In the world of elastomeric materials, storage and handling of product is critical to ensure suitability for use once it reaches final assembly. For parts made from some metals, improper storage can cause rust and degradation of both the appearance and integrity of the item. The situation is no different with elastomers. The proper storage, handling, and shelf-life of elastomeric materials is worth considering and taking steps to ensure product integrity is maintained all the way to point of use, to ensure the best results of the product in final application.
Since its creation in 1998, the SAE Aerospace Recommended Practice, ARP5316, has been the standard most elastomer manufacturers use for guidance on the storage and shelf-life of elastomers. SAE created the standard to suggest proper storage of product prior to use in application. Going beyond life in storage becomes near impossible given the infinite number of applications an elastomer may find use.
While in storage, SAE recommends product be contained within sealed packaging which is ideally opaque. Opaque bagging can cause challenges with quick identification that labeled bags match the contents, so UV resistant polyethylene bags are far more commonly used. These bags should be free of contamination or any additives that contain materials which may degrade the elastomers within.
A sealed bag can protect the finished goods from a great many factors, however temperature, humidity, direct sunlight or other ultraviolet generating lighting, radiation, and ozone exposure can still cause degradation of some materials. Bags should be kept in closed boxes when sunlight or other harmful UV light is present. Storage temperatures should remain above 59°F(15°C) and below 100°F(38°C) as possible and a relative humidity less than 75%. Product should be allowed to return to a consistent 68°F(20°C) prior to use. Product should be kept away from any ionizing radiation or ozone generating equipment as well.
Deformation of materials while in storage can also cause both problems with product integrity and assembly headaches on production lines. Products stored in overpackaged, tightly filled containers may experience some deformation that can make inspection and assembly of products challenging. A common issue with o-rings is a Pringles chip effect where o-rings removed from packaging will not lay flat on a surface. Parts with more intense deformation can cause assembly issues where product will not seat properly or install correctly which can cause pinched seals and premature failures. Guidelines to combat this issue aim to remove stress and tension from packaged product. For especially large sealing rings, product should be looped into three equal loops to avoid creasing or twisting.
Even with perfect storage and handling, time can cause elastomers on the shelf to fail. Outgassing of the chemical components, degradation of material over time, and other factors can eventually make some elastomers suspect prior to use. The SAE ARP 5316 standard provides the following maximum storage periods for elastomeric product families
These time periods use the cure date information provided by the manufacturer as the start date and advise destruction and disposal of any materials which have gone past their maximum storage life. While it is possible that product of an age beyond these guidelines may still function adequately, it is suggested the material be tested for fit, form and function prior to use.
Concern for ensuring the right seal is found for an application tends to be the driving focus for most elastomer users. How the product is treated by the manufacturer, distributor, and even shipping company can play a large part in the ultimate performance of that product once in the application. Fortunately, the SAE ARP 5313 guidelines exist to provide guidance in proper handling and storage of elastomers for every link in the production chain.
- Hydraulic Seals
- Pneumatic Seals