Quinoid cure

The quinoid cure is perhaps the most common. It is an old, easily controlled system that typically is formulated as a split batch, two-part cement designed to cure at or even below room temperature. The resultant network is tightly cured, highly resistant to ozone, heat, chemicals, and other environmental attack, and provides good electrical properties. Dark color bodies are formed during the reaction, so quinoid cures cannot be used to make white products, and even light colors require careful compounding. Differences in butyl polymer unsaturation have little effect on the speed of cure with quinoids. 

Quinoid cures depend on crosslinking through the nitroso groups of aromatic nitroso compounds. A commonly used system employs p-quinone dioxime (commercially known as QDO) or dibenzoyl p-quinone dioxime (DBQDO), combined with an oxidizing agent such as manganese dioxide, lead dioxide, red lead oxide (Pb304), or benzothiazyl disulfide. The DBQDO system is less active and thus is... 

Quinoid cures are, however, likely to be scorchy and to produce vulcanisates with lower than normal physical strength. Stearic acid and other acidic materials are omitted because they increase the risk of scorch. Antioxidants and antiozonants cannot be used because they react with the oxidising agent in the curing system. 

Despite the obvious merits of quinoid curing systems they have been used less extensively in recent years, partly because some of them are reported to be health hazards under some conditions, but also because of inroads made by the fastcuring halogenated butyl rubbers. 

Curing systems using quinoid derivatives (GMF or dibenzo GMF with oxidizing agents) give very fast cures, and they are used on a large scale in the CV wire insulation process aging behavior of these vulcanizates is superior to those obtained by sulfur or sulfur-donor systems. 

Quinone dioxime, or a suitably substituted form, used in conjunction with inorganic or organic oxidising agents will give very fast, tight cures. Quinoid systems have been used extensively in CV wire and cable insulation compounds and in adhesives that are required to cure at room temperature. 

Sulphur curing systems provide long service in air at 100°C or less quinoid systems give vulcanisates with greater stability than sulphur systems and are suitable for short-term or intermittent service in air at temperatures up to ISO C extended service in air at 150-200 °C demands resin cures. Tyre curing bladders, for example, are virtually always made from resin cured butyl rubber. However, at high temperatures in the absence of air, e.g. in super heated, deaerated steam, properly cured butyl rubbers perform exceptionally well, irrespective of curing system. 

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