The cross linking process
The cross-linking process consists of chemically joining two or more molecules. The bridge is constructed using a reagent (cross-linker) that contains at least two reactive end groups capable of binding to specific functional groups of the molecules to be joined.
This process is useful for proteomic methods (protein bioconjugation) but also to improve the performance, durability and weatherability of polymers. Cross-linkers increase the molecular weight of the cross-linked polymer and, in doing so, modify the film cohesion, surface and interlayer adhesion, chemical, impact and scratch resistance of the resulting material.
So, crosslinking involves a target functional group, available in the polymer chain, and a cross-linker that it is supposed to react with the target group in predetermined conditions.
Only a few functional groups within typical polymer chains are selectable targets for practical cross-linking methods. Most usual ones are:
- Alcohol (R-OH)
- Amine (R-NH2)
- Carboxyl (R-COOH)
- Carbonyl (R-CHO)
Cross-linkers are selected based on
- Chemical reactivity with the target groups
- Performance, in terms of stability of the newly created link
- Formulation and practical curing conditions. The reaction can be spontaneous after addition or can be triggered by temperature or radiation, can be immediate or it may take some specific
- Health, safety and environment considerations
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