Hello and welcome to this blog post in which we have a look at the UV-stabilization of Polyamides and how effective protection of your applications against exposure to weather can be achieved.
In a past post we already discussed the weather and UV resistance of styrene copolymers and PMMA.
In case one of your requirements of your application is long-term outdoor usage, then additional protection considerations of your polymer need to be taken into account during polymer material selection.
What is the difference between UV Stabilized and UV Resistant?
UV stabilized: adding stabilizer to your base polymer in order to have protection towards long-term degradation from UV light. They prevent damage by absorbing or screening out UV radiation. The best results being achieved with carbon black.
UV resistant: there are polymers which are inherently resist against UV rays and prevent UV degradation. Examples are polymers such as PMMA and high performance polymers (PEEK, PAI, PPS, PEI, PBI).
UV stabilization of Polyamides
For aliphatic Polyamides such as PA 6.6, adding 2 wt% of carbon black is resulting in a good protection against UV radiation.
Same is valid for semi-aromatic Polyamides such as the PolyArylAmide (PARA; MXD6), where 2 wt% up to 5 wt% will result in an excellent UV protection.
Example cable tie fasteners used for terrestrial photovoltaic (PV) modules- PA66 vs PA66 UV stabilized
HellermannTyton and Germany’s Fraunhofer Institute for Solar Energy Systems ISE investigated the impact of their cable tie fasteners which are used to fix cables of PV modules [3]. The test was 1,600 hours long using a test chamber were the cable ties were exposed to a UV dose of 156.78 kWh/m2 (equals the natural solar irradiation of 1,000 kWh/m2 per year). Altogether, this testing time corresponds to 3 years of outdoor exposure. The cable ties are made out of standard PA66, UV stabilized PA66, and PA11.
Figure 1 shows the results of the test, which indicates a reduction of loop pull strength of around 86% for the standard PA 66. The reduction of the UV stabilized PA 66 is minimal and the PA11 even shows a constant performance, which makes the PA11 a suitable outdoor material without needing too much additional protection.
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| Figure 1: Results of the 1600 hours UV test of PA66, PA66 UV stabilized and PA 11 cable ties [3]. |
Thanks for reading and #findoutaboutplastics
Greetings
Herwig Juster
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Literature:
[1] https://www.usplastic.com/knowledgebase/article.aspx?contentkey=601
[2] https://wurth-international.com/app/uploads/2016/10/CableTies_Technical_Information_2011.pdf
[3] https://blog.hellermanntyton.com/markets-and-industries/1275/uv-stability-hellermanntyton-products-tested-fraunhofer-ise
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