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3.1. The Discovery of Vulcanization
Goodyear thought that rubber might be improved by processing it with other substances. As Goodyear was dis- playing a mixture of rubber and sulfur, the piece slipped from his hand into the fire. When he looked it out he found to his amazement that the mass has charred without melting. Goodyear named this process of combining rubber with sulfur by heat “vulcanization”. Later he discovered that the addition of lime, magnesia, and lead compounds speeded up vulcanization process. Elastic substance obtained from the exudations of certain tropical plants (natural rubber) or derived from petroleum and alcohol (synthetic rubber) [5].
In the process of vulcanization, sulfur atoms form cross-links between the chain molecules of rubber, tying them firmly together. The vulcanization process causes some striking changes in the property of rubber. The rubber remains elastic at both low and high temperatures. Its strength is increased and it can be stretched to greater lengths than before. It will no longer dissolve in gasoline or benzene, though it will swell up if it is soaked in them.
Newly discovered rubber class such as vulcanizing gum is now utilized in repairing worn-out rubbers such as an automobile tire. Vulcanizing gum is classified according to its texture, bonding temperature and the content of accelerators. The three classes of the gum were as follows [5]:
Class A—usually bonds on the rubber 30˚C - 70˚C and is smooth;
Class B—usually bonds on the rubber 35˚C - 80˚C and is moderately rough;
Class C—usually bonds on the rubber 45˚C - 90˚C and is very rough.
3.2. Related Studies
A tire vulcanizer which can make a bladder supply pressurized fluid at a tire vulcanization position and a shap- ing position, disconnects the channel during movement of a lower container, and can move the bladder while keeping the internal pressure of the bladder. Under a state where the lower container (2) moved to the shaping position N, a downstream side moving tube (5) is connected to a second fixed tube (62) through a second joint (72), and pressurized fluid is supplied from a fluid supply unit (42) to the bladder (3) so that a green tire can be shaped. Under a state where the lower container moved to the tire vulcanization position M, the downstream side moving tube (5) is connected to a first fixed tube (61) [6].
A tire vulcanizer is equipped with an inner circumferential wall which surrounds a center post, an outer cir- cumferential wall which surrounds the aforementioned inner circumferential wall, a partitioning wall which ra- dially pides the space between the aforementioned inner circumferential wall and the aforementioned outer circumferential wall into an inner space toward the aforementioned inner circumferential wall and connected to a bladder, and an outer space toward the aforementioned outer circumferential wall and connected to the afore- mentioned bladder, and a circulation means which cyclically supplies and discharges a heated liquid into and out of the aforementioned bladder via the aforementioned inner space and the aforementioned outer [7].
Ramis [8] cited in his dissertation that technological development begins with basic research, when a scientist discovers some new phenomenon or advances new theory. Other researchers examined the breakthrough for its potential utility. If further developed, it leads to a prototype and engineering refinement makes commercial ex- ploitation practical. Then, the technology is finally put to, use may be widely adopted.
Technological change takes place in many directions at once, that is, it is multi-final. Bar codes, for example, are used to track items not only in grocery stores but also in warehouses, assembly lines, shipping docks, libra- ries, even in the Department of Defense. Technological changes are also nonlinear; Developments take irregu- larly. There are many dead ends, and each highly visible advance may depend on a host of small developments (including failures) [8].