Manufacturers must address several elements when joining difficult-to-bond (or adhere) materials such as advanced polymers, thermoplastics, metals, glasses, ceramics and composites. The first and arguably most important step in a bonding process is adequate surface preparation, comprising both surface cleaning and chemical-mechanical modification. This is especially true for materials which exhibit low surface energy or heterogeneous surface contamination and chemistry. Surface treatment challenges are amplified when joining surfaces with dissimilar cohesive energies; for example metal-to-polymer and metal-to-composite.
Particle-Plasma™ surface treatment technology is a highly robust process for preparing critical surfaces for adhesive bonding as well as for preparing surfaces for other manufacturing applications requiring clean, micro-etched and functionalized surfaces. Particle-Plasma™ surface treatment technology addresses adhesion challenges related to low energy or dissimilar surfaces.
Proper surface preparation is essential to provide consistent and reliable adhesive bond strength. Materials considered to be difficult-to-bond (or adhere) typically have surfaces which have low surface energy or are non-polar, or are dissimilar. For adhesive bonding, principal bonding elements comprise substrate treatment, adhesive selection, bond-line surface area, and joint design. Key adhesive bonding factors include the following:
- Surfaces free of contamination such as oils and microscopic particles;
- Maximum mechanical interlocking (bond-line surface area);
- Matching cohesion energy between adhesive and adherents; and
- Increasing surface absorption and reactivity of joining surfaces.
Referring to the figure above, the Particle-Plasma™ process combines unique microscopic and macroscopic treatment actions provided by two distinct but synergistic treatment processes. Micro-mechanical and chemical cleaning actions provided by a CO2 Composite Spray™ remove greases, thin organic films, and particles which mask the surface from atmospheric plasma. Following this, cleaned surfaces are quickly and homogeneously treated using thermal and photochemical treatment actions provided by the atmospheric plasma. The Particle-Plasma™ process simultaneously delivers solvent-like cleaning chemistry, acoustic scouring action, ultraviolet (UV) oxidation, micro-mechanical ablation, and surface functionalization.