What is Nylon?Nylon is a condensation polymer, which is an organic macromolecule prepared from a large number of small molecules called monomers.
The condensation polymerization reactions require starting monomers having certain functional groups such as the alcohol group, the amino group and the carboxylic group.
Condensation polymers are linear and almost devoid of branches and also have a higher tensile strength.
- The molecular weight is not an integer multiple of the monomer units of departure
- Generally requires more than one monomer unit
- The monomer units must have two functional groups
Polymers of poly-addition
- The molecular weight is an integer multiple of starting monomer
- Generally requires a single monomer unit
- The monomer units have one or more sites of unsaturation
The nomenclature of Nylon is Nylon word followed by 1 or 2 numbers.
If the numbers are 2, the first indicates the number of carbon atoms of diamine, the second number of carbon atoms (carboxylic) acid. Nylon 6.6, for example, is obtained from the reaction of hexamethylendiamine with adipic acid.
If there is only one number, the monomer is an amino acid, which contains two functional groups.
Nylon Nylon 6 and 11 are of this type and are the most widely used Nylon.
House chemical point of view, the nylon are polyamides. Are synthesized through a polymerization reaction.
The first to be produced were nylon nylon 6 and nylon 6.6.
After the development of nylon 6 and nylon 6.6 were many attempts at polymerization between a diacid and a diamine and the term nylon is passed to indicate the whole family of macromolecular species. In particular the numbers that follow the name indicate the number of atoms from carbon diamine and the number of carbons from the diacid. Thus one nylon, nylon 6.7 8.10 etc. If the number that follows is single then it means that the chain comes from the polymerization of a species containing a carboxylic acid and an amine carbon skeleton.
In addition to the 6.6 and nylon to nylon 6, nylon more widespread industrially are called 11 nylon and nylon 12.
Below is a table containing examples of nylon:
- Nylon 6.6
- Nylon 6
- Nylon 6.10
- 6.12 nylon
- Nylon 11
- Nylon 12
The Nylon 6.6 is the product of condensation polymerization of hexamethylendiamine and adipic acid; is the most widely used nylon.
This process theoretically, can be repeated several times depending on the quality of different plastics.
It can be produced by Interfacial polymerization using acyl chloride instead of adipic acid. In this case the diamine is dissolved in the aqueous phase, while the acyl chloride is dissolved in an organic solvent (e.g. chloroform). The synthesis reaction takes place at the interface between the two phases, so we talk about "curing superficial".
In the process of production of adipic acid takes place at temperatures of 200° C, while in the case of the surface curing temperatures down around 0-50° c.
The Nylon 6 is synthesized by polymerization from ε-caprolactam.
The 6.10 Nylon is made from hexamethylenediamine and 1.10-decandioico acid (sebacic acid)
The 6.12 Nylon is made from hexamethylenediamine and dodecane dioic acid.
The Nylon 11 is obtained from ricinoleic acid, contained in castor oil.
The 12 Nylon can be produced from Lauryl lactam (for ring opening) or ε-amminododecanoico acid.
According to the ISO definition, "the polyamide fiber (or nylon) is a fibre formed of linear macromolecules that arise in catena recurrence of amide linkages, of which at least 85% are joined to aliphatic groups or aliphatic cycle".
The spinning operation is conducted at a temperature of 30-40° C, higher than the melting point of the polymer; to avoid phenomena of depolymerization and degradation, it is important that the mass has a moisture content not greater than 0.1%.
The main features of this fiber are:
- excellent wear resistance;
- high elastic recovery;
- easy dyeing;
- good color fastness;
- ease of maintenance.
Nevertheless it should be noted the sensitivity to several chemicals (bleach, acids and minerals); poor resistance to high temperatures (100° C >) and particular environmental conditions such as light and rich atmospheres of nitrogen oxides.
In polyamides numerous hydrogen bonds intra-and inter-molecular evidence due to the presence of CONH groups give rise to intense that cohesion forces, together with the regularity of the chains, to have substantial percentages of crystallinity. This gives the material excellent mechanical properties: high elastic modulus, hardness and abrasion resistance. The melting point is generally high: 220° C for the Ny-6, 262/264° C 6.6 and 174° C for the Ny-12. The glass transition is observed at 50° C for the Ny-6 and at 37° C for the Ny-12.
The amide groups, in addition to making polyamides rather hydroscopic, greatly improve the impact resistance of the material. This is possible because the water molecules absorbed act as plasticizer, increasing the toughness.
Nylon is worked to complete the alignment of molecules and to give to the wire of the special features from an aesthetic point of view, and functional touch: in particular, the most important are ironing and texturizing, so wires are sold as a finished product or can be used in the case of textured, for they are coupled with elastomer to get the spiral wire and stretchone.
The yarns are distinguished depending of which have undergone and their size; the thickness of the yarn, because of its irregular nature and not compressible is expressed as diameter but as mass per unit length of a wire properly tensioned.
The traditional unit of measurement is the den (money), which corresponds to the mass in grams of 9000 meters of yarn, this unit is still used commercially to differentiate the opacity in the final product but the unit adopted internationally is Tex, by definition equal to the mass in grams of 1000 meters of yarn, especially for textile yarns increased use you prefer dtex (decitex) , i.e. the mass of 10000 meters of yarn to get whole numbers, given the small size z.
6.6 Nylon wires are generally longer for burrs where the textile threads are shown with two numbers "x/y" of which the first is the strength of thread expressed in dtex and the second the number of burrs that compose it, which correspond to the number of holes in the sector from which they come; If necessary, adding a third digit to indicate the number of "bars", i.e. clusters, for example a 22/20 x 2 will be a two-thread bunches from twenty burrs each for a total of 44 dtex.
The ratio x/y indicates the size of the burrs from which follows the softness to the touch. For example a 17/2 has a ratio of 8.5 and a fabric made from this yarn is hard and crespo, to decrease the ratio we "multifilament" such as the 78/68 and finally, when x/y ≈ 1, the microfilament '. "
Because the burrs can be very numerous, it is appropriate to somehow keep them Compact through a ligature, then with the "bind to air" that is to blow air from the nozzles so as to avoid messing up randomly burrs; These zones are formed "interlacing points" which, according to their amount, maintain more or less thread. The interlacing points provide a mild and reversible, in fact, by applying a voltage strong enough along the axis of the wire, you can make them fail, but are sufficient to compact the material prior to use.