Gluing techniques

Assembly foams

Main areas of use: heat-, sound- and water insolation
Assembly foam (polyurethane foam) = polyole+isocyanate
The mixture of the two components swell when exposed to humidity and solidify into hard foam easy to cut.

Characteristics
  • It sticks easily and well
  • It resists chemical effects (oil, petrol, seawater, etc.)
  • It can be painted,
  • cut,
  • and plastered.
  • Assembly foam is sold in aerosol packing, in single- or double-component versions.

Single-component assembly foam

Manual or gun foam (more accurate "dosage", less loss)
The assembly foam is a chemical mixture with gas-filled floating cells in it. The cheaper assembly foams are full of open cells (holes). Their structure resembles sponges. Their voice-, heat- and water insulation is poorer. The heat-insulating performance of the assembly foam is determined by the gas composition of the cells and the number of closed cells altogether. 

Using assembly foam

Keyword: Humidity!
Air humidity in itself is not sufficient for the assembly foam to harden, so the surface has to be wetted before using the foam, and then the foam needs to be additionally wetted. With holes larger than 5 cm, the assembly foam needs to be applied in two or more layers. The hole must not be filled more than to half because of the swelling.
Leave to rest for 2 to 3 hours. Do not forget about additional wetting to avoid the damaging of the assembly foam.
Important: the assembly foam is not UV-resistant, and therefore has to be protected from direct sunshine.
Economical issues: What is a flacon enough for?
The freely swelling foam (e.g. in an empty box) will increase by 30% more after swelling than it will in joints, a figure more important for the user.

Storing the assembly foam

Important: The expiry date is determined with regard to room temperature (20 °C); the expiry date will shorten considerably if the bottle is stored at too high temperatures.
At 50 °C, the assembly foam ages seven times quicker than it does at 20 °C. Above 50 °C, there is a danger of explosion.

Silicones

If our goal is to fill a gap between two surfaces with a flexible and UV-resistant substance, we recommend single-component silicone sealing and glue substances.
At room temperature, silicone volcanizes and hardens due to air humidity. The hardening speed of silicones is directly proportional to air humidity which we can, to some extent, further increase by augmenting environmental temperature.

Regrouping silicones

We categorize silicones based on the substances developed during hardening:
acetic acid – very corrosive 
neutral – alcohol is developed during chemical binding, which can be efficiently applied to electronic appliances. Features: sticks easily, UV-, acid- and lye-resistant, water-repellent, cannot be painted on (for gluing doors, windows and mirrors)
Sanitary silicone contains fungicides, so it is recommended for use in bathrooms, kitchens and in humid places, with the aim of avoiding the development of fungi.

Acrylics

Acrylic is a sealing material suitable for walls, metals, or wooden surfaces. Can be painted once it is dry.

Glues

We distinguish between soluble and non-soluble, mobile and immobile binding. Gluing is non-soluble and immobile, meaning that the binding can be broken only through destruction. 
Gluing means the binding of solid bodies of the same or different materials. The parts of the glued binding are the surface to be glued and the glue itself. The efficiency and quality of the glued binding is determined by the force that occurs on the material-glue connection surface. Gluing technique is an important part of our everyday lives, and provides the basis for several technologies, such as laminating, the covering of polymers with metal.

Glues can be categorized on the basis of their chemical structural, physical features, binding types and the materials they are used with.

Glues and macro-molecular substances, polymers, with can make secondary bindings with the material. Based on their chemical structure, we distinguish between natural (caoutchouc or bithumen)and synthetic polymer-based glues.

Of the synthetic polymer glues, the following are considered to be of greater importance:

  • epoxides
  • polyesters
  • polyutheranes
  • phenoplasts and aminoplasts
  • acrylic and meta-acrylic acidesters
  • cyanoacrylics, that is, instant adhesives
  • vinyl derivatives
  • polyamide-based glues
  • silicone waxes

If we would like to categorize glues based on their physical features, then we distinguish between liquid (monomers, olygomers, solutions, dispersions) and solid glues. Solid glues have a special sub-group which develops binding when encountering pressure. 
The third grouping is based on binding type. In glues belonging to different groups, binding develops with or without chemical reaction.

The advantages of gluing
  • Can glue together very different materials
  • Insignificant anomaly
  • Does not cause changes in structure like e.g., welding does (absorption binding)
The disadvantages of gluing

The solidity of binding may decrease with the passing of time, so its reliability is smaller than that of other bindings.

The steps of gluing

1. Preparing the surface you want to glue (cleaning the surface, polishing, chemical treatment)
2. Preparing and mixing the glue (depending on the glue type, measure and mix the necessary quantity)
3. Applying the glue to the target surface (smearing, dipping, rolling, spreading)
4. Put together and bind the materials you are working on
5. The drying of the glue (binding)
6. Additional steps (removing superfluous glue, cleaning the surface)