Aushärten

Aushärten is a German term used in materials science to describe the transition of a material from a pliable or liquid state to a rigid, stable one. In English, curing or hardening are common equivalents, depending on the material and mechanism. The concept spans polymers, resins, adhesives, paints, and cementitious systems.

Aushärten mechanisms vary. In polymers and adhesives, curing involves polymerization and cross-linking, often triggered by heat, catalysts, moisture, or light, producing a three-dimensional network. In cementitious systems, hydration of cement with water forms binding hydrates such as calcium-silicate-hydrate, releasing heat and gaining strength over time. Some coatings harden through solvent evaporation or moisture uptake.

The process typically unfolds in stages: an initial set where the material begins to stiffen, a hardening phase where strength develops, and a final cure when the designed properties are achieved. Time scales range from minutes to days and depend on formulation, temperature, humidity, thickness, and substrate.

Types include chemical curing (thermosets like epoxies), moisture curing (silicone sealants), UV or heat curing (coatings), and hydration curing (concrete). Each type has specific requirements to avoid defects such as incomplete cure, internal stresses, or shrinkage.

Quality control uses hardness, tensile or compressive tests, and, for polymers, methods like DSC or spectroscopy to assess degree of cure. Proper curing influences durability, bond strength, and dimensional stability.