Vulcanization or curing, creating a three-dimentional chemical network,
is the reason that gum natural rubber (NR) is useful in the tire industry.
Unfortunately, vulcanization has also created a serious environmental problem
as tremendous amounts of waste rubbers are dumped and stockpiled. Unlike
the thermoplastic polymers which can be easily reprocessed by heating,
the thermoset polymers, such as vulcanized NR cannot be simply reused
once they form the three-dimensional network. Therefore, the development
of technologies for recycling of such materials is important due to the
environmental and economic factors resulting from the increasing amount
of waste rubbers, especially scrap tires