Best Practices in Tires & Rubber Recycling
Material: Recycled Rubber
from Tires, Industrial Scrap
Issue: All recycled rubber chips or crumbs may degrade on storage especially in presence of iron particles and heat.
Best Practice: This best practice describes precautions that should be taken during the manufacture and storage of whole tires, shredded tires, chips and recycled rubber crumbs. Almost all recycling processes generate heat sometimes as high as 220-240°F, which in the presence of oxygen, can lead to spontaneous combustion. Also, for natural rubber (NR) compounds the presence of iron (Fe) can catalyze the oxidation process causing rubber degradation. This degradation is accelerated with heat. The presence of any metal can also act as a conductor of heat in rubber crumbs. During processing and storage, volatiles and toxicity chemicals may be generated from hot materials. The moisture content of current recycled rubber in specification is at a maximum of 1 percent. However, the relative humidity and temperature of the material during storage, shipment, and disposition prior to use may cause the moisture content to increase.
Implementation: The work force in plant and storage areas must be trained and aware of the effects of heat and the presence of steel (wire) pieces. During the processing and generation of crumbs, etc., the system and materials need to be cooled, either by water or air, so the temperature is below 200°F to avoid spontaneous combustion. Also, keep recycled rubber free of all metals, especially iron, to avoid conduction of heat and NR degradation. Before the material is stored in bins, piles, etc., make sure that it is cooled and the temperature is well below 200°F. Recycled rubber processors should provide MSDS to their employees and to the end-users. Store materials at ambient temperatures and not in tin sheds or tin-roof warehouses (see MSDS sheet on Vredestein for example). Store recycled materials in a covered and dry area. There have been reports of fires from shredded and ground rubber being stored when not cooled sufficiently after processing. Be aware of proper cooling requirement (i.e., do not store hot ground rubber).
Benefits: There is less safety hazard either during recycling processing or storage of recycled rubber. By eliminating/reducing degradation of crumb, it would impart improved compound properties.
Application Sites: All rubber recyclers during size reduction at various stages and during storage both at processors’ and end-users’ sites.
Contact: For more information about this Best Practice, contact the CWC at (206) 443-7746, email email@example.com.
1. MSDS sheet example attached in Appendix I, from Vredestein’s technical information “Natural Rubber Reclaim, RNR 30/B91.”
2. Baranwal, Krishna C., Akron Rubber Development Laboratory, Akron, OH.
3. Smith, Fernley, President, ETA, Port Clinton, OH.
4. Klingensmith, Bill, Akron Consulting Company, Akron, OH.
5. Rouse, Mike, Rouse Rubber, Inc., Vicksburg, MS.
`` Issue Date / Update: April 1998