Adhesive Bonding and Assembling Mechanism

Mechanism of adhesive bonding defined by the general factors:

Assembling and bonding process of adherends and adhesives is a complex phenomenon.  Some common factors can help to practice for prefect bonding of any adhesive application. It may be any type of adhesive or adherends.

Pre-process like sand blast, chemical treatment are done to make the surface fit for applying adhesive to make a strong bond between adherends. Sand blast is done when a plastic or wood material is to be bonded by using high pressure and temperature, if not just using a sand paper the surface is smoothed. In certain cases metal are chemically treated because due to the presence of grease and oil. The metal surface is washed with a solvent or with a detergent. Metal when going to expose to acidic chemical than it is treated with alkali or vapour dressed.

Wood and metal adherends are flatted and smoothed by machining the surface. By doing this, a thin film of adhesive is sufficient for strong attachment of the surfaces. Adhesive should be prepared in following ways like, dissolving it in some solvent, thinning of liquid adhesive, melting solid adhesive and adding additives like extenders, plasticisers, fillers,  harder’s, catalyst and fortifiers.

One of the following methods can be used for applying the prepared adhesive bonding:

  • Roller or knife coats molten adhesive.
  • Spraying
  • Brushing
  • By using pressure sensitive tape
  • By laying the film or sheet of adhesive.

One of the mostly used adhesive is chemical reactive type. It works in different manner. Two chemicals 1) thermosetting resin 2) catalyst or reactivating solvent are applied on each surface of adherends separately. One chemical on one component surface. When the tow components are attached, the chemicals react and gets harder. High temperature epoxy resins work based on this procedure.

What happens when adhesive applied on the adherend?

When thermosetting type adhesives are used in molten state they immediately become hard and strong enough to bond the assembled surfaces. Precaution to be followed is that when this type of adhesive is used adherends should be assembled immediately before they get harder.

Thermoplastic type adhesive has different mechanism. It is a rubber solution in an organic solvent. It is applied on the surface and allowed to expose in air so that solvent is vaporized than the surfaces are assembled. It can be handled without any caution of hardening immediately.

Wood working adhesive practice:

By laying the adhesive on the surface of the woods, the contact is assembled. However, the joint should be allowed for certain time under pressure to make the joint get harder. Under pressure the contact surface are attached by the reaction of the glue.