FAQ on Polymeric Photoinitiators

What is a polymeric photoinitiator?

A polymeric photoinitiator is a high-molecular-weight compound in which the photoinitiating chromophore is covalently attached to a polymer backbone. Unlike conventional small-molecule photoinitiators, the chromophore cannot diffuse freely through a cured matrix, which significantly reduces migration and lowers odor in the finished product. This feature is especially important for low-migration or indirect food contact industrial applications. 
 

How does a polymeric photoinitiator differ from a standard photoinitiator?

Standard photoinitiators are low-molecular-weight molecules that can migrate through a cured film over time. In a polymeric photoinitiator, the same active chemistry is bound into a polymer chain, preventing post-cure diffusion. This makes polymeric photoinitiators the preferred choice where migration compliance is required, such as in indirect food contact and low-migration packaging applications. 
 

Which applications are polymeric photoinitiators used in?

Polymeric photoinitiators are used wherever low migration or low odour is a formulation requirement. Typical applications include:

• Offset, flexo, screen and digital printing inks
• Overprint varnishes
• Coatings on plastics and wood
• Adhesives

Do GENOPOL  polymeric photoinitiators require a co-initiator?

GENOPOL*  TX-2 and GENOPOL*  BP-2 are Type II photoinitiators and perform most effectively in combination with a polymeric amine co-initiator such as GENOPOL* AB-2 or oligoamines likes GENOMER* 5695.  This combination improves surface cure efficiency and overall reactivity, particularly in pigmented ink and coating systems. 
 

Are GENOPOL  polymeric photoinitiators compatible with LED curing?

Yes. The GENOPOL range is suitable for use in both conventional UV lamp and UV-LED curing systems. The absorption profile of each product should be matched to the emission wavelength of the lamp system in use. For instant, GENOPOL* TX-2 is particularly recommended to add in UV-LED curable formulations. If you need extra application UV-LED curing support, please contact RAHN's application support. 
 

What loading levels are recommended for GENOPOL polymeric photoinitiators?

Recommended dosage levels depend on the application, substrate, and curing system and the selection of polymeric photoinitiator. While GENOPOL* BP-2 and GENOPOL* AB-2 is suggested from 2% to 10% of usage, GENOPOL* TX-2 is recommended to start with the level of 0.2% to 4%. It should be noted that polymeric photoinitiators have less reactive chromophore per equivalent molecular weight compared to standard photoinitiators.  Please log in or register to access the full Technical Data Sheets for each GENOPOL product.