for testing the mechanical properties of nitrocellulose, which can significantly shorten the preparation time and improve the preparation efficiency.

[0004] The technical solution adopted to solve the above technical problems is: a method for preparing a sample for testing the mechanical properties of nitrocellulose, wherein the method first adds a solvent to the nitrocellulose to melt the nitrocellulose, then puts the nitrocellulose into a kneading machine for stirring and kneading to form a dough-like nitrocellulose blank, then puts the blank into a vacuum hot press and presses it into a standard specimen for testing mechanical properties, and finally puts the standard specimen for testing mechanical properties into a supercritical reactor to remove the solvent therein with the cooperation of carbon dioxide gas to obtain a nitrocellulose mechanical properties test specimen.

[0005] Furthermore, the solvent added to the nitrocellulose is acetone or ethyl acetate.

[0006] A preferred embodiment of the above scheme is that, when adding acetone or ethyl acetate solvent, 10-50% of the total dosage of acetone or ethyl acetate is first added for pre-dissolution, and then 50-70% of the total dosage of acetone or ethyl acetate is added to the pre-dissolved nitrocellulose in a kneader to stir and knead to form a dough-like nitrocellulose blank to complete the melting of the nitrocellulose.

[0007] Furthermore, when the standard specimens for testing the mechanical properties of nitrocellulose are pressed and formed in a vacuum hot press, the hot pressing temperature is 25-80°C.

[0008] A preferred embodiment of the above scheme is that when removing the solvent in the supercritical reactor, the temperature of the input carbon dioxide gas is 50-120° C. and the pressure is 7-25 MPa.

[0009] Furthermore, the heat preservation and pressure maintenance time for removing the solvent in the supercritical reactor is not less than 4 hours.

[0010] The preferred method of the above scheme is that the pressure relief is carried out slowly and the pressure relief time is not less than 2 hours.

[0011] Furthermore, the temperature is slowly lowered while the pressure is released, and the cooling time is no less than 2 hours.

[0012] The beneficial effects of the present invention are as follows: the technical solution provided by the present application is to first add a solvent to the nitrocellulose to melt it, then put it into a kneading machine to stir and knead it to form a dough-like nitrocellulose blank, then put the blank into a vacuum hot press to press it into a standard specimen for mechanical property testing, and finally put the standard specimen for mechanical property testing into a supercritical reactor to remove the solvent therein in the cooperation of carbon dioxide gas to obtain the nitrocellulose mechanical property testing specimen. Since the amount of solvent added before preparing the specimen in the present application is not removed by natural volatilization, but is removed by a supercritical reactor in the cooperation of carbon dioxide gas, not only the solvent removal time is significantly shortened, but also the preparation time of the specimen is shortened, thereby achieving the purpose of significantly improving the preparation efficiency. DETAILED DESCRIPTION

[0013] In order to solve the technical problem of incomplete solvent removal during the preparation time in the prior art, the present invention provides a method for preparing a sample for mechanical property test of nitrocellulose, which can significantly shorten the preparation time and improve the preparation efficiency. The preparation method first adds a solvent to the nitrocellulose and melts it, then puts it into a kneading machine for stirring and kneading to form a dough-like nitrocellulose blank, then puts the blank into a vacuum hot press and presses it into a standard specimen for mechanical property test, and finally puts the standard specimen for mechanical property test into a supercritical reactor and removes the solvent therein under the cooperation of carbon dioxide gas to obtain the nitrocellulose mechanical property test specimen. The technical solution provided by the present application is to first add a solvent to the nitrocellulose and melt it, then put it into a kneading machine for stirring and kneading to form a dough-like nitrocellulose blank, then puts the blank into a vacuum hot press and presses it into a standard specimen for mechanical property test, and finally puts the standard specimen for mechanical property test into a supercritical reactor and removes the solvent therein under the cooperation of carbon dioxide gas to obtain the nitrocellulose mechanical property test specimen. Since the amount of solvent added before preparing the sample strips in the present application is not removed by natural volatilization, but by a supercritical reactor with the cooperation of carbon dioxide gas, it not only significantly shortens the solvent removal time, but also shortens the sample strip preparation time, thereby achieving the purpose of significantly improving the preparation efficiency. Combined with the existing technology, the solvent added to the nitrocellulose in the present application is also acetone or ethyl acetate.

[0014] Accordingly, in order to improve the quality of the prepared nitrocellulose mechanical property test strips and obtain test strips that meet the requirements, the present application first adds 10-50% of the total dosage of acetone or ethyl acetate for pre-dissolution when adding acetone or ethyl acetate solvent, and then adds 50-70% of the total dosage of acetone or ethyl acetate to the pre-dissolved nitrocellulose in a kneader to stir and knead to form a dough-like nitrocellulose blank to complete the melting of the nitrocellulose. When the nitrocellulose mechanical property test standard strips are pressed and formed in a vacuum hot press, the hot pressing temperature is 25-80°C.

[0015] Furthermore, in order to obtain the best solvent removal effect and the shortest removal time, when removing the solvent in the supercritical reactor, the temperature of the input carbon dioxide gas is 50-120°C and the pressure is 7-25MPa; the insulation and pressure maintenance of the solvent removal in the supercritical reactor is not less than 4h; the pressure relief is slow, and the pressure relief time is not less than 2h; and the temperature is slowly lowered while the pressure relief is released, and the cooling time is not less than 2h.

[0016] In summary, the present application aims to use supercritical carbon dioxide drying technology as a basis, make full use of the good compatibility of carbon dioxide and acetone, and achieve the purpose of assisting the removal of solvents in nitrocellulose mechanical samples, thereby greatly shortening the preparation cycle of nitrocellulose mechanical test specimens, and the test results of the prepared nitrocellulose mechanical properties test samples have good repeatability.

[0017] The technical solution of the present application is further described below through specific embodiments:

[0018] The technical problem to be solved by the present application is to remove the propylene solvent from the nitrocellulose mechanical test specimen while preventing the formation of micropores in the product that affect the test results.

[0019] The specific scheme is as follows: adding solvent to the nitrocellulose for pre-dissolution and then putting it into a kneading machine, adding solvent again and stirring and kneading to form a dough-like nitrocellulose blank; putting the blank into a vacuum hot press and pressing it into a standard specimen for mechanical testing; putting the specimen into a supercritical reactor and introducing carbon dioxide gas to reach a supercritical state, cooling and slowly releasing the pressure after saturation for a certain period of time, and taking out the specimen to obtain the nitrocellulose mechanical property test specimen.

[0020] Embodiment 1

[0021] Add 50g of acetone to 500g of nitrocellulose for pre-dissolution and put it into a kneader, then add 80g of acetone solvent again and stir and knead to form a dough-like nitrocellulose blank; put the blank into a vacuum hot press and press it into a mechanical test standard specimen at 50°C; put the specimen into a supercritical reactor and pass carbon dioxide gas to reach 80°C and 10MPa, saturate for 24 hours, then cool down and slowly release the pressure for 2 hours, take out the specimen to obtain the nitrocellulose mechanical property test specimen, and the tensile strength deviation of the nitrocellulose mechanical property sample prepared under the same conditions is less than 3%.

[0022] Embodiment 2

[0023] 80g of ethyl acetate was added to 500g of nitrocellulose for pre-dissolution and then put into a kneader, and 100g of ethyl acetate solvent was added again and stirred and kneaded to form a dough-like nitrocellulose blank; the blank was placed in a vacuum hot press and pressed into a mechanical test standard specimen at 80°C; the specimen was placed in a supercritical reactor and carbon dioxide gas was introduced to reach 100°C and 15MPa. After saturation for 18 hours, the temperature was lowered and the pressure was slowly released for 2 hours. The specimen was taken out to obtain a nitrocellulose mechanical property test specimen. The tensile strength deviation of the nitrocellulose mechanical property sample prepared under the same conditions was less than 3%.

[0024] Embodiment 3

[0025] Add 60g of ethyl acetate to 500g of nitrocellulose for pre-dissolution and put it into a kneader, add 120g of ethyl acetate solvent again and stir and knead to form a dough-like nitrocellulose blank; put the blank into a vacuum hot press and press it into a mechanical test standard specimen at 40°C; put the specimen into a supercritical reactor and pass carbon dioxide gas to reach 60°C and 20MPa, saturate for 12 hours, then cool down and slowly release the pressure for 3 hours, take out the specimen to obtain the nitrocellulose mechanical property test specimen, and the tensile strength deviation of the nitrocellulose mechanical property sample prepared under the same conditions is less than 3%.

[0026] Embodiment 4

[0027] Add 60g of acetone to 500g of nitrocellulose for pre-dissolution and put it into a kneader, add 60g of acetone solvent again and stir and knead to form a dough-like nitrocellulose blank; put the blank into a vacuum hot press and press it into a mechanical test standard specimen at 60°C; put the specimen into a supercritical reactor and pass carbon dioxide gas to reach 40°C and 20MPa, saturate for 6h, then cool down and slowly release the pressure for 2h, take out the specimen to obtain the nitrocellulose mechanical property test specimen, and the tensile strength deviation of the nitrocellulose mechanical property sample prepared under the same conditions is less than 3%.

[0028] Embodiment 5

[0029] 50 g of ethyl acetate was added to 500 g of nitrocellulose for pre-dissolution and then put into a kneader, and 120 g of ethyl acetate solvent was added again and stirred and kneaded to form a dough-like nitrocellulose blank; the blank was placed in a vacuum hot press and pressed into a mechanical test standard specimen at 50° C.; the specimen was placed in a supercritical reactor and carbon dioxide gas was introduced to reach 90° C. and 10 MPa. After saturation for 8 hours, the temperature was lowered and the pressure was slowly released for 4 hours. The specimen was taken out to obtain a nitrocellulose mechanical property test specimen. The tensile strength deviation of the nitrocellulose mechanical property sample prepared under the same conditions was less than 3%.

Claims

1. A method for preparing a sample for testing the mechanical properties of nitrocellulose, characterized in that: The preparation method comprises the following steps: firstly adding a solvent to the nitrocellulose to melt the solvent, and then placing the solvent in a kneading machine to stir and knead the nitrocellulose blank to form a dough-like nitrocellulose blank; then placing the blank in a vacuum hot press to press the blank into a standard specimen for mechanical property testing; and finally placing the standard specimen for mechanical property testing in a supercritical reactor to remove the solvent in the reactor in the presence of carbon dioxide gas to obtain the nitrocellulose mechanical property testing specimen.

2. The method for preparing a sample for testing mechanical properties of nitrocellulose according to claim 1, characterized in that: The solvent added to the nitrocellulose is acetone or ethyl acetate.

3. The method for preparing a sample for testing mechanical properties of nitrocellulose according to claim 2, characterized in that: When adding acetone or ethyl acetate solvent, first add 10-50% of the total dosage of acetone or ethyl acetate for pre-dissolution, and then add 50-70% of the total dosage of acetone or ethyl acetate to the pre-dissolved nitrocellulose in a kneader to stir and knead to form a dough-like nitrocellulose blank to complete the melting of the nitrocellulose.

4. The method for preparing a sample for testing mechanical properties of nitrocellulose according to claim 1, characterized in that: When the standard specimens for testing the mechanical properties of nitrocellulose are pressed and formed in a vacuum hot press, the hot pressing temperature is 25-80°C.

5. The method for preparing a sample for testing mechanical properties of nitrocellulose according to claim 1, characterized in that: When removing the solvent in the supercritical reactor, the temperature of the input carbon dioxide gas is 50-120°C and the pressure is 7-25MPa.

6. The method for preparing a sample for testing mechanical properties of nitrocellulose according to claim 5, characterized in that: The heat preservation and pressure maintenance time for removing the solvent in the supercritical reactor is greater than 4 hours.

7. The method for preparing a sample for testing mechanical properties of nitrocellulose according to claim 6, characterized in that: The pressure relief is carried out slowly and the pressure relief time shall not be less than 2 hours.

8. The method for preparing a sample for testing mechanical properties of nitrocellulose according to claim 7, characterized in that: The temperature should be lowered slowly while the pressure is released, and the cooling time should not be less than 2 hours.