How to improve the surface energy of acrylic and polycarbonate sheets

It is often necessary to coat sheets as part of the manufacturing process. In order for liquid adhesives, glues, coatings or inks to adhere to the surface of cast, moulded or extruded plastics we must first modify the surface. The process of increasing surface energy will improve surface wettability, thereby promoting stronger adhesion. Here at Tantec UK & Ireland, we take a look into how you can improve the surface tension of acrylics and polycarbonates.

What solution is best for improving the surface tension of acrylics polycarbonates?

The purpose of surface treatment of polymer based materials is to increase surface wettability through electrical discharge. The low surface energy of polymer based substrates often leads to poor adhesion of inks, glues and coatings. To obtain optimum adhesion, it is necessary to increase the surface energy of the substrate to just above that of the material to be applied. Corona treatment results in improved surface adhesion properties of acrylics polycarbonate.

Treatment of sheets and plates for this application may vary from 50mm to 2000mm, which gives the customer treatment flexibility of small and large plates.

SheetTEC can be installed as a stand-alone unit or with a conveyor system for integration into existing production lines. SheetTEC is available as a single or double-sided surface treatment system. SheetTEC is equipped with metal electrodes for the optimised treatment of non conductive polymer materials. Perfect for improving the surface tension of acrylics polycarbonate.

How have Tantec applied this treatment in practical use?

One of the leading manufacturers of optical filters and display windows is PSC. With more than 25 years of experience, PSC A/S has an in-depth knowledge of the guidance and design of solutions for exactly the customer’s requirements and application. A challenge and a desire for better adhesion of printing inks lead to the contact with Tantec.

PSC manufactures customer- and application-specific optical filters and display windows for professional electronic devices, and a wide array of other applications. The many solutions are often used under demanding conditions, where, in addition to achieving the least possible reflection, the parts must also be resistant against various chemicals, wear and cleaning, rough use, vandalism etc.

The company offers display window solutions made from a wide range of materials: Cast and Extruded Acrylic sheets, Polycarbonate and Glass. The Display windows are ‘cover

glasses’ placed in front of electronic displays to improve or enhance the appearance, performance, and functionality of the display or the equipment.

High-performance surface treatment 

In order for such solutions to provide the required functionality, high-performance surface treatments such as abrasion- and chemical resistant hardcoats, multi-layer anti-reflection (AR) coatings, are often applied to the sheet materials.

A common denominator for most of these, is that they efficiently repel dirt and contaminants “by design”, i.e. “anti-fingerprint or anti-smudge” functionality, and in technical terms show an extremely low surface tension or energy!

Perfecting adhesion 

In order to be able to print (screen, pad or inkjet) decorations such as passé partouts, symbols, logos etc. onto these surfaces, the surface tension has to be modified.

Easy to use

To meet the challenges of better adhesion, PSC chose to invest in a SheetTEC solution from Tantec. ”The solution is specially designed according to our needs, and the most important design requirements were fast, usable in both off-line (batch processing) and in on-line setups. Furthermore a high degree in treatment flexibility, i.e. speed, intensity, no. of passes and an intuitively easy-to-use interface. (HMI) making it easy for operators to select the correct treatment was paramount”, says Jesper Nielsen, Product Development Manager at PSC.

Environmentally friendly process

Corona treatment of sheets is considered an environmentally friendly process which runs at a fairly low power consumption. Although ozone is generated as a bi-product of the corona discharge, it is easily eliminated either through existing exhaust systems or through a custom-built Tantec ozone neutralising system. Materials such as PP, PE, PVC, PVDA, PMMA, PS and other non-conductive polymers are treated successfully with this concept.

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