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Carpet beauty is more than skin deep
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From installation to maintenance and traffic patterns, many factors influence how long a carpet will last in a particular application. But none is as important as the construction of the carpet. Match the carpet construction to the needs of the application, and facility executives will have an installation that performs well over its rated service live. Fail to consider how carpet construction affects performance however, and the installation almost certainly won’t live up to expectations.
Successfully selecting the most suitable carpet construction begins with an understanding of the particulars of the application. How is the space used? What functions will be performed in the space? What level of traffic will the carpet will be exposed to? What is the potential for spills, and what liquids are the most likely to be spilled? Will the carpet be exposed to dirt tracked in from outside of the building? By determining these and other usage factors, facility executives will be able to identify important factors to be used in evaluating different carpet options.
Facility executives have the option of installing carpet that uses natural or synthetic fibers. Nylon and olefin are the two leading carpet fibers used in commercial applications, while wool is the leading natural fiber in use. Synthetic fibers in general offer greater fiber strength and resistance to soiling, but there are applications where wool is the fiber of choice.
Analyzing Fiber Choices
The most commonly used fiber in commercial carpet installations is nylon. Nylon fibers are extremely strong and flexible. The naturally hard surface of nylon fibers offers excellent wearability, resilience, abrasion resilience, and resistance to oils and chemicals. Nylon fibers do not readily absorb moisture.
Most carpets made from nylon fibers are solution-dyed. During the solution dyeing process, the color is added to the nylon crystals before they are processed into individual fibers. As a result, the fibers offer very good color stability and resistance to fading.
One of the most significant drawbacks of nylon fibers is their inability to dissipate static electricity. In normal use, particularly under low humidity conditions, static charges can easily be generated in excess of 12,000 volts. Static charges of this level are well above the recommended maximum value for sensitive electronic equipment. To reduce the impact of static charges, manufacturers add carbonized fiber to the nylon yarn or put a conductive coating on the surface of the nylon fibers that helps dissipate static charges before they reach a level where they can damage electronic equipment.
The second most commonly used fiber in commercial carpet is olefin. Carpets constructed using olefin fibers are less expensive than those that use nylon. Olefin fibers are not as hard or crush-resistant as nylon. To help improve wear and limit crushing, manufacturers limit pile height while increasing the number of fibers installed per inch of carpet.
Olefin fibers offer excellent resistance to moisture, making them suitable for indoors or outdoors. They resist fading from sunlight and are chemical and stain resistant. While the fibers are stain resistant, the fibers tend to hold more dirt than nylon fibers. It might be necessary to clean carpets made of olefin fibers more frequently to prevent damage to the surface of the fibers from dirt abrasion.
One of the biggest drawbacks of olefin fibers is their low melting point. The heat generated by friction when objects are dragged across the carpet can be sufficient to damage the fibers, creating permanent burn marks.
Olefin fibers do not generate static electricity, making them particularly well suited for applications with installations of sensitive electronic equipment, such as telecommunications equipment or computers.
Wool is the most expensive of the fibers used in commercial carpet construction. Its fibers are durable, resisting both crushing and matting. The fibers will resist moisture to a point, but will shrink if saturated with water. Wool fibers are more susceptible to abrasion than either nylon or olefin. Its biggest drawback is the ease with which the fibers can be stained.
Wool fibers hide dirt very well due to the fiber’s construction that tends to scatter light. The fibers also resist binding to dirt, making cleaning an easy task. It is recommended that wool carpets be cleaned more frequently than those made from synthetic fibers as embedded dirt, while not visible, can readily damage the surface of the fibers.
In spite of its expense and limitations, wool remains the fiber of choice in applications such as board rooms and hotel corridors where its elegance is unmatched by synthetic fibers.
While fiber selection is an important factor in matching application requirements, other construction elements will determine how well a particular carpet will perform in a given application, including dyeing methods, pile types, attachment methods, and the type of backing used.
There are two major ways in which color is added to carpet fibers: solution dyeing and stock dyeing. In solution dyeing, the color pigment is added to the yarn during the manufacturing process, resulting in color that extends throughout the yarn material. This gives the fibers outstanding resistance to fading and excellent color stability, making them well-suited for applications where the carpet may be exposed to sunlight, bleach or harsh detergents.
When fibers are stock dyed, the pigments are added to the yarn after they have been manufactured but before they are turned into spun yarn. It is a lower cost process than solution dyeing, with only a slight decrease in fiber performance. A wider range of colors are available for carpets that have been stock dyed.
Two basic types of piles are used in carpet construction: cut pile and loop pile. For all piles, the quality of the carpet and how well it performs depends on density and the amount of twist in the pile. In cut pile construction, the fibers are cut at the top surface of the carpet rather than looped back into the backing. The cut construction results in tufts of yarn that stand up. Fibers can be cut all at the same level to produce a flat, non-textured surface, or they can be cut at various heights to produce a textured finish. Quality carpets use tufts that are constructed from two or three plies of yarn that are tightly twisted together and heat-treated to prevent unraveling. The tighter and denser the tufts, the better the performance of the carpet. In general, cut piles are not as durable as looped piles.
In loop pile construction, individual strands of yarn are looped through the backing. Loops can be set all at the same level or set at different levels to create patterns. When the loops are subjected to pressure, they flex then return to their previous position. This rebounding ability makes them well-suited for use in high-traffic areas.
Carpets with short, tightly packed loops are effective dirt-blockers, giving them good performance in areas with high traffic levels. Loosely packed loops are better used in areas with only moderate traffic. Carpet made with multilevel loops works well to hide traffic patterns.
Backing materials also help determine the performance of carpet by providing strength and stability. Nearly 90 percent of commercial carpet is tufted. In tufted carpet construction, the yarn is stitched through a backing fabric and locked in place with a latex coating. To provide additional strength, additional backing materials, such as polypropylene and jute, are added.
Both polypropylene and jute are strong, resilient and durable. Polypropylene offers better mildew resistance, making it better suited for applications in damp or high humidity applications.
Backings are available with a moisture barrier designed to keep fluid spills from seeping through and causing damage to the sub-floor or creating conditions that would support the growth of mildew. Moisture barrier backings are best suited for applications where the potential exists for frequent spills, such as eating areas.
Some manufacturers use a foam backing instead. While the foam backing is not as strong as polypropylene or jute, it allows the carpet to be glued directly to the flooring material without the use of an underpad.
Quality can vary widely between different carpets even though they use the same fibers, construction techniques and backing materials. For example, the number of yarn tufts installed in one row of one inch of carpet, known as the stitches per inch, will vary with the quality of the carpet. In general, the higher the number of stitches per inch, the higher the quality and the greater the durability of the carpet.
Other Measures of Quality
Another measure of quality is the yarn count, the amount of yarn needed to fill a given length of carpet. The higher the yarn count, the finer the yarn used in the construction of the carpet.
Face weight, expressed in ounces per square yard, measures the yarn’s face fiber. For high quality carpet, face weight is typically 32 ounces per square yard or higher.
A carpet’s density is a measure of the weight of the pile yarn corrected for the height of the yarn. A carpet with a low density number risks “uglying out” before it actually wears out. For most commercial applications, a carpet density of 4,000 to 7,000 is considered suitable, with high traffic areas requiring densities of 5,000 or more.
Carpet is no longer considered primarily a decorative material to be selected solely on it appearance. Carpet is a building material, whose quality and construction will impact is performance and its life-cycle costs.
When selecting carpet for a particular application, it is essential to consider the level of wear that the carpet will be exposed to, the construction of the carpet, the level of luxury desired, and the available budget. It’s crucial to balance all of the elements to find the most suitable carpet for the application.
James Piper, PhD, PE, is a writer and consultant who has more than 25 years of experience in facilities management. He is a contributing editor for Building Operating Management.