Both rubber types (natural rubber and synthetic rubber) are high molecular compounds.
Natural rubber is derived from a milky colloidal suspension, or latex, found in the sap of some plants.
Synthetic rubber is made from pure monomers by polymerization or polycondensation. Due to manufacturing method rubbers are divided into polymerizing and polycondensating.Main synthetic rubber types:Isoprene, butadiene, butadiene-styrene and butadiene-methylstyrene, carboxylated, butadiene-methylvinylpyridine, butadiene-nitrile, chloroprene, ethylene-propylene, fluor rubbers and others.Initial monomers for polymerization are diene hydrocarbons and ethylene derivatives. Main dienes are: isoprene and butadiene, chloropene, piperylene. Ethylene derivatives (isobutylene, acrylic acid nitrile, styrene, methylstyrene) are used in rubber synthesis by combined polymerization with diene hydrocarbons. Monomers synthesizing materials are natural gas, oil gas, ethanol, coal, limestone etc.Siloxane, urethane and other rubbers are manufactured by polycondensation. Silicon organic compounds, esters, dyisocyanates are used in this synthesizing method.Rubbers are divided into saturated and non-saturated rubbers. Non-saturated rubbers are manufactured by diene hydrocarbons polymerization or by their copolymerization with etylene derivatives. Different types of saturated rubbers have different structure, characterictics, vulcanization properties.Due to characteristics and applications general-purpose rubbers and special rubbers are defined.
General-purpose rubbers are butadiene-styrene, butadiene and isoprene rubbers. General-purpose synthetic rubber applications are tires and the wide range of mechanical rubber goods production.
Special rubbers are used in production of goods with special properties (heat resistance, oil resistance, gas impermeability). These rubbers are polysulphide, butadiene-methylvinylpyridine, siloxane, butadiene-nitrile, chloroprene, ethylene-propylene and fluorine rubbers.Rubber vulcanization Vulcanization refers to a specific curing process of rubber involving high heat and the addition of curatives. It is a chemical process in which polymer molecules are linked to other polymer molecules by atomic bridges.The combined vulcanization package in a typical rubber compound comprises sulfur, together with accelerators, activators. Fillers, antioxidants, plasticizing agents are used to get required properties. Typical cure agent is sulfur. Rubber and sulfur blend is warmed-up to 130-160 о C. This process is referred to as a hot vulcanization. If rubber is vulcanized with sulfur chloride at the room temperature, process is referred to as a cold vulcanization. Hot vulcanization is more wide-spread. Some rubber types can be vulcanized without sulfur at 100 - 200 о C. For special rubbers vulcanization peroxides, metal oxides, polysulphides, isocyanides, diamines are used as curing agents.