4 Most Common Problems With 2-Pack Polyurethane Paint & Lacquer
4 Most Common Problems With 2-Pack Polyurethane Paint & Lacquer
2-Pack Polyurethane Coatings provide a very durable and attractive finish - however, you MUST be aware of these common problems...
What Are 2-Pack Polyurethane Paints & Lacquers?
These coating materials are made up of a base resin (polymer) and an activator (hardener). When these two parts are mixed together the chemical reaction forms very strong bonds between the polymer chains.
This provides an excellent solution for products/objects that require a high-quality and durable finish.
4 Most Common Problems With 2-Pack Polyurethane Paint & Lacquer...
- Risk of Isocyanate exposure
- Product mixing complexities
- Limited pot-life
- Yellowing
Risk Of Isocyanate Exposure
PU coatings should only be used in enclosed and correctly ventilated areas to minimise health risks.
Hardeners for most 2k PU coatings contain isocyanate which has a high risk of causing serious respiratory reactions.
The idiocyanates are only hazardous whilst the paint is being sprayed as atomised particles.
Therefore it is essential that all sprayers should wear the correct equipment (an air-fed respiratory mask) whilst spraying.
Further methods of ensuring safe use involve observing the 'Air Clearance Time' stated by the spray booth installer. Do not remove your mask or allow others into the spray booth until after this time from the completion of spraying.
Ensure safe practice is performed to prevent health risks to the sprayer and others in the vicinity.
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Product Mixing Complexities
2-Pack Polyurethane coatings require the accurate mixing of 3 components (paint or lacquer + hardener + thinner) at the ratio specified on the data sheet.
This may sound straightforward but it is not always done correctly if the user is in a rush and can cause a negative outcome.
Incorrect mixing can cause incomplete drying/curing effects with a negative impact on the finish quality and durability.
A reliable solution for minimising the risks of poor finish quality involves the use of clear graduated mixing cups with pre-set markings for multiple mixing ratios to ensure consistency is maintained.
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Limited Pot-Life
2k PU products have a pot life ranging from 2-6 hours which is shorter than alternative acid-catalysed coatings. If the product is left for too long the coating will inevitably thicken up, making it far more difficult to spray resulting in an uneven finish.
Likewise, curing may well be negatively affected and durability could become compromised.
It is advised that products not used within the optimum time frame should be disposed of safely according to the safety data sheet. This creates an increase in material waste and the cost of hazardous waste disposal.
As a simple solution to minimise waste and additional costs, it is highly advised to read the datasheet carefully, developing a clear understanding of the correct mixing ratios and pot life of each product to maximise usage.
Calculating an accurate estimation of the amount of paint required to be applied within the recommended time frame will help to reduce wastage. Don't forget to factor in potential interruptions to spraying when calculating usage time.
'Yellowing'
The natural process of oxidation causes coatings to 'yellow'. In particular, 2K PU hardeners have the potential for “yellowing” of clear lacquers and pastel colours to occur.
For 2K PU coatings, in particular, there are hardeners available that are specifically formulated to minimise this risk of 'yellowing'. It is important to select these when this factor is critical.
Bonus Tip: If spraying large volumes of 2K PU coatings, plural mixing spray equipment is recommended which mixes the components as it is being sprayed and therefore eliminates the risk of incorrect mixing, minimises downtime and virtually removes product wastage.
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