硫化Vulcanization

硫磺（S₈）在促进剂和活化剂（氧化锌、硬脂酸）作用下与橡胶分子双键旁的烯丙位氢反应，在链间形成单硫键、双硫键或多硫键交联。通常每 100–200 个单体单元有一个交联点。硫用量 1–3 份得到软橡胶；用量 30–50 份得到坚硬的硬质橡胶（胶木）。促进剂（如噻唑类、次磺酰胺类）大幅缩短硫化时间、降低硫化温度。

With accelerators and activators (zinc oxide, stearic acid), sulfur (S₈) reacts at the allylic hydrogens next to the double bonds and forms mono-, di- or polysulfide crosslinks between chains, typically one per 100–200 monomer units. One to three parts of sulfur per hundred of rubber give soft rubber, while 30–50 parts give hard ebonite. Accelerators such as thiazoles and sulfenamides greatly shorten cure times and lower cure temperatures.

1839 年美国人查尔斯·固特异在一次实验中意外地把橡胶与硫磺的混合物掉在热炉上，发现它没有熔化而是变成了有弹性的物质，由此发明硫化法，1844 年获美国专利。几乎同时英国的汉考克也独立获得专利，并采用了 vulcanization 一词（来自罗马火神伏尔甘）。1906 年奥恩斯拉格发现有机促进剂苯胺。

In 1839 the American Charles Goodyear accidentally dropped a mixture of rubber and sulfur on a hot stove and found it charred into an elastic material instead of melting; he patented vulcanisation in the United States in 1844. Thomas Hancock in England patented it independently at about the same time and used the word vulcanisation, after Vulcan, the Roman god of fire. In 1906 Oenslager discovered aniline as an organic accelerator.

饱和橡胶（如乙丙橡胶、硅橡胶）缺少双键，常用过氧化物交联；氯丁橡胶用金属氧化物交联；也可用电子束辐射交联。硫化后的橡胶不能再熔融加工，废轮胎回收主要采用粉碎为胶粉、脱硫再生和热解等方法。

Saturated rubbers such as EPDM and silicone lack double bonds and are usually cured with peroxides; neoprene is cured with metal oxides; electron-beam irradiation also crosslinks rubber. Vulcanised rubber cannot be remelted, so scrap tyres are recycled mainly by grinding to crumb, devulcanisation and pyrolysis.