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Resin Bound Knowledge Base

Resin Bound Knowledge Base

Information - UV Resistance

When used for indoor applications such as industrial screeds, aromatic systems are ideal. Their suitability for indoor/screed applications is largely due to the fact that they are not clear and can be formulated with additives such as pigments/fillers (titanium and zinc oxides) that protect them from UV radiation. 

When formulated into a clear binder for outdoor surfacing applications, aromatic isocyanate systems suffer from discolouration however this is a symptom of a more complex problem. The discolouration is a result of oxidation reactions in the backbone of the polymer as it degrades. In simple terms, both aliphatic and aromatic resin bound surfaces are made by reacting a polyol, an isocyanate and trace amounts of water (airborne moisture).

Unlike UV resistant, aliphatic isocyanates, the aromatic isocyanates will form an amine which will oxidize to a quinone if subjected to UV radiation. Quinones are yellow and their formation will make the resin surface appear increasingly yellow as the oxidation progresses over time. Since the quinone structure is part of the backbone of the polymer, the resin surface will appear discoloured before there is any degradation however once the oxidation starts breaking chemical bonds, the degraded polyurethane will lose strength.

 

Isocyanate oxidized to a Quinone

Within the resin bound industry there is no debate regarding the chemistry or discolouration of non-UV resistant systems and the only question is to what extent does UV degradation affect the physical properties of a resin bound surface and over what period of time?

Non-UV resin and UV resin
Non-UV resin aggregate particle

It is our opinion that no level of degradation or reduction in performance is acceptable and Star Uretech have made the commercial decision that we will not supply non-UV resistant, aromatic products for use in the resin bound surfacing industry.

Star Uretech will only provide the highest quality products available, utilising the most up-to-date technology, high specification raw materials and the countries leading experts on polyurethane chemistry.