Hot melt allophanate reaction: effect of overheating on PUR

The melting and application units should be equipped with a precise temperature control to prevent local overheating and unwanted secondary reactions.

Heating the adhesive to a temperature above the recommended processing temperature will usually lead to a fast increase in viscosity of the melt due to a so-called thermal crosslinking reaction in the adhesive (the allophanate reaction), which is triggered by heat and does not need moisture.