Raw Materials for Rubber Lining

A wide variety of materials are required for the manufacture of rubber lining. A basic necessity is to identify and decide on the correct choice of materials to suit individual requirements of the compound for each type of application. 

The raw materials for manufacturing rubber lining compounds are grouped as  

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At the production lines for rubber profile extrusion as installed at the industrial partners site, most process values were already available from automatic control. Yet, these values were only available for direct display, but not recorded in any way. This is partially due to the fact that production lines in this domain usually run without major changes for several decades. Some important process values, e.g., the power consumption of the extruder engines, were not measured at all. Thus, a first important step of the project was the integration and recording of these values. Appropriate hard- and software had to be installed. Additionally, environmental conditions with possible influence on the properties of the raw materials and thus the process behavior had to be recorded, e.g., temperature, humidity and pressure. 

LIBS/RELMA was tested on a series of industrial NBR compounds with various deliberate recipe errors of all components (rubber, fillers, carbon-black, plasticisers, FRs, AOs, accelerators, ZnO, sulfur, mineral oil). UV excimer laser wavelengths must be employed on polymeric surfaces since only then sharp and regular ablation patterns are produced without any thermal side-effects (at variance with IR NdiYAG). LIBS/RELMA can be used for off-line analysis of vulcanisates, homogeneity testing and particle analysis in mixtures and element analysis of raw materials (in particular for fillers). RELMA... 

Because incorporation and dispersion are different unit processes, having different requirements, design of the internal mixer optimised for one of the processes may not be the optimum for the other. Therefore, in some production lines only incorporation is done with the internal mixer and the contents are dumped onto a mill or fed into a transfer mixer to complete dispersion. Also, the mixing is not always done in one step from the raw material-charge to dump. The charging of the rubber and additives may be done in two or three steps. 

Production Fresh native gluten, as well as dried or devitalized gluten, with at least 70% protein are the raw materials. Hydrolysis is performed, in rubber- or plastic-lined, stirred autoclaves with steam jacket, on 1 1 1-mixtures of dry gluten, water and concentrated hydrochloric acid at a 113-116 °C for 8-12 hours. 

In any application, cost is an important factor. The price of the polymer in the form of a powder, latex, solution, or bale is just part of the economic picture. The cost of other ingredients, equipment for fabrication, labor, power, and all the indirect costs, may well overshadow the polymer s share. A first-line tire containing the best rubber sells for 10-20 times the cost of the raw rubber it contains. Even in a much less complicated structure, such as plasticized poly(vinyl chloride) laboratory tubing, the raw material cost may be less than one-tenth of the selling price. Some properties that might be considered for a single application are as follows ... 

Figure 7.7 shows a typical rubber profile extrusion line. Several days prior to the extrusion itself, the raw rubber is prepared in an internal mixer, where certain materials such as sulfur or carbon black are added to achieve the required properties. One or more extruders form the head of the production line. There, the rubber is kneaded, heated, intermixed, and then extruded through specially formed dies (final delivery elements) which are responsible for attaining the required profile geometry. A major part of the line is taken by the vulcanization process, usually achieved by near infra red and microwave heating. After optical quality control, the profile is cooled down and cut into pieces of a certain length. 

This can be followed by considering the changes in the stress-strain diagram (Fig. 5). The material, tested immediately after being prepared at 250° C, is rather stiff on applying a stress of 40 kg/cm it shows an extension of only about 150%, whereas for the 350 C material this value is 500%. The stress-strain curve for the last-mentioned material shows a close resemblance to that for raw rubber, as appears by comparison with the dotted line in Fig. 5b. Upon storing, the highly elastic sulphur becomes stiffer. 

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