Rubber Shelf Life
Elastomers are susceptible to aging. As a rubber ages, its material properties deteriorate. This happens as the rubber polymer reacts with the environment around it, causing chemical changes in the material. These changes can occur due to new crosslinks being formed or main chain and crosslink scission and can lead to either the embrittlement or softening of the material. Ageing of a rubber material is an irreversible process and the rate of deterioration depends on a number of factors including temperature, exposure to light, humidity, ozone, chemical contact, and deformation.
The shelf life of a material is the recommended amount of time that a rubber material can be kept in storage. The recommended shelf live varies between different rubber materials. Silicone tends to last much longer than other rubber materials and can be stored for up to 20 years. The standard shelf life of rubber materials shown in the table below is based on information found in MIL-HDBK-695D Military Standardization Handbook Rubber Products: Recommended Shelf Life.
Table 1: Recommended Shelf Lives of Rubber.
|Rubber Material||Recommended Shelf Life|
|Natural Rubber||3-5 years|
The shelf life of a material will be affected by the storage conditions and bad storage conditions can shorten the expected shelf life of a material. It is recommended to store rubber at temperatures below 38°C and away from direct sunlight, UV rays or intense artificial light. Ideally, rubber should be stored at humidity levels of less than 75% or kept in sealed moisture proof bags. Rubber should not be placed near electrical motors or high voltage equipment and exposure to any liquids or vapours should be avoided. To stop the material from deteriorating, the rubber product should not be hung, folded, or rolled in storage as this can lead to tension and bending. Ideally, rubber materials should be kept in storage for as short a time as possible.