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Static electricity in plastics and its prevention and control 1. What is static electricity: It refers to electric charges that are relatively stationary; these charges usually arise on the surface of objects as a result of friction between different objects, resulting in positive and negative charges. II. Electrostatic discharge: Refers to the transfer of static electric charge between objects that have different electrostatic potentials, caused by direct contact or electrostatic induction. It generally denotes the phenomenon of discharge that occurs when the energy of the electrostatic field reaches a certain level, resulting in the breakdown of the medium between those objects. III. Causes of electrostatics: 1. Microscopic causes According to atomic physics theory, matter is in an electric equilibrium state when it is electrically neutral. The contact of atoms from different substances leads to the gain or loss of electrons, causing the substances to lose their electrical balance and resulting in electrostatic phenomena. 2 Macroscopic reasons: Friction between objects generates heat, which induces electron transfer ； Contact and separation between objects result in electron transfer ； Electromagnetic induction causes an uneven distribution of charges on the surface of objects ； The combined effects of friction and electromagnetic induction; 4. Plastics are all polymer materials, with both surface resistance and volume resistance being greater than 10 to the 12th power. Therefore, it endows plastic materials with good insulating properties. And for this very reason, he is highly prone to generating static electricity, as plastic and its products are extremely likely to encounter situations such as production, handling, contact, separation, friction, collision, and electromagnetic induction – situations that are simply impossible to avoid. That then leads to the factors that cause static electricity. How to effectively prevent it has been a topic of concern and anticipation for many years. V. Concept of plastic anti-static properties: When the surface resistance value of plastics and their products is greater than 10 to the power of something, static electricity is very likely to be generated ； It possesses certain anti-static properties in the range of 8 to 10 to the power of something ； It exhibits excellent anti-static properties in the range of 6 to 8 powers ； It exhibits the best anti-static performance between 4 and 6 powers ； When the exponent is 4 or less, it exhibits considerable electrical conductivity and is classified as a conductor or semiconductor material. 6. Prevention and control of plastic static electricity: 1. Add some materials with moisture-absorbing properties that are harmless to plastics (additives) to reduce their surface resistance; these are known as anti-static agents for plastics, and the type of anti-static agent used depends on the type of plastic ； Both ionic and non-ionic types belong to hygroscopic antistatic agents; that is, after adding these additives, such materials absorb moisture from the air, reducing surface resistance in order to achieve antistatic properties. 2 By directly using plastics with electrical conductivity to manufacture products, conductive plastics (resins) came into being. Looking at the current domestic market, most conductive plastics are still black in color; they are additive-type conductive plastics ； Light-colored conductive plastic varieties are still under development. They are in the process of being created. 7. Antistatic agents. Selection of conductive plastics: 1. Antistatic agents are mainly produced in regions such as Zhejiang, Shanghai, and Beijing. Depending on the type of plastic, they are used in PVC, PP, PE, ABS, HIPS, etc. The price of these agents is in the range of several dozen yuan per kilogram, with an addition level of 1–3%. After addition, the surface resistance typically ranges from 10 to 10 to the power of 8; this value is significantly lower in areas with high humidity. Imported products from abroad perform better than domestic ones; even in drier areas, they can achieve a value of 8. Since the mechanism of action of such antistatic agents cannot be used to further improve antistatic performance. Antistatic masterbatches are designed to be used with most plastic raw materials that are in granular form, and they are easy to manufacture. Their main components include a carrier + antistatic agent + other additives, with the carrier usually being LLDPE resin or other types of resin. 2 Conductive plastics: Those commonly found in China are made by adding nanoscale conductive carbon black to resins. The types include PC, PET, PP, PE, ABS, HIPS, PVC, as well as various plastic alloys, but most of them are black in color. Light colors are rare. The prices range from 16 to 30 yuan per kilogram. The main production areas include Guangdong, Zhejiang, Shandong, Beijing, and other places. 3 Light-colored anti-static plastic: The addition of nano-zinc oxide whiskers to the plastic helps reduce the surface resistance of the plastic; however, it is currently expensive. Less commonly used; it is being promoted and is still in the trial phase. The emergence of anti-static plastics has played a very important role in promoting and developing plastic products, and it has also ensured the demand for anti-static products. Especially the packaging for electronic products and plastic products used in anti-static environments. An analysis of the current situation shows an increasing demand; it has excellent growth prospects! 3 Principles of Anti-static Packaging Static electricity is a common physical phenomenon. The generation of static electricity is not scary; it is the accumulation and discharge of static electricity that cause damage to optoelectronic products, ammunition, and explosives, leading to serious accidents. Knowing this, it is not difficult to prevent the hazards of static electricity. Simply put, as long as conditions can be created to prevent the accumulation of static electricity, its hazards can be avoided. The generation of static electricity mainly comes from two aspects. One is the mutual friction between objects (especially insulators), and the other is the induction by external electric or electromagnetic fields. Generally speaking, the higher the electrical conductivity of a material (the lower its resistivity), the less likely it is to generate and accumulate static electricity. Because in objects with high conductivity, once electrons are lost due to external forces such as friction, electrons from other areas quickly fill in the vacancies; this results in a transfer of charge, allowing the object to regain electrical neutrality. Conversely, if an object has an extremely low electrical conductivity (high resistivity, such as insulators), when friction causes some part of it to lose electrons, charge transfer cannot occur in a short period of time. As a result, one part of the object accumulates positive charge (due to the loss of electrons), while another part accumulates negative charge (due to the gain of electrons). Since charge accumulation occurs only on the surface of an object, the surface conductivity of that object (usually expressed as surface resistivity) becomes an important physical parameter for studying the generation and accumulation of static electricity. Numerous studies and practices have shown that, from a packaging perspective, there is a relationship between the surface resistivity of the material and the level of electrostatic protection, as illustrated in Figure 1. Effective electrostatic protection requires not only an understanding of the relationship between the surface resistivity of the aforementioned materials and the level of protection, but also familiarity with the product’s own electrostatic sensitivity as well as the environments through which it may pass during transportation and storage. The static electricity sensitivity of the product itself determines which antistatic material is most suitable to use. For example, for products that are less sensitive to static electricity (insensitive), packaging materials with a surface resistivity of 109–2012 Ω are more suitable. Since such materials are not prone to generating static electricity due to frictional vibrations, they possess antistatic properties, are low in cost, and are easily available. Ordinary paper and products made from natural fibers such as cotton and linen generally possess this function. If the products are highly sensitive to static electricity, such as field-effect transistors, large-scale integrated electronic components, electric detonators, and electric igniters, then packaging materials with a surface resistivity of less than 109 Ω must be used. An understanding of the product distribution environment helps us understand the potential magnitude of static electricity. As we all know, the degree of static electricity accumulation is highly related to the relative humidity of the environment. The lower the relative humidity (the drier the air), the easier it is for static electricity to accumulate ； The higher the relative humidity (the damper the air), the less likely static electricity is to accumulate. This is because water molecules in the air are polar molecules, and the presence of a large number of such molecules can carry away some of the charge, especially when there is air circulation. By knowing the product flow and storage conditions, it is possible to predict the extent of static electricity hazards. For example, in the cold regions of the north during winter, in dry deserts, or between product packaging materials and among those materials, as well as between the products and their packaging, extremely high static voltages can be generated due to vibrations and friction during transportation, posing a serious threat and hazard to the products. In such cases, extra care must be taken to protect against static electricity. 4 Development of anti-static packaging technology in China. In industrialized countries abroad, the hazards associated with static electricity were fully recognized back in the 1960s, leading to the establishment of numerous standards for anti-static packaging. Anti-static packaging materials have also developed rapidly, effectively controlling the hazards of static electricity. In the industrial sector, the reliability of electronic products is continuously improving, the service life of electronic devices is increasing, and accidents related to flammable and explosive materials are significantly decreasing. In recent years, there has also been an awareness of the hazards of static electricity in China; this is reflected in the fact that attention is now widely paid to its prevention during the production process. However, it must be acknowledged that for products that are extremely sensitive to static electricity, such as electronic devices, military equipment, explosives, and ammunition, there is still no clear mention of anti-static packaging solutions, let alone the establishment of corresponding technical standards. There are several aspects that deserve our exploration. First, there is still a lack of sufficient understanding of the hazards of static electricity. Some electronic component manufacturers actually use ordinary plastic boxes that lack any anti-static functionality for storing semi-finished products. Fire** manufacturers also use ordinary plastic bags as the inner packaging for nitrocellulose. The analysis of the causes of certain combustion and explosion accidents has also never considered the issue from the perspective of static electricity hazards, among other things. Second, there is a lack of in-depth research on anti-static packaging technology. To this day, we are not entirely clear as to the static electricity sensitivity of certain products, especially electric detonators. Research on anti-static packaging materials is also lacking in systematicness, leaving very limited options for packaging materials available. Since 1986, in response to the severe shortage of anti-static packaging materials in the country. 59 institutions have conducted research in this area. To date, a series of materials for anti-static packaging have been initially developed. This mainly includes plastic films for anti-static packaging, cushioning foam, and anti-static plastics for injection molding and extrusion molding. The electrical and mechanical properties of these materials can meet the requirements for electrostatic protection in various products, with some of them achieving performance levels equivalent to those available abroad in the 1980s. It initially meets the needs of some current domestic markets. We believe that as awareness of the hazards of static electricity grows, anti-static packaging technology will inevitably see rapid development in the electronics and military industries. 5 Conclusions and Recommendations The accumulation and discharge of static electricity have caused significant losses to the microelectronics industry and the military industry. The dangers of static electricity are not terrifying; what’s scary is people’s lack of awareness about it. With the advancement of science and technology, the hazards of static electricity will surely draw increasing attention from more and more sectors. Anti-static packaging technology will also develop rapidly. To minimize the hazards of static electricity, it is necessary to take decisive actions to enforce antistatic technologies. Here are some suggestions: (1) Strengthen the promotion of the hazards associated with static electricity. Raise the awareness of anti-static measures among all types of personnel in the industry dealing with electrostatically sensitive products. (2) The research and production departments of military products work together to further understand the electrostatic sensitivity of certain commonly used agents through a combination of theory and practice, thereby laying a theoretical foundation for anti-static packaging. (3) Conduct a comprehensive investigation of explosives, propellants, and ammunition (including fuses, combustible cartridges, etc.) in the military industry, to determine the level of static electricity during the handling and storage of these products under various environmental conditions. Provides basic information for anti-static packaging. (4) For electrostatically sensitive products, strict control of electrostatic protection at every stage is implemented from the production process to the time the products leave the factory. To address the weak link of factory packaging, expedite the legislative work on anti-static packaging. UHMW PE refers to ultra-high molecular weight polyethylene. There is also low-density polyethylene, also known as high-pressure polyethylene, with a density of 0.91–0.92; and high-density polyethylene, also known as low-pressure polyethylene, with a higher density than the former. The molecular weight of these two types of polyethylene is generally below 400,000. Polyethylenes with even higher molecular weights are referred to as “high” or “ultra-high” molecular weight polyethylenes; those with a molecular weight greater than 1.5 million are classified as ultra-high molecular weight polyethylenes. Currently, the molecular weight can reach up to 600–700. Due to their high molecular weight, these materials exhibit improved properties, among which wear resistance is particularly notable, being several times to dozens of times better than that of other known materials. They also have excellent low-temperature resistance, maintaining their strength at temperatures below -100 degrees Celsius, and can even retain their structural integrity at -296 degrees Celsius in liquid nitrogen conditions. Their resistance to stretching, impact, low temperatures, and corrosion is also quite outstanding! In the widespread use of engineering plastics, it is one of the essential materials. Its density ranges from 0.94 to 1.00. However, the high molecular weight results in poor processability, so sintering and molding are commonly used methods, though these are less efficient. In recent years, some universities have conducted research on extrusion and injection molding, achieving significant results. To my knowledge, Beijing University of Chemical Technology has successfully produced extruded pipes in China, while Northwest Polytechnical University has also achieved success in injection molding. Universities in South and East China have also produced products using various methods. Nanomaterials play a crucial role in the application of ultra-high molecular weight polyethylene; nanomodification improves the plasticity of this material significantly. There are production facilities for this material in Beijing and Northeast China. Manufacturers of ultra-high molecular weight polyethylene resin include those in Beijing with an annual production capacity of 20,000 tons, those in Shanghai with a capacity of 500 tons per year, and those at Qilu Petrochemical Institute with a capacity of 1,500 tons per year. As a modification specialist, Chengdu Zhengguang is also involved in this field. The price of the resin is generally between 14,000 and 11,000 yuan per ton, while the price of modified materials exceeds 25,000 yuan per ton. To facilitate research among industry professionals, I hope we can exchange information. Briefly speaking, the principle of single-screw extrusion involves dividing the effective length of the screw into three sections, determined by the screw diameter, pitch, and depth. These three sections are usually divided equally, with each accounting for one-third of the total length. Starting from the last thread at the feed inlet, this section is called the conveying section. In this section, the material does not need to be plasticized, but rather it needs to be preheated, compressed, and compacted. Traditional extrusion theories considered the material in this section to be in a loose state, but it has been proven that it actually forms a solid mass. In other words, after being compressed, the material behaves like a solid plug. Therefore, its function is simply to transport the material. The second section is called the compression section, and this is when the volume of the screw groove changes! ! It gradually decreases in size, and the temperature must reach a level at which the material becomes plasticizable; compression occurs here in section three of the conveying process, where it is reduced to one – this is what is known as the compression ratio of the screw: 3:1. Some machines may have different ratios. The material that has been plasticized then enters next. Third metering section: Here, the material remains at the plasticization temperature; it is transported in precise quantities, just like in a metering pump, to supply the nozzle. The temperature must not be lower than the plasticization temperature, and it is usually set slightly higher. This is the essence of the extrusion theory. Biodegradable plastics: First, let’s explain the mechanism behind biodegradable plastics: Plastics that are easy to degrade (such as polypropylene PP) are used, along with biodegradable masterbatches, to create sheets, which are then thermoformed into various packaging boxes. This requires a sheet machine and a blister molding machine. In recent years, new processes have emerged (the sheet thermoforming integrated machine), which allows for direct feeding into the forming machine while the sheet is being produced, making it particularly suitable for the molding of large quantities of identical products. Looking at the market for biodegradable meal boxes, **local authorities once made great efforts to promote such boxes, but due to national conditions, the end result was a system in which plastic biodegradable meal boxes coexisted with paper meal boxes. The reason is ； Pollution after use of biodegradable plastic meal boxes; the degradation is not optimal ； Pollution in the early stage of paper meal box manufacturing (pulp). In one region, regulations were issued prohibiting the entry of non-degradable food containers into the market (usually referring to EPS), but for various reasons, enforcement was not thorough enough, especially in small and medium-sized cities. Taking the railway passenger transport market as an example, paper meal boxes and plastic-degradable meal boxes are currently in use side by side; the Ministry of Railways has established a dedicated agency called the \"Railway Pollution Control Office\" for this purpose, while local environmental protection and sanitation departments are responsible for handling such matters. In other words, biodegradable meal boxes must be approved by relevant authorities before they can be sold in areas where such approval applies. This is a reasonable and legal channel. From a manufacturing perspective, the difficulty is not very high. It is worth noting, however, that counterfeit degraded products are difficult to manage. In the Beijing market, lunch boxes made of polypropylene (PP) with calcium carbonate added to it remain widespread due to their low cost; they have even managed to establish a \"monopoly\" position there, all because of their low prices! At its lowest, the meal box (usually priced per gram) costs 4 cents per gram; each box weighs around ten grams, so the cost is only 4–6 cents per box, which is even lower than that of foam meal boxes. But the demand is very high; therefore, in today’s market conditions, this is the only way it can develop. However, such products find it difficult to enter large supermarkets. Since there is room for development in some areas, it remains a good project