Polyamide
Overview
 
A polyamide is a polymer
Polymer
A polymer is a large molecule composed of repeating structural units. These subunits are typically connected by covalent chemical bonds...

 containing monomer
Monomer
A monomer is an atom or a small molecule that may bind chemically to other monomers to form a polymer; the term "monomeric protein" may also be used to describe one of the proteins making up a multiprotein complex...

s of amide
Amide
In chemistry, an amide is an organic compound that contains the functional group consisting of a carbonyl group linked to a nitrogen atom . The term refers both to a class of compounds and a functional group within those compounds. The term amide also refers to deprotonated form of ammonia or an...

s joined by peptide bond
Peptide bond
This article is about the peptide link found within biological molecules, such as proteins. A similar article for synthetic molecules is being created...

s. They can occur both naturally and artificially, examples being protein
Protein
Proteins are biochemical compounds consisting of one or more polypeptides typically folded into a globular or fibrous form, facilitating a biological function. A polypeptide is a single linear polymer chain of amino acids bonded together by peptide bonds between the carboxyl and amino groups of...

s, such as wool
Wool
Wool is the textile fiber obtained from sheep and certain other animals, including cashmere from goats, mohair from goats, qiviut from muskoxen, vicuña, alpaca, camel from animals in the camel family, and angora from rabbits....

 and silk
Silk
Silk is a natural protein fiber, some forms of which can be woven into textiles. The best-known type of silk is obtained from the cocoons of the larvae of the mulberry silkworm Bombyx mori reared in captivity...

, and can be made artificially through step-growth polymerization
Step-growth polymerization
Step-growth polymerization refers to a type of polymerization mechanism in which bi-functional or multifunctional monomers react to form first dimers, then trimers, longer oligomers and eventually long chain polymers. Many naturally occurring and some synthetic polymers are produced by step-growth...

 or solid-phase synthesis
Solid-phase synthesis
In chemistry, solid-phase synthesis is a method in which molecules are bound on a bead and synthesized step-by-step in a reactant solution; compared with normal synthesis in a liquid state, it is easier to remove excess reactant or byproduct from the product. In this method, building blocks are...

, examples being nylon
Nylon
Nylon is a generic designation for a family of synthetic polymers known generically as polyamides, first produced on February 28, 1935, by Wallace Carothers at DuPont's research facility at the DuPont Experimental Station...

s, aramid
Aramid
Aramid fibers are a class of heat-resistant and strong synthetic fibers. They are used in aerospace and military applications, for ballistic rated body armor fabric and ballistic composites, in bicycle tires, and as an asbestos substitute. The name is a portmanteau of "aromatic polyamide"...

s, and sodium poly(aspartate)
Sodium poly(aspartate)
Sodium poly is a condensation polymer based on the amino acid aspartic acid.-Polymerization:The polymerization reaction is an example of a step-growth polymerization to a polyamide and in one practical procedure aspartic acid is simply heated to 180 °C resulting in water release and the formation...

. Polyamides are commonly used in textiles, automotives, carpet and sportswear due to their extreme durability and strength.
According to the composition of their main chain, polyamides are classified as follows:


According to the number of repeating units' types, polyamides can be:
  • homopolymers :
    • PA 6 : [NH−(CH2)5−CO]n made from ε-Caprolactam
      Caprolactam
      Caprolactam is an organic compound with the formula 5CNH. This colourless solid is a lactam or a cyclic amide of caproic acid. Approximately 2 billion kilograms are produced annually...

       ;
    • PA 66 : [NH−(CH2)6−NH−CO−(CH2)4−CO]n made from hexamethylenediamine and adipic acid
      Adipic acid
      Adipic acid is the organic compound with the formula 42. From the industrial perspective, it is the most important dicarboxylic acid: About 2.5 billion kilograms of this white crystalline powder are produced annually, mainly as a precursor for the production of nylon...

      ;
  • copolymers :
    • PA 6/66 : [NH-(CH2)6−NH−CO−(CH2)4−CO]n−[NH−(CH2)5−CO]m made from caprolactam, hexamethylenediamine and adipic acid ;
    • PA 66/610 : [NH−(CH2)6−NH−CO−(CH2)4−CO]n−[NH−(CH2)6−NH−CO−(CH2)8−CO]m made from hexamethylenediamine, adipic acid and sebacic acid
      Sebacic acid
      Sebacic acid is a dicarboxylic acid with structure 8, and is naturally occurring.In its pure state it is a white flake or powdered crystal...

      .


According to their crystallinity
Crystallinity
Crystallinity refers to the degree of structural order in a solid. In a crystal, the atoms or molecules are arranged in a regular, periodic manner. The degree of crystallinity has a big influence on hardness, density, transparency and diffusion. In a gas, the relative positions of the atoms or...

, polyamides can be:
  • semi-crystal
    Crystal
    A crystal or crystalline solid is a solid material whose constituent atoms, molecules, or ions are arranged in an orderly repeating pattern extending in all three spatial dimensions. The scientific study of crystals and crystal formation is known as crystallography...

    line:
    • high crystallinity : PA46 et PA 66 ;
    • low crystallinity : PA mXD6 made from m-xylylenediamine and adipic acid;
  • amorphous
    Amorphous solid
    In condensed matter physics, an amorphous or non-crystalline solid is a solid that lacks the long-range order characteristic of a crystal....

     : PA 6I made from hexamethylenediamine and isophthalic acid
    Isophthalic acid
    Isophthalic acid is an organic compound with the formula C6H42. This colourless solid is an isomer of phthalic acid and terephthalic acid. These aromatic dicarboxylic acids are used as precursors to commercially important polymers, e.g. the fire-resistant material Nomex...

    .


According to this classification, PA66, for example, is an aliphatic semi-crystalline homopolyamide.
The amide link is produced from the condensation reaction
Condensation reaction
A condensation reaction is a chemical reaction in which two molecules or moieties combine to form one single molecule, together with the loss of a small molecule. When this small molecule is water, it is known as a dehydration reaction; other possible small molecules lost are hydrogen chloride,...

 of an amino group and a carboxylic acid
Carboxylic acid
Carboxylic acids are organic acids characterized by the presence of at least one carboxyl group. The general formula of a carboxylic acid is R-COOH, where R is some monovalent functional group...

 or acid chloride group.
Encyclopedia
A polyamide is a polymer
Polymer
A polymer is a large molecule composed of repeating structural units. These subunits are typically connected by covalent chemical bonds...

 containing monomer
Monomer
A monomer is an atom or a small molecule that may bind chemically to other monomers to form a polymer; the term "monomeric protein" may also be used to describe one of the proteins making up a multiprotein complex...

s of amide
Amide
In chemistry, an amide is an organic compound that contains the functional group consisting of a carbonyl group linked to a nitrogen atom . The term refers both to a class of compounds and a functional group within those compounds. The term amide also refers to deprotonated form of ammonia or an...

s joined by peptide bond
Peptide bond
This article is about the peptide link found within biological molecules, such as proteins. A similar article for synthetic molecules is being created...

s. They can occur both naturally and artificially, examples being protein
Protein
Proteins are biochemical compounds consisting of one or more polypeptides typically folded into a globular or fibrous form, facilitating a biological function. A polypeptide is a single linear polymer chain of amino acids bonded together by peptide bonds between the carboxyl and amino groups of...

s, such as wool
Wool
Wool is the textile fiber obtained from sheep and certain other animals, including cashmere from goats, mohair from goats, qiviut from muskoxen, vicuña, alpaca, camel from animals in the camel family, and angora from rabbits....

 and silk
Silk
Silk is a natural protein fiber, some forms of which can be woven into textiles. The best-known type of silk is obtained from the cocoons of the larvae of the mulberry silkworm Bombyx mori reared in captivity...

, and can be made artificially through step-growth polymerization
Step-growth polymerization
Step-growth polymerization refers to a type of polymerization mechanism in which bi-functional or multifunctional monomers react to form first dimers, then trimers, longer oligomers and eventually long chain polymers. Many naturally occurring and some synthetic polymers are produced by step-growth...

 or solid-phase synthesis
Solid-phase synthesis
In chemistry, solid-phase synthesis is a method in which molecules are bound on a bead and synthesized step-by-step in a reactant solution; compared with normal synthesis in a liquid state, it is easier to remove excess reactant or byproduct from the product. In this method, building blocks are...

, examples being nylon
Nylon
Nylon is a generic designation for a family of synthetic polymers known generically as polyamides, first produced on February 28, 1935, by Wallace Carothers at DuPont's research facility at the DuPont Experimental Station...

s, aramid
Aramid
Aramid fibers are a class of heat-resistant and strong synthetic fibers. They are used in aerospace and military applications, for ballistic rated body armor fabric and ballistic composites, in bicycle tires, and as an asbestos substitute. The name is a portmanteau of "aromatic polyamide"...

s, and sodium poly(aspartate)
Sodium poly(aspartate)
Sodium poly is a condensation polymer based on the amino acid aspartic acid.-Polymerization:The polymerization reaction is an example of a step-growth polymerization to a polyamide and in one practical procedure aspartic acid is simply heated to 180 °C resulting in water release and the formation...

. Polyamides are commonly used in textiles, automotives, carpet and sportswear due to their extreme durability and strength.

Classification

According to the composition of their main chain, polyamides are classified as follows:
Polyamide family Main chain Examples of polyamides Examples of commercial products
Aliphatic polyamides Aliphatic PA 6
Nylon 6
Nylon 6 or polycaprolactam is a polymer developed by Paul Schlack at IG Farben to reproduce the properties of nylon 6,6 without violating the patent on its production. Unlike most other nylons, nylon 6 is not a condensation polymer, but instead is formed by ring-opening polymerization. This makes...

 and PA 66
Nylon 6-6
Nylon 6-6, also referred to as nylon 6,6, is a type of nylon. Nylon comes in many types, the two most common for textile and plastics industries are: nylon 6 and nylon 6,6.- Composition :...

 
Nylon
Nylon
Nylon is a generic designation for a family of synthetic polymers known generically as polyamides, first produced on February 28, 1935, by Wallace Carothers at DuPont's research facility at the DuPont Experimental Station...

 from DuPont
DuPont
E. I. du Pont de Nemours and Company , commonly referred to as DuPont, is an American chemical company that was founded in July 1802 as a gunpowder mill by Eleuthère Irénée du Pont. DuPont was the world's third largest chemical company based on market capitalization and ninth based on revenue in 2009...

Polyphthalamide
Polyphthalamide
Polyphthalamide is a thermoplastic synthetic resin of the polyamide family that is used to replace metals in high temperature automotive applications, as the housing for high temperature electrical connectors and multiple other uses. It has found a degree of favor for use in cutlery...

s
Semi-aromatic PA 6T = hexamethylenediamine
Hexamethylenediamine
Hexamethylenediamine is the organic compound with the formula H2N6NH2. The molecule is a diamine, consisting of a hexamethylene hydrocarbon chain terminated with amine functional groups. The colorless solid has a strong amine odor, similar to piperidine...

 + terephthalic acid
Terephthalic acid
Terephthalic acid is the organic compound with formula C6H42. This colourless solid is a commodity chemical, used principally as a precursor to the polyester PET, used to make clothing and plastic bottles. Several billion kilograms are produced annually...

 
Trogamid from Evonik Industries, Amodel from Solvay
Solvay
Solvay may refer to* Solvay , an international chemicals and plastics company* the Solvay process* Ernest Solvay, its inventor* Solvay Conference* the Solvay Business School* Solvay, New York* Solvay Hut, on the Matterhorn...

Aramides = aromatic polyamides Aromatic Paraphenylenediamine + terephthalic acid Kevlar
Kevlar
Kevlar is the registered trademark for a para-aramid synthetic fiber, related to other aramids such as Nomex and Technora. Developed at DuPont in 1965, this high strength material was first commercially used in the early 1970s as a replacement for steel in racing tires...

 and Nomex
Nomex
Nomex is a registered trademark for flame resistant meta-aramid material developed in the early 1960s by DuPont and first marketed in 1967.- Properties:...

 from DuPont, Teijinconex, Twaron and Technora from Teijin, Kermel from Kermel


According to the number of repeating units' types, polyamides can be:
  • homopolymers :
    • PA 6 : [NH−(CH2)5−CO]n made from ε-Caprolactam
      Caprolactam
      Caprolactam is an organic compound with the formula 5CNH. This colourless solid is a lactam or a cyclic amide of caproic acid. Approximately 2 billion kilograms are produced annually...

       ;
    • PA 66 : [NH−(CH2)6−NH−CO−(CH2)4−CO]n made from hexamethylenediamine and adipic acid
      Adipic acid
      Adipic acid is the organic compound with the formula 42. From the industrial perspective, it is the most important dicarboxylic acid: About 2.5 billion kilograms of this white crystalline powder are produced annually, mainly as a precursor for the production of nylon...

      ;
  • copolymers :
    • PA 6/66 : [NH-(CH2)6−NH−CO−(CH2)4−CO]n−[NH−(CH2)5−CO]m made from caprolactam, hexamethylenediamine and adipic acid ;
    • PA 66/610 : [NH−(CH2)6−NH−CO−(CH2)4−CO]n−[NH−(CH2)6−NH−CO−(CH2)8−CO]m made from hexamethylenediamine, adipic acid and sebacic acid
      Sebacic acid
      Sebacic acid is a dicarboxylic acid with structure 8, and is naturally occurring.In its pure state it is a white flake or powdered crystal...

      .


According to their crystallinity
Crystallinity
Crystallinity refers to the degree of structural order in a solid. In a crystal, the atoms or molecules are arranged in a regular, periodic manner. The degree of crystallinity has a big influence on hardness, density, transparency and diffusion. In a gas, the relative positions of the atoms or...

, polyamides can be:
  • semi-crystal
    Crystal
    A crystal or crystalline solid is a solid material whose constituent atoms, molecules, or ions are arranged in an orderly repeating pattern extending in all three spatial dimensions. The scientific study of crystals and crystal formation is known as crystallography...

    line:
    • high crystallinity : PA46 et PA 66 ;
    • low crystallinity : PA mXD6 made from m-xylylenediamine and adipic acid;
  • amorphous
    Amorphous solid
    In condensed matter physics, an amorphous or non-crystalline solid is a solid that lacks the long-range order characteristic of a crystal....

     : PA 6I made from hexamethylenediamine and isophthalic acid
    Isophthalic acid
    Isophthalic acid is an organic compound with the formula C6H42. This colourless solid is an isomer of phthalic acid and terephthalic acid. These aromatic dicarboxylic acids are used as precursors to commercially important polymers, e.g. the fire-resistant material Nomex...

    .


According to this classification, PA66, for example, is an aliphatic semi-crystalline homopolyamide.

Production from monomers

The amide link is produced from the condensation reaction
Condensation reaction
A condensation reaction is a chemical reaction in which two molecules or moieties combine to form one single molecule, together with the loss of a small molecule. When this small molecule is water, it is known as a dehydration reaction; other possible small molecules lost are hydrogen chloride,...

 of an amino group and a carboxylic acid
Carboxylic acid
Carboxylic acids are organic acids characterized by the presence of at least one carboxyl group. The general formula of a carboxylic acid is R-COOH, where R is some monovalent functional group...

 or acid chloride group. A small molecule, usually water
Water
Water is a chemical substance with the chemical formula H2O. A water molecule contains one oxygen and two hydrogen atoms connected by covalent bonds. Water is a liquid at ambient conditions, but it often co-exists on Earth with its solid state, ice, and gaseous state . Water also exists in a...

, or hydrogen chloride
Hydrogen chloride
The compound hydrogen chloride has the formula HCl. At room temperature, it is a colorless gas, which forms white fumes of hydrochloric acid upon contact with atmospheric humidity. Hydrogen chloride gas and hydrochloric acid are important in technology and industry...

, is eliminated.

The amino group and the carboxylic acid group can be on the same monomer, or the polymer can be constituted of two different bifunctional
Bifunctional
In organic molecules, functional groups are atom or atoms which are responsible for the characteristic properties of that molecule with the exceptions of double and triple bonds which are also functional groups....

 monomers, one with two amino groups, the other with two carboxylic acid or acid chloride groups.

Amino acid
Amino acid
Amino acids are molecules containing an amine group, a carboxylic acid group and a side-chain that varies between different amino acids. The key elements of an amino acid are carbon, hydrogen, oxygen, and nitrogen...

s can be taken as examples of single monomer (if the difference between R groups is ignored) reacting with identical molecules to form a polyamide:

Aramid
Aramid
Aramid fibers are a class of heat-resistant and strong synthetic fibers. They are used in aerospace and military applications, for ballistic rated body armor fabric and ballistic composites, in bicycle tires, and as an asbestos substitute. The name is a portmanteau of "aromatic polyamide"...

 (pictured below) is made from two different monomers which continuously alternate to form the polymer and is an aromatic polyamide:

Antistatic need

These materials are commonly completely insulating, and generate static electricity, which can cause dangerous sparks that can damage electronics in manufacturing plants and in consumer products. This has resulted in an interest in incorporation of conductive fillers such as carbon black
Carbon black
Carbon black is a material produced by the incomplete combustion of heavy petroleum products such as FCC tar, coal tar, ethylene cracking tar, and a small amount from vegetable oil. Carbon black is a form of amorphous carbon that has a high surface-area-to-volume ratio, although its...

, metals and conducting polymers. The most common conducting fillers are silver and carbon black. Both of these materials have processing deficiencies, while silver is also prohibitively expensive for applications such as antistatics.
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