More than 1 billion tires are discarded around the world every year. Disposal of waste tires is a challenging task because tires have a long life and are non-biodegradable. The traditional method of tire waste management is stockpiling or illegally dumping or landfilling, all of which are short-term solution.
Crumb rubber is a term used for recycled rubber from automotive and truck scrap tires. The main method for producing crumb rubber are ambient mechanical grinding.
Ambient Mechanical Grinding
In ambient mechanical grinding process, the breaking up of a scrap tire happens at or above normal room temperature. Ambient grinding is a multi-step technology and uses whole or pre-treated car or truck tires in the form of shred or chips, or sidewalls or treads. The rubbers, metals and textiles are sequentially separated out. Tires are passed through a shredder, which breaks the tires into chips.
The chips are fed into a granulator that breaks them into small pieces while removing steel and fiber in the process. Any remaining steel is removed magnetically and fiber through a combination of shaking screens and wind sifters. Finer rubber particles can be obtained through further grinding in secondary granulators and high-speed rotary mills.
Ambient grinding is the production process used by the majority of crumb producers. The machines most commonly used for fine grinding in ambient plants are:
- Secondary granulators
- High speed rotary mills
- Extruders or screw presses
- Cracker mills
Because of its brittle state, fibres and metal are easily separated out in a hammer mill. The granulate then passes through a series of magnetic screens and sifting stations to remove the last vestiges of impurities. This process requires less energy than others and produces rubber crumb of much finer quality.
Uses of Crumb Rubber
Rubber crumb is sold as feedstock for chemical devulcanization or pyrolysis processes, added to asphalt for highway paving and pavement sealers, or used for the production of a large number of recycled rubber-containing products.
Some of the major applications of crumb rubber are as follows:
1. Sport Surfaces
- Kindergarten Playgrounds and Recreation Areas
- School Sports Areas
- Athletic Tracks
- Tennis and Basketball Courts
2. Automotive Industry
- Bumpers
- Splash Guards and Fenders
- Floor Mats for Cars and Trucks
- Floor Liners for Trucks and Vans
3. Construction
- Hospital, Industrial, and Bathroom Flooring
- Floor Tile
- Foundation Waterproofing
- Dam, Silo, and Roof Liners
4. Geotechnical/Asphalt Applications
- Rubberized Asphalt for Roads and Driveways
- Drainage Pipes
- Soil Conditioner
- Porous Irrigation Pipes
- Road Building and Repair
5. Adhesives and Sealants
- Adhesives and Sealing Compounds
- Textured and Non-Slip Paints
- Roof Coating and Waterproofing
6. Shock Absorption and Safety Products
- Shock Absorbing Pads for Rails and Machinery
- Sound Barriers for Highways
- Abrasion Lining in Mining Equipment
7. Rubber and Plastic Products
- Pipe Insulation and Lining
- Garbage Cans
- Shoe Soles and Heels
- Wire and Cable Insulation