Do you need to improve surface adhesion for bonding?

Bonding applications may show poor adhesion because of low surface energy of the substrate, lack of bonding sites or the presence of contaminants. Therefore, materials properties and substrate chemistry and conditions need to be taken into account.

Such cases require a pre-treatment process to increase the surface energy, and provide optimal conditions to ensure good adhesion between the substrate and the dispensing material.

In this context, an advanced surface treatment via plasma is a promising and effective solution.

What is plasma?

Plasma is a mixture of charged ions and energetic electrons generally in equilibrium. It is defined also as the fourth state of matter (solid, liquid, gas, and plasma). That is, matter changes its state from solid to liquid and from liquid to gas when energy is supplied to it. Similarly, if energy is supplied to a gas, this is ionized and goes into the energy-rich plasma state.

Atmospheric plasma technology is based on this physical principle. It supplies an additional energy to a gas by means of an electric discharge, and the gas turns into a plasma state.

Atmospheric plasma promotes adhesion success by:

  • CLEANING – it removes contaminants from the surface
  • ETCHING – creates more bonding sites thus increasing the surface area
  • ACTIVATION – increases polar groups

 

This technology can be used in almost all types of materials (plastics, metals, glass, ceramics, carton, textiles and composites). It can also be easily integrated in continuous production lines.

The most common plastics requiring treatment include:

BS, ASA, EPDM, EVA, HDPE, LDPE, PC, PE, PET, PMMA, PP, PS, PU, PVC, PBT, TPU

MCP TECHNOLOGY

Specifically, we show here the Micro Cold Plasma (MCP) technology from INOCON. This is a cold plasma source for surface activation, which enables high efficient and environmentally friendly manufacturing processes.

The main advantages of MCP technology are as follows:

  • Better reachability of areas because of the torch dimension and nozzle construction.
  • Compact power electronics and longer and flexible hose assemblies, thus better space- and installation possibilities.
  • Lower temperatures at the nozzle (max. 255 ºC)
  • Lower operating costs:
    • no reactive power loss
    • lower compressed air consumption
  • High process speed
  • High product life of the nozzle and the electrode
  • Low-maintenance continuous operation
PlasmaTorch

Plasma gases that can be used with MCP technology are compressed air and nitrogen.

On the other hand, the level of surface activation depends basically on the speed of the plasma and the distance from the surface to be treated. Common parameter values are speeds of 200 mm/s and distances between the substrate and the nozzle of about 10 mm.

The following pictures show some measures of the surface activation at different speeds and for several materials with both plasma gases.

Mesures_200mm/s
SurfaceEnergy_500mm/s
Source: INOCON Technologie, GmbH

APPLICATIONS

MCP advanced surface treatment can be used in almost all sectors of manufacturing industry for:

  • Selective surface activation before bonding, printing, coating and/or painting
  • Gluing of dissimilar materials
  • Pre-treatment of injection components

 

From automotive, electronics and packaging, to customer goods, life sciences, textiles and renewable energies. All sectors may beneficiate from this environmentally friendly and efficient manufacturing process.

Plasma application