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  UV Curing Technology

UV curing is analogous to conventional thermosetting (or thermally cured reaction) technology.  However, instead of solvents or water, UV coatings contain low viscosity reactive diluents (also called monomers).  This makes them 100% solids, but still low viscosity.  Instead of solid polymers either dissolved in solvent or dispersed in water, they contain oligomers that give the formulations most of their performance.  And instead of either a two pack reaction or a temperature reactive catalyst or initiator, they contain photoinitiators that cause an almost instant reaction when exposed to UV light.  A comparison of conventional to UV cure technology is as follows:


Conventional Component

 

UV Component

 

Comments

Water dispersible or solvent soluble polymer

 

Oligomer

 

100% solids, cured materials can be thought of having properties primarily given by oligomers

Solvent or water

 

Reactive Diluents

 

100% solids, no VOC, no need for drying step

Curing agent- catalyst/initiator

 

Photoinitiator

 

Instant cure under exposure to UV light

Pigment

 

Pigment

 

While similar, specific grades of pigments work best for UV

Two pack system

 

Single component

 

Instant cure, no waste

Additives

 

Additives

 

Similar in both systems



UV Curing Equipment

UV curing equipment typically consists of high intensity medium pressure mercury filled lamps.  They put out very specific wavelengths of light, and the photoinitiators in the coating are tuned to match the absorbance to the UV light emission.  For example, specially modified lamps are often used for pigmented systems, and the photoinitiators used for pigmented systems will be different than those used for thin film clear coatings. 

Since the cure of these systems is very fast (some UV cure applications run as fast as 2000 fpm), typically only one or at most 3 to 4 banks of lamps are used.  This results in the very small footprint of UV cured lines.  Typically, UV coating lines can be less than ½ the size of thermally cured lines.  Also, there is no need for cooling of the parts, and they can be handled immediately after exiting the UV cure chamber.   

Because these systems are 100% solids with no potential for any of the raw materials to evaporate and change the performance of the coating, they can be filtered and reused in most applications.  Therefore, transfer rates for UV can be extremely high, approaching 100% in some operations. 

Clean up of these materials is easy as well.  Since the material will not cure unless exposed to UV light, there are no issues with clogging of spray heads or extensive cleaning with solvent.  In fact, many lines are simply drained at the end of a production run and do not need to be completely cleaned at all except for scheduled maintenance. 

XSER Coatings partners with a number of UV equipment providers and we would be more than willing to help them come up with the equipment that is correct for your application. 

     
Copyright 2010