**2. Brief history and production technology of tires**

Automotive tires are made of synthetic rubber which is obtained from petroleum. The development of tires was based on improving the performance of natural rubber which is obtained from the liquid latex secreted by certain plants. At the beginning, natural rubber was used to produce waterproof fabrics and to make balls, containers and shoes by Pre-Colombian people in South and Central America. Until the 18th century, Europeans did not make use of rubber except that they utilized it for manufacturing elastic bands and pencil erasers. Joseph Priestley, a founder of the modern study of chemistry, named the substance "rubber" for its use as an eraser (Oven, 2004).

During the 19th century, Charles Goodyear studied on making rubber more resistant to various chemicals. He started his working by mixing rubber with various dry powders, and aimed to find a way to make natural rubber stickier. In 1839, he achieved to obtain the best

heading below. The outcomes of scrap tire recycling are not only limited by easy access to cost-efficient material such as rubber and steel, but also have positive effects on the environment: Recycling of scrap tires on a global scale can drastically reduce waste yards,

soil and atmospheric contamination caused by dump yards and large scale tire fires.

Fig. 1. Scrap tire storage areas and fires.

"rubber" for its use as an eraser (Oven, 2004).

**2. Brief history and production technology of tires** 

Automotive tires are made of synthetic rubber which is obtained from petroleum. The development of tires was based on improving the performance of natural rubber which is obtained from the liquid latex secreted by certain plants. At the beginning, natural rubber was used to produce waterproof fabrics and to make balls, containers and shoes by Pre-Colombian people in South and Central America. Until the 18th century, Europeans did not make use of rubber except that they utilized it for manufacturing elastic bands and pencil erasers. Joseph Priestley, a founder of the modern study of chemistry, named the substance

During the 19th century, Charles Goodyear studied on making rubber more resistant to various chemicals. He started his working by mixing rubber with various dry powders, and aimed to find a way to make natural rubber stickier. In 1839, he achieved to obtain the best product by applying steam heat under pressure, for four to six hours at 132 Celsius (270 Fahrenheit) degrees (Goodyear, 2011).

Following the discovery of vulcanization, manufacturers began producing tires from solid rubber which yielded a strong material to resist cuts and abrasions. Although this was a great progress, the tires were too heavy and rigid. In order to decrease vibration and improve traction, Robert W. Thomson, first produced the pneumatic rubber tire which consisted of rubber filled in with air. His idea could not a commercialized since it was introduced too early for its time. John Boyd Dunlop from Ireland, who did not know about Thomson's earlier invention, once more introduced the pneumatic tire to the market in 1888. This time, pneumatic tire caught the public's attention because bicycles were becoming extremely popular and the lighter tire provided a much better ride (Rubberis, 2011).

In early 19th century, manufacturers started producing vehicle tires comprising two parts, i.e., an inner part and an outer part. The inner part, called the inner tube, contained compressed air and the outer part was a casing protecting the inner tube and providing the tire with a better grip. An important element of the outer part were the layers called plies which were made of rubberized fabric cords embedded in the rubber and they were strengthening the casing. They were known as bias-ply tires because the cords in a single ply run diagonally from the beads on one inner rim to the beads on the other rim. The orientation of the cords change from ply to ply so that the cords crisscross each other (Rubbentire, 2011).

The steel-belted radial tires were first produced in 1948 by the Europeans. In those first tires, the ply cords radiate at a 90 degree angle from the wheel rim. Together with this, a belt of steel fabric that wrapped the circumference of the tire reinforced its casing. Radial tire ply cords are composed of nylon, rayon or polyester. The advantages of radial tires include longer tread life, better steering and less rolling resistance. On the other hand, radials have a harder riding quality, and are about twice as expensive as the tires without radials. The production sequence of steel-belted radial tires is briefly illustrated in Fig. 2.
