Crosslinking chemicals – application in rubber compounds
What are crosslinking chemicals?
Crosslinking agents are reactive additives used in rubber compounds to create chemical bridges between polymer chains during vulcanisation. This crosslinking transforms a plastically deformable material into an elastic, dimensionally stable material with significantly improved mechanical, thermal, and chemical properties – thereby forming the indispensable basis for the production of high-quality Molded Rubber and Molded Silicone as well as composite parts based on rubber.
What function do cross-linking chemicals have?
During the crosslinking process, the crosslinking chemicals react with the functional groups of the polymer chains. The type of crosslinking significantly determines the final properties:
- Sulphur crosslinking - Linking the polymer chains using chains of up to eight sulphur atoms - a classic process for many elastomers such as NR, SBR or EPDM; results in good elasticity and dynamic load capacity
- Peroxide crosslinking - Direct connection between individual carbon atoms of the polymer chains - for high temperature resistance and good ageing resistance, e.g. in the case of FKM or heat-resistant EPDM-Compounds
- Metal oxide crosslinking - Formation of metal complexes with functional groups of the polymer chains - typically with CR or IIR, often with zinc oxide
- Silane crosslinking - Connection of the polymer chains through Si-O-Si chains - for moisture-reactive polymers such as polyolefin or EPDM-based systems
- Azo and urea compounds - Special crosslinkers for individual properties
Vernetzungschemikalien haben einen erheblichen Einfluss auf die Materialeigenschaften. Sie führen zu einer verbesserten mechanischen Festigkeit, höheren Temperaturbeständigkeit und reduzierter Löslichkeit.
The type and quantity of crosslinking chemicals influence Hardness, elasticity, Tensile strength, elongation at break, compression set, hysteresis as well as temperature and media resistance. Too low a cross-linking density can lead to reduced mechanical properties, while too high a cross-linking density makes the material brittle.
