Incollaggio

L’incollaggio è l'unione di due materiali simili o diversi attraverso utilizzando le proprietà di adesione e coesione. Per adesione si intende la forza attrattiva o adesiva tra l'adesivo e il materiale al quale aderisce, per coesione invece intendiamo la forza di cui è dotato l’adesivo (forza coesiva).

Attraverso l’incollaggio è possibile unire  tra loro vari materiali come: legno, metalli, vetro, pietra naturale e una varietà di diversi materiali plastici.

Per ottenere un incollaggio perfetto, è necessario tenere in considerazione una serie di fattori che influenzano l’incollaggio – sia durante che dopo il processo di incollaggio. Durante l'uso quotidiano, l’incollaggio deve poi essere in grado di resistere a tutti i tipi di carichi e sollecitazioni come l'umidità e sbalzi termici, nonché diverse sollecitazioni meccaniche (per esempio la compressione, trazione e taglio). Alcuni esempi di fattori che durante il processo di incollaggio influiscono sulla qualità del risultato finale sono: la temperatura l’ ambiente, l'umidità, la circolazione dell'aria e la precisione di montaggio del giunto. La conoscenza preventiva del successivo utilizzo del pezzo incollato è quindi fondamentale quando si deve scegliere l’adesivo adatto.

Types of adhesives

Natural adhesives

Protein adhesives

 

Skin glue

Bone glue, fish glue, glutin, casein

 

Resins

Synthetic adhesives

Thermosets

Thermoplastics

Elastomers

Urea resins [3]

Polyvinyl acetates [1]

Silane-crosslinked polymers (e.g. Flextec) [7]

Melamine resins

EVA hotmelts [4]

 

Phenolic resins

Contact adhesives - Polychlorobutadiene [5]

 

Resorcinols

Acrylic dispersions [6]

 

Polyurethane adhesives (PUR)

 

 

Cyanoacrylates

(instant adhesives) [2]

 

 

An extremely high resistance to water and heat, as required for example in boat building or outdoor applications without surface protection, cannot be achieved with the adhesives that are commonly used today in the joiner’s workshop. For such applications, phenolic resins or resorcinol resins are the adhesives of choice. However, they are more difficult to use and can also be harmful to health.

Please also refer to the types of adhesives listed under Construction adhesives.


[1] White glues (= polyvinyl acetates) are thermoplastic dispersion adhesives – also in their fully cured state.
They are excellently suited for all applications in interior finishing work and furniture-making and reach very good strengths. They are easy to use, highly transparent (Pattex Classic) and also feature good storage stability and tool-friendly finishing work. 
However, they should only be used outdoors if the wood surface is sufficiently protected by a coating or adequate structural measures. If in doubt, we recommend using a thermosetting adhesive like PUR adhesives.

[2] Cyanoacrylates are primarily used in the construction of PVC windows. When installing roller shutters, the end pieces of roller shutter profiles are bonded with cyanoacrylates. Furthermore, cyanoacrylates are used for fixing PVC sealing strips in corners.

[3] Urea resins are used almost exclusively for veneering applications today. They feature short press times at temperatures from 85 °C upwards.

[4] EVA hotmelts are used for the machine gluing of edge bands. They offer a broad adhesion spectrum.

[5] Contact adhesives (= polychlorobutadiene or polychloroprene) are mainly used for joining two non-absorbent surfaces, for gluing surface coatings (HPL = high-pressure laminates) on pre-shaped parts and for fixing thick veneer edge banding. In addition, they are used for repairing delaminated edge bands and for fixing edge bands on pre-shaped parts that cannot be applied by machine.

[6] Acrylic dispersions are physically drying adhesives. They are often used as assembly adhesives with joint- or gap-filling properties. Usually, they can bridge up to 10 mm. As they are water-based, any adhesive residues or stains can be easily removed while the adhesive is still fresh. These adhesives require at least one absorbent surface.

[7] Silane-crosslinked polymers (e.g. Flextec® by Henkel in Pattex PL 300) are a new type of adhesive and offer a very broad adhesion spectrum. They feature excellent initial tack as well as high water and heat resistance. These polymers are not only able to join two non-absorbent surfaces, but can also bridge gaps. They can even be used to produce elastic, vibration-damping bonds, for example when fixing stair treads on a galvanized steel construction.