How do Cold Repairs work?

Cold repair compounds are basically chemical reactions between resin (Base) and hardener (Activator) producing an extensive interlocking polymer network.

The adhesion to the base material (substrate) is partly mechanical (approx. 75%) and partly chemical hydrogen bonding (approx. 25%). It is a cold curing repair method that needs no specialised application equipment or outside energy.

Since it is mostly a mechanical bonding, it does not influence the base material by diluting it. The type of base material is thus of no concern.

All these repair materials are essentially polymers, i. e. extremely long, chain-like molecules resulting from the chemical reaction between a large number of much smaller molecules.

Provided that these small molecules contain at least two reactive "groups" of "sites" per molecule, the chemical reaction can proceed in a progressive, chain building fashion to yield long molecules made up for regular, repeating units.

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In the uncombined state ,the reactive components are generally liquids on account of their relatively small size or low "molecular weight". As the chemical reaction or "cure" progresses, the size of the polymer chain increases until ultimately the material becomes a solid.

How to prepare the surface

Abrading tool for rubber.

Heavy contamination due to oil or grease must be removed using a cleaner. Remove all loose rust and surface coatings

Roughen surface with a coarse file, rasp, abrasive paper or saw blade. Create if possible a cross scoring pattern. A die grinder, needle scaler or angle grinder may also be used.

If grinding, make sure the surface is roughened, not polished. Carry out a final degreasing with a cleaner before applying product. Rubber surfaces must be roughened using the special abrading tool.

Use release agent on the threads of a bolt.

CRITICAL applications (eg. pump repairs) should be abrasive blasted to a minimum standard SA 2 1/2. Profile 75-125 microns. The blasting medium should be angular grit. Parts which have been salt or chemically impregnated should be heated to 80°C by hot air overnight to sweat out the contamination. Remove contamination using a cleaner then re-blast the surface. Parts which should not adhere to the products must be coated with a release agent.

Most castings have an open structure that contaminants can penetrate into.

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Roughening increases the surface area and gives a better "key"

Updated: 20.05.2014 — 19:32