Expertise that sticks.
Basically, bonding is the act of joining parts by means of an adhesive layer. The adhesive hardens by drying or through a chemical reaction, thereby keeping the bonded materials together. Two factors influence the durability of a bond:
Strong adhesion is achieved when there is close contact between the surface of the part and the adhesive. This is only possible if there are no foreign substances in the space in between. The adhesive surfaces must be clean and free of grease and dust. Adhesion is improved by sanding the surface of the material with sandpaper, as this cleans the part of foreign bodies and enlarges the surface area.
Cohesion is how well the parts (molecules) bond with each other.
The stronger the cohesion, the greater the strength of the adhesive.
When bonding, cohesion is used to its full advantage if the adhesive is not applied excessively thickly.
Clean the surface of dirt, rust, paint residues and other foreign substances.
Roughen the surface with sandpaper.
Degrease the adhesive surfaces thoroughly with a suitable liquid such as acetone, alcohol or nitro thinner.
Allow the areas to be bonded to dry.
Do not touch the prepared areas to avoid the transfer of oil from your skin.
Apply the adhesive evenly and thinly (be aware of the flash-off time when using contact adhesives).
Keep dirt and dust away from surfaces freshly coated with adhesive.
Stop sanding and other work until the parts are bonded together.
Determining adhesive surfaces according to shape and size
The type of load is one of many vital factors in determining the adhesion strength of a bond. Weak adhesive bonds can be strengthened and made more durable using a few simple techniques. Hold the parts to be glued together and replicate the effect of any subsequent stress. This will show you which forces are acting in which direction to enable you to identify the type of stress.
For low load/tensile load, choose a butt joint.
For heavier loads, increase the size of the surface area to be bonded by cutting the material to form a scarf joint.
For heavier loads, increase the size of the surface area to be bonded by cutting the material to form a scarf joint.
For heavier loads, enlarge the bonding surface with a single strap joint.
For heavier loads, enlarge the bonding surface with a double strap joint.
Here, the entire adhesive surface is unevenly loaded (horizontal to the bonding surface). Reinforce as per the tensile load or place a sleeve around it.
Stress forces may cause pliable materials to peel away from the adhesive surface. The bonding point can be strengthened against peeling by:
GlueING on a stiffened strip of material.
Securing the more pliable part around the edge of the more rigid part.
Rounding off the vulnerable corners.