Polyurethane (PU) is widely used as a versatile and durable coating and finish. Polyurethane is the result of a chemical reaction, which can be composed of different resins, the two most common types being alkyd and acrylic.<\/p>\n
In this blog, we\u2019ll explore the key differences between alkyd and acrylic PUs, so you can decide which is best suited for your next project.<\/p>\n
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What is the difference between alkyd and acrylic PUs?<\/u><\/strong><\/p>\n Alkyd PUs are made using an alkyd resin base, whereas acrylic PUs are formulated by using acrylic resin base. Two very different styles of coating that both use isocyanate hardeners to create the chemical reaction that forms polyurethane.<\/p>\n The most noticeable differences between the two are:<\/p>\n Health and safety<\/strong><\/p>\n Alkyd PUs: Contain high levels of aromatic isocyanates, which can be harmful to users and raise health and safety concerns. Alkyds need to be handled correctly, with proper safety measures in place.<\/p>\n Acrylic PUs: Are safer and do not use aromatic isocyanates to trigger the reaction.<\/p>\n Yellowing<\/strong><\/p>\n \u00a0<\/strong>Alkyd PUs: Are more prone to yellowing over time, especially when exposed to UV light, which can affect the appearance of the finish.<\/p>\n Acrylic PUs: Do not yellow, making them a better choice for maintaining the original colour and appearance of the coated surface, especially when using pale colours or coating pale substrates.<\/p>\n Durability<\/strong><\/p>\n \u00a0<\/strong>Both styles of product can be equally durable depending on the intentions of the manufacturer with regard to the end use of the product.<\/p>\n Drying time<\/strong><\/p>\n \u00a0<\/strong>Alkyd PUs: Tend to have a shorter drying time for a given solids level, although this is not a hard and fast rule.<\/p>\n Acrylic PUs: Acrylic polyurethanes tend to dry slower for a given solids level.<\/p>\n For example, the opposite may appear true in many cases because the general clear multicoat acrylic PU will dry faster than the average alkyd equivalent due to to its lower solids level.\u00a0 A high solids acrylic base coat will be much slower drying than it\u2019s alkyd equivalent.<\/p>\n Odour<\/strong><\/p>\n Alkyd PUs: Have a sweeter solvent-based odour, which can be quite noticeable during application.<\/p>\n Acrylic PUs: Have a more fruity odour.<\/p>\n In either case the safety of a product is not linked to its level of safety.\u00a0 Very often the most toxic solvents can be very subtle indeed.<\/p>\n <\/p>\n The pros and cons of Alkyd<\/u><\/strong><\/p>\n Alkyd PUs are still very popular, especially within the Italian market, where they are typically produced, for various reasons:<\/p>\n Pros of alkyd<\/strong><\/p>\n \u00a0<\/strong>Very high build product<\/p>\n However, there are some cons to be considered:<\/p>\n Cons of alkyd<\/strong><\/p>\n \u00a0<\/strong>Contains high levels of aromatic isocyanates, which can be toxic to users if not handled properly<\/p>\n\n