Antistatic packaging design of the hottest field a

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Abstract: This paper expounds the causes and harmful forms of electrostatic discharge under field conditions, analyzes the basic principle of electrostatic protection, and introduces several protective materials that can be used in Ammunition Packaging under field conditions, so as to provide help for the long-term storage of ammunition to prevent static

key words: field ammunition; Electrostatic discharge: antistatic packaging design

with the increasing application of electronic components and Electric Initiating explosive devices in ammunition, the electrostatic sensitivity of ammunition is getting higher and higher, and its antistatic performance is getting weaker and weaker. The accidents of spontaneous combustion and self explosion of ammunition caused by electrostatic discharge often occurred in foreign and Chinese armies. Especially in field conditions, there are more accidental factors for ammunition to produce electrostatic discharge, but many anti-static measures are difficult to implement. Improving the packaging structure and performance and enhancing the anti-static ability of ammunition have become the inevitable choice of anti-static of field ammunition, which can effectively eliminate the occurrence of electrostatic hazards, and is also of great significance to the anti-static of long-term stored ammunition

1 the generation and harmful forms of static electricity under field conditions

the generation of static power supply under field conditions mainly includes the following three aspects: 1) contact separation electrification. In the transportation and handling of ammunition, static electricity will be generated when the packaging materials are separated from other objects and rubbed. When people undress or stand up from the leather chair, they will generate thousands of volts or even tens of thousands of volts; 2) Peel off and power on. When opening the sealed package of ammunition to take it out, the human body and packaging materials will generate high voltage. In addition, high voltage will also be generated when the plastic shed cloth on the surface of ammunition is uncovered; 3) Induction electrification. When lightning occurs near the ammunition pile, the extremely high potential of lightning can induce a very high voltage on the ammunition surface. Although the probability of direct lightning strike in ammunition pile is very small, there are many induction mines, especially in the thunderstorm season in the south, the voltage of the induced charge on the ammunition surface is enough to puncture the internal circuit of the ammunition and ignite Electric Initiating explosive devices. This kind of accident has happened in our army before. The rocket shells stacked on a certain position spontaneously flew out due to the spontaneous combustion of electric ignition shells caused by lightning induction. When these high-voltage dangerous static power supplies form energy coupling with the circuit of ammunition and Electric Initiating explosive devices, electrostatic discharge will occur. The discharge voltage can reach tens of thousands of volts, the discharge current can reach hundreds of AMPS, the spectrum range can reach dry MHz, and the rise time of the current waveform can be less than 1ns. Electrostatic discharge can cause accidental ignition and explosion accidents of Electric Initiating explosive devices, and can also cause serious interference and hard damage to electronic equipment. The electromagnetic pulse generated by electrostatic discharge may also lead to the malfunction of microelectronic circuits and the potential reduction of working reliability

2 principle of electrostatic protection

although there are many dangerous electrostatic sources in the field, and the means of electrostatic protection are limited, electrostatic hazards can still be controlled and eliminated. Three conditions must be met to form electrostatic discharge at the same time: 1) there is a dangerous static power supply with sufficient high voltage; 2) Places with sensitive electrostatic hazards; 3) Form electrostatic energy coupling. According to the electrostatic discharge conditions, it is necessary to eliminate electrostatic discharge at least, especially mercury, cadmium, lead, chromium, etc; Organic colorants also often decompose some carcinogenic, mutagenic and other organic toxic materials. One condition is not tenable. Without changing the ammunition design, the discharge phenomenon can only be eliminated by reducing the danger of electrostatic power supply and cutting off the electrostatic energy coupling channel. Although increasing the humidity can significantly change the surface resistance of the object and enhance the conductivity, the humidity of the field ammunition storage site is difficult to control, so it is impossible to improve the escape speed of electrostatic charge and reduce the voltage of dangerous electrostatic power supply by adjusting the humidity of local space

using anti-static materials to improve the packaging is a simple and effective protection method, which can not only facilitate the rapid leakage of electrostatic charges on the ammunition packaging, but also play the role of electromagnetic shielding to prevent some powerful radar and electromagnetic pulse weapons from generating RF intrusion into the ammunition, forming energy coupling, causing damage to electronic circuits or failure or even explosion of Electric Initiating explosive devices. For example, the minimum safe current of the thermal bridge wire type electric blasting device is only 50mA

3 methods to be taken

under high-tech conditions, anti-static packaging has become a basic requirement for ammunition packaging. The anti-static packaging materials and products of the United States, Japan, Germany and other countries have taken the lead in the world. The United States has also specially revised the ammunition packaging specification to optimize and improve the ammunition packaging. According to the actual situation of our army and drawing on the packaging experience of foreign armies, the necessary anti-static packaging of ammunition can greatly improve the living space of ammunition. There are mainly the following methods:

3.1 use antistatic agents

according to different adding methods, antistatic agents are divided into external coating type and internal addition type. Externally applied antistatic agents are applied to the surface by brushing, spraying or dipping. They have fast effect and wide application. Especially, it is better to use this method when improving the ammunition packaging with no electrostatic protection ability or poor protection ability produced earlier. The original packaging can be used, which saves money and is easy to operate. Some shielding coatings are generally sprayed with metal powders such as gold, silver, copper, nickel or graphite powder on the inner and outer surfaces of the package, which can also play a good anti-static and shielding effect, but its price is high, and it is not suitable for large ammunition packaging boxes

the additive antistatic agent is added to the resin when batching, so that it can be evenly dispersed into the polymer. These substances are soluble in water, and it can migrate from the interior of the polymer material to the surface, forming a uniform antistatic layer on the surface. It has friction resistance, good stability, long-lasting efficiency, and low price. It is suitable for packaging materials of ammunition, because the storage life of general ammunition is more than 15 years

3.2 use structural conductive polymer material

structural conductive polymer material is a new type of conductive unsaturated polymer. Through the action of their own chemical structure, they have the same effect as the free electrons of metals п The molecular structure of electrons and the movement of electrons present conductivity through π conjugation system, which are synthesized by electrolytic polymerization and doped. Now their highest conductivity level is comparable to that of copper, silver and other metals

polyacetylene is the most cost-effective conductive material at present. After doping, its conductivity can be as high as 105 Ω - 1, while the conductivity of copper and silver is only 106 Ω -1. It can be seen that the conductivity of doped polyacetylene is close to that of a good conductor. However, due to the existence of double bonds in polyacetylene that are very easy to be oxidized, its stability is not very high. In addition, polyacetylene is neither soluble nor molten, so it is difficult to process and shape

compared with polyacetylene, the goal of this project is "Building and testing whether the space structure is suitable for the use of spacecraft has greater advantages. It is stable in nature, easy to process, easy to form a film, and the film is soft and elastic. More importantly, the price is low. Pan has excellent electrical properties, and its conductivity changes between ~ 10 Ω -1 with different doping degrees.

3.3 using filled materials

the so-called conductive filler is a kind of material that can give conductivity. According to its In terms of performance, there are mainly five series, namely metal series, carbon series, metal oxide series, metallized fiber series and organic polymer series. Carbon series is the most commonly used conductive filler, and carbon black is a natural semiconductor material with a volume resistivity of about 0.1 ~ 10 Ω Cm, the raw material is easy to obtain, the conductivity is durable and stable, and the resistivity of the material can be greatly adjusted (1 ~ 108 Ω.Cm). Therefore, the composite conductive polymer material filled with carbon black is currently the most widely used and used conductive material in antistatic and electromagnetic shielding

carbon fiber is a new coating with good conductivity, which is characterized by uniform and firm coating and good adhesion with resin. The conductivity of metallized carbon fiber is 50 ~ 100 times higher than that of ordinary carbon fiber. However, its price is expensive, and it is only suitable for the protection of internal electronic circuits and Electric Initiating explosive devices of some munitions with high electrostatic sensitivity

the matrix polymer filled with metal powder and metal oxide can obtain excellent conductivity, and high conductivity can be obtained with little filling. However, metal fibers are easily broken and oxidized during processing, and the price is also more expensive

4 conclusion

the anti-static packaging of ammunition should be combined with the actual situation of our army. When designing the packaging, we should combine the packaging and electrostatic protection, choose different protective packaging for different ammunition, and choose appropriate packaging materials, so as to avoid excessive packaging, increasing costs, or insufficient packaging. In addition, the internal and external packaging should be combined for comprehensive consideration to determine the best protection scheme, which cannot be satisfied with the improvement of only one packaging. We should integrate the design of electrostatic protection into the design of sub munitions packaging, and strive to achieve the best performance price ratio. In a word, the popularization and application of anti-static packaging will effectively improve the anti-static ability of our military ammunition and further strengthen the field survival ability of ammunition

Author: Ma Hui, Gao Xuyong, Yang Shiliang

information source: Packaging Engineering

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