Enhanced EB Curing at a glance  [ Return towards  Enhanced radiation curing  ]

The EB curing process is a polymerisation reaction, initiated by an electron beam, which transforms, within a fraction of a second, a liquid coating film applied to a substrate into a solid cross-linked polymer material.

The typical formulation of EB-curable resins is made of two basics components: a monomer and an oligomer, both containing reactive functions. Additives and pigments / dyes are also added in order to fit printability requirements and afford the products the desired final physical properties.

EB curing processes use highly energetic electrons which interact directly with the functionnal groups of the coating formulation leading to cross-linked polymer material, so no photo-initiators are needed.

The EB-polymerisation reactions take place in three steps:

• Initiation: during the collisions between the high energy electrons and the organic molecules present in the formulation, the electrons transfer part of their energy and form free radicals which are capable of initiating polymerisation.
• Propagation: the free radicals combine with the reactive groups from the oligomer and monomer and start the polymerisation reactions. During this step the molecular weight of the coating increases.
• Termination: chain termination reactions occur when there is no reactive function available or not accessible, leading to a highly cross-linked solid coating in which all components are connected through covalent bonds.

However, this technology is very sensitive to oxygen, because oxygen reacts very fast with the free radicals generated through the initiation step. Inerting with nitrogen is therefore always necessary.

Air Liquide has developed a special Gas Seal Kit (GSKit) that enables to cure under reduced flow rates of nitrogen atmosphere. Our Gas Seal Kit is a cost effective, reliable and safe inerting device which can be retrofitted to existing EB chambers. A fully automated Process Control System will allow you to easily regulate the nitrogen flow rate according to your acceptable residual oxygen concentration and afford you full control of the cost and quality of your production processes.

The EB curing method, under inert conditions, is used in very different sectors that benefit from its numerous advantages.