Testing for the weather resistance or permanence of materials is of major concern to manufacturers. Multiple factors in the weather that materials are exposed to can degrade the looks and performance of items. These test help to check on just how materials and products will react to the environments they will be used in.
Ultraviolet (UV) Exposure
The UV radiation component of sunlight is very harsh on on polymers. Heat caused by the infra red component will not only degrade but can physically distort a product over time. Combined with rain and humidity, a chemical change or breakdown may also occur. Any of these can lead to lower strength, loss of color (fading), distortion and corrosion. Ultimately the effects of sunlight on the atmosphere in conjunction with emissions from man and his industries causes everything from acid corrosion to ozone breakdown of materials. Testing of UV exposures is done in specialized equipment that allows controlled amounts in time and effect of sunlight on materials and products.
Exposing materials and products to Ozone is done to test their resistance to such an aggressive atmospheric chemical. Elastomers especially need to resist ozone or they will become embrittled prematurely and fail.
Sulfur dioxide, hydrogen sulfide and ozone are a few of the pollutants found in the atmosphere through both natural and man made sources. Combined with carbon dioxide and water these pollutants become very corrosive. Exposure testing to these gases can prove how a material or product will stand up to such environments.
Cycling between high and low humidity and temperature variants as well as exposure to high humidity alone effects the performance of most materials. The proper balance and effect of humidity is not only important to performance of a material or product but in the manufacturing as well. Some plastics and polymers will not process or mold properly with high moisture content, but they gain strength after molding when moisture is added.
Thermal cycling is going from very hot to very cold and back to very hot. Very rapid cooling or heating induces Thermal Shock a variant of normal thermal cycling. These types of testing accelerate product and material failures under extreme conditions of environmental use. It ensures the stability and performance in the material or product tested.