Information on Adhesion

Types of Adhesives

Acrylic Adhesives

are synthetically manufactured adhesives with many positive properties. Acrylic adhesives are age-resistant, usually have very high adhesive strength and may be used from -50°C to 180°C. They are distinguished by a high resistance to ageing, good chemical resistance and, if desired, high shear resistance.

Suitable for gluing tasks in indoor and outdoor areas.

  • Extremely resistant to ageing and UV

  • Good immediate adhesion, outstanding final adhesion force

  • High thermal resistance (-50 to +180 °C)

  • Very good resistance to chemicals and solvents

Polysiloxane Adhesives

can be used in a wide range of temperatures (approx. -100°C up to 350°C). They are distinguished by their removavility even after high temperature strain. Polyisiloxane adhesives also stick to difficut subsurfaces and even silicon. Stick even to repellent surfaces, provide good shear resistance and can also be made removable. They have extremely good thermal resistance and they are extremely resistant to ageing.

  • Low immediate adhesion, but increases significantly within 72 hours
  • Very good internal strength (can be removed without leaving residue)
  • Also sticks to very low-energy surfaces
  • Extremely good chemical resistance
  • Outstanding thermal resistance between -60 °C and approx. 300 °C

Rubber Adhesives

are adhesives made from natural or synthetic resins. Their main features are usually high initial tack and good adhesive strength on a variety of surfaces. These adhesives can be used from -30°C to 155°C, and temporarily also higher (paint drying). However, this type of adhesive has limited resistance to ageing.

Particularly suitable for general tasks indoors.

  • Very good immediate adhesion
  • Good adhesion even on repellent surfaces such as PP or PE
  • Limitations in terms of ageing and chemical resistance
  • Can also be made removable
  • Temperatures from -20 °C to a maximum of 155 °C

Hot Seal Adhesives

offer maximum adhesion. The adhesive is melted by heating and then achieves its final firmness. This results in a highly reliable bond which is virtually invisible with transparent setting of the adhesive. The melting temperature can be set.

Hot Melt Adhesives

are 100% systems. This means no solvent needs to be used to apply the adhesive. Instead, the adhesive resin is melted, and solidifies when applied to the film. Through subsequent cross-linking, it is also possible to achieve high temperature-resistant settings. The adhesive tape is self-adhesive at room temperature, similar to a rubber or acrylic adhesive.

Liners

Depending on the adhesive tape or application, different release films and papers are used. For double-sided adhesive tapes with only one liner, both sides are repellent to differing degrees, so that the processing can be performed reliably.

Cohesion and Adhesion

The base for the adhesive capacity of an adhesive/adhesive tape are the two strengths - cohesion and adhesion.

 Adhesion generates the adhesive tape's bond with the surface. The forces in action here are greater the closer together the two surfaces are. The strength of the bond directly depends on the contact between the adhesive and the surface, thus a clear improvement is achieved by bonding under pressure (e.g. with squeegee). In addition, the adhesion of the surfaces to be bonded can be improved using a primer (adhesion promoter).

 Cohesion describes the adhesive's internal mechanical stability. An extreme example of an adhesive with low cohesion would be "honey". Good adhesion is in this case coupled with lower chesion (soft, fluid). The adhesion to the subsurface increases with time.

Good adhesion values are achieved within just 10 minutes; the end values are usually almost achieved after 72 hours. Moderate heating (e.g. to 70°C) shortens this time through accelerated surface wetting.

Kohäsion und Adhäsion

Bond Stress Types

Different types of adhesives react differently to the possible types of stresses.

Belastungsarten einer Verklebung

In general, it can be said that softer ahesives can absorb dynamic tensile stresses better. Harder adhesives cope better with shear forces than soft adhesives. An extreme example: The adhesive "honey" for which the two surfaces would be lightly greased. Delamination and peeling forces are combinations of the two types of stresses: Tensile stress and Shear stress. By contrast, however, the force is only transmitted in a very small, linear part of the adhesive area here. These stresses must be avoided, as they are not absorbed very well by adhesive tapes.

Surface tension and adhesion

Different materials having differing degrees of adhesion. The non-adhesive surface of a frying pan behaves differently to a metal surface when it comes to adhesion. We're talking about surface tension here (measured in dyn or mN/m). Put very simply, you could compare this to the magnetic force which attracts molecules to one another (surface polarity). If the surface tension is low, you can sometimes greatly improve adhesion through plasma or corona pre-treatment or with a so-called primer (adhesion promoter). Extensive transmission and distribution of force reduces the component stress (unlike, for example, for screws or rivets).

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 Advantages of bondy

  • Quick and economical binding technique

  • Bonding also of very thin materials, thereby enabling lighter construction

  • Unlike other joining techniques, the material structure is not affected (no high temperature like during welding, no drilling etc.)

  • Elastic binding to absorb vibrations

  • If applicable, electric insulation between metal parts, prevention of contact corrosion

  • Increased construction freedom for designers, as no visible screw or welded joints are necessary

  • Equalisation of tolerances and unevenness

  • Sealing through adhesion