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Tires are created through a process known as vulcanization,
which gives them a springy, flexible nature as well
as makes them more durable. Vulcanization also makes a
tire difficult to melt for
reuse, so they are typically broken down by powerful
machines.
First the tires are shredded into strips using
rugged machines. The shredded material is then placed
in grinding machines that use
rotors to further shred the material and remove the
steel fibers from the tire. Powerful magnets are also used
to further draw
metal from
the rubber.
Once the bulk of the steel is removed, the
strips are placed into granulators. Depending on the
product requirements, rubber from
the shredded tires can be milled into assorted sizes.
The final step has the milled rubber chemically sealed
for health safety and durability.
After WWI, large-scale tire recycling was observed largely
due to shortages of natural rubber coupled with high
prices. Key milestones in the history of recycled rubber
include the establishment
of The Environmental Protection Agency (EPA) in 1970,
and the rubber recycling industry’s upheaval in the mid-1990s. In 2000, new
rubber recycling rules were set by the EPA, and the industry changed
and became more diverse.
Rubber recycling dates back to the 1800s, the time when
industrial rubber manufacturing began. A machine called a masticator,
or pickle, invented by Thomas Hancock around 1820, ground up rubber
scraps into shreds that could then be mashed into blocks and reused.
This type of rubber recycling was very basic and easy, but short-lived.
In 1843, Charles Goodyear invented vulcanization, a process of weatherproofing
rubber by linking all the molecules in a rubber product into one big
molecule to prevent separation. Goodyear’s process received a
patent on June 24, 1844.
In the 1900s, since vulcanization links the molecules,
it was difficult to separate the molecules again for recycling, meaning
the product could not be re-melted. Vulcanized rubber could still
be shredded and ground, but it had to be mixed with natural rubber
for reuse. A shortage of natural rubber caused by the need for tires
during World War II led to the building of synthetic rubber plants
around the world in 1945.
In the 1960s, cheap oil imports and an increased use of
synthetic rubber brought down manufacturing costs. and the tire and
rubber industry's recycled rubber content dropped to 20%. Use of
synthetic rubber surpassed that of natural rubber for the first time.
The 1960s also brought about steel-belted radial tires, which made
recycling even more difficult. The steel would now have to be removed
after slicing and grinding. A national wave of Tire-Derived Fuel
(TDF) development occurred in the mid 1980s. TDF is not the recycling
of tires, but it eliminates tires from landfill buildup and provides
a fuel for utilities. In 1990, markets began in TDF, with 17% of
used tires used for that purpose, as compared to 78% in 2001. In
2003, 80.4% was used for TDF.
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Recycled Rubber (RR) Beginnings
