ABC film blowing method for the most popular antis

2022-08-02
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Anti static polyethylene film ABC blowing method

Abstract: using the three-layer (ABC) Co extrusion blowing process, through the exploration of the formula, the processing temperature of layer a, the extrusion amount of layer a and the control of corona treatment, SABIC has always been committed to turning challenges into opportunities (38d surface wetting tension makes it more convenient for people to travel yn/cm), Can be reliably combined with other plastic substrates key words: surface energy; Anti static; Polyolefin

with the rapid development of soft plastic packaging industry and the development and application of high and new technologies, polyolefin film is constantly adhesive tensile bonding strength tensile speed: 5mm/min is endowed with new special functions, and anti-static polyolefin film is a kind of film in urgent demand. At present, the market-oriented antistatic polyolefin film can not be combined with other plastic substrates to form layered packaging materials because of its low surface energy; The low mechanical and physical properties of simple films limit its wide application. Therefore, the soft plastic packaging industry urgently needs to develop an antistatic polyolefin film with high surface energy and reliable composite with other substrates. Taking the newly developed antistatic polyethylene film as an example, this paper discusses its manufacturing process and product performance with peers

1 production process

1.1 process optimization

at present, the common production process of anti-static polyethylene film is the film blowing method, and the anti-static polyethylene film produced by the film blowing method cannot be corona treated because of its low internal and external surface resistivity (P. within the range of 10 '- 109q). As a non-polar material, its surface energy is low and can not be combined with other substrates. The mechanical and physical properties of the simple film, such as water vapor permeability, tensile strength, breaking force and puncture resistance, can not meet the requirements for packaging materials of electronic, chemical, civil explosive and military products. It can only be used for the lining packaging of powder products such as pyrotechnic agents sensitive to static electricity and microelectronic products. Some use extrusion compounding (tape casting compounding) process to make layered packaging materials, but the disadvantage is that the peel strength is low, and the sealing strength after bag making can not meet the use requirements. After full demonstration, the three-layer co extrusion (ABC) film blowing process is selected, that is, semi-conductive particles are added to layer a (heat sealing layer) in a certain proportion, and layer C (composite layer) is corona treated to prepare composite anti-static polyethylene film

1.2 process key points

1.2.1 formula

the formula of particles added to layer a (heat sealing layer) is one of the process key points, and the proportion of semi conductive particles shall be determined according to the content of its effective substance (conductive carbon black). It is necessary to find out the critical amount of semiconducting particles. If the amount is higher than the critical amount, the film will be easily broken down by electric spark during corona treatment, and the product cost will be increased; If the addition amount is much lower than the critical amount, the resistivity of the film is higher than 1012, which is approximately insulated and does not have anti-static function. Therefore, it is an important subject to explore the critical amount of semiconducting particles and the relationship between conductive carbon black content and surface resistivity. Secondly, semi conductive particles with high MFR (melt flow rate) and good plasticization should be selected, and the viscous flow temperature and MFR of semi conductive particles, LDPE and LLDPE should be as close as possible, which is conducive to the control of processing temperature

1.2.2 processing temperature of layer a extruder

the effective component of semi conductive particles is conductive carbon black. If the processing temperature of the extruder is too high, it is easy to damage the phase structure of carbon black, and even carbonization occurs, which not only reduces the plastic and mechanical properties, but also fails to have the effect of anti-static. Therefore, under the condition of ensuring good plasticization of layer a, the processing temperature of layer a extruder should be properly reduced

1.2.3 extruding amount of layer a

extruding amount of layer a is also one of the key points of the process. If the extruding amount of layer a is too large, the thickness of layer a film will increase, and the conductivity of the whole film will be enhanced. During corona treatment, the film will be easily broken down by electric spark, which will also increase the product cost and the sealing strength will become worse; If the extrusion amount of layer a is too small, the thickness of layer a film decreases. According to the conductive mechanism of conductive carbon black, the formation of conductive complex is three-dimensional, which is related to the thickness of the film. The thickness of layer a film is too low to form a conductive complex, so it has no anti-static effect

1.2, the distance between 4 electrodes and corona treatment voltage

corona treatment makes the film surface have higher energy and adhesion. Its principle is to use high frequency and high voltage to corona discharge the plastic surface to produce low-temperature isocyana, and the plastic surface will produce free radical reaction, so that the polymer will be crosslinked, the surface molecules will be oxidized to produce polarity, and the surface will become rough, increasing its wettability to polar solvents or adhesives. The effect of corona treatment is related to input high voltage, film thickness and distance between electrodes. The distance between electrodes is generally in the range of 1-1.5mm. When blowing ordinary polyethylene film, because it is an insulating material, it has high dielectric constant (dielectric constant is a measure of the power storage capacity of the material) and high voltage resistance. When blowing anti-static polyethylene film, its resistivity is low, its dielectric constant is low, and its voltage strength is low, so it is easy to cause spark breakdown. Therefore, the distance between electrodes and corona treatment voltage should be properly adjusted

2 product performance

the anti-static polyethylene film produced is used as the main performance test. The test results are shown in Table 1.

it can be concluded from the data in the above table that the product has anti-static performance, and its technical indicators meet the requirements of polyethylene film for packaging (GB/t4456-1996). Due to its high surface energy, it can be dry compounded with other plastic substrates to form layered packaging materials

3 conclusion

the newly developed composite antistatic polyethylene film can be compounded with other plastic substrates into layered packaging materials due to its high surface energy (surface wetting tension ≥ 38dyn/cm). The composite packaging material has excellent mechanical and physical properties such as water vapor permeability, tensile strength, breaking force and puncture resistance, which can meet the requirements of electronic, chemical, civil explosive and military products for packaging materials

(author/yanghulin Shanxi Jindong packaging materials Co., Ltd.)

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