Editing Nylon (section)

=== Nylon 66 and related heteropolymers ===
{{Main|Nylon 66}}

Nylon 66 and related polyamides are [[condensation polymer]]s forms from equal parts of [[diamine]] and [[dicarboxylic acid]]s.<ref name="Ratner">{{cite book|last1=Ratner|first1=Buddy D.|title=Biomaterials science : an introduction to materials in medicine|date=2013|publisher=Elsevier|location=Amsterdam|isbn=9780080877808|pages=74–77|edition=3rd|url=https://books.google.com/books?id=8hBq-dLLaxwC&pg=PA75|access-date=5 July 2017}}</ref> In the first case, the "repeating unit" has the ABAB structure, as also seen in many [[polyester]]s and [[polyurethane]]s. Since each monomer in this copolymer has the same [[functional group|reactive group]] on both ends, the direction of the [[peptide bond|amide bond]] reverses between each monomer, unlike natural [[polyamide]] [[protein]]s, which have overall directionality: [[carboxyl|C&nbsp;terminal]]&nbsp;→ [[amino|N&nbsp;terminal]]. In the second case (so called AA), the repeating unit corresponds to the single monomer.<ref name="McIntyre"/>{{rp|45–50}}<ref name="Denby">{{cite book|last1=Denby|first1=Derek|last2=Otter|first2=Chris|last3=Stephenson|first3=Kay|title=Chemical storylines.|date=2008|publisher=Heinemann|location=Oxford|isbn=9780435631475|page=96|edition=3rd|url=https://books.google.com/books?id=Qj8qryYjlX0C&pg=RA1-PT68|access-date=5 July 2017}}</ref>

Wallace Carothers at DuPont patented [[nylon 66|nylon&nbsp;66]].<ref name="US 2130523">{{cite patent |country=US |number=2130523 |status=patent |gdate=1938-09-20 |fdate=1935-01-02 |pridate=1935-01-02 |invent1 =Carothers W.H. |title=Linear polyamides and their production |assign1=EI Du Pont de Nemours and Co.}}</ref><ref>{{cite web|title=Diamine-dicarboxylic acid salts and process of preparing same US 2130947 A|url=https://patents.google.com/patent/US2130947|website=Patents|access-date=19 June 2017}}</ref><ref>{{cite web|title=Synthetic fiber US 2130948 A|url=https://patents.google.com/patent/US2130948|website=Patents|access-date=19 June 2017}}</ref> 
In the case of nylons that involve reaction of a diamine and a dicarboxylic acid, it is difficult to get the proportions exactly correct, and deviations can lead to chain termination at molecular weights less than a desirable 10,000 [[Dalton (unit)|dalton]]s. To overcome this problem, a [[crystal]]line, solid "nylon [[Salt (chemistry)|salt]]" can be formed at [[room temperature]], using an exact 1:1 [[ratio]] of the [[acid]] and the [[Base (chemistry)|base]] to neutralise each other. The salt is crystallised to purify it and obtain the desired precise stoichiometry. Heated to {{cvt|285|C}}, the salt reacts to form nylon polymer with the production of water.

Nylon&nbsp;510, made from [[pentamethylene diamine]] and sebacic acid, was included in the Carothers patent to nylon&nbsp;66<ref name="US 2130523" /> Nylon 610 is produced similarly using hexamethylene diamine. These materials are more expensive because of the relatively high cost of sebacic acid. Owing to the high [[hydrocarbon]] content, nylon 610 is more hydrophobic and finds applications suited for this property, such as bristles.<ref>{{cite book |doi=10.1002/14356007.a10_567.pub2|chapter=Fibers, 4. Polyamide Fibers |title=Ullmann's Encyclopedia of Industrial Chemistry |year=2011 |last1=Estes |first1=Leland L. |last2=Schweizer |first2=Michael |isbn=978-3527306732 }}</ref>
<!--In keeping with this naming convention, "nylon&nbsp;6,12" or "PA 612" is a copolymer of a 6C diamine and a 12C diacid. Similarly for PA 510 PA 611; PA 1012, etc. Other nylons include copolymerised dicarboxylic acid/diamine products that are ''not'' based upon the monomers listed above. For example, some fully [[aromatic]] nylons (known as "[[aramids]]") are polymerised with the addition of diacids like terephthalic acid (→ [[Kevlar]], [[Twaron]]) or isophthalic acid (→ [[Nomex]]), more commonly associated with polyesters. There are copolymers of PA 66/6; copolymers of PA 66/6/12; and others. In general linear polymers are the most useful, but it is possible to introduce branches in nylon by the condensation of dicarboxylic acids with [[polyamine]]s having three or more [[amino group]]s.

The general reaction is:
[[Image:Condensation polymerization diacid diamine.svg|centre|600px]]

Two molecules of [[water (molecule)|water]] are 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&nbsp;=&nbsp;4C and R'&nbsp;=&nbsp;6C [[alkane]]s, but one also has to include the two carboxyl [[carbon]]s in the diacid to get the number it donates to the chain. In Kevlar, both R and R' are [[benzene]] rings.

Industrial synthesis is usually done by heating the acids, amines or lactams to remove water, but in the laboratory, diacid chlorides can be reacted with diamines. For example, a popular demonstration of interfacial polymerisation (the "[[nylon rope trick]]") is the synthesis of nylon 66 from [[adipoyl chloride]] and hexamethylene diamine.
-->

{| class="wikitable"
|+Commercial heteropolymer polyamides
!  !! [[Putrescine|1,4-diamino&shy;butane]]  || [[Cadaverine|1,5-diamino&shy;pentane]] !! [[2-Methylpentamethylenediamine|MPMD]] !! [[Hexamethylenediamine|HMD]] !! [[m-Xylylenediamine|MXDA]] !! Nonane&shy;diamine !! Decane&shy;diamine !!Dodecane&shy;diamine !! [[4,4-Diaminodicyclohexylmethane|Bis&shy;(para-amino&shy;cyclohexyl)&shy;methane]] !![[trimethylhexamethylenediamine|Trimethyl&shy;hexamethylene&shy;diamine]]
|-
|[[Adipic acid]]              ||[[Nylon 46|46]]|| || D6|| [[nylon 6-6|66]] ||MXD6||       ||        ||       ||       ||
|-
|[[Sebacic acid]]            ||  410  ||   510  ||   ||  610   ||         ||  ||     1010   ||     ||        ||
|-
|[[Dodecanedioic acid]]||     ||    ||     ||612||  ||     ||       ||1212 ||[[Qiana|PACM12]]||
|-
|[[Terephthalic acid]]   || 4T||  ||  DT||6T ||      || 9T || 10T||12T ||       ||[[Trogamid|TMDT]]
|-
|[[Isophthalic acid]]    ||  ||     || DI ||6I ||   ||     ||         ||       ||       ||
|}

Examples of these polymers that are or were commercially available:
* PA46 DSM Stanyl<ref>{{cite web|title=Stanyl® Polyamide 46: Driving change in automotive|url=http://www.dsm.com/markets/automotive/en_US/products-brands/stanyl.html|website=DSM|access-date=19 June 2017}}</ref>
* PA410 DSM Ecopaxx<ref>{{cite web|title=EcoPaXX: The green performer|url=http://www.dsm.com/products/ecopaxx/en_US/home.html|website=DSM|access-date=19 June 2017}}</ref>
* PA4T DSM Four Tii<ref>{{cite web|title=ForTii® Pushing peak performance|url=http://www.dsm.com/products/stanylfortii/en_US/home.html|website=DSM|access-date=19 June 2017}}</ref>
* PA66 DuPont Zytel<ref>{{cite web|title=zytel - PA6, PA610, PA612, PA66 - dupont|url=http://www.materialdatacenter.com/ms/en/zytel/dupont/839|website=Material Data Center|access-date=19 June 2017}}</ref>