Technology basics
Cationic curing is a photoinitiated, acid catalyzed ring opening polymerization of epoxy resins using onium salts.
On exposure to UV light energy and in the presence of a hydrogen donor (typically the resin components of a formulation) cationic photoinitiators produce a long lived acidic species. This species ring opens an epoxy group to form a carbocation which goes on to react with other epoxy groups producing a crosslinked network.
The principle is similar to free radical polymerization, with initiation, propagation and chain transfer steps. However, only the initiation phase is dependent on the use of a UV light source. All other stages of the polymerization reaction are thermally driven. The acid generated remains active after the removal of UV light energy until it is consumed and the entire film is cured. This is known as dark cure.
Formulations typically consist of 3 materials:
- Photoinitiator onium salts supplied under the SpeedCure name.
- Cycloaliphatic epoxide resins supplied under the UviCure name.
- Oxetane resins supplied under the UviCure name.
Polymerization steps:
1. Initiation – Photoinduced reaction
On exposure to UV light energy onium salt photoinitiators produce a strong Brønsted acid which goes on to propagate the polymerization reaction.
2. Propagation - Thermally driven reaction
The strong acid ring opens an epoxy and/or oxetane
Cationic curing benefits
Cationic curing technology offers several benefits to help you achieve high performance properties for your project
UviCure cationic resins
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Structure |
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UVICURE S105 | ![]() |
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UVICURE 128 |
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Structure |
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UVICURE S130 | ![]() |
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UVICURE140 |
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Structure |
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UVICURE S150 |
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UVICURE S160 |
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UVICURE S170 |
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SpeedCure cationic photoinitiators
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