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Fundamentals of Adhesion

 wettability principle

Selecting the proper adhesives for a nameplate, label or membrane switch application requires consideration of environmental, surface, appearance and other performance requirements. Our purpose here is to cover some of the principles of adhesion.

Surface contact is fundamental to adhesive performance. To maximize adhesive contact on a surface:

  • It must be dry and free of contaminates.
  • Firm pressure must be applied to increase the flow and contact of the adhesive with the substrate.
  • Time and temperature will increase the surface contact and adhesion values.
  • Oil contaminated materials may be addressed with the 3M™ Adhesive 300LSE or 350 families.

Adhesion is the molecular force of attraction between unlike materials. The strength of attraction is determined by the surface energy of the material. The higher the surface energy, the greater the molecular attraction. The lower the surface energy, the weaker the attractive forces.

Greater molecular attraction results in increased contact between an adhesive and substrate. In other words, on a high surface energy material, the adhesive can flow (or "wet-out") to assure a stronger bond.

Consider an automobile that has not been waxed for a long time. When water contacts the surface, it spreads in large puddles. The unwaxed car surface exhibits high surface energy - the molecular attraction allows the water to flow.

In comparison, water beads up into small spheres on freshly waxed car. It is an example of low surface energy - the liquid (or adhesive) does not flow out. Surface energy is measured by dynes per centimeter. The dyne level is the actual reading of the critical surface tension.

Modified acrylic and synthetic adhesives with better flow (or "wet-out") characteristics have been developed to adhere to low surface energy substrates. The Surface Energy Chart below compares the relative surface energy of commonly used substrates.

3M™ High Performance Acrylic Adhesive 200MP will not readily adhere to substrates categorized as having "low surface energy." However, 3M™ Adhesives 300, 320, 350, and 300LSE modified acrylics or 700 synthetic rubber adhesives have been designed to adhere to low surface energy plastics, and should be considered for those applications.

Wettability Principle

 
This illustration demonstrates the effect of surface energy on adhesive interfacial contact. High surface energy materials draw the adhesive closer for high bond strength.

wettability principle

Adhesive Surface Contact

Applying firm pressure to the bond increases adhesive flow and contact for more secure bonding. Time and temperature will typically further increase contact and adhesion values.

adhesive surface contact

3M Product Constructions

Click construction name and/or image to view these products in the online product catalog.

double coated foam tape construction

3M™ VHB™ and Double Coated Foam Tapes


adhesive transfer tape construction

3M™ Adhesive Transfer Tapes


double coated tape construction

3M™ Double Coated Tapes


single coated foam tape construction

3M™ Single Coated Foam Tapes


single coated tape construction

3M™ Single Coated Tapes


performance label materials construction

3M™ Performance Label Materials


double linered adhesive transfer tape sheet construction

3M™ Double-Linered Adhesive Transfer Tapes - Sheets


double coated spacer sheet construction

3M™ Double Coated Spacers - Sheets


hook and loop fastener construction

3M™ Hook & Loop Reclosable Fasteners


reclosable fastener construction

3M™ Dual Lock™ Reclosable Fasteners


Try the 3M TSR Program

Using the 3M Technical Service Request (TSR) Program, a 3M representative will work with you on initial testing of an adhesive design solution. One or two best options will be identified then a sample of your substrate is brought to the 3M Laboratories and tested for stress or other factors the product will encounter. The 3M test results will help you select the best design solution for your manufacturing process and customer needs.

Work with 3M at your manufacturing plant through the 3M IATD Design Solutions Program: Using the 3M IATD Design Solutions Program, we identify a design solution then work side-by-side with you, at your manufacturing plant, to ensure your personnel are trained in the new manufacturing process. Follow-up visits and ongoing support are key parts of the program.

We are eager to work with you. Please contact us by email to discuss your project or call: 800-362-3550.

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