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Application of openair plasma treatment technology in the automotive industry

among many pretreatment methods, atmospheric pressure plasma technology plays an increasingly important role in the automotive industry. It can not only provide extremely clean surface for plastic parts, but also improve the adhesion ability of the surface. There is almost no restriction in the diversity of applications. Compared with traditional treatment methods, it is more economical and has absolutely no negative effect on the environment

for the processing of most plastic parts, in order to ensure the bonding quality of the plastic bonding surface and the long-term stability of its load-bearing performance, it is necessary to correctly pretreat the material surface, which has become a key step in the processing of plastic parts. For this reason, a pretreatment process called "openair atmospheric pressure plasma treatment technology" has been applied more and more

openair atmospheric pressure plasma process makes the pretreatment work simpler and more reliable, and it is more environmentally friendly because it does not need solvents. Therefore, in the automotive industry, at present, more than 30 different processes have adopted this process: from the pre-treatment of automotive windshield bonding to the packaging of automotive engine controller box, from the structural bonding of refrigerated truck refrigerated container to the bonding of automotive body parts, openair9 The main engine electric atmospheric pressure plasma process shows its unique technical advantages

Figure 1. The principle of plasma generation is that the gas cannot be given more energy by discharging,

make the substance change from gaseous state to plasma state

basic principle of openair atmospheric pressure plasma process

plasma refers to a state in which the substance is in a high-energy and unstable state. Usually, through the input of energy (such as heating), substances can change from solid to liquid and then to gas. Plasma goes further in this process, that is, it injects more energy into the material through discharge, and the electrons get more kinetic energy and break away from their existing orbits in the atom, thus producing free electrons, ions and molecular fragments, as shown in Figure 1. However, due to the unstable state of this material, it can basically not be used under normal pressure

Figure 2 according to the geometry of the nozzle, effective plasma can be obtained within the processing range of 50 mm at most or within the processing distance of 40 mm

(the picture is from plasma company)

so far, only the patented openair atmospheric pressure plasma process has created the possibility of the application of this new process: by using a plasma spray gun, The stable plasma produced under atmospheric pressure can be successfully applied to industrial production processes, and even "treatment" can be realized. Generally, only air and high voltage are introduced into the plasma gun to generate plasma. Of course, other process gases can also be used if the process needs. According to the geometry of the nozzle, an effective plasma can be obtained within a maximum width of 50 mm or a distance of 40 mm, as shown in Figure 2. Usually, the plasma formed has the function of experimental data operation and analysis. The beam also has a unique property, that is, electrical neutrality, which greatly expands its application field and greatly improves the convenience of operation. The temperature of the emitted plasma depends on the configuration of the power supply and plasma source, and can vary between 300 ℃ ~ 1500 ℃, so as to give consideration to the best treatment effect and the highest treatment efficiency. With this treatment method, the typical temperature variation range is less than 20 ℃ when treating the plastic surface

structural bonding of refrigerated truck containers

as early as the 1990s, with the development of a new generation of models, Schmitz cargobull has expanded the application of electrically neutral atmospheric pressure plasma to a new field. The company plans to use structural bonding as the only way to cool the container assembly, as shown in Figure 3

Figure 3 in Schmitz cargobull company, openair plasma technology has undertaken all surface pretreatment work in the past two years

(the picture is from Schmitz cargobull company)

relevant experience and expertise involved in realizing this processing requirement include:

● structural design related to bonding

● special surface pretreatment and cleaning technology

● automatic gluing technology

● process monitoring technology

with the actual mass production of new models, the new assembly technology integrated with structural bonding technology has also been improved. In this process, all the surface pretreatment work of this model is completed by penair atmospheric pressure plasma technology. This specially designed plasma treatment device integrates the latest rotary plasma system, which makes the whole pretreatment of the surface before bonding more efficient

pretreatment of plastic parts

in order to save weight, automotive body parts are no longer processed only with steel or aluminum, but more and more high-performance plastic materials are used, as shown in Figure 4

Figure 4 at present, automobile body parts are no longer just steel plates or aluminum plates, but more high-performance plastic materials. With the help of atmospheric pressure plasma pretreatment technology, SMC or PPO materials have been successfully bonded together with two-component PU glue (the picture is from plasma company)

when assembling these plastic automobile parts, such as the inner fender parts, it is generally to bond individual plastic parts together on the automatic assembly line. As we all know, in order to make plastic bond well, plastic needs to have a certain surface tension, and its surface tension is greater than that of glue. However, in fact, the surface tension of most plastic materials is very low. Therefore, appropriate surface pretreatment technology must be adopted to improve the surface tension of plastics. Using atmospheric pressure plasma pretreatment technology, the material surface can be thoroughly cleaned and effectively activated at the same time

atmospheric pressure plasma surface treatment process can replace the traditional SMC surface pretreatment methods, such as grinding or acetone cleaning. This process substitution can not only simplify the process, reduce the cost, but also further improve the bonding quality. Automotive parts assembled after treatment and made of high-performance thermoplastic or thermosetting materials can meet various technical requirements including light structure, passive safety, mechanical properties, etc., and also have first-class surface processing quality. At present, SMC or PPO materials have been successfully bonded together with two-component PU adhesive by using this technology. Table 1 describes in detail the surface energy of SMC after plasma treatment

openair atmospheric pressure plasma pretreatment technology can be used not only for the pre-treatment of automotive parts before bonding, but also for their surface pretreatment before coating. Successful cases in this regard even include high-end models such as BMW and Rolls Royce

plasma technology in two-component injection molding

the processing of plastic automotive interior parts with strong functionality, beauty and good handle is often a cumbersome process, and the manufacturing cost is also very high

generally, the base material of the part is made of rigid materials, such as PP, PA or ABS, while the surface of the part needs to use flexible materials, such as leather, synthetic leather, Pu or TPO skin. In this way, through the flexible material on the surface and the foaming layer under the surface material, a good hand feel of the parts can be obtained. However, processing such components is an extremely cumbersome production process, and it needs to pay a high assembly cost, which is not only inefficient, but also lack of reliability

Figure 5 in two-component injection molding, the base material of automotive parts is first molded by injection molding, then the interface is processed by openair plasma technology, and then the flexible materials are immediately molded by secondary injection molding (the picture is from Krauss Maffei company)

now, a more economical and reliable processing method is to use two-component injection molding technology to directly process such parts at one time, as shown in Figure 5. In the process of injection molding, the base material is first injected, then the interface is treated by openair plasma technology, and then the "second" flexible material is immediately re injected. In this process, there is no need to manually process the parts, and the finished products can be directly obtained after each processing cycle

another advantage of adopting this process is that by selecting the appropriate second "flexible" material, it can meet the requirements of function, aesthetics and hand feel, such as PU material (such as "skinform" technology provided by Krauss Maffei, the manufacturer of injection molding machine) or TPU material. The atmospheric pressure plasma process is used to improve the bonding ability of the material, which provides the necessary conditions for bonding the rigid substrate and the flexible second component

bonding door seals in automobile assembly

as an application example in the automotive industry, door seal bonding is also a typical application case of openair plasma technology. In many German Volkswagen models, additional door seals are added to the upper part of the front door in order to improve the sound insulation effect of the car, reduce the impact of road noise and enhance driving comfort

Figure 6 almost all the door assembly lines of Volkswagen are equipped with openair plasma pretreatment system

(picture source: Volkswagen AG authorizes plasma company)

Volkswagen chose a thermoplastic elastomer (TPE) as the base material of the sealing strip, which is a non-polar material with very low surface energy. From the beginning, Volkswagen decided to use solvent-free treatment as the pretreatment process before applying MS polymer adhesive to the sealing strip. After comparing various corona and plasma methods, Volkswagen finally chose openair plasma technology. Table 2 describes in detail the processing effect of openair plasma technology. Since then, almost all the door assembly lines of Volkswagen have been equipped with this system, as shown in Figure 6


the above applications show that there are almost no restrictions on the diversity of applications of openair plasma pretreatment process. The most remarkable advantage of this process is that it can provide reliability and quality assurance for the production process. As we all know, automobile manufacturers have extremely high requirements for quality, but even such high requirements can be well met after being treated by openair plasma pretreatment process. In addition, this treatment process can also be easily integrated into the existing process flow. Compared with traditional treatment methods, it is more economical and has absolutely no negative effect on the environment. (end)

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