Nylon continues to hold over half the carpet market. Nylon, a polyamide polymer, has excellent resilience (the ability of a fiber to “spring back” to its original configuration), abrasion resistance, mildew resistance, and very good color retention. It can be acid dyed or solution dyed, which is discussed later. On the downside, it is melted by very strong acids such as hydrochloric acid toilet bowl cleaners, is easily stained by acid dyes (the dyes in most foods and drinks), and is bleached out by chlorine bleach. Nylon comes in two forms: Type 6,6 and Type 6.
Type 6,6, invented by Dr. Carothers of DuPont in 1938, is formed by the reaction between adipic acid, which has 6 carbon atoms, with hexamethylene diamine, which also has 6 carbon atoms. The advantage of Type 6,6 is that it has greater stain resistance than Type 6, is 12% harder than Type 6, and has a slightly higher melt point. This is the type of nylon used by DuPont and Solutia (formerly Monsanto).
Type 6, invented by Paul Schlack in Germany in the 1930’s, is made by co-polymerizing caprolactam, a 6-carbon molecule. This is the type of nylon used by Allied Signal and BASF. This type of nylon has a slightly lower melting point than Type 6,6 nylon, but it has superior light degradation, better dyeability, elastic recovery, fatigue resistance, and thermal stability.
While these are the pros and cons of type 6,6 versus type 6 nylon, there really isn’t enough difference to matter very much – it’s more a matter of marketing than anything else. There have been tests done that indicate identical carpet performance when all aspects of the carpet construction such as yarn size, color, construction, etc. are exactly the same.
There are five generations in nylon fiber:
|First generation||The first nylon fibers. These performed poorly because the soil could be seen through the fiber (unlike wool) and because, due to the round cross-section of the nylon fiber, the soil was actually magnified. As a result, apparent soiling was extremely rapid compared to wool. Later, delustering agents such as chalk were added to eliminate this problem, but the fibers had a dull appearance with this treatment.|
|Second generation||This is first generation nylon fiber with modified cross-section for soil hiding, such as tri-lobal. This eliminated the round shape problem causing the magnification problem.|
|Third generation||Anti-static qualities were added.|
|Fourth generation||Fluorochemical soil/stain protection was added.|
|Fifth generation||Acid dye stain blocker was added (stain-resist nylon). Note: Nylon stain resist warranties are most often covered under installations in owner-occupied residences.|
Polypropylene (olefin), a by-product of gasoline refining, continues to gain market share for two reasons: it costs significantly less than nylon and it is inherently stain resistant. Its inherent stain resistance arises from its lack of dye sites and the fact that it is chemically inert. In fact, chlorine bleach and even battery acid have no effect on it. It is inherently mold resistant. It is also resistant to fading from sunlight and is, therefore, the fiber of choice for outdoor use. Olefin’s biggest drawbacks are its lack of resilience, its strong attraction for oily soils, and its propensity to wick more than nylon resulting in more frequent complaints of “reappearing spots”, streaking, yellowing, and resoiling. Also, because it has a much lower melting point than nylon, friction from moving furniture or casters can permanently damage the fibers. Additionally, a broken vacuum cleaner belt will seriously and permanently damage an olefin rug or carpet, melting the rubber into the fiber. Fortunately, because it is so resistant to most chemicals, more aggressive cleaning agents can be used on olefin.
Olefin is used in most Berber carpets or for use where a less expensive product is required and life expectancy and long-term appearance are unimportant. Olefin is the fiber of choice to use outdoors. Olefin should NEVER be used where the primary soil is oil; for example, olefin should never be used in a car showroom.
To reduce wicking on olefin carpets and rugs, it is best to prevacuum, make extra drying passes, and use air movers to speed up drying. The new Advanced Teflon® is recommended for olefin. Olefin should never be treated with a solvent-based protector. The mill can apply protector to olefin, by essentially fusing it into the fiber
Polyester fiber produces some of the most beautiful colorations available. It also is extremely fade resistant and provides excellent resistance to stains. However, like olefin, it does have poor resilient properties and thus is susceptible to crushing. Polyester fabrics are generally sold in heavy face weights with high-density construction. Avoid high pile heights with low-density construction. These products tend to flatten and "ugly" out. Also look for high twist levels rather than "blown" yarns. Loose twists (blown yarn) tend to untwist and the yarn tips tend to fuse together creating a matted appearance. Most consumers like to dig their fingers into the carpet pile and if it provides a luxurious feel (hand) they believe this is excellent quality. This is referred to as "perceived" quality. True quality exists when it is difficult to insert your fingers into the pile. This is a true test for all carpet constructions, but it is a necessity for polyester fibers. This will be discussed in detail under construction basics.
Polyester is manufactured in staple fiber only. While it's not as durable as nylon, it's quite durable and resists wear. Polyester offers a wide selection of textures and colors. It is non-allergenic, sheds moisture and resists moths and mildew at a lower cost than wool or nylon. While it's susceptible to pilling, shedding and oil-based stains, it otherwise cleans fairly easily and is enhanced by stain treatments. Some polyester fibers are recycled from plastic pop bottles, so if environmental concerns are a major issue for you, ask for polyester fibers that have been reclaimed from post consumer use products
Wool is normally from fleece (sheep hair), but in antique rugs the wool can also come from other animals like goat hair, etc. At one time, wool was the primary fiber in carpet, but its cost resulted in steadily decreasing market share. Wool has several excellent qualities. It hides soil much better than synthetic fibers because it is not clear and, therefore, soil cannot be seen through it, plus it has scale edges to further hide microscopic particles of soil. It is also the preferred fiber where cigarette burns are a problem, because it does not melt. Wool's high moisture content and protein constituents provide natural flame resistance. Wool also “feels” softer to the touch. Wool carpets wear well and age beautifully and have a look and feel that is unmistakably their own. However, nylon and olefin carpets will last longer in high traffic areas.
Wool cells come in two different types: the paracortex and the orthcortex, which lie on opposite sides of the fiber and grow at slightly different rates. This causes a three-dimensional corkscrew pattern of coiled springs much like shock absorbers, giving wool high elasticity and a “memory” that allows the fibers to recover and resume normal dimensions. Wool fibers can be stretched up to 30 percent without rupturing and still bounce back.
However, wool is expensive, is easily stained by nearly everything, has very poor chemical resistance making spotting and stain removal much more difficult, mildews, is attacked by carpet beetles and moths, fades easily in direct sunlight, and attracts and stubbornly holds on to protein soils such as urine, blood, and meat juices.
Cotton and acrylic are used in very few carpet styles in the U.S., but their use is increasing in area rugs. Both offer poor resiliency and tricky carpet cleaning requirements. Both offer extremely beautiful colorations and in the right construction can provide a beautiful flooring alternative.
Acrylic is the closest to wool of any of the synthetics. Its use is primarily because of its springy feel, soil resistance, excellent cleanability, and resistance to static, moths and mildew. It's available in a wide choice of colors, and is less likely to fade in bright sunlight than some fibers. It is susceptible to pilling and is slightly more expensive than nylon. Brand names include Acrilan, Orlon, Creslan and Zefron.
Cotton is soft, but it does not resist stains or matting well. It also absorbs moisture, which makes it difficult to keep clean. Cotton is subject to browning if cleaned with alkaline solutions.
|Dissolves in formic acid. Burns to a hard black bead; puffs white smoke; extinguishes||Floats in water. Burns to a round hard tan bead.||Dissolves in hot meta-cresol. Burns rapidly to a round hard bead and gives off a pungent odor.||Dissolves in chlorine bleach. Burns with a burned-hair odor to a black crumbly residue.|
|Moisture Absorption||4.2-4.5%||0.01%||0.04-0.08%||Up to 30%|
|Abrasion Resistance||Excellent||Very Good||Good||Good|
|Effects of Acids, Alkalis, and Solvents||Resistant to weak acids, but decomposes in strong mineral acids||Chemically inert||Resistant to most acids and solvents||Sensitive to acids and alkalis|
|Dye Methods||Acid; some solution dyed||Solution dyed||Dispersed Dyes||Various|
|Resistance to Mildew, Aging, Sunlight||Excellent resistance to mildew and aging. Prolonged sunlight can cause degradation.||Good resistance to all three||Excellent resistance to mildew and aging. Prolonged sunlight can cause degradation||Damaged by sunlight, mildew, moths, beetles. Sunlight can cause yellowing.|
|Color Retention||Very good||Excellent||Good||Good|
|Stain Resistance||Poor (5th generation very good)||Excellent||Excellent||Very Poor|
|Stains/Soils Attracted to Fiber||Acid dyes, except for 5th generation||Oil based||Oil based||Protein, urine, blood, meat juices|
|Melt Point °F||Type6-435º F; Type6,6-490º||320º F||509º F||None (ignites)|
|Cigarette Burn Resistance||None||None|