Astlett Rubber Inc.: Customer Help Sheets

Rubber Storage and Aging
Astlett Customer Help Sheet

Natural rubber, when properly stored, has a storage life measured in years. Under international trade practice, rubber less than 12 months old is considered prime tenderable. However, certain (reversible) changes may take place over time.

Rubber should be stored in a dry place with no direct exposure to sunlight. Every effort must be made to keep rubber dry.
Transport and storage at lower temperatures (e.g. <15°C) will result in crystallization. The lower the temperature, the faster the crystallization. Fully crystallized rubber is very hard. This is reversible by conditioning in a hot room (recommended in any case) and/or by mastication.
Storage hardening occurs over time as spontaneous crosslinking. This is measurable as increased viscosity. This is reversible by mastication. Controlled Viscosity (CV) grades harden much slower than non-controlled rubbers, but all rubbers are affected.
The pallet/crate packaging is only designed for a one-way trip. Caution should be used if rubber units are to be stacked.
All rubber units are protected by at least two layers of low melt polyethylene. A thin inner layer wraps each bale. This layer usually has grade and producer marks. A thick poly outer shroud gives further protection.
Units of rubber have various useful marks on their exterior. Shipping marks establish unique lot identity, the producer, the importer and destination port. Grade names and symbols verify the standards used. Serial production lot numbers are keyed to Certificates of Analysis (for TSR's). Net and gross weights indicate the quantity.
Rubber will burn but is not easy to ignite.