PolymersPolymersWhat is a polymer?

A molecule of large molar mass that consists of many repeating subunits called monomers.

What is a monomer?

A monomer is a molecule of relatively low molar mass that is linked with other similar molecules to form a polymer.

PolyamidesPolyamides

What are polyamides?What are polyamides?

A polyamide is a polymer A polyamide is a polymer family that contains family that contains recurring amide groups recurring amide groups of: R-CO-NH-R’ of: R-CO-NH-R’ as integral parts of the as integral parts of the main polymer compound.main polymer compound.

They are formed either by the polymerization They are formed either by the polymerization of an amino acid or the condensation of a of an amino acid or the condensation of a polyamine with a carboxylic acid in which the polyamine with a carboxylic acid in which the structural units are linked by amide or structural units are linked by amide or thioamide groupings bonding them together.thioamide groupings bonding them together.

PolyamidesPolyamides

The monomers in polyamide are joined together by peptide bonds, The monomers in polyamide are joined together by peptide bonds, they occur both naturally such as in proteins but mostly they occur both naturally such as in proteins but mostly synthetically such as various nylons.synthetically such as various nylons.

Peptide bond: A peptide bond is a chemical bond formed between Peptide bond: A peptide bond is a chemical bond formed between two molecules when the carboxyl group of one molecule reacts with two molecules when the carboxyl group of one molecule reacts with the amino group of the other molecule, releasing a molecule of the amino group of the other molecule, releasing a molecule of water. This usually occurs between amino acids and can be seen water. This usually occurs between amino acids and can be seen here:here:

Forming a Polyamide

History of PolyamidesHistory of Polyamides

Polyamides have existed in nature Polyamides have existed in nature (proteins) longer then humans (proteins) longer then humans have existed on earth. However have existed on earth. However the first signs of polyamides the first signs of polyamides synthetically were in 1664 when a synthetically were in 1664 when a Chinese emperor developed a Chinese emperor developed a project to manufacture synthetic project to manufacture synthetic yarn. Many types of polyamides yarn. Many types of polyamides were discovered at different times were discovered at different times in history but they were not in history but they were not recognized as such until later on. recognized as such until later on. Polyamide 6 for example was Polyamide 6 for example was discovered in 1936 by Paul Slack discovered in 1936 by Paul Slack and sold as Perlon but nylon was and sold as Perlon but nylon was truly discovered in 1933 by Dr. truly discovered in 1933 by Dr. Wallace Hume Carothers (as Wallace Hume Carothers (as polyamide 6.6).polyamide 6.6).

NylonNylonNylons are synthetic polyamides that are in their own family of synthetic polymers.It is made of monomers linked by peptide bonds and is frequently referred to as polyamide (PA).

A molecule of water is given off and the nylon is formed. Its properties are determined by the R and R' groups in the monomers. In nylon 6,6, R' has 6 carbon alkanes and R has 4 carbon alkanes, but one also has to include the two carboxyl carbons in the diacid to get the number it donates to the chain. In Kevlar, both R and R' are benzene rings and this shows how broad and limitless the polyamide group is.

Nylon-6,6 is made by polymerizing hexanedioic acid and 1,6-diaminohexane.

Industrial Fabrication of Nylon 6.6

Adipic Acid = Hexanedioc Acid

Hexamethylene Diamine = 1,6-diaminohexane

Nylon Polymerization ReactionNylon Polymerization Reaction

Because the hexanedioc acid is acidic and the amine is basic, they first react together to form a salt. The salt is then converted into nylon-6,6 by heating it under pressure at 350°C.

Lewis Structure of the Nylon 6,6 polymer – note the amide bond

Formation of Nylon MonomersFormation of Nylon Monomers

The monomers can both be made from cyclohexane.

Oxidation of the cyclohexane opens the ring of carbon atoms and produces a -COOH group at each end. That gives you the hexanedioic acid.

Some of that can then be converted into the 1,6-diaminohexane. The acid is treated with ammonia to produce the ammonium salt. The ammonium salt is heated to 350°C in the presence of hydrogen and a nickel catalyst. This both dehydrates the salt and reduces it to the 1,6-diaminohexane. “ (ChemGuide.com)

DisadvantagesDisadvantages High moisture pick-up causes instabilityHigh moisture pick-up causes instability

Requires UV stabilization Requires UV stabilization

High shrinkage in molded sections High shrinkage in molded sections

Low moisture resistance limits mechanical/electrical applicationsLow moisture resistance limits mechanical/electrical applications

Low resistance to strong acids and basesLow resistance to strong acids and bases

Attacked by oxidizing agents Attacked by oxidizing agents

AdvantagesAdvantages High heat resistanceHigh heat resistance

Resistant to abrasionResistant to abrasion

Tough and resistantTough and resistant

Strong chemical resistanceStrong chemical resistance

Flame RetardantFlame Retardant

Heat StabilizedHeat Stabilized

ApplicationsApplications

Automotive ApplicationsAutomotive Applications

BearingsBearings

Electrical/Electronic ApplicationsElectrical/Electronic Applications

Industrial ApplicationsIndustrial Applications

Clothing and Consumer ProductsClothing and Consumer Products Housing and construction (gears)Housing and construction (gears)

Bibliography

www.wikipedia.com

www.britannica.com

http://www.chemguide.co.uk/organicprops/amides/polyamides.html

http://www.bpf.co.uk/bpfindustry/plastics_materials_Nylons_PA.cfm

http://www.chemheritage.org/EducationalServices/nylon/story/story03.html