All posts by Paul Edwards

Super-hydrophobic coatings and there impact on anti-friction and corrosion performance.

The techno sounding term ‘hydrophobic nano-coatings’ describes the application of thin films onto various substrates normally for protection against the elements. These thin films may be simple in nature and applied manually (polishing and waxing of automotive paint finishes as an example).

These coatings are usually without structure (flat) acting as a barrier coating to repel water away from the substrate using the relative surface tension properties of the coating verses the water droplets while also providing an aesthetically pleasing shine. There are many other more complex methods of applying thin films for protection of various metallic and polymeric substrates such as ion exchange and spatter techniques.

Our accelerated weathering and environmental testing laboratories have helped provide numerous thin film manufacturers with a means of measuring weathering performance by exposure to simulated sunlight with controlled variations in humidity with or without water spray to provide thermal shock and to mimic rain.

This test method is called xenon arc weathering and is the best laboratory replication of full sunlight spectrum between 290 and 800nm. Geographical location can be taken into account by adjustment of irradiance, temperature and relative humidity levels.

Super-hydrophobic coatings are even better at water repulsion as well as providing excellent anti-friction / non-stick properties. These coatings must have a topographical structure to work well and there impact on corrosion protection is vast due to there ability to repel water and keep oxygen from the air away from the substrate therefore stifling the corrosion reaction equation in metallic materials.

There are many examples in nature of super-hydrophobic surfaces and probably the best known one can be described with the saying ‘water off a ducks back’. The complex ridged structure of feathers help to provide super-hydrophobic properties causing the water to be attracted to itself so it will ‘ball up’ and roll away without a trace.

Take a look at this video (see link below) and let your imagination run wild with the numerous applications in all sectors (industrial, aerospace, automotive, electronic, textile, bio-medical etc…) where super-hydrophobic coatings can protect and enhance the performance of low cost substrates.

https://www.youtube.com/watch?v=SIiv-hkRvZE&list=UUctU7ssWjBx6E3HQ5xV6hDQ

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Number plate material importers beware!

UK importers of materials to be used for manufacturing number plates shall need to ensure the product can satisfy the requirements of the new number plate quality standard BS AU 145e.

When a full suite of testing cannot be justified due to cost or time restraints then material quality may be initially qualified by satisfactory performance after thermal resistance against distortion (clause 12), resistance to bending (clause 10) and resistance to solvents and abrasion (clauses 11 & 14).

The most expensive and time consuming test is xenon arc weathering (clause 16) which exposes fully manufactured product to UV exposure and moisture in accordance with the standard for around 2200 hours (13 weeks) in order to provide 4500MJ/m2 radiant energy exposure.

Initial qualification will NOT be sufficient to allow use of the BS mark, but may provide the importer with greater confidence regarding the required quality of these materials for number plate end usage. The additional clauses required for full validation can be added later when greater confidence is confirmed.

AWL are still concerned that acceptable equipment required for measuring retro-reflection in accordance with the standard remains unclear. We are currently in discussions with BSI and NPL concerning this but progress is moving at glacial pace.

If there are any suppliers of laboratory equipment that may be able to help us with retro reflection measurements, then please contact us.

AWL are pleased to offer a cost-down opportunity for our clients that contract us to carry out the full suite of testing so they can use the BS mark. Visit our number plate testing page and/or contact us for additional information.

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Taber Abrasion: ASTM D4060 Video

Taber abrasion in accordance with ASTM D4060 remains popular at our accelerated weathering and environmental testing laboratory with our coatings clients, particularly before and after UV weathering in accordance with ISO 4892-2 ISO 4892-3, ISO 11341 and ISO 20340. There is a nice little movie on YouTube that shows how this standard can be used for comparing abrasion performance under the same conditions with other coatings perhaps from the competition. Click on the video link below.

Should your company be in the coatings sector and you produce, or provide a service for the application of hard-wearing coatings on softer substrates, and you want to shout about it, then we can help using our Taber Abrasion capabilities to provide relative performance data. Contact us to discuss your requirements.

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