Nylon 6 or polycaprolactam is a

polymer A polymer (; Greek '' poly-'', "many" + ''-mer'', "part") is a substance or material consisting of very large molecules called macromolecules, composed of many repeating subunits. Due to their broad spectrum of properties, both synthetic a ...

, in particular

semicrystalline 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 ...

polyamide. Unlike most other

nylon Nylon is a generic designation for a family of synthetic polymers composed of polyamides ( repeating units linked by amide links).The polyamides may be aliphatic or semi-aromatic. Nylon is a silk-like thermoplastic, generally made from pe ...

s, nylon 6 is not a condensation polymer, but instead is formed by ring-opening polymerization; this makes it a special case in the comparison between condensation and addition polymers. Its competition with nylon 6,6 and the example it set have also shaped the economics of the

synthetic fibre Synthetic fibers or synthetic fibres (in British English; see spelling differences) are fibers made by humans through chemical synthesis, as opposed to natural fibers that are directly derived from living organisms, such as plants (like cotton) ...

industry. It is sold under numerous trade names including Perlon (Germany), Dederon (former East Germany), Nylatron, Capron, Ultramid, Akulon, Kapron (former Soviet Union and satellite states), Rugopa (Turkey) and Durethan.

History

Polycaprolactam was developed by Paul Schlack at IG Farben in late 1930s (first synthesized in 1938) to reproduce the properties of

Nylon 66 Nylon 66 (loosely written nylon 6-6, nylon 6/6, nylon 6,6, or nylon 6:6) is a type of polyamide or nylon. It, and nylon 6, are the two most common for textile and plastic industries. Nylon 66 is made of two monomers each containing 6 carbon atoms, ...

without violating the

patent A patent is a type of intellectual property that gives its owner the legal right to exclude others from making, using, or selling an invention for a limited period of time in exchange for publishing an enabling disclosure of the invention."A ...

on its production. (Around the same time, Kohei Hoshino at Toray also succeeded in synthesizing nylon 6.) It was marketed as Perlon, and industrial production with a capacity of 3,500 tons per year was established in Nazi Germany in 1943, using phenol as a feedstock. At first, the polymer was used to produce coarse fiber for artificial bristle, then the fiber quality was improved, and Germans started making parachutes, cord for aircraft tires and towing cables for gliders. The Soviet Union began its development of an analog in the 1940s, and while basic scientific work was ongoing in 1942, the production only started in 1948 in Klin.

Synthesis

Nylon 6 can be modified using comonomers or stabilizers during polymerization to introduce new chain end or functional groups, which changes the reactivity and chemical properties. It is often done to change its dyeability or flame retardance. Nylon 6 is synthesized by ring-opening polymerization of caprolactam. Caprolactam has 6 carbons, hence ''Nylon 6''. When caprolactam is heated at about 533 K in an inert atmosphere of

nitrogen Nitrogen is the chemical element with the symbol N and atomic number 7. Nitrogen is a nonmetal and the lightest member of group 15 of the periodic table, often called the pnictogens. It is a common element in the universe, estimated at se ...

for about 4–5 hours, the ring breaks and undergoes

polymerization In polymer chemistry, polymerization (American English), or polymerisation (British English), is a process of reacting monomer molecules together in a chemical reaction to form polymer chains or three-dimensional networks. There are many fo ...

. Then the molten mass is passed through spinnerets to form fibres of nylon 6. During

, the amide bond within each caprolactam

molecule A molecule is a group of two or more atoms held together by attractive forces known as chemical bonds; depending on context, the term may or may not include ions which satisfy this criterion. In quantum physics, organic chemistry, and bioche ...

is broken, with the active groups on each side re-forming two new bonds as the

monomer In chemistry, a monomer ( ; '' mono-'', "one" + ''-mer'', "part") is a molecule that can react together with other monomer molecules to form a larger polymer chain or three-dimensional network in a process called polymerization. Classification ...

becomes part of the polymer backbone. Unlike nylon 6,6, in which the direction of the

amide In organic chemistry, an amide, also known as an organic amide or a carboxamide, is a compound with the general formula , where R, R', and R″ represent organic groups or hydrogen atoms. The amide group is called a peptide bond when it i ...

bond reverses at each bond, all nylon 6 amide bonds lie in the same direction (see figure: note the N to C orientation of each amide bond).

Properties

Nylon 6 fibres are tough, possessing high tensile strength, elasticity and lustre. They are wrinkleproof and highly resistant to abrasion and chemicals such as acids and alkalis. The fibres can absorb up to 2.4% of water, although this lowers tensile strength. The glass transition temperature of Nylon 6 is 47 °C. As a synthetic fibre, Nylon 6 is generally white but can be dyed in a solution bath prior to production for different color results. Its tenacity is 6–8.5 gf/ D with a density of 1.14g/cm. Its melting point is at 215 °C and can protect heat up to 150 °C on average.

Biodegradation

''Flavobacterium'' sp. 5and ''Pseudomonas'' sp. (NK87) degrade oligomers of Nylon 6, but not polymers. Certain

white rot A wood-decay or xylophagous fungus is any species of fungus that digests moist wood, causing it to rot. Some species of wood-decay fungi attack dead wood, such as brown rot, and some, such as ''Armillaria'' (honey fungus), are parasitic and col ...

fungal strains can also degrade Nylon 6 through oxidation. Compared to aliphatic polyesters, Nylon 6 has poor

biodegradability Biodegradation is the breakdown of organic matter by microorganisms, such as bacteria and fungi. It is generally assumed to be a natural process, which differentiates it from composting. Composting is a human-driven process in which biodegradati ...

. Strong interchain interactions from hydrogen bonds between molecular nylon chains is said to be the cause by some sources.

Production in Europe

At present, polyamide 6 is a significant construction material used in many industries, for instance in the automotive industry, aircraft industry, electronic and electrotechnical industry, clothing industry and medicine. Annual demand for polyamides in

Europe Europe is a large peninsula conventionally considered a continent in its own right because of its great physical size and the weight of its history and traditions. Europe is also considered a subcontinent of Eurasia and it is located entirel ...

amounts to a million

tonne The tonne ( or ; symbol: t) is a unit of mass equal to 1000 kilograms. It is a non-SI unit accepted for use with SI. It is also referred to as a metric ton to distinguish it from the non-metric units of the short ton ( United State ...

s. They are produced by all leading chemical companies. The largest producers of polyamide 6 in Europe: #

BASF BASF SE () is a German multinational chemical company and the largest chemical producer in the world. Its headquarters is located in Ludwigshafen, Germany. The BASF Group comprises subsidiaries and joint ventures in more than 80 countries ...

, 240,000 tonnes per year #

Lanxess Lanxess AG is a German specialty chemicals company based in Cologne, Germany that was founded in 2004 via the spin-off of the chemicals division and parts of the polymers business from Bayer AG. Shares in Lanxess AG were listed in Germany’s DA ...

, 170,000 tonnes per year # Radici, 125,000 tonnes per year # DOMO, 100,000 tonnes per year # Grupa Azoty, 100,000 tonnes per year

References

{{Reflist, 30em

External links

The Promise of Nylon 6: A Case Study in Intelligent Product Design by William McDonough & Michael Braungart
Polyamides Plastics Synthetic fibers German inventions