The properties of the key fibers employed in carpet manufacture are presented during this chapter. Nylon yarns account for over seventieth of the yarns accustomed type the tufted face of the substrate, with polyester, polypropene, acrylic, modacrylic, and wool yarns being employed to lesser extents. Nylon dominates the tufted carpet market thanks to its overall toughness and resiliency. Polypropylene is additionally used each in primary and secondary backing.
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Fig 1: Chemical structures of Nylon 6 and Nylon 6,6 |
1. NYLON 6 AND NYLON 6,6 FIBERS
The polymeric amide fibers embrace the nylons, 6 and 6,6, and also the aramid fibers. each fiber sorts are fashioned from polymers of long-chain polyamides. The nylons usually are tough, strong, sturdy fibers helpful in an exceedingly big selection of textile applications. the amount of carbon atoms in every monomer or comonomer unit is often selected for the nylons. Therefore, the nylon with six carbon atoms within the continuation unit would be nylon 6 and also the nylon with six carbons in every of the monomer units would be nylon 6,6.
Nylon 6 and nylon 6,6 are terribly similar in properties and structure (Fig. 1) and, therefore, are delineated along. The key structural distinction is thanks to the location of the organic compound teams in an exceedingly continuous head-to-head arrangement in nylon 6, whereas in nylon 6,6, the organic compound teams reverse direction whenever in an exceedingly head-to-tail arrangement thanks to the variations within the monomers and chemical action techniques used.
Nylon 6,6 was developed within the u. s., whereas nylon 6 was developed in Europe, and a lot of recently in Japan. The key variations within the fibers are that nylon 6,6 dyes lighter, features a higher freezing point, and a rather harsher hand than nylon 6.
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Fig 2: |
1.1 Structural Properties
Nylon 6 is made by ring-opening chain growth polymerization of caprolactam within the presence of vapour associated an acid catalyst at the soften. Once removal of water and acid, the nylon 6 is soften spun at 250°-260°C into fibers. Nylon 6,6 is ready by step growth chemical action of hexamethylene organic compound and carboxylic acid. Once drying, the nylon 6,6 is soften spun at 280°-290°C into fibers. Each nylon 6 and 6,6 square measure drawn to automatically orient the fibers following spinning.
The degree of chemical action of nylon 6 and 6,6 molecules varies from one hundred to 250 units. The polyamide molecular chains lay parallel to at least one another in an exceedingly "pleated sheet" structure with robust hydrogen bonding between amide linkages on adjacent molecular chains. The degree of crystallinity of the nylon can depend upon the degree of orientation given to the fiber throughout drawing. Nylon fibers are typically rounded with a sleek surface or are trilobal in cross section (Figs. 2 and 3). Multilobal (star) cross sections and alternative advanced cross sections also are found.
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Fig 3: |
1.2 Effect of Single-Step Versus ballroom dance Production of Nylon
Nylon fibers made in an exceedingly single-step method tend to possess a lot of open polymer structure compared to nylon made in an exceedingly ballroom dance method. The cause for this distinction is that the polymer structure isn't allowed to relax or condition within the single-step method before the everyday second step. This relaxation or acquisition step permits the nylon to make a lot of crystalline structure among the polymer matrix. Fibers made in an exceedingly single-step technique tend to abrade and stain a lot of simply than those factory-made in an exceedingly ballroom dance method.
High levels of uncrystallized structure produce associate simply dyeable fiber. This conjointly will increase the chance of staining and soilure along side poor wear performance. a lot of stain resistant chemical is applied to a fiber of lower crystallinity to attain a similar performance as a fiber of upper crystallinity.
1.3 Physical Properties
Nylon 6 and 6,6 fibers are robust, with a dry tenaciousness of 4-9 g/d (36-81 g/tex) and a wet tenaciousness of two.5-8 g/d (23-72 g/tex). These nylons have elongations at break of 15%-50% dry, which increase somewhat on wetting. Recovery from stretch deformation is extremely sensible, with ninety nine recoveries from elongations up to 100 percent. The nylons are stiff fibers with wonderful resiliency and recovery from bending deformation. They’re of rarity, with a selected gravity of one.14. They’re moderately hydrophilic with a wetness regain of 4%-5% below commonplace conditions and a regain of Sept. 11 at 100 pc RH. Nylon vi and vi,6 are soluble in H bond-breaking solvents like phenols, ninetieth acid, and benzyl radical alcohol. They need moderate heat conduction properties and are unaffected by heating below 150°C. The nylons have high ohmic resistance and promptly build up static charge.
1.4 Chemical Properties
The nylons are fairly immune to chemical attack. They’re attacked by acids, bases, and reducing and oxidizing agents below extreme conditions not found in traditional use. They’re unaffected by biological agents, however at elevated temperatures or within the presence of sunlight; they'll bear aerobic degradation with yellowing and loss of strength.
1.5 Nylon End-Use Properties
Nylon has the subsequent properties:
1. The fiber is hard and has sensible abrasion resistance.
2. Nylon 6 and nylon 6,6 square measure very robust fibers with wonderful recovery and resiliency.
3. It’s a coffee wetness content.
4. The fiber has sensible resistance to house chemicals, however exhibits poor resistance to attack by daylight unless treated with antioxidants.
5. Daylight degrades the polymer over a chronic amount of time.
6. Continuous filaments hide soil higher than staple ones.
7. Nylon fibers have high luster unless delustered.
8. Electricity will simply be generated.
9. Decomposition happens in robust mineral acids.
10. Soil-hiding properties square measure modified by the form of the fiber.
11. Melting happens at 414°-480°F.
12. Lit cigarettes simply soften it.
13. It’s limiting oxygen Index (L01), the quantity of oxygen in air necessary to cause combustion, is 20.
14. Nylons soften, drip, and have a tendency to self extinguish on burning.
15. Continuous filaments are generally employed in high traffic areas.
16. Fibers have wonderful dyeability with wonderful color-fastness.
17. Nylon 6 is somewhat deeper coloring than nylon 6,6.
18. Staining could be a downside unless the merchandise is treated with a stain resistant chemical.
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