• Tecman Speciality Materials

Adhesive Tape for Bonding Low Surface Energy (LSE) Plastics

Tecman has a range of PSA tapes for bonding LSE substrates, including transfer adhesives, film tapes and Very High Performance Bond (Vhpb) tapes regularly specified by Application Engineers.

Adhesive Tape for Bonding Low Surface Energy (LSE) Plastics

 

The basic principle of adhesion is the molecular attraction between dissimilar materials. The strength of adhesion is determined by the surface energy of the material and for adhesive to form a strong bond with a substrate it must ‘wet out’, flowing across the surface of the substrate, increasing the adhesives surface area and allowing maximum bond strength.  It's crucial that the correct selection is made when using adhesive tape for bonding low surface energy (LSE) plastics.

Fig.1 represents a High Surface Energy that supports adhesion and the droplet of liquid is wetting out to the surface.

Fig.2 is a Low Surface Energy and the droplet is clinging to itself rather than the solid surface.

Wetting out

Many material manufacturers will not publish the surface energy of a substrate and identifying this at an early stage is critical to providing a successful bonding solution. Surface energy is normally measured in energy units called dynes/cm. A dyne is the amount of force required to produce an acceleration of 1 cm/sec² on a mass of 1g. Traditionally the surface energy of a substrate is measured using a contact angle measuring device. This is often impractical in a normal manufacturing environment so a more common solution is to apply a dyne solution to the solid surface.

 

Typical Surface Energies (Dynes/CM)

High Surface Energy Medium Surface Energy Low Surface Energy
Material Surface Energy Material Surface Energy Material Surface Energy
Copper 1103 Kapton 50  PVA  37
Aluminium 840 Nylon 46  Polystyrene  36
Stainless Steel 700-1100 Polycarbonate 46  Acetal  36
Lead 458 Polyester 43  Polypropylene  29
Glass 250-500 Polyurathane 43  Silicone  22-24
    ABS 42  Teflon  18
     PVC 42    
    Acrylic 38    


The dyne level of a substrate is one of the most significant factors in selecting the correct bonding solution. With the ever increasing use of LSE engineering plastics in many areas this element of bonding considerations is becoming more and more important. Many Pressure Sensitive Adhesive (PSA) manufacturers are directing a large percentage of R&D resource into developing PSA technologies that will provide superior adhesion to LSE substrates.

It is strongly recommended that an adhesive Application Engineer is consulted at the design stage of any project which requires adhesion. For one they will have an in depth knowledge of the polymer construction of materials and secondly they are in touch with the latest developments within PSA technology. Tecman Speciality Materials offer technical support to Design Engineers for selecting the most effective adhesive product.

There are two basic ways that adhesion can be formed to a LSE substrate:

  1. Increase the surface energy of a substrate through use of a surface treatment process. This can be a mechanical treatment such an Inline Corona Treatment or plasma or a chemical treatment. There are many chemical treatments commercially available today which will promote superior adhesion. There are a number of benefits to selecting a surface treatment. Perhaps the most significant is that it opens up the range of PSA’s that can be used in an application. The Design Engineer has greater freedom of choice to meet all of the requirements of the project including adhesion performance and cost considerations.
  2. It is often not possible or unviable to apply a surface treatment in a manufacturing environment. In these cases an LSE compatible adhesive needs to be selected to achieve the adhesion performance required. These PSA’s have additional polymers within their core construction which will increase adhesion to LSE substrates. These polymers are a mix of synthetic and natural resins. By their very nature rubber based adhesives, whether hot-melt rubber or a solvent rubber have superior bond strength to LSE substrates. However there are a number of limitations to a rubber adhesive which often exclude them from selection when choosing a bonding solution.


Typical Rubber PSA Characteristics

Pro
Very high initial bond with as much as 80% of total bond strength on contact
Good adhesion to LSE substrates
Soft adhyesive causes rapid 'wet out' for quick adhesion build up
Cost effective

 

Con
Low temperature resistance
Little or no UV resistance making them unsuitable for external environments
Soft adhesive lacks cohesive strength giving low shear adhesion values
Low resistance to chemicals, alkalis and acids



This leaves acrylic PSA technology to provide high performance bonding to LSE. However pure acrylic PSA in its natural state will not bond to LSE substrates without the aid of a surface treatment. To overcome this, special tackifier additives are blended with the pure acrylic PSA construction. There is always a compromise on the performance of pure acrylic as it will take on some of the characteristics of a rubber. However a modified acrylic PSA will still offer significantly higher levels of performance than a rubber based PSA. Some of the characteristics of a pure acrylic and modified acrylic are as follows;

 

Typical pure acrylic PSA characteristics

Pro
Very high ultimate bond
Excellent resistance to high temperatures (up to 280℃ short term)
Hard adhesive gives good cohesive strength and excellent shear properties
Excellent resistance to chemicals and solvents
Excellent resistance to UV light

 

Con
Low initial tackwith as little as 20% of bond strength on contact                 
Hard adhesive causes slow wet-out
Very low adhesion to LSE substrates
High cost base


 
Modified acrylic adhesives with carefully selected additives give the best of both acrylic and rubber adhesives, however not all modified acrylics will give high adhesion to LSE substrates. It is important to consult an Application Engineer before making a selection.

Most common alternatives for bonding or fixing LSE substrates are mechanical fixings such as welds, rivets and screws or solvent welds. These traditional methods require investment in major equipment for labour intensive operations to be carried out, such as hole spotting, drilling, tapping welding and surface refinishing. These create structural weak points or areas were rust or corrosion can set in.

Solvent welds rely on hazardous solvents which require specialist equipment for dealing with fumes and health and safety requirements.

Tecman has a range of PSA tapes for bonding LSE substrates, including transfer adhesives, film tapes and Very High Performance Bond (Vhpb) tapes. Tecman’s Application Engineers regularly specify adhesive tape for bonding LSE substrates as they are fast becoming the preferred choice for design and engineering projects due to the demand for cleaner, quicker and more cost effective solutions. 

 

Adhesive Tapes for Bonding LSE Substrates

Product Name
ColourData sheetOrder Sample
11-TR10 Adhesive Transfer Tape Hazy Data sheet Order sample
12-TS02 Tissue Tape Hazy Data sheet Order sample
13-FL02 Film Tape                            
Hazy Data sheet Order sample
13-FL03 Film Tape                                White Data sheet Order sample
15-Vhpb06 Vhbp Tape Grey Data sheet Order sample
15-Vhpb07 Vhbp Tape Grey Data sheet Order sample

 

Benefits of Adhesive Tape for LSE Substrates

  • Cleaner
  • Quicker
  • Lightweight
  • No need for investment in machinery
  • Eliminates structural weak points
  • Spreads stress evenly
  • Can withstand movement and vibration
  • Invisible
  • Economical

 

Here to Help

For more information about our range of adhesive tapes for bonding LSE substrates, please contact us on +44 (0) 1926 337466 or alternatively email us and we will be in touch.



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