Ebonites processing

Chemical Stabilization Processes. Cellular mbber and ebonite are produced by chemical stabili2ation processes. 

Cellular Ebonite. CeUular ebonite is the oldest rigid ceUular plastic. It was produced in the early 1920s by a process similar to the processes described for making ceUular mbber. The formulation of mbber and vulcani2ing agent is changed to produce an ebonite rather than mbber matrix (114). 

The resins act as a plasticiser during processing but they cross-link while the rubber is vulcanising to give a harder product with improved oxidation resistance, oil resistance and tensile strength. The addition of sufficient resin will lead to an ebonite-like product. 

Hard products may also be made by vulcanising rubber (natural or synthetic) using only about two parts of sulphur per 100 parts of rubber. In these cases either the so-called high-styrene resins or phenolie rubber compounding resins are ineorporated into the formulation. These compounds are processed using the methods of rubber technology but, like those of ebonite, the produets are more akin to plastics than to rubbers. Examples of the usage of these materials are to be found in battery boxes, shoe heels and ear washer brushes. 

The use of a special ebonite as the thermoplastic material in the printing process of electro typing, a method of producing metal replicas of printing surfaces. 

However, for construction purposes, solid ebonites were chosen. As is known from rubber chemistry, solid ebonite, commonly known as hard rubber, is a polymer material with sulfur content used for vulcanization. Ebonite, like elastomeric or flexible rubber, is made from a combination of sulfur with polydienes (unsaturated rubbers containing double bonds). The sulfur and polydienes are combined with some auxiliary additives and heated to produce vulcanization. Typical mass ratios of sulfur to rubber are 2 100 for elastomeric rubber and 40 100 for hard rubber. Due to the large degree of sulfide cross linking formed in the vulcanization process, solid ebonite is a hard, non-flexible, plastic-like material possessed of... 

Basic operations such as mastication, mixing, calendering and extrusion are similar for ebonite and soft rubber. The problems, especially in the compounding and vulcanization process which arise in the manufacture of ebonites, are quite different from those with soft rubbers and different tests are used for control of manufacture and for the assessment of the quality of the product. The outstanding differences between ebonites and soft rubbers are detailed below. 

It has been estimated that the consumption of rubber in ebonite products increased on an average of about 6% a year until 1951 when different plastics appeared in the market as competitive materials [6]. But because of the superiority of ebonites in acid and chlorine duties, it still maintains its place in the process industries as a material of construction as evidenced by its increased use in anticorrosive lining of chemical process vessels and tanks for the process industries and rolls for steel and textile and paper and pulp industries. 

Chemicals, Chlor alkali. Paper and pulp, Fertilizers, Oil drilling and Pharmaceu ticals Chemical resistant linings for storage tanks, road and ship tankers, process vessels, pipelines, valves, pumps, filters, agitators, centrifuges, impellers, etc. Soft natural rubber or ebonite, neoprene, butyl and hypalon depending on operating temperature, and application. 

The calendering process and its conditions are developed or modified according to the requirements of subsequent operations and the purpose for which the sheet is used. Thus for sheets which are to be open cured, such as in chemical plant lining and custom built items such as inflatables and ebonite pipes, roll coverings for paper and steel mills, the calendering needs to be more exact than the sheets which are used for blank preparation for molding of... 

Physical Stabilization Process. Cellular polystyrene, cellulose acetate, polyolefins, and poly(vinyl chloride) can be manufactured by this process, Chemical Stabilization Processes. Cellular rubber and ebonite are produced by chemical stabilization processes. 

If the sulfur atoms are not part of the polymeric backbone, the polymers are not included in this class. For example, in the vulcanization process of the polymers with unsaturated carbon chain backbone, -S-S- bonds are introduced in the polymer, but the resulting product is not classified as polymer with C-S bonds in the backbone, although in hard rubber (ebonite), for example, the content of sulfur can be as high as 32%. 

In appearance, HR resembles natural crepe rubber, since it is an aliphatic, hydrocarbon polymer the density being the minimum (0.91) attainable for elastic materials of this type. In HR, the original unsaturation is very small, and even this low unsaturation is greatly reduced and may even be entirely eliminated during the compounding and curing process. The fact that once vulcanised it is extremely resistant to chemical attack is understandable because it becomes, after vulcanisation, not only a nonthermoplastic strong elastic material, but also essentially a chemically saturated product as well. This means that whilst physically vulcanised HR resembles soft vulcanised natural rubber, chemically it may be considered most similar to ebonite almost devoid of any unsaturation. 

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