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Thursday, 19 September 2019
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Raw materials & technologies, Technologies, UV/EB Coatings

European Coatings LIVE! questions answered

Wednesday, 23 October 2013

Dr Philippe de Groote, Allnex presented on 22 October his development about waterborne UV coating resins. Here are his answers to the questions from the audience after his presentation

Philippe de Groote, Allnex and Sonja Specks, Vincentz Network talking about the questions coming from the audience

Philippe de Groote, Allnex and Sonja Specks, Vincentz Network talking about the questions coming from the audience

Yesterday the first European Coatings LIVE! took place. This is from now on a monthly add on for our readers. Every 4th Tuesday in the month, at 15 h (CET) the author of the main technical article presents his publication. Via a "drop a question"-box, viewers were able to interact.

Watch yesterdays presentation in the stream again.

Yesterdays speaker Philippe de Groote answered his questions from the audience

Question:.Do you see further markets or applications that could be served with this technology in the future, apart from the four markets which you have already mentioned?
 
Philippe de Groote: The talk focussed on protective coatings at 10 to 20 g/m² dry coatweight, beyond which a hardcoat based on WBUV-7200 might show a too high brittleness, possibly resulting in cracks or loss of adhesion, at least if not combined with the EXP-1800 flexibilizer. Another application which comes in mind would be that of low coatweight (< 5 g/m² dry) coatings for large display applications (plastics & others) where protective properties have to be combined with excellent optical properties (no haze, full light transmission, no optical distortion).
 
What about adhesion on metal?
 
De Groote: The scope of the talk focused mainly on plastics (and coated paper when using opacity charts for high gloss/mat finishes). No test on metal substrates were done so far, the expected challenge would be that of adhesion, depending on the type of metal substrate obviously (stainless steel, aluminum, HDG …). Best would be to try for sure.
 
How should I use the binder in an existing formulation?
 
De Groote:The talk illustrated the use of WBUV-7200 as property enhancer (scratch and abrasion resistance) for other WB UV resins like UVPUDs. In this case, the WBUV-7200 binder has to be neutralized before any formulation work, in order to prevent any destabilization due to pH mismatch. WBUV-7200 is supplied at pH 3 to 5, and most UVPUDs are at neutral pH and destabilize under acidic conditions. Also, most additives for WB coatings work optimally around/close to neutral pH. Optimal combination is 70/30 of UVPUD/WBUV-7200, at which colloidal stability is still OK.
 
Is it possible to develop a coloured coating cured by UV radiation?
 
De Groote: This would require using dyes or pigments which resist the UV curing step. Most practicial would be to use a pigment paste for WB (UV) coatings at low concentration in order to get the color but prevent any opacity/hiding power being developed in the coating, these pigment pastes are readily available on the market.
 
Does it give a good adhesion on PP and PS?
 
De Groote: WBUV-7200 shows no direct adhesion on PP and PS, which are two substrates with low surface-energy substrates notoriously known to develop bad adhesion with coatings in general. One approach would be to develop a 2 coat system, primer + topcoat (based on WBUV-7200)
 
How does WBUV 7200 coating affect impact strength of polycarbonate?
 
De Groote: We have no data on this.
 
Can we imagine having food contact materials with such technologies?
 
De Groote: Food contact is a delicate topic (whether direct or indirect food contact) and should be discussed with Allnex R&D and Regulatory Affairs specialists, feel free to contact us off-line to discuss further.
 
What thicknesses can be reasonably reached for a curing, without curing problems?
 
De Groote: We reported results around 10 g/m² (dry) in the talk and no curing problem was observed. The high gloss coated panel I showed during the talk was obtained by using a roller-coater method and coatweight was around 5 g/m² dry, with no curing problem reported.
 
Should I do a pre cure the film (for exit of water) before UV cure?
 
De Groote: A thermal flash-off step (water evaporation) is required before UV curing, otherwise coating properties (including adhesion) might not reach their full performance if residual water is present.
 

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