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CN-122010649-A - Hot press forming process of Mg/PVDF smoke powder

CN122010649ACN 122010649 ACN122010649 ACN 122010649ACN-122010649-A

Abstract

The application discloses a hot press molding process of Mg/PVDF pyrotechnic composition, and relates to the technical field of pyrotechnic composition preparation. The process takes magnesium powder and modified polyvinylidene fluoride as raw materials, no additional adhesive is needed, and the modified polyvinylidene fluoride is prepared by compounding polyvinylidene fluoride and silane modified nano lanthanum fluoride. The pyrotechnic composition finished product is prepared through the steps of sieving, wet mixing grinding, die filling and oscillating, hot press forming, demoulding, trimming and the like. Polyvinylidene fluoride is selected to replace the traditional polytetrafluoroethylene as an oxidant, has the characteristics of proper melting point and decomposition point, forms a stable thermal processing interval, has high fluorine content, and can fully react with magnesium powder to release energy. The process improves the molding quality and combustion stability of pyrotechnic compositions.

Inventors

  • ZHU CHENGUANG
  • HE XINGYING
  • LIN ZHIWEN
  • ZHANG CHENGCHEN
  • HUANG QIAN
  • ZENG YUYANG

Assignees

  • 南京理工大学

Dates

Publication Date
20260512
Application Date
20260305

Claims (10)

  1. 1. The hot press molding process of the Mg/PVDF pyrotechnic charge is characterized by comprising the following steps of: S1, selecting magnesium powder and modified polyvinylidene fluoride as raw materials, and screening the magnesium powder; s2, mixing the sieved magnesium powder with modified polyvinylidene fluoride, adding a dispersion medium, stirring to form a suspension, grinding and drying to obtain mixed powder; s3, filling the mixed powder into a die, spreading the powder by using a scraper, and then mechanically oscillating the die; s4, heating a die filled with the mixed powder to a preset temperature, then applying preset pressure and maintaining the pressure for preset time for hot press molding; s5, decompressing after the pressing is finished, performing demoulding operation after the die is cooled to the ambient temperature, and trimming and cutting to obtain a Mg/PVDF pyrotechnic composition finished product; Wherein the modified polyvinylidene fluoride is prepared from polyvinylidene fluoride and silane modified nano lanthanum fluoride.
  2. 2. The hot press molding process of the Mg/PVDF pyrotechnic composition according to claim 1, wherein in S1, the sieving treatment is carried out by adopting a 200-250 mesh sieve, and the sieving is carried out for 2-4 times continuously.
  3. 3. The hot press molding process of the Mg/PVDF smoke powder according to claim 1, wherein in S2, the preparation step of the modified polyvinylidene fluoride comprises: Taking nano lanthanum fluoride powder with the particle size of 50-100 nm, performing ultrasonic dispersion for 25-35min by using absolute ethyl alcohol, and then performing vacuum drying for 1.5-2.5h at 75-85 ℃ to obtain pretreated nano lanthanum fluoride powder; Adding a silane coupling agent into absolute ethyl alcohol according to 5-8% of the mass of nano lanthanum fluoride, uniformly stirring, regulating the pH to 4-5 by using dilute hydrochloric acid, adding pretreated nano lanthanum fluoride powder, stirring for 1.5-2.5 hours at 55-65 ℃, centrifugally separating, washing for 3-4 times by using absolute ethyl alcohol, and vacuum drying for 2.5-3.5 hours at 65-75 ℃ to obtain silane modified nano lanthanum fluoride; Weighing silane modified nano lanthanum fluoride accounting for 1-3% of the mass of polyvinylidene fluoride, adding the silane modified nano lanthanum fluoride and polyvinylidene fluoride powder into a high-speed mixer together, mixing for 12-18min at 95-105 ℃, cooling to room temperature, crushing and sieving with a 180-200-mesh sieve to obtain modified polyvinylidene fluoride powder.
  4. 4. A hot press molding process of Mg/PVDF pyrotechnic according to claim 3, wherein the silane coupling agent comprises γ -aminopropyl triethoxysilane or γ -aminopropyl trimethoxysilane.
  5. 5. The hot press molding process of the Mg/PVDF powder as set forth in claim 1, wherein in S2, the mass ratio of the magnesium powder to the modified polyvinylidene fluoride powder is (0.8-1.2): 1; The ratio of the total mass of the magnesium powder and the modified polyvinylidene fluoride powder to the volume of the dispersion medium is 1g (1-1.5) mL, and the dispersion medium is absolute ethyl alcohol.
  6. 6. The hot press molding process of the Mg/PVDF pyrotechnic composition according to claim 1, wherein in S2, the stirring time is 25-35min, and the stirring speed is 200-300rpm; The drying temperature is 55-65 ℃ and the drying time is 0.8-1.2h.
  7. 7. The hot press molding process of the Mg/PVDF smoke powder according to claim 1, wherein in S3, the loading of the mixed powder is 0.15-0.35g; The size of the die is 3cm long and the width of the die is 0.5cm; the speed of the mechanical oscillation die is 150-200rpm, and the time is 5-10min.
  8. 8. The hot press molding process of the Mg/PVDF pyrotechnic composition according to claim 1, wherein in S4, the preset temperature is 25-170 ℃, the preset pressure is 450-650Kg, and the pressure maintaining preset time is 2-4min.
  9. 9. The hot press molding process of the Mg/PVDF powder as set forth in claim 1, wherein in S4, the heating mode of the die is heating by a heating table, and the heating speed is 10-20 ℃ per minute.
  10. 10. The hot press molding process of the Mg/PVDF pyrotechnic composition according to claim 1, wherein in S5, the pressure release speed is 50-100Kg/min.

Description

Hot press forming process of Mg/PVDF smoke powder Technical Field The application relates to the technical field of preparation of pyrotechnic compositions, in particular to a hot press molding process of Mg/PVDF pyrotechnic compositions. Background The smoke powder is used as an important energetic material and widely applied to the fields of infrared baits, ignition systems, propellants and the like, and the performance quality of the smoke powder directly influences the use effect of the terminal product. The conventional molding process for the gunpowder mainly comprises two steps of wet mixing, granulating, cold press molding and hot press molding of a low-melting-point binder. The hot press forming process of the low-melting-point binder needs to additionally introduce the binder to ensure the mechanical strength of the product, and the addition of the binder can dilute the effective contents of the combustible agent and the oxidant to obviously weaken the energy output and combustion performance of the pyrotechnic composition. Meanwhile, polytetrafluoroethylene is often adopted as an oxidant in a traditional pyrotechnic composition formula, but the melting point of the pyrotechnic composition is higher (327-342 ℃), the thermal processing interval is narrow, the temperature control precision requirement on forming equipment is extremely high, PTFE is almost insoluble in any solvent, the raw material mixing uniformity is poor, and the combustion stability and consistency of the pyrotechnic composition are further affected. Other fluorocarbons such as hexachloroethane have the problem of overlapping melting and sublimation temperatures, and the melting temperature and the decomposition temperature of the polytrifluoroethylene are too close, so that a proper hot pressing processing interval is lacked, and the dual requirements of a forming process and performance are difficult to meet. Therefore, development of a pyrotechnic composition preparation process which does not need an organic solvent, does not need an additional binder, is simple in molding process and excellent in product performance becomes a technical problem to be solved in the field. Disclosure of Invention The application aims to overcome the defects of potential safety hazard, weakened combustion performance, high molding difficulty and the like of the existing cigarette powder molding process and provides a hot press molding process of Mg/PVDF cigarette powder. The technology utilizes the dual functions of the oxidant and the binder by reasonably selecting the oxidant and optimizing the molding flow, does not need to additionally add the binder, avoids the use of an organic solvent, effectively improves the molding quality, the mechanical strength, the combustion stability and the energy output efficiency of the gunpowder, and provides technical support for the large-scale production of the high-performance gunpowder. In order to achieve the above purpose, the application adopts the following technical scheme: The application provides a hot press molding process of Mg/PVDF smoke powder, which comprises the following steps: S1, selecting magnesium powder and modified polyvinylidene fluoride as raw materials, and screening the magnesium powder; s2, mixing the sieved magnesium powder with modified polyvinylidene fluoride, adding a dispersion medium, stirring to form a suspension, grinding and drying to obtain mixed powder; s3, filling the mixed powder into a die, spreading the powder by using a scraper, and then mechanically oscillating the die; s4, heating a die filled with the mixed powder to a preset temperature, then applying preset pressure and maintaining the pressure for preset time for hot press molding; s5, decompressing after the pressing is finished, performing demoulding operation after the die is cooled to the ambient temperature, and trimming and cutting to obtain a Mg/PVDF pyrotechnic composition finished product; Wherein the modified polyvinylidene fluoride is prepared from polyvinylidene fluoride and silane modified nano lanthanum fluoride. Further, in S1, the screening treatment adopts a 200-250 mesh screen, and the screening is carried out for 2-4 times continuously. Further, in S2, the preparation step of the modified polyvinylidene fluoride includes: Taking nano lanthanum fluoride powder with the particle size of 50-100 nm, performing ultrasonic dispersion for 25-35min by using absolute ethyl alcohol, and then performing vacuum drying for 1.5-2.5h at 75-85 ℃ to obtain pretreated nano lanthanum fluoride powder; adding a silane coupling agent into absolute ethyl alcohol according to 5-8% of the mass of nano lanthanum fluoride, uniformly stirring, regulating the pH to 4-5 by using dilute hydrochloric acid, adding pretreated nano lanthanum fluoride powder, stirring at a constant temperature of 55-65 ℃ for 1.5-2.5h, centrifugally separating, washing by using absolute ethyl alcohol for 3-4 times, and vacuum drying at 65-75