Processing applications vulcanisation

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. 

It is explained that acrylic coagents can improve processability and vulcanisation of elastomers used in automotive applications, and that Saret coagents from Sartomer Co. of the USA provide scorch-retarding properties along with improved radiator hose properties for all curing situations. This article describes tests comparing several coagents in ethylene propylene diene monomer radiator hose formulations. Results are presented and discussed. 

Vulcanised (cross-linked) polyethylene is being used for cable application where service temperatures up to 90°C are encountered. Typical cross-linking agents for this purpose are peroxides such as dicumyl peroxide. The use of such agents is significantly cheaper than irradiation processes for the cross-linking of the polymer. An alternative process involves the use of vinyl silanes (see Section 10.9). 

A process for making hollow mbber articles from a single sheet of calendered unvulcanised mbber. The surface of the sheet is semi-vulcanised and the application of a swelling agent causes the sheet to split thus forming the hollow article, the vulcanisation of which is completed thereafter. Homo polymer... 

A method of manufacturing latex foam. Compounded latex is partially frothed and fully expanded by application of vacuum to the mould the gel is frozen, set by carbon dioxide and vulcanised by raising the temperature of the mould. See Dunlop Process. 

Apphed to a high polymer which undergoes a chemical change when it is subjected to heat, after which its shape cannot be changed by the application of further heat and pressure. Although vulcanisation of rubber is a thermosetting process the term is usually applied to plastics . See Thermoplastic. 

For some applications, such as when it is necessary to dissolve or solvate rubbers, or rubber compounds to form doughs and solutions it is desirable to use a machine in this category. Various types of machines can be used to produce the required form. Grinders are also used to reduce scrap vulcanisate to form a rubber crumb for purposes of working this waste product back into cheap compounds, or prior to reclaiming rubber by chemical processes. 

Frequent mould cleaning is essential in long-run production to ensure good product appearance. The cleaning frequency is dependent on the application of the components being manufactured, the type of compound being processed and the temperature of vulcanisation. 

As a result of its saturated polymer backbone, EPDM is more resistant to oxygen, ozone, UV and heat than the low-cost commodity polydiene rubbers, such as natural rubber (NR), polybutadiene rubber (BR) and styrene-butadiene rubber (SBR). Therefore, the main use of EPD(M) is in outdoor applications, such as automotive sealing systems, window seals and roof sheeting, and in under-the-hood applications, such as coolant hoses. The main drawback of EPDM is its poor resistance to swelling in apolar fluids such as oil, making it inferior to high-performance elastomers, such as fluoro, acrylate and silicone elastomers in that respect. Over the last decade thermoplastic vulcanisates, produced via dynamic vulcanisation of blends of polypropylene (PP) and EPDM, have been commercialised, combining thermoplastic processability with rubber elasticity [8, 9]. 

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