Hello and welcome to a new post. Today I answer another community question, this time around how to integrate a permeant UV protection for parts made out PC and PET, as well as PETG without losing the optical appearance over time, together with mechanical properties.
There are engineering polymers such as Polymethylmethacrylate (PMMA; known by its famous trade name “Plexiglas”) which have very good optical properties (light transmission up to 92%) and a very good inherent weatherability and ageing properties. There are other polymers such as Polycarbonate (PC) and Polyethylene terephthalate (PET) which, when exposed to UV radiation, change their appearance and properties over time. To prevent this, UV stabilizers can be added, however over time they are consumed and loose their effectiveness. Also, optical properties are influenced by adding additives.
Another approach for having a long-lasting UV protection is by blenidng PC and PET with Polyarylate (PAR), an amorphous high performance polymer.
Polyarylates (PARs) are a class of high-performance thermoplastics derived from aromatic dicarboxylic acids and bisphenols. They possess a combination of excellent properties, including high heat resistance, chemical resistance, and mechanical strength, making them suitable for a wide range of applications.
Why?
The UV-stability of PARs is high, since UV radiation causes the formation of a protective layer which in turn serves as UV protection. It could be shown in various 8,000-hour long-term tests that PAR, in contrast to PS and PC, retains its almost untarnished shine even under the influence of UV. Also, almost as transparent as Polycarbonate and PMMA.
Additional effects of blending PET with PAR is the decrease of shrinkage and warpage, as well as an increase in thermal stability. The later is valid for PC too.
Check out my new Youtube #shorts on this topic too:
If you want to learn more about high performance polymers and their "special skills", check out here my high performance thermoplastics selection blog post series I recently started.
Thanks for reading and watching!
Greetings and #findoutaboutplastics
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Literature:
[1] https://www.findoutaboutplastics.com/2023/10/design-properties-for-polymer-engineers.html
[2] https://www.unitika.co.jp/plastics/e/products/par/upolymer/
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