Rubber compounding ingredients

The production of a rubber lining includes the preparation of the rubber compound followed by processing to form the lining sheet, substrate preparation, lining application, vulcanisation and inspection. All these stages require thorough quality control, especially compound manufacture and sheet preparation, as chemical resistance depends on satisfactory dispersion of the individual ingredients and undetected flaws in the sheet will cause problems in service. 

Report 79 Rubber Compounding Ingredients - Need, Theory and Innovation, Part I Vulcanising Systems, Antidegradants and Particulate Fillers for General Purpose Rubbers, C. Hepburn, University of Ulster. 

Rubber compounds were made using A1 and A2 shown in Table 17.2 and using a model tire recipe shown in Table 17.4. The ingredients listed in Table 17.4 are in grams per 100 g of rubber (PHR). The mixing procedure used for the samples presented in Table 17.5. Both cured and un-cured compounds were tested and the mechanical testing results are shown in Table 17.6. 

C. Hepburn, Rubber compounding ingredients—need, theory and innovation Part II—Processing, bonding, fire retardants. Report 97, Rapra, 1997. 

Scheme 2.4 Rubber compounds with or without compounding ingredients. After Chu [73]. Reproduced by permission of Hiithig...

Assist the widely dissimilar ingredients used in a rubber compound to coalesce and mix into a homogeneous uniform processable mass. Homogenisers are low-MW polymeric resin blends. The homogenising resin blend contains portions that are compatible with aliphatic, naphthenic and aromatic parts of the elastomers in a blend and higher-MW homologues of the plasticisers. They have a wetting effect. Fatty acid derivatives and phenolic resins are used. 

For identification of other organic rubber compounding ingredients such as waxes, and most antioxidants/antiozonants, sample extraction with diethyl ether, followed by GC-MS of the resulting extract is commonly employed. Examination of volatile species can also provide information on the nature of curatives employed. 

An ingredient added to a rubber compound to protect the product against deterioration by... 

The development of rubber compounds which will effectively withstand the conditions under which the products made from them are to be used the mixes so developed must be capable of being processed in the factory without undue difficulty. The term is also applied to the assembling of elastomer and compounding ingredients ready for the mixing proper. 

Rubber Technology) The statement of the kinds and amounts of elastomers and compounding ingredients which comprise a rubber compound. 

The motion of particles, ions or molecules in a given direction under the influence of a force. In rubber compounding it denotes the movement of any compounding ingredient from an area of high concentration to one of low concentration. 

A compounding ingredient which retards the rate of cure of a rubber compound, thus increasing processing safety. 

A rubber to fabric bonding system comprising resorcinol, a formaldehyde donor and a hydrated silica filler. Incorporated as dry ingredients in the rubber compound and activated by heat. 

The degree to which one substance will dissolve in another. In rubber compounding it should be noted that many compounding ingredients are soluble in rubber and may also be soluble in each other. See Blooming, Insoluble Sulphur, Staining. Solution... 

A compounding ingredient used to reduce the plasticity (increase the stiffness) of rubber compound and thus enable, e.g., an extruded section, to retain its shape or to reduce air trapping in moulding soft rubbers. 

Removing foreign matter and agglomerates of compounding ingredients from rubber or rubber compound by passing it through a strainer. 

A compounding ingredient which enhances the surface tack of uncured rubber compounds. Tackifiers, exemplified by pine tar are classed under softeners and processing aids . 

Resorcinol formaldehyde latex (RFL) cord dips have only a limited application within the general rubber goods industry and for adhesion to be achieved with synthetic fibres it is necessary to use the systems developed by Bayer and Degussa. These systems are based upon a combination of resorcinol, a formaldehyde donor and a hydrated silica filler (commonly called the RFK system). This system is incorporated as dry ingredients into the rubber compound and is activated by the application of heat. 

A process additive is an ingredient which is added in a small dosage to a rubber compound solely to influence the performance of the compound in factory processes, or to enhance physical properties by aiding filler dispersion. 

A further complicating factor with rubber compounds is that some compounding ingredients, e g., 2-mercaptobenzothiazole, will accelerate and increase the sulphur blooming. 

The solubility of wax in vulcanised rubbers is low (of the order of 0.5% for NR) but enough wax has to be added to a rubber compound to ensure that once the compound has been vulcanised and the rubber cools, the rate of migrational movement of the wax from the rubber mass to the surface of the rubber is rapid. Dependant upon the application, the addition level of wax can be up to about 10 phr. Migration of the wax to the rubber surface will also carry other ingredients such as antioxidants, antiozonants and other materials (e.g., vulcanisation residuals), to enhance the surface protection. 

Advances in quality control requirements for rubber compounds have demanded that special care is exercised in the weighing of the various fillers and critical small volume powders necessary for the formulation. Ingredient weighing systems are available which can be tailored to the specific requirements of individual factories. Additional components can include conveyors, bagging units and pneumatic conveyance systems. 

Uses Intermediate in the manufacture of azo dyes and pigments for printing inks, textiles, paints, plastics, and crayons curing agent for isocyanate-terminated polymers and resins rubber compounding ingredient analytical determination of gold formerly used as chemical intermediate for direct red 61 dye. 

Types of Latex Compounds. For comparison with dry-rubber compounds, some examples of various latex compounds and the physical properties of their vulcanizates are given in Table 23. Recipes of natural rubber latex compounds, including one without antioxidant, and data on tensile strength and elongation of sheets made from those, both before and after accelerated aging, are also listed. The effects of curing ingredients, accelerator, and antioxidant are also listed. Table 24 also includes similar data for an SBR latex compound. A phenolic antioxidant was used in all cases. 

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