Rubber Technology and Introduction
The term “rubber” meant the material obtained from the rubber tree Hevea brasiliensis. Today, a distinction is made between crude rubbers and vulcanized rubbers, or elastomers. Elastomer is the preferred term for vulcanized rubber. Other terms that are less frequently used in clued vulcanizate and crosslinked rubber. Elastomers or rubbers are classes of materials like a wood, fibers, metals, glasses, or plastics. The annual consumption of rubber amounts more than 13 million tons. About one third of total global rubber usage is natural rubber that produced in plantations in Thailand, Malaysia, Indonesia as well as in West Africa, and South or Central America. Two thirds of the required rubber is produced synthetically by industrial countries which oil is used to raw material for producing synthetic rubber. More than half of the global production of natural and synthetic rubber is used in tires and great variety of consumer products from motor mounts, fuel hoses over window profiles and heavy conveyor belts to membranes for artificial kidneys. The property of elastomers is the elastic behavior after deformation in compression or tension. It is possible to stretch and elastomer ten times its original length and after removal of the tension it will be return to its original shape and length. Moreover elastomers are characterized by a great toughness under static or dynamic stresses, an abrasion resistance which is higher than steel, by an impermeability to air and water, by a high resistance to swelling solvents and chemicals attack. Rubbers are also capable of adhering to metals and textile fibres. By joining elastomers with metals components which combine the elasticity of elastomers with the rigidity of metals. In combination with fibres such as rayon, polyamide, polyester, glass or steelcord and depenting on the properties of the reinforcing member the tensile strength is increased considerably with and attending reduction in extendibility. This can be of great importance to designers. The properties profile which can be obtained with elastomers depends mainly on the choice of the particular rubber, the compound composition, the production process, and the shape and design of the product. Properties which do justice to elastomers can only by proper compounding with chemicals and other additives of which there are about 20000 different ones, and subsequent vulcanization. Depend on type and chemicals additives and degree of vulcanization given rubber different properties with respect to hardness, elasticity, or strength. And the typical properties of the specific rubber, namely oil, gasoline, aging resistance remain unaltered in the different valcanizates.
Yangpara or Caoutchouc
Yang-pa-ra (for Thai word), Caoutchouc (derived from the Indian word “caa-o-chu” or “weeping tree”) is referred to natural rubber (NB) that can be reacted with sulpher (S) at high temperatures to from crosslinds (vulcanization). Thus, it’s transformed a sticky into highly elastic one or it’s transform caout chouc to elastomer or rubber. In the course of developing synthetic analogues to NR, similar compounds were found, which could also be crosslinked with sulphur. The first group of synthetic rubbers (SR) was extended after the discovery of other macromolecular compounds which cannot be cured with sulfur but can be converted into elastomers with different systems to form network structure. Caoutchouc is great variety of raw macromolecular compounds which can be crosslinked to form network structure which have to satisfy the following requirements: Preferably they should be long chain molecules forming coils which can be extended when subjected to stresses. Caoutchouc or raw rubbers should be largely amorphous at ambient temperatures so that the chain flexibility is not inhibited by crystallization, which would interfere with the elasticity of the material and make it rigid or stiff instead.
The vulcanization is a process that transforms the predominantly raw rubber into an elastic rubbery. This process which involves the association of macromolecules through their reactive sites, also called crosslinking or curing. As long as only natural rubber (NB) and synthetic rubber (SR) which are crosslinkable with sulphur were known as “vulcanization” was used to describe the crosslinking reaction with sulphur. With the availability of high molecular weight compounds which do not react with sulphur, but have to be crosslinked by other means instead, it was recognized that the sulphur-vulcanization is only a special case of crosslinding mechanisms of which there are indeed many. The vulcanization reaction is determined in large measure by the type of vulcanizing agents, temperature, process and time.The degree of vulcanization referred to the number of crosslinks formed, had depend on the elastic and other properties of the vulanizate. So the type of vulcanization process is the important connecting link between the raw material and the finished product.