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Domestic plastic anti-static / conductive products demand is booming, electronic product packaging needs a large number of varieties, plastic products anti-static / conductive products, especially people's attention, is one of the goals pursued by the plastic packaging industry, using domestic The basic materials, research and development of products, additives, masterbatch suitable for plastic conductive / anti-static requirements, replace the high-priced imported similar products, develop electronic product packaging and anti-static product packaging more suitable for market demand. Common products such as: plastic conductive / anti-static gas transmission, infusion pipeline; low-resistance plastic packaging tray for electronic products, conductive / anti-static plastic sheet, sheet, foam, conductive film.
Common anti-static plastic packaging generally requires 10 to 8 ohms or more, which can be any color, and the resistivity is below 10 to the power of 8 and more conductive carbon black is used as the main conductive material, so the black color is more More, the following is a brief description of the method of making conductive plastic or conductive masterbatch by using conductive carbon black and plastic blending.
Choice of conductive carbon black
For suitable conductive carbon black, it is preferred to use a special conductive carbon black. Special conductive carbon black is relatively common in domestic sales, and good dispersion is the first choice factor. According to the specific application of the product, suitable conductive carbon black can be selected. For example, for the application of thin film, the dispersion and particle size of conductive carbon black are more critical. And thick-walled pipes, the choice of conductive carbon black is relatively simple.
For general-purpose conductive masterbatch, linear polyethylene LLDPE with wide applicability is generally used, mainly powdery. For example, the brand name 7042 resin can be selected as a carrier, which is beneficial to the dispersion and processing of the special conductive carbon black. It is also suitable for extrusion blown film, and is also used for HIPS aBS PP LDPE HDPE after grafting. The special conductive masterbatch generally selects a resin which is close to the melt index of the plastic matrix resin as a carrier, and it is preferable to select a resin of the same system as a carrier.
The use of additives requires good heat resistance and good compatibility. Considering the suitability of multiple varieties as a carrier, the necessary grafts, dispersants, antioxidants, and rheological agents should be added appropriately to achieve processing performance and a wide range of applications.
Processing Equipment
High-speed mixer, flat twin-screw extruder (building block) granulation production line, according to their own circumstances, do not exaggerate the same set.
Processing technology
(1) Low-grade conductive masterbatch: The conductive carbon black and the carrier are fed to a high agitator according to a predetermined ratio, and a dispersant, an antioxidant, a grafting agent and the like are added, stirred and mixed together, and then extruded by a twin-screw. This is called a low-level conductive masterbatch and can be used for ordinary pipe use. The amount added is about 20%.
The carbon black concentration in the common carbon black conductive masterbatch is not very high, especially the mixing of the nano-scale carbon black and the resin, it is difficult to achieve a high addition amount, and the excessive addition amount is easy to see an open flame until the resin is decomposed. .
(2) Drying of low-grade masterbatch, secondary extrusion granulation after installation of filter screen, which can be made into special/universal masterbatch according to need, or diluted to the required concentration, and can be used as conductive masterbatch after packaging. use. As a plastic masterbatch, it must have sufficient concentration and its electrical conductivity resistance, and the conductivity is generally less than 50 ohms. As the masterbatch is the ultimate product, please pay attention to the filter threshold value of various conductive carbon black used in the resin, too much use is not practical!
Applications
The low-grade conductive masterbatch is made of LLDPE powder as the carrier, the special conductive carbon black content is more than 20%, and the grafting, dispersing agent, antioxidant, rheological agent is added, and the plastic reduced-resistance masterbatch obtained by the secondary processing is reduced. Surface resistance), its surface resistance is less than 100 ohms.
For high-impact polystyrene plastic sheet, add 15 parts of reduced-resistance masterbatch to obtain a permanent anti-static sheet with a surface resistance of 10 to 8-6. Add 30 parts to obtain a resistance of less than 10. Conductive sheet of 4th power. Fully meet the needs of packaging in the electronics industry.
For the application of aBS and PP injection molding, 50 parts of the reduced-resistance masterbatch can be added to produce a 6-th power to 6-th power injection product with a resistance value of 10.
For the application in blown film, 40 parts of the reduced-resistance masterbatch can be added to obtain a product with a resistance value of about 10 to the fifth power.
It should be noted here that the surface resistance is greatly reduced due to the injection pressure and shearing effect; the difference in the stretching of the blown film also reduces the electrical conductivity.
Application of reducing resistance masterbatch in plastic sheet
Machine requirements: screw diameter: 90-105mm, length to diameter ratio of <33:1, screw: PS.PP special type, a mixing section at the front end, sheet forming pressure 12-14MPa
Stirring of raw materials: high-speed kneading machine, according to the required surface resistance of the sheet, add different proportions of reduced-resistance masterbatch, put into the kneading machine, stir for 3-10 minutes, if there is a small amount of water, get in the process Eliminate, if too much water, it is recommended to use the dryer or increase the mixing time
High-speed stirring can also be used in the past for non-sheet materials that are mixed for unknown reasons. They will be adsorbed on the upper end of the pot due to centrifugal force/electrostatic separation, so you can easily remove them.
Calendering rolls: use temperature 60 degrees. Cooling roll temperature is less than 40 degrees; drum pressure: 6KG/cm 2 or below 6MP. The temperature is too high. If the pressure is too high, the surface resistance will be lost. The residual material between the calender rolls should not be too much, otherwise the pressure orientation will occur, and there will be similar effects of excessive stretching, the longitudinal strength is lowered, and the surface resistance is lowered.
Sheet stretching: has an effect on the surface resistance, and the larger the stretching, the lower the resistance. In particular, hot stretching, that is, the interval between the die exit die and the calender roll is 5-10 CM, slightly sag to unstretched straight to lightly stretched excessively to stretch or stretch excessively; Hot stretching of material - often the surface resistance is reduced, the transverse strength of the sheet is reduced, and the sheet is easily folded/cracked in the lateral direction. If the longitudinal and transverse folding performance is similar, the sheet quality is good for the blister; if both directions are Poor, the quality of the raw materials is poor, and the raw materials/formulations are replaced.
Selection of raw materials: HIPS raw materials are extrusion grade, common PH88 series 476L466F825
The reason why the PP raw material is the extrusion grade 1300F401 has a melt index of preferably less than 1 g/10 min because the hot melt sag is too large and it is difficult to blister.
Recycled raw materials: It can be used in the manufacture of non-food contact blister products. Due to heat aging/degradation, relevant enhancements and toughening auxiliaries can be added to supplement some of the lost properties. BS, SBS and other compatible thermoplastic elastomers can be used as a toughening agent in HIPS; a small amount of aBS can be added to obtain a reinforcing effect, and some organic liquid lubricants can be aged and toughened.
Use of certain incompatible materials: sheet delamination/separation cracking can occur.
Electrostatic generation/treatment: In the case of high resistance, if the plastic is more than 10 to the 12th power, there will be static electricity caused by displacement friction, which can reach several thousand volts or even tens of thousands of volts of electrostatic voltage, which hinders production and is easy to appear. Fire sources, especially in the presence of flammable gases, are very dangerous and even cause fires.
Adding more than 10 parts of the reduced-resistance masterbatch can reduce the surface resistance of the sheet, and 15 parts - 30 can obtain the surface resistance of 10 to 8 in the HIPS sheet, and the static electricity will not be generated under the action of conduction. And it is permanent, can be stored for a long time / repeated effective!
Ordinary antistatic agent is a time-sensitive additive. It relies on the principle of absorption of anions and cations for more than 3-6 months or repeated heating. The volatile and antistatic effect is gradually lost until it is completely ineffective and dried according to regional characteristics. The role of wet areas varies.
Ordinary sheet production, after the inevitable generation of static electricity, the grounding dissipation can be adopted to increase the indoor/local humidity guide elimination, and the use of the static eliminator is very effective.
Measuring the surface resistance of the sheet: At present, the surface resistance tester is often used to test the surface static charge of the sheet. Its range is 10 to 3 to the power of 10, and a better method is to use a high resistance meter.
Proposed ratio of reduced-resistance masterbatch: 15 parts of surface resistance is added to HIPS sheet below 8th power: 30 parts can reach below 4th power in PP sheet due to high PP edge and HIPS. 20-40 servings.
Use of other plastic products: Injection molding products Extrusion stretching products are not suitable for this amount, and the surface resistance of the desired products can be obtained by appropriately increasing.
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