Polysiloxane Coatings

Polysiloxane coatings are industrial coatings used in applications where abrasion, chemicals, high UV and high temperatures are experienced.

A Polysiloxane is a polymer with a Silicon-Oxygen backbone. This type of backbone is much more resistant to the effects of UV radiation than the Carbon-Carbon backbone of organic polymers.

Polysiloxanes have excellent aesthetic weathering attributes in terms of gloss retention.

They also exhibit excellent abrasion and corrosion resistance, good chemical resistance, good anti-graffiti properties and resilience to dirt pickup.

UV is electromagnetic radiation with a wavelength from 10 nm to 400 nm, shorter than that of visible light but longer than X-rays. One nanometre, nm, is one billionth of a metre. Ultra Violet, UV, radiation is naturally present in sunlight. Approximately 10% of the sun’s output that reaches the Earth is in the UV wavelength range and it is responsible for tanning our skin, amongst other things.

UV radiation effects paint and coatings in two different ways.

UV-A radiation (at the longer wavelength end of the UV spectrum) will dry out the resin in a paint or coating leading to cracking.

UV-B radiation leads to a fading or loss of colour of the paint or coating by breaking down it’s chemical bonds.

The technical term for colour fading is photodegradation. The colours we can see are based on which colours (wavelengths) the paints or coatings absorb as well as the nature of the chemical bonds holding the paint or coating together.

Certain resins, like acrylics and polyurethane are slow to absorb UV rays and are thus much slower to dry up and lose their colour. The addition of UV blockers during the design stage of any coating or paint is clearly an essential step.

UV radiation also breaks down organic compounds within coatings and paints, such as binders.  This break down will clearly mean the paint is no longer retaining the chemical and physical properties with which it was designed. It is not uncommon for coating and paint break down to accelerate over UV exposure time as the initial damage results in the coating or paint being increasingly unable to withstand the UV attack.