Changes

==Formation==

==Formation==

Polymers are formed through the reaction of base units called [[monomer|monomers]]. These units will join together to form chains of thousands or even millions of recursions. Polymerization tends to occur under intense heat and pressure required to supply the [[activation energy]] for the reaction, this can be monitored and changed to affect the final properties of the polymer. The products or monomers can also be altered, a polymer consisting of more than one type of base unit is called a copolymer.

Polymers are formed through the reaction of base units called [[monomer]]s. These units will join together to form chains of thousands or even millions of recursions. Polymerization tends to occur under intense heat and pressure required to supply the [[activation energy]] for the reaction, this can be monitored and changed to affect the final properties of the polymer. The products or monomers can also be altered, a polymer consisting of more than one type of base unit is called a copolymer.

===Steps of Basic Polymerization===

===Steps of Basic Polymerization===

====Initiation====

====Initiation====

A chemical (called the initiator) is added to a substance containing the monomers. It activates one of the monomers (in many cases when alkenes are used the double [[bond]] is split producing two free [[electrons]] which can react with other molecules) allowing polymerization to occur. It is important to note that the initiator is not a catalyst as in most cases it is absorbed into the final product. Common initiators include organic peroxides (used to produce LDPE).

A chemical (called the initiator) is added to a substance containing the monomers. It activates one of the monomers (in many cases when [[alkene]]s are used the double [[bond]] is split producing two free [[electron]]s which can react with other molecules) allowing polymerization to occur. It is important to note that the initiator is not a catalyst as in most cases it is absorbed into the final product. Common initiators include organic peroxides (used to produce LDPE).

====Propagation====

====Propagation====

The active monomer activates another unit (eg by causing its double bond to split), as there are now four free electrons a covalent bond can form between the two units and two electrons (one on each atom) will be left to combine with other units. This process continues and the chain grows in size with every unit added. During propagation side branching can occur, in which monomers start a secondary chain leading off the first. These chains can affect the properties of the end polymer, and can be controlled depending on the conditions in which polymerization occurs.

The active monomer activates another unit (eg. by causing its double bond to split), as there are now four free electrons a covalent bond can form between the two units and two electrons (one on each atom) will be left to combine with other units. This process continues and the chain grows in size with every unit added. During propagation side branching can occur, in which monomers start a secondary chain leading off the first. These chains can affect the properties of the end polymer, and can be controlled depending on the conditions in which polymerization occurs.

====Termination====

====Termination====

===Reactions Involved in Basic Polymerization===

===Reactions Involved in Basic Polymerization===

The basic chemistry involved in polymerization can be concised in the reactions that take place. The main types of polymerization reactions are:

The basic chemistry involved in polymerization can be compacted in the reactions that take place. The main types of polymerization reactions are:

''Addition Polymerization''

''Addition Polymerization''

''Condensation Polymerization''

''Condensation Polymerization''

In this process two monomers react and form a larger unit and a byproduct. A common condensation reaction occurring in nature is the reaction between glucose units to produce the polymer [[cellulose]], the two monomers are fermented with yeast and combine to form the larger chain, expelling a water molecule in the reaction (C6H12O6 + C6H12O6 - C12H22O11 + H2O, as the number of each type of atom is the same the law of conservation of mass is adhered to).

In this process two monomers react and form a larger unit and a byproduct. A common condensation reaction occurring in nature is the reaction between glucose units to produce the polymer [[cellulose]], the two monomers are fermented with yeast and combine to form the larger chain, expelling a water molecule in the reaction (C₆H₁₂O₆ + C₆H₁₂O₆ - C₁₂H₂₂O₁₁ + H₂O, as the number of each type of atom is the same the law of conservation of mass is adhered to).

===Additives===

===Additives===

*''Plastifiers'' - Soften the plastic or fiber produced

*''Plastifiers'' - Soften the plastic or fiber produced

*''Fillers'' - Reinforce a particular property of the polymer (eg boiling point, hardness)

*''Fillers'' - Reinforce a particular property of the polymer (eg. boiling point, hardness)

*''Stabilizers'' - Protect the polymer against oxidation, UV decomposition etc

*''Stabilizers'' - Protect the polymer against oxidation, UV decomposition etc

*''Pigments'' - Color the polymer (commonly used in plastics)

*''Pigments'' - Color the polymer (commonly used in plastics)

*''Cold Drawing'' - Individual fibers are drawn from the vessel and wrapped around a rod. This is not used extensively in industry as it is a slow process (similar to winding thread around a thimble).

*''Cold Drawing'' - Individual fibers are drawn from the vessel and wrapped around a rod. This is not used extensively in industry as it is a slow process (similar to winding thread around a thimble).

*''Extrusion'' - The polymer in liquid form is forced through a nozzle, resulting in thin threads being formed. This process is common in the formation of synthetic fibers (eg rayon).

*''Extrusion'' - The polymer in liquid form is forced through a nozzle, resulting in thin threads being formed. This process is common in the formation of synthetic fibers (eg. rayon).

*''Moulding'' - The liquid polymer is set into a particular shape and left to cool. This is used when clearly defined shapes are required (eg in making microscopic tools the polymer can be poured into a cast and left to solidify, where it will then form the exact shape).

*''Molding'' - The liquid polymer is set into a particular shape and left to cool. This is used when clearly defined shapes are required (eg. in making microscopic tools the polymer can be poured into a cast and left to solidify, where it will then form the exact shape).

*''Calendering'' - The polymer is rolled into sheets where the chains are compacted against each other to give the impression of a solid object, this is the practice commonly used to produce plastics.

*''Calendering'' - The polymer is rolled into sheets where the chains are compacted against each other to give the impression of a solid object, this is the practice commonly used to produce plastics.

==Future of Polymers==

==Future of Polymers==

The base unit for most industrial polymers is ethylene or an alkene [[allotrope]], these in turn are commonly extracted from crude oil either directly (through [[fractional distillation]] or through [[cracking]] of the larger carbon chains. Oil reserves are being depleted, and may last anywhere between 20 and 50 years. Although the petrochemical industry (the market producing polymers) only uses 5% of the fossil fuels extracted it will still be affected by the decreasing supplies, and as such scientists are looking to alternative produces which can be used to produce polymers. The alternative most intensely researched is the possibility of biopolymers, carbon chains obtained from organic sources (eg trees and plants such as sugarcane). These would have the benefit of being renewable (able to be replaced in a few years, compared to the millions of years needed to reform crude oil), biocompatible (able to be used in the human body, could see new applications of plastics in the medical sector) and biodegradable (a major problem with current plastics is that they don't break down and can remain in landfill for hundreds of thousands of years). However, current biopolymers tend not to be as durable as their industrial counterparts, and they are less economically viable (large areas of land, fertilizer and energy are required to produce and extract the monomer units). That said, with increasing advances in technology biopolymers may become the norm, and new possibilities may open up the the field of polymer chemistry.

The base unit for most industrial polymers is ethylene or an alkene [[allotrope]], these in turn are commonly extracted from crude oil either directly (through [[fractional distillation]] or through [[cracking]] of the larger carbon chains. Oil reserves are being depleted, and may last anywhere between 20 and 50 years. Although the petrochemical industry (the market producing polymers) only uses 5% of the fossil fuels extracted it will still be affected by the decreasing supplies, and as such scientists are looking to alternative produces which can be used to produce polymers. The alternative most intensely researched is the possibility of biopolymers, carbon chains obtained from organic sources (eg. trees and plants such as sugarcane). These would have the benefit of being renewable (able to be replaced in a few years, compared to the millions of years needed to reform crude oil), biocompatible (able to be used in the human body, could see new applications of plastics in the medical sector) and biodegradable (a major problem with current plastics is that they don't break down and can remain in landfill for hundreds of thousands of years). However, current biopolymers tend not to be as durable as their industrial counterparts, and they are less economically viable (large areas of land, fertilizer and energy are required to produce and extract the monomer units). That said, with increasing advances in technology biopolymers may become the norm, and new possibilities may open up the the field of polymer chemistry.

[[Category:Chemistry]]

[[Category:Chemistry]]