A carpet is a textile floor covering consisting of an upper layer of “pile” attached to a backing. The pile is generally either made from wool or a man-made fibre such as polypropylene, nylon or polyester and usually consists of twisted tufts which are often heat-treated to maintain their structure.
The carpet is produced on a loom quite similar to woven fabric. The pile can be plush or Berber. Plush carpet is a cut pile and Berber carpet is a loop pile. There are new styles of carpet combining the two styles called cut and loop carpeting. Normally many coloured yarns are used and this process is capable of producing intricate patterns from predetermined designs (although some limitations apply to certain weaving methods with regard to accuracy of pattern within the carpet). These carpets are usually the most expensive due to the relatively slow speed of the manufacturing process. These are very famous in India, Pakistan and Arabia.
These carpets are more technologically advanced. Needle felts are produced by intermingling and felting individual synthetic fibres using barbed and forked needles forming an extremely durable carpet. These carpets are normally found in commercial settings such as hotels and restaurants where there is frequent traffic.
On a knotted pile carpet (formally, a supplementary weft cut-loop pile carpet), the structural weft threads alternate with a supplementary weft that rises at right angles to the surface of the weave. This supplementary weft is attached to the warp by one of three knot types (see below), such as shag carpet which was popular in the 1970s, to form the pile or nap of the carpet. Knotting by hand is most prevalent in oriental rugs and carpets. Kashmir carpets are also hand-knotted.
These are carpets that have their pile injected into a backing material, which is itself then bonded to a secondary backing made of a woven hessian weave or a man-made alternative to provide stability. The pile is often sheared in order to achieve different textures. This is the most common method of manufacturing of domestic carpets for floor covering purposes in the world.
Fibres and yarns used in carpet
Carpet can be made from many single or blended natural and synthetic fibres. Fibres are chosen for durability, appearance, ease of manufacture, and cost. In terms of scale of production, the dominant yarn constructions are polyamides (nylons) and polypropylene with an estimated 90% of the commercial market.
Nylon is the most common material for construction of carpets. Both nylon 6 and nylon 6-6 are used. Nylon can be dyed topically or dyed in a molten state (solution dying). Nylon can be printed easily and has excellent wear characteristics. In carpets nylon tends to stain easily because it possesses dye sites on the fibre. These dye sites need to be filled in order to give nylon any type of stain resistance. As nylon is petroleum-based it varies in price with the price of oil.
Polypropylene is used to produce carpet yarns because it is inexpensive. It is difficult to dye and does not wear as well as wool or nylon. Polypropylene is commonly used to construct berber carpets. In this case, polypropylene is commonly referred to as olefin. Large looped olefin berber carpets are usually only suited for light domestic use and tend to mat down quickly. Berber carpets with smaller loops tend to be more resilient and retain their new appearance longer than large looped berber styles. Commercial grade level-loop carpets have very small loops, and commercial grade cut-pile styles are well constructed. When made with polypropylene these styles wear very well, making them very suitable for areas with heavy foot traffic such as offices. Polypropylene carpets are known to have good stain resistance but not against oil based agents. If a stain does set, it can be difficult to clean. Commercial grade carpets can be glued directly to the floor or installed over a 1/4″ thick, 8-pound density padding. Outdoor grass carpets are usually made from polypropylene.
Wool and wool-blends
Wool has excellent durability, can be dyed easily and is fairly abundant. When blended with synthetic fibres such as nylon the durability of wool is increased. Blended wool yarns are extensively used in production of modern carpet, with the most common blend being 80% wool to 20% synthetic fibre, giving rise to the term “80/20″. Wool is relatively expensive and consequently a small portion of the market.
The polyester known as “PET” (polyethylene terephthalate) is used in carpet manufacturing in both spun and filament constructions. After the price of raw materials for many types of carpet rose in the early 2000s, polyester became more competitive. Polyester has good physical properties and is inherently stain-resistant because it is hydrophobic, and, unlike nylon, does not have dye sites. Colour is infused in a molten state (solution dyeing). Polyester has the disadvantage that it tends to crush or mat down easily. It is typically used in mid- to low-priced carpeting.
Another polyester, “PTT” (Polytrimethylene terephthalate), also called Sorona or 3GT (Dupont)or Corterra (Shell), is a variant of PET. Lurgi Zimmer PTT was first patented in 1941, but it was not produced until the 1990s, when Shell Chemicals developed the low-cost method of producing high-quality 1,3 propanediol (PDO), the starting raw material for PTT Corterra Polymers.
Acrylic is a synthetic material first created by the Dupont Corporation in 1941 but has gone through various changes since it was first introduced. In the past acrylic used to fuzz or pill easily. This happened when the fibres degraded over time and short strands broke away with contact or friction. Over the years acrylics have been developed to alleviate some of these problems although the issues have not been completely removed. Acrylic is fairly difficult to dye but is colourfast, washable, and has the feel and appearance of wool, making it an ideal rug fabric.
Carpet binding is a term used for any material being applied to the edge of a carpet to make a rug. Carpet binding is usually cotton or nylon, but also comes in many other materials such as leather. Non-synthetic binding is frequently used with bamboo, grass and wool rugs, but is often used with carpet made from other materials.