Weather Resistance

Organic polymers, including thermoplastics, gradually decline when exposed to outdoor environments over extended periods. This is mainly due to the direct impact of the ultraviolet rays in sunlight breaking polymer bonds with their energy and the resulting highly reactive radicals (mainly comprising oxygen atoms) destroying polymers in a chain reaction. This is due to the secondary effect (autooxidation mechanism).

Moisture in atmosphere accelerates this process by supplying more oxygen atoms to the system, helping Autoxidation, and with another different mechanism of polymer degradation, called Hydrolysis.

Butadiene rubber, one of the main components of ordinary ABS, contains many double bonds in its molecular chain and is particularly susceptible to weather deterioration. Accordingly, untreated ABS resin is not suitable for use in locations exposed to strong UV rays for extended periods, e.g. outdoors. Adding UV absorbers may mitigate the deterioration, but as mentioned above, the weather resistance largely depends on the properties of the base resin itself.

Techno Polymer offers special types of styrenic polymers suitable to this unforgiving conditions: Techno AES® and Techno ASA. These resins substitutes especially UV vulnerable parts of ABS polymer with more UV stable substances, along with added UV absorbing agents, resulting in significantly improved weather resistance while keeping excellent properties balance of original ABS polymer.

For more detail about above materials, please contact us.
A comparison table with other general-purpose resins is shown below.

*NOTE: Above table illustrates general characteristics of various resins.
For the actual performance of a specific polymer grade, please refer to its datasheets supplied by the original manufacturer.

Weather Resistance of Resins and Colorants

One important yet often being missed point in terms of weather resistance is the individual consideration of resin and colorant.

Degradation due to UV light first becomes obvious in the resin's appearance. As you may have seen in daily life, plastics exposed outside fade (color saturation lowers), and the surface eventually forms a whitish powder ("chalking").

At this point, the mechanical properties of the plastic parts are more or less the same as before degradation, because the UV lights has only affected a few hundred micrometers depth from the surface. However the color-fade can often be the very problem.
(continue exposing and the degradation goes deeper inside, and eventually the plastic part fails mechanically by cracking, etc.)

To effectively prevent discoloring, weather resistant resins AND weather resistant colorants should be selected.
This is usually managed by resin providers, but customers should be aware that "weather resistance" could mean both resistance to color-degradation and resistance to degradation of mechanical properties.
If possible please specify which you are contacting us about.

“weather resistance” and “light resistance” differ

Allow us to clarify the difference between the terms “weather resistance” and“light resistance” used in plastic resin catalogs. Although sometimes used interchangeably depending on the context, strictly speaking, “weather resistance” refers to deterioration in outdoor environments, including rain.Meanwhile, “light resistance” refers to deterioration caused by the effects of light, mainly ultraviolet rays, in the context of endurance. As mentioned above, since moisture exacerbates the decline, so “weather resistance” generally refers to harsher environments.

Conversely, even through glass indoors, some ultraviolet rays pass through normal glass (*), so long-term exposure can cause resins and colorants to deteriorate.
Accordingly, “light resistance” is often required, even for applications like office automation equipment and vehicle interiors.

Accelerated tests using light sources with a spectrum to like sunlight, such as xenon and carbon-arc lamps, are generally used to evaluate the weatherability/light resistance of resins, but the test standards also reflect the above differences. Configuration is normally possible.
For example, the Sunshine Weather Meter, which is a typical accelerated testing device, can be set to emit water intermittently to simulate rainfall.In cases where outdoor use is assumed, tests are conducted under rainy conditions.

* Glass treated with UV protection can block almost all UV rays.