25 августа, 2015 
Pokraskin Hot-melt adhesives, which are also physically setting adhesives, exist in a solid, high- molecular state and do not contain any solvents. They are applied in the molten state or as a powder or foil that is applied between the adherents and then melted under contact pressure and heat in order to obtain an appropriate wetting ofthe adherents. Immediately after cooling, hot-melt adhesives are capable of transmitting forces. By using high heating and cooling rates, manufacture processes using hot melts can be carried out with split-second timing.
When bonding metals care must be taken that, due to the good thermal conductivity of the adherents, the hot-melt adhesive must not solidify too rapidly near the interface; otherwise, complete wetting of the surfaces would be prevented. It is therefore advisable to preheat the adherents when this type of adhesive is used. An increase in the strength and long-term durability of hot-melt adhesives can be obtained if the adhesives continue to crosslink after the melting point has been reached; this can be achieved by the addition of specific substances or by the specific structure of the polymers. Either approach is possible with epoxy systems and
polyurethane hot melts with postcure; this is the most widely used method at present, in which the subsequent chemical reaction is initiated by moisture from the outside (see Section 5.6.1). These systems are used on a large scale to bond windscreens in automotive bodyworks (see Section 8.2.2.1). A slight disadvantage of hot-melt adhesives is that, by their nature, when used without postcure they are only resistant to heat up to the processing temperature. However, an advantage of such a bond is that it can be debonded and reconstituted by heat. Hot-melt adhesives with postcure can be applied at relatively low temperatures (about 60-80 °C), while being able to resist temperatures of 120-150 °C in the cured state.
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