Changes

====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 (e.g. 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====

*''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 (e.g. 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 (e.g. rayon).

*''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).

*''Molding'' - The liquid polymer is set into a particular shape and left to cool. This is used when clearly defined shapes are required (e.g. 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.

===HDPE===

===HDPE===

High Density Polyethylene, undergoes the same process as LDPE except lower temperatures are used and a Zeiger Natta catalyst is added (this has a large surface area on which polymerization occurs, reducing possibility of side branching). The chains of HDPE can be more closely packed together, resulting in higher density and a more rigid structure. HDPE is used extensively in the modern world, including lunch boxes, computer cases etc

High Density Polyethylene, undergoes the same process as LDPE except lower temperatures are used and a Zeiger Natta catalyst is added (this has a large surface area on which polymerization occurs, reducing possibility of side branching). The chains of HDPE can be more closely packed together, resulting in higher density and a more rigid structure. HDPE is used extensively in the modern world, including lunch boxes, computer cases etc.

===Vinyl Chloride===

===Vinyl Chloride===

==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 (e.g. 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 field of polymer chemistry.

==See Also==

==See also==

* [[Glock]] polymer [[receiver (firearms)|receiver]]

* [[Glock]] polymer [[receiver (firearms)|receiver]]

* [[Polymer receiver]]s

* [[Polymer receiver]]s

[[Category:Chemistry]]

[[Category:Chemistry]]