PU systems mostly have an isocyanate hardener. Some of these hardeners (usually component B) have a melting point in the range of room temperature (RT). If these are stored longer below RT (for example by transport in winter) crystallization occurs and the liquid becomes solid. This crystallization can be re-liquefied by heating to about 60 ° C for about 45 min. Then the hardener should be stirred well once.
Use of the hot hardener is not recommended as the pot life of the system will be shortened. Therefore, the recrystallized hardener must be cooled to RT again before use.
The “freezing” and “melting” have no adverse effects on the product.