Developing the science of pre-treatment of steel and plastic into an artform

German company, Plasma Technik Grun, has developed the science of pre-treatment of steel and plastics before they are used in a number of industries into an art.

The company, which developed its PulsPlasma technology in 1985, with the intention to suppress the well known difficulties of the DC plasma nitriding like arcing and irregularities of temperature, went on to deliver the first plant that used the technology in 1983. In 1985 Plasma Technik Grun delivered the first plant for the industrial development of the PA CVD technology for TiN coatings. It went on in 1990, to deliver the first plant for PulsePlasma Nitriding in North America. By 1996, the company had built a plant for the cleaning and activating of plastics and metal. This plant is a combination of conventional cleaning on alcoholic basis and cleaning with the assistance of RF and DC plasma excitation.

In 1998, Plasma Technik Grun delivered its first plant for PA CVD coating for the Asian market. In 2001, the company went on to build the world?s biggest plant in the world for Plasma Activation of plastic parts used in the automobile industry.

Plasma Technik Grun’s Plasma Activation process, changes the surfaces of plastic parts significantly by using plasma treatments. This is done by the surface tension can be reducing (plasma activation) to achieve a better ability to wet surfaces. This helps to paint or print on or bond the plastic surfaces. In automotive engine manufacturing, plastic parts are plasma-activated before elastomer seals and gaskets are vulcanized onto the plastic surface. This pre-treatment greatly improves the seal-to-substrate adhesion on plastic components.

The removal of coatings or the cleaning of plastic parts with a plasma process is possible (plasma etching). According to the company, its plasma technology has numerous advantages compared to other surface technologies – it is pollution free, because no toxic media are used or produced by the processes. The results of the process can be reproduced by the use of free programmable computers. It is possible to go in for automatic handling and integration in the production cycle. And the gentle treatment of the plastic parts due to no remarkable temperature increase means no use of acids and other agents.

The Plasma Activation process can be used in the automotive sector for the following products: dashboards – getting them prepared for foaming/adhesive bonding (polypropylene/polyurethane). In bumpers, where the plastic is prepared for painting (polypropylene). Plastics used for door trim panels are prepared for adhesive bonding (hemp/sisal). Airbag parts preparation for adhesive bonding (various plastics). Silicone switch preparation for (laser) painting (silicone rubber). Plastic bodywork parts such as bumpers and rearview mirror housings can be reliably coated with water-based car paint, even after extended storage period, if pre-treated by plasma activation.

The plasma for the treatment of plastics is produced by microwaves or high-frequent alternating voltages. With the plasma technology as a key technology for different areas, new fields will be opened. The use of these technologies is increasing especially for compound materials like plastic, metals and ceramics. Automotive interior trim components are subjected to plasma surface activation to enhance their adhesion properties before application of leather by adhesive bonding.

Similarly, Plasma Technik Grun’s PulsePlasma Nitriding process is used for surface treatment of steel work pieces for protection against wear. Some of the uses of this process in the automotive sector are for gear parts which can be built in without grinding after PulsPlasma Nitriding. Valves can be nitrided by PulsPlasma – without separate depassivation and can be built in without any post cleaning. Extrusion dies have their durability extended by 50% as the surface finish of the profile will be improved after using the process. Conveyor screws made of spherolitic iron for the food industry can be made corrosion and wear resistive by a special PulsPlasma diffusion treatment.

For the treatment of steel by plasma, the parts have to be placed in a vacuum vessel and are electrically insulated from the case. The plasma is generated by an electric field in the vacuum treatment chamber. The resulting ionized gas molecules and atoms will re-combine into a variety of defined polymer coatings on the component surface. A broad range of different coatings can be obtained, depending on the composition and type of the process gas and the individual plasma parameters. The plasma is produced by means of a high or medium-frequency alternating voltage. Plasma systems are evolving into a key technology in many areas, and the number of applications is growing continually as many coating tasks can no longer be effectively addressed by conventional methods.

Automotive Industries caught by with Dr Reinar Grun, and asked him how Plasma Technik Grun’s technologies could revolutionize the automotive sector.

AI: How will plasma pre-treatment of plastics help future vehicles or their users?

In the past as well as in the future more and more steel parts for car manufacturing will be replaced by plastics. This will be of interest for the manufacturing of cars as well as for the user afterwards. By this development the weight of cars will be reduced, so that fuel consumption will be reduces also. New cars in future might not smell new by the plastic parts of the interior like today. By using plasma pre-treatment of plastic parts, solvent-based colors and adhesives can be replaced by non smelling and non outgasing ingredients. The reduction or even the complete avoidance of the use of solvents can be achieved by plasma pre-treatment so that during the production of cars the pollution inside the factory will be reduces also.

AI: How do you feel your plasma technology is different than others in the pre-treatment of plastics?

The plasma pre-treatment of plastic parts will modify surfaces only in a nanoscaled dimension. Without changing the characteristics of the piece itself. The use of such plasma technologies will be more economic and environmental friendly for the production for cars as well as for a use later. Other technology like activation by burning gas flames seems to be cheap, but only at the first step due to lower investments for the equipment. During the use the consumables will be much more and more expensive compared plasma technologies, especially by the use of low pressure vacuum technologies. The quality of the surface preparation will be also more uniform and reproducible.

AI: How does your plasma pre-treatment of plastics help in improving the adhesiveness and uniformity of plastic surfaces of automotive components and why is this so important?

The plasma technology is able to prepare plastic surfaces very accurate and controllable, so that adhesives or paintings and printings will get a good chemical bonding to the substrate. It is so important due to a long term stability required, especially for safety parts in the car industry.

AI: How important is the fact that your PulsePlasma Nitriding process is environmentally friendly to your customers and why?

Industrialized countries have more and more restrictive rules to avoid any pollution in house during the manufacturing of cars. Therefore the use of standard technologies like salt bath nitriding, using sienitesor gas nitriding using Ammonia is restricted or even forbidden in some countries and some companies. Therefore the new PulsPlasma – nitriding technology has an increasing demand on the world market.

AI: What are some of the challenges facing the automotive sector in the pre-treatment of steel? And how does your company’s plasma technologies help?

The pre-treatment of steel or other metal components by plasma technologies is used for the cleaning and activation to achieve best results on top of such surfaces by hard coating or others. The plasma technology helps in the field due to its excellent quality and controllable process.

AI: Where (in geographical terms) do you think is the biggest automotive market for your kind of technology? How have developing markets taken to your technologies or do they tend to use lower-cost, homegrown technologies?

The biggest automotive market for our technology today is Europe and we can realize that in North America is coming also with such a demand, mainly due to the pollution problems with standard technologies. The Far-East markets are developing also new technologies, but there we can realize a certain delay compared to the a.m. areas. A further point is the higher quality of the results for steel parts as well as for plastic parts by using plasma technologies.

AI: What are some of the breakthroughs we can expect in the next few years in the plasma pre-treatment of the steel that is used in automobiles?

I see some further breakthroughs in the Automotive Industry in the future, not only due to the pollution problems with old technologies, but also, in addition to this, we will see a lot of technical advantages and higher quality for the final products. A further, very important point is the consideration of production lines, considering the used material like steel of plastics including all mechanical manufacturing and finally heat treatment and surface treatments on top of it. Here we can see the consideration of such production lines as one system can be optimized to reduce costs including the use of a final more sophisticated plasma technology. It will be necessary in future to consider the different production steps as a system instead of the focus on each manufacturing step, independent from each other. With new surface technologies hard coatings steel parts can be reduced in weight and size with the result of better surface quality and longer lifetime.