Types of adhesives.

Wet adhesives

Wet adhesives are applied to only one side of the assembly, which is then immediately stuck to the other side. The parts need to be held together while the solvent evaporates. In "solvent-free" adhesives, the carrier substance is water. Wet adhesives dry best when used with open-pored materials.

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Contact adhesives

Contact adhesives are applied to both sides of the assembly. After a designated evaporation time the parts are put together for an immediate bond which can rapidly resist stress.

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Reaction adhesives

Reaction adhesives are adhesives that harden as a result of a chemical, physical or catalytic reaction. Depending on the type of reaction, these adhesives may be single- or two-component adhesives.

Single-component reaction adhesives

These are adhesives that, depending on their type, react to ambient humidity, UV radiation or ambient oxygen (aerobic adhesives) or to the exclusion of air, e.g. using metal ions (anaerobic adhesives). When using single-component adhesives, the product is applied to one side of the assembly. The reaction is triggered immediately by the second reaction component present in the surrounding area or on the other side of the assembly.

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Two-component reaction adhesives

These are adhesives that, depending on their type, are made of components in liquid, paste or powder form. The components must usually be mixed in exactly the stated proportions. They must be used quickly as they only have a limited working life. They begin to set immediately. The time taken to set also depends on the type of adhesive and the ambient temperature. The assembly needs to be held in place until the adhesive has set completely.

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Hot-melted adhesives

These are available in the form of sticks, paste, powder, granulate, mesh and film. They contain no solvent. No mixing or dosing is usually necessary. They are melted by applying heat.

This can take place at the actual assembly site (e.g. ironing veneers in place) or by using a glue gun, applying the hot adhesive to the parts to be assembled.

Hot-melted adhesives melt at temperatures of either 110°C (UHU LT 110 gun) or over 220°C (other systems).

Pressure-sensitive adhesives

These remain adhesive permanently.

They are used wherever the assembly is only temporary and subsequent separation is required. Pressure-sensitive adhesives are usually used in the form of adhesive films and strips and double-sided adhesive strips and pads, as well as on pressure-sensitive notices and self-adhesive labels and films.