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Carpet Fibers

By Michael Hilton

The majority of the carpet produced in the United States contains one of six pile fibers: nylon, polypropylene (olefin), acrylic, polyester, wool, or cotton. Synthetic fibers make up more than 99% of the fiber used by the U.S. carpet industry. Each fiber has strengths and weaknesses that must be recognized and should influence how it is to be used and constructed. Some fibers have very low resiliency and only should be manufactured in high-density loop pile constructions to limit crushing (pile flattening). Other fibers have the tendency to absorb oily soils and other oil-based compounds (including body oils) and should be carefully considered before installing in areas subject to these contaminants. It should be emphasized that there is no perfect fiber and carpet is a fabric that is subjected to incredible abuse through foot traffic, accidental spills, environmental contaminants, and other abuses.

Pile fiber represents greater than 80% of the cost of most residential carpet; therefore differences in price between carpet styles usually can be attributed to differences in fiber. Of the three most commonly used fibers (nylon, olefin, and polyester), nylon is by far the most expensive fiber and the best all around performer. In comparing price alone, a polyester fabric could be one-third less than the cost of a comparable nylon product.

In addition, when comparing two like fibers, there can be considerable cost differences between the two. Nylon, for example, may be type 6 or type 6,6 and may be branded or unbranded. These factors influence value, price and performance as well. It is impossible to purchase carpet and anticipate performance or value by fiber ounce weight alone. In essence, two 40-ounce nylon fabrics may differ in price by 30% or more. There are a number of variables to consider in selecting the proper carpet product. Hopefully, the descriptions contained in this explanation will make the decision easier rather than more confusing.

Staple and continuous filament

Each of the fiber systems used in the manufacture of carpet can be divided into two classifications: staple and bulked continuous filament (BCF). Nylon is produced in both staple and BCF yarn. Olefin is typically produced in BCF only. Polyester is manufactured in staple only; cotton and wool are inherently staple. Staple yarns are yarns that are produced in short lengths and spun and twisted together (like cotton) to form long threads of yarn and tufted into carpet. BCF yarns are actually long filaments of fiber that are plied together to form continuous bundles of fiber.

Many lower face weight products and higher end carpet products are manufactured using staple yarns. These yarns can be spun by the manufacturer into any size yarn bundle and provide more styling flexibility. This allows manufacturers to spin very small yarn plies for pinpoint saxonies and very large bundles for shag or cabled yarns. Staple fiber also is used to manufacture the beautiful velvet plushes that signify luxury and comfort.

Some consumers prefer bulked continuous filament fibers, because they do not shed loose filaments following carpet installation. Staple fibers will shed loose filaments for a short time following carpet installation. In some cases with staple fibers, you may notice your vacuum cleaner bag filled with these short staples. In lower quality staple fibers (short staple length) these filaments will work loose and accumulate on the carpet surface. As mentioned, staple fibers offer design opportunities that BCF fibers cannot. Better quality staple fibers shed very little because of their length (8-10 inches vs. 3-4 inches). This loose fiber is generated when the tufts are cut to form cut pile. While one end of the staple is anchored in the synthetic latex adhesive (see construction), the cutting of the tuft may sever the end of the staple that is not anchored. This unanchored cut staple will eventually work loose of the yarn tuft.

While this shedding does not affect carpet performance or long-term appearance, you should be aware that this is a normal occurrence and the shedding will stop with time depending upon the frequency of vacuuming or the amount of foot traffic. In rare instances, when shedding exceeds six months and frequent vacuuming has been performed, you should contact the manufacturer. In these cases, poor encapsulation of the yarn bundle with synthetic latex may have occurred. As stated, this is very rare but it should be noted.

To distinguish between staple and BCF yarns, look on the sample label for the description BCF or CFN (continuous filament nylon). Any sample label that does not carry this designation is probably a staple fiber. If you are looking at roll goods, where a sample is not available, rub your thumb across the fiber over the same area. If short filaments work loose, it is probably a staple fiber.

Nylon

Nylon is utilized in approximately 65% of the carpet sold in the U.S. It is a very durable fiber with excellent performance characteristics. Its strengths include good resiliency, good yarn memory to hold twist, good carpet cleaning efficacy, good stain resistance with stain treatment applied, good soil hiding ability, and good abrasion resistance. Nylon is manufactured in both BCF and staple fiber. It is the strongest fiber, making it an excellent choice for the heavy traffic of an active household or commercial facility. It's also the most durable of the synthetics. It is soil and mildew resistant and resilient, but is prone to static. Most nylon is treated with an anti-static treatment to reduce static. Continuous filament fibers minimize pilling and shedding.

There are two basic types of nylon (type 6 and type 6,6) and each provides different performance characteristics. For many years, type 6,6 has been considered to be the premium nylon fiber, but technological advances in dyeing and twisting processes have narrowed the gap between the two. However, type 6,6 remains the premium nylon fiber used today. If you are looking for value goods, type 6 nylon fibers offer a considerable benefit for the money. Nylon fibers also can be branded or unbranded. For example, DuPont nylon (type 6,6) is manufactured by DuPont and is a premium fiber. Many fibers that do not carry a brand name may be extruded by the carpet manufacturer (typically type 6) and can be considered value goods. Branded fibers traditionally cost more than value goods. This can be attributed to a number of factors including the shape of the fiber (soil hiding), topical treatments (stain inhibitors), minimum construction requirements (twist level, pile weight), and consistency of fiber quality. However, you should not base your purchase decision solely on branded vs. unbranded or type 6 vs. 6,6. Because of lower cost for the fiber, an unbranded type 6 fiber may be able to provide better construction attributes for the same dollar amount.

Polypropylene

Polypropylene, also called olefin, is the fastest growing fiber segment in use today. It is a relatively inexpensive fiber, which is easily extruded by most carpet manufacturers. There are very few, true branded olefins available other than those brands registered by carpet manufacturers. Olefin makes up about 30 % of the fiber used in U.S. carpet manufacturing today. Its strengths include superior stain resistance, with the exception of oil-based stains, and low cost. It is a solution-dyed product, which means color is added during extrusion in its molten state rather than topically applied. (Imagine a carrot vs. a radish). Because of this dye method it has superior resistance to bleaches and sunlight fading. However it has poor resiliency, which can lead to crushing. Color selection is limited due to its dye method. It has poor abrasion resistance and its low melt point can cause fibers to fuse if furniture or other objects are dragged across its surface. Olefins clean very well and most staining is non-existent. Olefin was originally favored for outdoor carpeting and basements due to its resistance to moisture, mildew, water damage, staining, pilling, shedding and static—all for lower cost than nylon. Now it’s more widely used for its durability and appearance. Since it’s dyed before it's made into a fiber, olefin is extremely colorfast.

This description should not scare you away from olefin, because constructed properly, olefins provide an excellent value and good performance. Olefin would not work well in a busy airport or school environment, but will perform well in a busy family room. In acknowledging it’s weaknesses, it is easy to find a suitably constructed olefin Berber or other loop pile product. Steer clear of big loop Berber with low density and never consider any cut pile olefin for residential use. These constructions typically fail with any fiber system, but olefin is especially susceptible to pile crush in these constructions. A properly constructed olefin will outperform a similarly constructed nylon product because of its inherent stain and fade resistance, but a poorly constructed olefin will ultimately lead to dissatisfaction. Olefin is manufactured in BCF only.

Polyester

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

This traditional favorite offers a deep, rich look and feel. Wool remains the premier fiber in carpet construction, but it's price is out of reach of most consumers. It has excellent resilience and durability, but is very expensive—often twice as much per yard as nylon. Other synthetic fibers have done an excellent job of duplicating the characteristics of wool, although none can duplicate all of these characteristics. Wool cleans especially well, provides beautiful colors, and has good resiliency, but special care should be used in cleaning wool carpet. Unfortunately, wool tends to "wear down" or the pile tends to wear away. In some cases bald spots may occur as a result heavy traffic loads. Wool is naturally a staple fiber. Although it is naturally stain resistant, it requires a high level of maintenance including mothproofing. Most wool products manufactured in the U.S. have been permanently mothproofed. While it's still extremely popular for rugs, it accounts for less than 1% of the fiber used in carpet.

Since wool can hold 10 times its weight in moisture, it is susceptible to shrinking and mold and mildew growth.

Comments Wool Nylon Polypropylene Olefin Acrylic Modacrylic' Polyester
Resiliency -- Determined by fiber structure and modifications. Good to excellent Excellent Excellent Fair to excellent Good to excellent
Abrasion Resistance -- Determined by fiber and density of face fiber -- the more tightly packed the yarns, the more resistant to wear. Good to excellent Excellent Excellent Fair to excellent Good to excellent
Soil & Stain Resistance/Cleanability -- Determined by color, texture, dyes, fiber structure and modifications. Good to excellent Good to excellent Good if oily soils and stains are treated promptly. Good Good to excellent -- oily stains should be promptly treated.
Resistance to Sunlight -- Determined by fiber structure and modifications. Poor -- If protected from ultraviolet rays, degradation does not occur as rapidly. Good -- special dyes may be used to inhibit sun damage. Loses strength and deteriorates unless chemically modified to resist sunlight damage. Excellent resistance. Prolonged exposure may cause deterioration in some pieces. Good -- may weaken with prolonged exposure.
Static -- Determined by fiber structure and modification. Builds up in low humidity unless modified. Builds up in low humidity unless modified. Builds up in low humidity but at a lower level than nylon or polyester Builds up in low humidity unless modified. Builds up in low humidity unless modified.
Hand Warm, soft Varies from warm and soft to cold and coarse. Waxy, soft Warm, soft Varies -- finer deniers are soft and silky.
Resistance to Mildew --Determined by fiber structure and modifications Poor if damp or soiled. Fiber may be modified Excellent Excellent Excellent
Flammability -- Determined by fiber structure, modification, construction methods, dyes, padding and carpet installation methods Burns slowly indirect flame; considered self-extinguishing. Burning hair odor. Burns slowly, melts in direct flame; self-extinguishing. Structure may alter what occurs. Celery-like odor. Melts at low temperatures (170°C); burns and emits heavy, sooty, waxy smoke. Paraffin wax odor. Pulling a heavy object across the carpet surface can cause enough friction to melt the carpet fibers. Acrylic burns readily unless modified. Modacrylics are difficult to ignite, will not support combustion, are self-extinguishing and dripless. Acrid odor for both. Burns slowly, melts; some are self-extinguishing. Chemical odor.

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.

Did you know?

Carpet pile fibers significantly impact carpet performance. In buying carpet make sure you understand the various types of carpet fiber and how each clean (carpet cleaning) mat and crush, resistance to sunlight fading and resist carpet stains. Some discount carpet wholesalers utilizes special yarn buys from carpet fiber producers to carpet manufacturers to reduce carpet prices.

About the Author
Michael Hilton was the original creator of Carpet Buyers Handbook. Having owned and operated a carpet wholesale company, Hilton has a vast knowledge about all-things carpet related as well as other types of flooring.

Other Helpful Links
Construction Basics
Needle Punch Carpet
Carpet Fibers
Identifying Carpet Fiber Types
Carpet Fiber Processing
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