Butadiene occurs naturally in small amounts in petroleum gases and is usually produced industrially by cracking of petroleum products. On exposure to air, it undergoes auto-oxidation and becomes polymeric. It is soluble in most organic solvents like ethanol, acetone and benzene but is only slightly soluble in water. Butadiene dissolves readily in gasoline and is highly flammable, forming explosive mixtures with air in the concentration range of 2-11% by volume. Its flashing point is -60°C.
Main Industrial Uses of Butadiene
Synthesis of Synthetic Rubbers: The largest application of Butadiene is in the manufacturing of synthetic rubbers like styrene-butadiene rubber (SBR) and polybutadiene rubber (PBR). These synthetic rubbers find wide usage in automotive tire manufacturing due to their excellent abrasion resistance and mechanical properties. SBR is also used in footwear and other molded products while PBR is used in tires and resilient products.
Production of Nylon: Butadiene acts as an intermediate in the industrial production of nylon 6,6 fibers. In this process, butadiene reacts with ammonia to form cyclohexanone which on further reactions yields adiponitrile and ultimately nylon 6,6 polymer.
Manufacturing of ABS Resins: ABS or acrylonitrile-butadiene-styrene resins are tough engineering thermoplastics produced using butadiene. ABS finds applications in electronic casings, automotive interior and exterior trim parts due to its warp resistance, impact strength and easy processability.
Usage in Latex Coating: Butadiene emulsion polymers are used in latex paints, caulking compounds and adhesives due to their outstanding water resistant and flexibility properties. These latexes offer advantages like fast drying, durable bonding and resistance to cracking, peeling and chalking.
Other Derivative Products: Butadiene is also involved in manufacturing specialty chemicals like adiponitrile, hexamethylenediamine, nylon intermediates, plasticizers and synthetic fibers. It is an important monomer base used for production of various resins, plastics and elastomers as well.
Health and Environmental Aspects of Butadiene
While being indispensable in manufacturing synthetic rubbers, plastics and various chemicals, butadiene is also quite hazardous to human health and environment if not handled carefully. The International Agency for Research on Cancer has categorized butadiene as a Group 1 carcinogen to humans based on sufficient evidence that it can cause cancer in humans as well as experimental animals.
Inhalation of butadiene vapor or gas has shown to cause toxicity in central nervous system and irritation in eyes, nose and throat. Prolonged or repeated exposure may negatively impact blood, liver and spleen in living organisms. It is also a reproductive toxicant and may cause birth defects if inhaled by pregnant women. Proper protective equipment must be worn while working with butadiene in industrial settings.
Being a gas with high vapor pressure, butadiene discharged into the air spreads quickly and persists for days in lower atmosphere and troposphere. It does not persist in soil or water but readily undergoes hydrolysis. The chief environmental concern of butadiene release is production of harmful photochemical oxidation products on reaction with sunlight and atmospheric pollutants. Strict emission controls and treatment of effluents are compulsory before discharge from manufacturing facilities.
In summary, this article aimed to provide a comprehensive overview of butadiene - its chemical properties, main industrial uses, production processes as well as associated health and environmental risks. With growing polymer and synthetic rubber demand, butadiene will continue to be an indispensable industrial chemical. However, safer production and handling practices must be adopted to mitigate human and ecological risks arising from butadiene emissions and exposure.
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