Plastics Chemical Structure
The Plastics are very large group of synthetic materials whose structures are based on the chemistry of carbon as on organic chemistry structure. Plastics are also called polymers because they are made of extremely long chains of carbon atoms. An important characteristic of plastics is that they can be readily molded into finished products by the application of heat. The group has now become so diverse that some polymers, such as silicons, do not conform comfortably to this definition. Since the 1940s many outstanding and indispensable plastics have been developed, and these have been used in a wide range of critical applications, including machine gears, artificial hearts, and bonding cements for such things as aircraft structures.
History of Plastic
The first snthetic plastic was celluloid, a mixture of celulose nitrate and camphor, invented in 1856 by Alexander Parkes. In 1909 the second synthetic plastic, phenol formaldehyde (also called Bakelite), was invented by Leo Baekeland when he simply heated a mixture of phenol and formaldehyde. Shortly before World War II a number of synthetic polymers were developed, including casein, Nylon, Polyester, Polyvinyl chloride, polystyrene, and polyethylene. Since then the number as well as the types and qualities of plastics have greatly increased, producing superior materials such as epoxies, polycarbonate, teflon, silicones and polysulfone.
Two modern trends in the development of plastic materials are the increased number of foamed plastics that are imbeded with gas, and the custom designing of plastics to satisfy particular service requirement.
Chemical Structure of Plastics
The bonding properties and chemical versatility of carbon account for the great number of plastics. Although carbon is the backbone of polymer chains, other elements are included to varying degrees, in chemical structure of plastics. These include hydrogen, oxygen, nitrogen, chlorine, fluorine, and occasionally other elements, such as sulfur and silicon.
High molecular weight polymer molecules are built up by joining together into chains repeating chemical units called monomers. Monomer molecules may be either gases or liquids. In case of polyethylene the monomer unit is ethylene, C 2 H 2 , which is obtained from the dehydrogenation of ethane, C2H 6 . With the aid of catalyst, ethylene molecules attach to each other in a process known as polymerization. The lengths of monomer units, and the average molecular weight, can be controlled. This is important because large variations in chain lengths can result in variations in properties.
History of Plastic
The first snthetic plastic was celluloid, a mixture of celulose nitrate and camphor, invented in 1856 by Alexander Parkes. In 1909 the second synthetic plastic, phenol formaldehyde (also called Bakelite), was invented by Leo Baekeland when he simply heated a mixture of phenol and formaldehyde. Shortly before World War II a number of synthetic polymers were developed, including casein, Nylon, Polyester, Polyvinyl chloride, polystyrene, and polyethylene. Since then the number as well as the types and qualities of plastics have greatly increased, producing superior materials such as epoxies, polycarbonate, teflon, silicones and polysulfone.
Two modern trends in the development of plastic materials are the increased number of foamed plastics that are imbeded with gas, and the custom designing of plastics to satisfy particular service requirement.
Chemical Structure of Plastics
The bonding properties and chemical versatility of carbon account for the great number of plastics. Although carbon is the backbone of polymer chains, other elements are included to varying degrees, in chemical structure of plastics. These include hydrogen, oxygen, nitrogen, chlorine, fluorine, and occasionally other elements, such as sulfur and silicon.
High molecular weight polymer molecules are built up by joining together into chains repeating chemical units called monomers. Monomer molecules may be either gases or liquids. In case of polyethylene the monomer unit is ethylene, C 2 H 2 , which is obtained from the dehydrogenation of ethane, C2H 6 . With the aid of catalyst, ethylene molecules attach to each other in a process known as polymerization. The lengths of monomer units, and the average molecular weight, can be controlled. This is important because large variations in chain lengths can result in variations in properties.
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