# Polyamide

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Macromolecule with repeating units linked by amide bonds

A **polyamide** is a [polymer](/source/Polymer) with [repeating units](/source/Repeating_unit) linked by [amide](/source/Amide) bonds.[1]

Polyamides occur both naturally and artificially. Examples of naturally occurring polyamides are [proteins](/source/Protein), such as [wool](/source/Wool) and [silk](/source/Silk). Artificially made polyamides can be made through [step-growth polymerization](/source/Step-growth_polymerization) or [solid-phase synthesis](/source/Solid-phase_synthesis) yielding materials such as [nylons](/source/Nylon), [aramids](/source/Aramid), and [sodium polyaspartate](/source/Sodium_polyaspartate). Synthetic polyamides are commonly used in textiles, automotive industry, carpets, kitchen utensils and sportswear due to their high durability and strength. The transportation manufacturing industry is the major consumer, accounting for 35% of polyamide (PA) consumption.[2]

## Classification

Polymers of [amino acids](/source/Amino_acid) are known as [polypeptides](/source/Polypeptides) or [proteins](/source/Proteins).

According to the composition of their main chain, synthetic polyamides are classified as follows:

Family Main chain Examples Commercial products Aliphatic polyamides Aliphatic Nylon PA 6 and PA 66 Zytel from DuPont, Technyl from Solvay, Rilsan and Rilsamid from Arkema, Radipol from Radici Group Polyphthalamides Semi-aromatic PA 6T = hexamethylenediamine + terephthalic acid Trogamid T from Evonik Industries, Amodel from Solvay Aromatic polyamides, or aramids Aromatic Paraphenylenediamine + terephthalic acid Kevlar and Nomex from DuPont, Teijinconex, Twaron and Technora from Teijin Aramid, Kermel from Kermel.

All polyamides are made by the formation of an amide function to link two molecules of monomer together. The monomers can be amides themselves (usually in the form of a cyclic lactam such as [caprolactam](/source/Caprolactam)), α,ω-amino acids or a stoichiometric mixture of a diamine and a diacid. Both these kinds of precursors give a homopolymer. Polyamides are easily copolymerized, and thus many mixtures of monomers are possible which can in turn lead to many copolymers. Additionally many nylon polymers are miscible with one another allowing the creation of blends.

## Polymerization chemistry

Production of polymers requires the repeated joining of two groups to form an amide linkage. In this case this specifically involves [amide](/source/Amide) bonds, and the two groups involved are an [amine](/source/Amine) group, and a terminal [carbonyl](/source/Carbonyl) component of a [functional group](/source/Functional_group). These react to produce a carbon-nitrogen bond, creating a singular [amide](/source/Amide) linkage. This process involves the elimination of other atoms previously part of the functional groups. The carbonyl-component may be part of either a [carboxylic acid](/source/Carboxylic_acid) group or the more reactive [acyl halide](/source/Acyl_halide) derivative. The amine group and the carboxylic acid group can be on the same monomer, or the polymer can be constituted of two different [bifunctional](/source/Bifunctional) monomers, one with two amine groups, the other with two carboxylic acid or acid chloride groups.

The [condensation reaction](/source/Condensation_reaction) is used to synthetically produce nylon polymers in industry. Nylons must specifically include a straight chain ([aliphatic](/source/Aliphatic_compound)) monomer. The amide link is produced from an amine group (alternatively known as an amino group), and a [carboxylic acid](/source/Carboxylic_acid) group. The hydroxyl from the carboxylic acid combines with a hydrogen from the amine, and gives rise to water, the elimination byproduct that is the namesake of the reaction.

As an example of condensation reactions, consider that in living organisms, [amino acids](/source/Amino_acid) are condensed with one another by an enzyme to form amide linkages (known as [peptides](/source/Peptide_bond)). The resulting polyamides are known as proteins or polypeptides. In the diagram below, consider the amino-acids as single aliphatic monomers reacting with identical molecules to form a polyamide, focusing on solely the amine and acid groups. Ignore the substituent [R groups](/source/Alkyl) – under the assumption the difference between the R groups are negligible:

 The reaction of two amino acids. Many of these reactions produce long chain [proteins](/source/Protein)

For fully aromatic polyamides or *aramids* e.g. [Kevlar](/source/Kevlar), the more reactive [acyl chloride](/source/Acyl_chloride) is used as a monomer. The polymerization reaction with the amine group eliminates [hydrogen chloride](/source/Hydrogen_chloride). The acid chloride route can be used as a laboratory synthesis to avoid heating and obtain an almost instantaneous reaction.[3] The aromatic [moiety](/source/Moiety_(chemistry)) itself does not participate in elimination reaction, but it does increase the rigidity and strength of the resulting material which leads to Kevlar's renowned strength.

In the diagram below, an [aramid](/source/Aramid) is made from two different monomers which continuously alternate to form the polymer chain. Aramids are aromatic polyamides:

The reaction of 1,4-phenyl-diamine (para-phenylenediamine) and terephthaloyl chloride to produce an aramid

Polyamides can also be synthesized from dinitriles using acid catalysis via an application of the Ritter reaction. This method is applicable for preparation of [nylon 1,6](/source/Nylon_1%2C6) from [adiponitrile](/source/Adiponitrile), [formaldehyde](/source/Formaldehyde) and water.[4] Additionally, polyamides can be synthesized from [glycols](/source/Diol) and dinitriles using this method as well.[5]

Synthesis of Nylon 1,6 from adiponitrile, formaldehyde, and water using sulfuric acid as a catalyst

## See also

- [Polyamide-imide](/source/Polyamide-imide)

- [Pyrrole–imidazole polyamides](/source/Pyrrole%E2%80%93imidazole_polyamides)

## References

1. **[^](#cite_ref-1)** Palmer, R. J. 2001. Polyamides, Plastics. Encyclopedia Of Polymer Science and Technology. [doi](/source/Doi_(identifier)):[10.1002/0471440264.pst251](https://doi.org/10.1002%2F0471440264.pst251)

1. **[^](#cite_ref-2)** [Market Study Engineering Plastics, Ceresana, Sep 2013](http://www.ceresana.com/en/market-studies/plastics/engineering-plastics/)

1. **[^](#cite_ref-3)** ["Making nylon: The "nylon rope trick""](http://www.rsc.org/learn-chemistry/resource/res00000755/making-nylon-the-nylon-rope-trick). Royal Society of Chemistry. Retrieved 19 April 2015.

1. **[^](#cite_ref-4)** Magat, Eugene E.; Faris, Burt F.; Reith, John E.; Salisbury, L. Frank (1951-03-01). "Acid-catalyzed Reactions of Nitriles. I. The Reaction of Nitriles with Formaldehyde1". *Journal of the American Chemical Society*. **73** (3): 1028–1031. [doi](/source/Doi_(identifier)):[10.1021/ja01147a042](https://doi.org/10.1021%2Fja01147a042). [ISSN](/source/ISSN_(identifier)) [0002-7863](https://search.worldcat.org/issn/0002-7863).

1. **[^](#cite_ref-5)** Lakouraj, Moslem Mansour; Mokhtary, Masoud (2009-02-20). "Synthesis of polyamides from p-Xylylene glycol and dinitriles". *Journal of Polymer Research*. **16** (6): 681. [doi](/source/Doi_(identifier)):[10.1007/s10965-009-9273-z](https://doi.org/10.1007%2Fs10965-009-9273-z). [ISSN](/source/ISSN_(identifier)) [1022-9760](https://search.worldcat.org/issn/1022-9760). [S2CID](/source/S2CID_(identifier)) [98232570](https://api.semanticscholar.org/CorpusID:98232570).

## Further reading

- Kohan, Melvin I. (1995). Nylon Plastics Handbook. Hanser/Gardner Publications. [ISBN](/source/ISBN_(identifier)) [9781569901892](https://en.wikipedia.org/wiki/Special:BookSources/9781569901892)

v t e Plastics Chemical types Acrylonitrile butadiene styrene (ABS) Cross-linked polyethylene (PEX, XLPE) Ethylene vinyl acetate (EVA) Poly(methyl methacrylate) (PMMA) Poly(ethyl methacrylate) (PEMA) Polyacrylic acid (PAA) Polyamide (PA) Polybutylene (PB) Polybutylene terephthalate (PBT) Polycarbonate (PC) Polyetheretherketone (PEEK) Polyester (PEs) Polyethylene (PE) Polyethylene terephthalate (PET, PETE) Polyimide (PI) Polylactic acid (PLA) Polyoxymethylene (POM) Polyphenyl ether (PPE) Poly(p-phenylene oxide) (PPO) Polypropylene (PP) Polystyrene (PS) Polysulfone (PES) Polytetrafluoroethylene (PTFE) Polyurethane (PU) Polyvinyl chloride (PVC) Polyvinylidene chloride (PVDC) Styrene maleic anhydride (SMA) Styrene-acrylonitrile (SAN) Tritan copolyester Mechanical types Thermoplastic Thermosetting polymer Fibre-reinforced plastic Corrugated plastic Polymeric foam High-performance plastics Additives Polymer additive Colorants Plasticizer Polymer stabilizers Biodegradable additives Filler (materials) Plastics processing Injection moulding Plastic extrusion Blow molding Film blowing Thermoforming Compression molding Calendering Transfer molding Laminating Fiberglass molding Pultrusion Plastic welding Filament winding Solvent bonding Vacuum forming Rotational molding Products Plastics industry segments Commodity plastics Construction Engineering plastics Geosynthetics High-performance plastics Nurdle Category:Plastics applications Plasticulture (Agriculture) Specific goods Blister pack Chairs Packaging film Bottles Bags Cutlery Shopping bags Foam food containers Environment and health v t e Health issues of plastics and polyhalogenated compounds (PHCs) Plasticizers: Phthalates DIBP DBP BBP (BBzP) DIHP DEHP (DOP) DIDP DINP Miscellaneous plasticizers Organophosphates Adipates (DEHA DOA) Monomers Bisphenol A (BPA, in Polycarbonates) Vinyl chloride (in PVC) Miscellaneous additives incl. PHCs PBDEs PCBs Organotins PFCs Perfluorooctanoic acid Health issues Teratogen Carcinogen Endocrine disruptor Diabetes Obesity Polymer fume fever Pollution Plastic pollution Rubber pollution Great Pacific Garbage Patch Persistent organic pollutant Dioxins List of environmental health hazards Regulations California Proposition 65 European REACH regulation Japan Toxic Substances Law Toxic Substances Control Act Waste Plastic pollution Garbage patch Great Pacific Garbage Patch Persistent organic pollutant Dioxins List of environmental health hazards Plastic recycling Biodegradable plastic Identification codes

v t e Fibers Natural Plant Abacá Bagasse Bamboo Bashō Coir Cotton Fique Flax Linen Hemp Jute Kapok Kenaf Lotus silk Piña Pine Raffia Ramie Rattan Sisal Wood Animal Alpaca Angora Byssus Camel hair Cashmere Catgut Chiengora Guanaco Hair Llama Mohair Pashmina Qiviut Rabbit Silk Tendon Spider silk Wool Vicuña Yak Mineral Asbestos Synthetic Regenerated Artificial silk Milk fiber Semi-synthetic Acetate Diacetate Lyocell Modal Piñatex Rayon Triacetate Mineral Boron Basalt Carbon Glass Wool Metallic Mineral wool Polymer Acrylic Aramid Twaron Kevlar Technora Nomex Microfiber Modacrylic Nylon Olefin Polyester Polyethylene UHMWPE Spandex Vectran Vinylon Vinyon Zylon Category Commons

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Adapted from the Wikipedia article [Polyamide](https://en.wikipedia.org/wiki/Polyamide) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Polyamide?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.