Editing Nylon (section)

== Environmental impact ==
[[file:amide hydrolysis.svg|thumb|The general chemical reaction involving hydrolysis of an amide to form a carboxylic acid and an amine]]

All nylons are susceptible to [[hydrolysis]], especially by [[strong acid]]s, a reaction essentially the reverse of their synthesis. The [[molecular weight]] of nylon products so attacked drops, and cracks form quickly at the affected zones. Lower members of the nylons (such as nylon 6) are affected more than higher members such as nylon 12. This means that nylon parts cannot be used in contact with [[sulfuric acid]] for example, such as the electrolyte used in [[Lead–acid battery|lead–acid batteries]].

When being molded, nylon must be dried to prevent hydrolysis in the molding machine barrel since water at high temperatures can also degrade the polymer.<ref name="Reltek">{{cite web|url=http://reltekllc.com/adhesivesfornylon.aspx|title=Adhesive for nylon & kevlar|website=Reltek|access-date=27 January 2015}}</ref> The reaction is shown above.

The average [[GHG footprint|greenhouse gas footprint]] of nylon in manufacturing carpets is estimated at 5.43&nbsp;kg CO<sub>2</sub> equivalent per kg, when produced in Europe. This gives it almost the same [[carbon footprint]] as [[wool]], but with greater durability and therefore a lower overall carbon footprint.<ref name="Berners-Lee">{{cite book|title=How bad are bananas? : the carbon footprint of everything|last1=Berners-Lee|first1=Mike|date=2010|publisher=Profile Books|location=London|page=112, table 6.1}}</ref>

Data published by PlasticsEurope indicates for nylon 66 a [[GHG footprint|greenhouse gas footprint]] of 6.4&nbsp;kg CO<sub>2</sub> equivalent per kg, and an energy consumption of 138 kJ/kg.<ref>{{cite book|url=http://www.plasticseurope.org/plasticssustainability/eco-profiles/browse-by-flowchart.aspx?LCAID=r307|title=Eco-profiles and Environmental Product Declarations of the European Plastics Manufacturers: Polyamide 6.6|date=2014|publisher=PlasticsEurope AISBL|location=Brussels|access-date=2015-04-19|archive-url=https://web.archive.org/web/20150427111338/http://www.plasticseurope.org/plasticssustainability/eco-profiles/browse-by-flowchart.aspx?LCAID=r307|archive-date=2015-04-27|url-status=dead}}</ref> When considering the environmental impact of nylon, it is important to consider the use phase.

Various nylons break down in fire and form hazardous smoke, and toxic fumes or ash, typically containing [[hydrogen cyanide]]. [[Incineration|Incinerating]] nylons to recover the high energy used to create them is usually expensive, so most nylons reach the garbage dumps, decaying slowly.{{efn|Typically 80 to 100% is sent to landfill or garbage dumps, while less than 18% are incinerated while recovering the energy. See {{cite book|url=https://books.google.com/books?id=TBrOGJqvgcMC&pg=PA19|title=Handbook of plastics recycling|author=Francesco La Mantia|date=August 2002|publisher=iSmithers Rapra Publishing|isbn=978-1-85957-325-9|pages=19–}}}} Discarded nylon fabric takes 30–40 years to decompose.<ref>{{cite web|url=https://www.des.nh.gov/organization/divisions/water/wmb/coastal/trash/documents/marine_debris.pdf|title=Approximate Time it Takes for Garbage to Decompose in the Environment|publisher=NH Department of Environmental Services|archive-url=https://web.archive.org/web/20090413220235/https://www.des.nh.gov/organization/divisions/water/wmb/coastal/trash/documents/marine_debris.pdf|access-date=31 March 2018|archive-date=2009-04-13}}</ref> Nylon used in discarded fishing gear such as fishing nets is a contributor to debris in the ocean.<ref name="chhabra">{{cite web |last1=Chhabra |first1=Esha |title=Recycling nylon is good for the planet – so why don't more companies do it? |url=https://www.theguardian.com/sustainable-business/2016/may/18/recycling-nylon-bureo-patagonia-sustainable-clothing |website=The Guardian |access-date=21 April 2021 |date=18 May 2016}}</ref> Nylon is a robust polymer and lends itself well to recycling. Much nylon resin is recycled directly in a closed loop at the injection molding machine, by grinding [[Sprue (manufacturing)|sprues]] and runners and mixing them with the virgin granules being consumed by the molding machine.<ref name="Boydell">{{cite journal|last1=Boydell|first1=P|last2=Bradfield|first2=C|last3=von Falkenhausen|first3=V|last4=Prautzsch|first4=G|date=1995|title=Recycling of Waste from Glass-reinforced nylon resins|journal=Engineering Design|volume=2|pages=8–10}}</ref>

Because of the expense and difficulties of the nylon recycling process, few companies utilise it while most favor using cheaper, newly made plastics for their products instead.<ref name="chhabra"/> US clothing company [[Patagonia, Inc.|Patagonia]] has products containing recycled nylon and in the mid-2010s invested in Bureo, a company that recycles nylon from used fishing nets to use in sunglasses and skateboards.<ref name="chhabra"/> The Italian company Aquafil also has demonstrated recycling fishing nets lost in the ocean into apparel.<ref>{{cite journal |last1=Maile |first1=Kelly |title=How abandoned fishing nets are recycled into nylon |journal=Recycling Today |date=January 18, 2019 |url=https://www.recyclingtoday.com/article/abandoned-fishing-nets-recycled-into-nylon/ |access-date=15 March 2019}}</ref> Vanden Recycling recycles nylon and other polyamides (PA) and has operations in the UK, Australia, Hong Kong, the UAE, Turkey and Finland.<ref>{{cite web |publisher=Vanden Recycling |title=PA / Nylon fibres are used in textiles, fishing line and carpets. |url=https://www.vandenrecycling.com/en/products/pa/ |access-date=7 Feb 2020}}</ref>

Nylon is the most popular fibre type in the residential carpet industry today.<ref>{{cite web |author=EPA |title= Nylon Carpet: Pros and Cons |date= 19 October 2018 |url=https://www.avalonflooring.com/ideas/blog/nylon-carpet-pros-cons |access-date=27 May 2021}}</ref> The US [[EPA]] estimates that 9.2% of carpet fibre, backing and padding was recycled in 2018, 17.8% was incinerated in [[waste-to-energy]] facilities, and 73% was discarded in [[landfill]]s.<ref>{{cite web |author=EPA |title= Durable Goods: Product-Specific Data (Carpets and Rugs)|date= 7 September 2017|url= https://www.epa.gov/facts-and-figures-about-materials-waste-and-recycling/durable-goods-product-specific-data#CarpetsandRugs |access-date=27 May 2021}}</ref> Some of the world's largest carpet and rug companies are promoting "cradle to cradle"—the re-use of non-virgin materials including ones not historically recycled—as the industry's pathway forward.<ref>{{cite web |author=Floor covering weekly |title=Shaw recognized for Cradle to Cradle commitment. |url=https://www.floorcoveringweekly.com/main/topnews/shaw-recognized-for-cradle-to-cradle-commitment-33204 |access-date=27 May 2021}}</ref><ref>{{cite web |publisher=Shaw Industries |title= Cradle To Cradle® |url=https://shawinc.com/cradletocradle |access-date=27 May 2021}}</ref>