Vulcanisation autoclave

Modern bonding systems usually consist of a primer coat, often with a secondary tie coat, plus a tacky solution to assist in the application of the rubber. The bonding systems currently in use are usually suitable both for autoclave vulcanisation and vulcanisation at 100°C with atmospheric pressure steam or hot water. Ambient vulcanisation bonding systems have to be chemically active at the lower temperatures and are therefore specialist in nature. 

Autoclave vulcanisation - rollers, pipes, hoses, stators,... 

Crosslinking Systems for Room Temperatitre In the rubber-lining of pipes and large vessels autoclave vulcanisation is superfluous if vulcanisation systems are available which crosslink the compound at the ambient temperature over a period of several weeks and which have just sufficient processing safety for this application. 

More specific recipes appear in Table 3. The ingredients are added to the elastomers on standard two-roU mills or in internal mixers. Finished compounds are readily extmded, calendered, or molded in standard equipment. Vulcanisation of extmdates is accompHshed in Hve steam autoclaves, Hquid salt baths, fluidized beds, and microwave equipment. 

Vulcanisation being a chemical reaction, is time/temperature dependant. In factory operations, vulcanisation is usually carried out in an autoclave using steam under pressure at temperatures up to 160°C. If the lined unit is a vessel too large to fit in an autoclave and has an adequate pressure rating, all outlets can be sealed and it can itself be pressurised. If this technique is employed then care must be taken, as a failure of the steam supply with consequent condensation, can cause a vacuum and subsequent collapse of the vessel. 

In the vulcanisation of rubber products, aftercure is the amount of cure received after the termination of the cure proper, e.g., the cure effect resulting from the heat remaining in the product after removal from the mould or autoclave. The term is also applied to the continuation of the curing effect that results from exposure of the article to heat in use, or from accelerated ageing. See Post Cure. 

A pressure vessel constructed of steel, used for the vulcanisation of rubber products by the open steam method. The autoclave may be horizontal (vulcanisation of footwear, cables, hose), or vertical and fitted with a hydraulic ram (e.g., moulding pneumatic tyres). 

In the mbber industry a heat is a number of products comprising a press or autoclave load vulcanised at the same time. 

A term applied to a variety of vessels used in vulcanising mbber articles. See Autoclave and Dry Heat Cure. Also refers to heater bands used on extruder barrels and similar machines. 

The method of vulcanising those rubber products which do not require the precision of shape given by a mould. The heat for curing is supplied by steam circulating openly in an autoclave, the products being supported on mandrels or embedded in chalk. See Moulding. 

A hot air chamber used for heating or drying raw rubber, for vulcanising rubber products by the dry heat method, or for carrying out accelerated ageing by the air oven method. On the continent of Europe, the term oven is sometimes used in the sense of autoclave. 

A term used to describe certain types of vertical autoclaves for the vulcanising of large-size pneumatic tyres sometimes called a kettle . 

An obsolete process for reheading pneumatic tyres. The vulcanisation of the new head rubber is not done in a mould but by the open steam method in an autoclave, and the deshed pattern is cut on the head after cure. 

Autoclaves for rubber product vulcanisation are available in a wide range of sizes to suit the product type. The main use for autoclaves is in the production of extrusions, sheeting and components which are of unsuitable size or construction for conventional mould vulcanisation. Examples of this type of product can range from roller coverings to hand-built products such as footwear. 

An advantage of the autoclave for smaller components, is that a large volume of the same or different products can be vulcanised at the same time, provided that the curative systems in use do not interact between the different compounds. It is usual to support extrusions and low hardness products in talc. Products formed on mandrels and sheeting, for example, are cloth wrapped to prevent distortion. 

In some sections of the industry, it is still common practice to use the hydraulic press only to close the mould, which is fitted with clamps while it is under pressure and is then removed from the press vulcanisation is carried out in an autoclave. This technique is often used for bulky components requiring long low-temperature cures. 

Retreading of tyres may be undertaken in a variety of ways. Unvulcanised material can be applied and then cured at 150-180 °C ( hot retreading), or prevulcanised tread can be applied at temperatures of around 100 °C ( cold retreading). Vulcanisation may take place with or without moulds, or in an autoclave. 

An extruder equipped with a reciprocating die forms the tread pattern directly onto the compound as it is applied to the casing. The casing is then vulcanised in an autoclave. 

A layer of retreaded rubber is formed on the casing and consolidated by pressure. The tread pattern is cut out of the applied rubber either in the same operation or subsequently. Vulcanisation takes place in an autoclave. 

Equipment which cannot be vulcanised in autoclave would require one of the following... 

The welds should not be porous or should not have any cracks. As the lining is usually subjected to vulcanisation in autoclave at temperatures of 130 °C to 150 °C, the entrapped air inside the weld could expand and blow out the lining thereby necessitating repair work on the lined vessel. 

The lining sequence for each kind of vessel and piping should be planned ahead and the design of sheet to match the contours and shapes of the vessels needs to be done meticulously, to achieve a properly finished, smooth lining with perfect joints. After the vessel is lined, it is ready for vulcanisation either in the autoclave, or by an open steam or... 

In road tankers transporting different chemicals in the same rubber lined tankers is a common practice since it is uneconomical to have the tank lined for each type of acid/chemical. In this case, it is advisable to rinse the tank with water before filling up different chemicals each time. In general, the transportation tankers such as railway tankers, road tankers and ship tankers have dimensions, which can still be vulcanised in autoclaves [4]. The size of the tank is limited by the maximum size of the autoclave and also depends on the feasibility to transport them before and after rubber lining. The author s opinion is that the maximum size of the autoclave can be 5 m diameter x 10 m long which is considered to be a techno-economically viable size for factory operations, which in most cases can accommodate road tankers, railway tankers and ship tankers. 

ASTM D429-02, Method D, Post Bond Vulcanisation butt test [16]. Parts are clamped in a jig and put into an autoclave or oven. 

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