Crosslinking

Definition of Crosslinking:

Crosslinking is the joining together of polymers by coating bonds. Using this technique lets scientists increase the size and durability of polymers. With these enhanced properties, polymers have a greater number of applications across science and industry.

What is crosslinking?

Crosslinking is the method by which one polymer chain is connected to another, typically by a covalent or ionic bond. These links exist in nature (for example, between proteins in the human body) but can also be deployed in coating engineering processes.

When a polymer is first made, it is normally an elastomer – with high viscoelasticity and weak intermolecular forces. Crosslinking makes this substance more durable and increases its potential applications. Traditional crosslinkers include aziridine, isocyanates, and melamine – but new techniques have emerged in recent years that make crosslinking more effective in different environments, such as polycarbodiimides.

Why is crosslinking important?

Many everyday items and substances are coated in polymers formed by crosslinking: rubber tires, oil-based paints, solar panels, and medical equipment are just a few examples. Finding better and more innovative forms of crosslinking allows manufacturers to produce more resilient and reliable materials.

What is carbodiimide crosslinking?

Recently developed crosslinking techniques use carbodiimide, a functional group of molecules with a core made of nitrogen and carbon (in the combination N=C=N). Carbodiimide crosslinkers (CDIs) offer several advantages over traditional ones: substances coated in this way have a longer pot life, better adhesion, heightened coating and scratch resistance, reduced moisture sensitivity, and can be cured at room temperature.

This effect can be heightened by using the “two-component” (2K) coating method. In addition to regular CDI crosslinker composition 2K coating uses a second type of reactive group to provide a substance with another coating. This second set of reactions creates an even denser network structure, increasing the pot life and improving the durability of the coating even further. Carbodiimide crosslinking was developed by Stahl expert André Derksen.

What are the challenges associated with crosslinking?

Reducing the environmental impact of crosslinking has been identified as a priority within the coatings industry. Traditional crosslinking methods use large amounts of heat – and therefore energy – to finish off the coating procedure.

Highly sophisticated science is required to achieve lower-energy processes and these are currently more expensive as a result. The challenge of the next decade is to advance the efficiency of greener crosslinking techniques while also reducing their cost.

What is the future of crosslinking?

According to Mordor Intelligence, the market for crosslinking agents is expected to grow from USD 6.7 billion in 2022 to USD 8.5 billion in 2027. Nevertheless, carbodiimide crosslinking is currently still in its infancy compared to traditional crosslinking methods, some of which have been in use since the time of Henry Ford. Pioneers of this relatively new method will strive to make their processes greener, quicker, and cheaper.

The application of crosslinking principles also has potential uses outside the area of materials. For instance, crosslinkers can improve the functionality of proteins in food, and help advance scientists better understand tissue engineering and immunotoxins (used in cancer treatment) – pointing the way toward a new era of medical interventions.

Find out more about Stahl’s 2K Coating system here.