Plasma coating for residue-free demolding of plastic components

In the production of plastic parts from reactive resins such as epoxies or polyurethanes, conventional release agent systems are generally used for demolding, regardless of the manufacturing process. These contaminate both the component surfaces and the molds (mold buildup). In addition, they often contain environmentally harmful solvents and other auxiliaries. Employees and the operating environment are also contaminated by very fine, long-lived aerosols. The mold structure and, if necessary, the release agent-contaminated components have to be cleaned in subsequent steps - with negative consequences for productivity, energy consumption, and the environment. Fraunhofer IFAM has developed a Release^PLAS® release coating for molds which completely avoids the use of these conventional release agent systems and the associated disadvantages. 

 

Elimination of release agents through plasma polymer coating

Plastic components are used millions of times a day in a wide variety of industries such as automotive, mechanical engineering and plant construction. The plastic parts are manufactured in a mold, and the application of release agents prevents the component from sticking to the mold. In most cases, however, release agent residues remain on both the component surface and the mold surface, which must be removed before further processing. Cleaning is time-consuming and costly, and also leads to tool wear. Certain surfaces with a matte or defined structure are often not even accessible economically because the frequency of mold cleaning is too high. In addition, conventional release agents often contain harmful substances for the environment and health. The call for release agent-free production is therefore becoming louder and louder in the plastics processing industry.

The Release^PLAS® release coating system can provide a remedy here. It can be used in a wide variety of applications, as the properties of the individual layers can be adapted to the specific requirements of the different types of plastic, processing methods and component geometries. It should be noted, however, that this step converts a cohesive release process into an adhesive process. Therefore, specific adaptations, e.g. in the area of materials, processing parameters or also the release process, must be expected in individual cases. It is not possible to make general statements about the service life of the coating. However, in wax injection molding, for example, well over 100,000 demoldings can be expected without any problems.

 

Thin films for perfect imaging of tool surface structures

Release^PLAS® release coatings are amorphous, plasma-polymeric coating systems designed to adhere particularly well to the mold surface and yet enable the separation process again and again due to their chemically inert surface. In individual cases, the release forces can even be lower than those of conventional release agents. These are highly cross-linked organosilicon systems (modulus of elasticity between typ. 1.5 - 10 GPa), which are not consumed during the release process. Accordingly, the manufactured component is not contaminated in any way. The integrity of the mold surface is also maintained.

The thin films (typ. 0.1 - 4 µm) are capable of perfectly mapping tool surfaces. This opens up the possibility of producing meso- and microstructured surfaces, such as grains, kinegrams or bionic surface structures, as well as high-gloss surfaces at low cost.

A unique feature is the use of the coating on (surface-structured) applicator rolls or sleeves, for example to apply coatings or printing inks. If necessary, it is possible to adapt the wetting properties to the requirements. Applicator rolls up to 1.65 m long can be processed.

 

One coating for a wide range of plastic types, processing methods and component geometries 

When using Release^PLAS® technology, the mold surfaces are directly provided with the coating. The process can thus be easily adapted to individual requirements, for example the type of plastic or the component geometry. The coating can be used not only for reactive plastics, such as polyurethanes or epoxies, but also for thermoplastics, elastomers, coatings, adhesives and glues. The release coating has also proven outstanding in the field of wax injection molding for investment casting.

Specific application examples are:

• Polyurethane/PUR processing - RIM (reaction injection molding), IMC (in-mold coating), injection molding
• RTM (Resin Transfer Molding), prepreg technology, infusion processes
• Cold and hot melt processing
• Wax injection molding
• Application plants for coatings and inks
• Polyvinyl chloride/PVC slush processes
• Organic sheet forming
• Thermoplastic injection molding
• Thermoplastic polyurethane/TPU injection molding
• Rotational molding

 

From the shortening of cycle times to the reduction of VOC emissions: The benefits of Release^PLAS® coating at a glance: 

• Reduction in cycle time; increase in productivity.
• Elimination of intermediate mold cleaning
• Longer mold service life
• Clean component surfaces, so that direct further processing is possible
• Uniform and improved surface quality, even with demanding surfaces
• Reduction of VOC (Volatile Organic Compounds) emissions from release agents and mold cleaners
• No exposure of employees to aerosols
• No pollution in the vicinity of the production area 

 

Overview of new project results: Release agent-free demolding with permanent release coatings

As an alternative to conventional demolding technologies, Fraunhofer IFAM and IKV - Institute of Plastics Processing at RWTH Aachen University demonstrate that non-destructive and trouble-free part removal can be realized in polyurethane processing without additional application or cleaning intervals. Read the article in PU Magazine International (issue 06/2020), to which Dr. Klaus Vissing, group leader for low pressure plasma technology at Fraunhofer IFAM, contributed.

You can download the article as a PDF here: Dry demoulding – practical demonstration of a mould coating with long service life

(Source: PU Magazine International 06/2020, Dr. Gupta Verlags GmbH)

 

Dr. Klaus Vissing heads the "Low Pressure Plasma Technology" working group in the "Plasma Technology and Surfaces" department. Together with his team, he has been researching for several years not only ways to permanently avoid release agents, but also to provide plasma-supported functional processes reliably and cost-effectively. The environmentally friendly plasma coatings developed for this purpose are for example used in the semiconductor industry, in painting and filter processes, and in mechanical engineering.