The plastics industry finds it extremely difficult to forecast a product's durability based on the abrasions it will experience over the course of its shelf life. Manufacturers of equipment, those who simulate these aggressions through accelerated ageing tests, and testing facilities are some of the affected agents. The latter ones frequently have to meet constraints, including estimating the bare minimum of time for a product to perform properly. A product may be exposed to particular environmental conditions linked to temperature, humidity, and sunlight, which may jeopardise expected aesthetic, functional, or safety requirements, aside from tensile tension, vibration, or chemical attacks that develop with extended usage.
It makes sense to think about subjecting items to the service circumstances anticipated, or better yet, to the worst conditions they must contend with, as a method to understand their behavior. Weathering testing is one tool that can be used to predict how our products will fare against the passage of time, despite the fact that forecasting a product or material's weathering or degradation due to single or multiple factors (cold, heat, rain, etc.) over time is nothing more than an estimate.
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Accelerated weathering climate chambers
Documents describing cold and heat cycles, damp heat cycles, or temperature or humidity cycles contain standards for these tests. Although it is common practice to modify the test duration and aggressiveness at extreme temperatures based on the demands of the final product and the durability requirements, the duration of accelerated weathering may also be established in standards. For instance, in the automobile industry, every car manufacturer has their own criteria to simulate the behavior of the components that will be installed within the vehicle and subjected to high temperature and radiation fluctuations.
In these tests, the component's final position within the car's cabin determines the cycle's extreme temperatures. As a result, components placed above the waistline, where they would receive more sun exposure, must withstand a more rigorous test than those placed below the waistline or at ground level, like feet-fitted carpets in automobiles.
Remember that plastics are man-made materials produced through polymerization processes or the multiplication of carbon atoms in lengthy molecular chains of oil-based organic chemicals and other naturally occurring substances. The mobility of these lengthy chains is largely dependent on the ambient temperature, which naturally has an impact on the characteristics of plastics.
Given its makeup, the movement of molecular chains during weathering tests and aging tests impacts the qualities of plastics, nearly usually making them worse. Here are some effects of several weathering agents:
Cool: Chains get immobilized at low temperatures, below the material's glass transition point, making the substance more brittle. Chains cannot lose their shape to absorb forces, hence this is the reason.
Dry Heat: High temperatures make molecules more mobile, which affects the crystalline structure and consequently the qualities of the material. Heat also promotes migratory processes, which causes consequences like plasticizer loss to occur more quickly since they travel to the surface.
Heat+High Humidity: polymers (PA, PET, PUR, etc.) have the capacity to absorb a significant amount of water and result in a variety of structural and final property changes. Some attributes are impacted by this water absorption:
- It alters the dimensional stability.
- It increases resilience while decreasing resistance and hardness.
- It lowers electrical resistance.
Cool-heat cycles: Temperature and humidity changes cause stresses in the material, allowing cracks, breaks, and dimensional changes to appear. All of these factors and damages caused by weathering factors, whether naturally or artificially through accelerated weathering, must be assessed and quantified if possible.
Maeonlabs has a large number of weathering testing equipment as well as devices to quantify the changes that the structure, material, or part's surface side may undergo. A common method for assessing the degradation of a material is to measure certain properties before and after subjecting the part or product to an ageing test and observing the decrease of some properties at the end of the test.
Here's you can find the website for Plastic Material Testing