Carpet Backing and Coating

The backing of a carpet can often be overlooked and yet it is one of the most important factors of the carpet's construction. A carpet's primary backing is the depository of the face yarn. Both the primary and secondary back provide dimensional stability. A carpet with poor dimensional stability will tend to shrink and pull away from the walls, or will stretch resulting in ripples on both glue down and stretch in installations. A carpet's backing additionally plays a very important role in how well a carpet will seam.

Which way does the fuzzy side go?

Most everyone in the carpet business is familiar with the saying "fuzzy side up." That fuzzy side is the "face" of the carpet. The "back" is that other side, and it can be made from a variety of fabrics, yarn, natural or synthetic materials. A carpet may have only a primary back, which is the fabric that the fuzzy material is tufted, woven or bonded into. A tufted carpet with a single back is referred to as a "single" or "unitary" back carpet. A "conventional tufted carpet" is one with both a primary and secondary back with some type of scrim or attached cushion that is laminated to it.

Back, Woven & Knitted Carpet:

The most common backing materials are jute, kraftcord, linen, polyester, olefin (polypropylene), rayon, cotton and combinations of these materials. These materials are the "construction yarns" comprising chain warp, stuffer warp, and shot or fill which are interwoven with the face yarn during the manufacturing of the carpet.

Primary Back Tufted Carpet

Primary backing materials are manufactured as both woven and non-woven fabrics in which the pile yarn is inserted by tufting, needle punching, stitching, embedding or bonding. Primary back is the carrier fabric for the pile yarn and should not be confused with secondary backing which is a reinforcing fabric laminated to the back of tufted carpet subsequent to the tufting process. Some synthetic primary backings have nylon fiber attached to their upper surfaces to make them union dyeable with nylon pile yarns.

Secondary Back "Fabric" Tufted Carpet

Usually woven jute, or woven or non-woven olefin (polypropylene). The fabric is laminated to the back of carpet (usually with latex adhesive) to reinforce and increase dimensional stability, strength, stretch resistance, stiffness, and hand. Because secondary backing is visible, whereas primary backing is concealed under the pile yarn in finished carpet, dealers and installers often refer to secondary backing simply as "backing."

Backing Fabrics

Both woven and non-woven primary and secondary backing is made for tufted carpet. It is primarily polypropylene, but some jute and other materials are used. It is important to remember that woven backing is not the same as woven carpet. Woven polypropylene backing presently accounts for 95% of the secondary market and 90% of the primary market. As of 1996 the secondary market was shared by Amoco and Synthetic Industries with additional companies sharing part of the primary production. Amoco is the world's largest backing supplier with their woven polypropylene primary backing representing more than 50% of the North American primary backing and their ActionBac representing more than 50% of the secondary backing market. Polypropylene backing can now be made from recycled polypropylene and these are expected to be a player in the near future. Spunbonded backings are made in both polyester and polypropylene. They are primarily used in the automotive industry as moldability and dimensional stability are very important. They also represent about 80% of the carpet tile and six-foot roll market. Some spunbonded is used for lower price printed loops as they create less needle deflection than woven backing. Secondary Back Attached Cushion This cushion is laminated to the primary back. The most common cushions are polyurethane foam, high-density foam, sponge rubber, woven fiber, latex with an embossed pattern, solid vinyl and foam-type vinyl. Unitary Backing. A single fabric backing with high rubber content latex or hot-melt resin compound laminated to the bottom side. A unitary backing system is used to increase dimensional stability, tuft bind of the individual fibers, minimize edge ravel at seams and snagging of rows on looped pile construction.

Secondary Back "Coating" Tufted Carpet

Synthetic foam, synthetic latex or other polymers. The most common coatings are rubber latex, hot melt compounds and PVC back coating. A backing with a coating of latex or other polymer only is commonly referred to as a unitary back. A backing system is composed of one or more components. Below a number of those systems are discussed: EVA copolymers (ethylene vinyl acetate) hot melt An inert material consisting of an EVA resin and limestone filler. EVA has superior tuft bind and edge-ravel resistance. Polyurethane Introduced in the late 70's they represented less than 4% of the backings market in 1996. Due to the desire for increased carpet performance they are expected to increase their market share. Unlike latex, these products will maintain their integrity in the presence of water and moisture. PVC, hard-backed or closed-cell is most commonly used in carpet tile or 6' wide goods, due to its weight and stiffness. PVC gives a stiff, stable backing with little cushioning but excellent tuft bind and overall dimensional stability. Closed cell vinyl adds a cushion effect.

SBR Latex

A water emulsion of synthetic rubber, natural rubber, or other polymer. In carpet, latex is used for laminating secondary backings to tufted carpet, backcoating carpet and rugs, and for backcoating woven carpet and rugs. Almost all carpet latex consists of styrene-butadiene synthetic rubber SBR latex compounded with large quantities of powdered filler. The latter is most often whiting, which is calcium carbonate. SBR is easily degraded by adding too much filler and this increases the loss of tuft bind and flexibility, and leads to delamination problems and degradation from water.

Backing and Coating

Urethane is an organic compound, more expensive than SBR latex based backing systems. While more expensive it is impossible to add too much filler so the product has its own built in censor. Urethane is also hydrophobic (dislikes water) so water will not degrade it which is a benefit for environments where things get spilled on a regular basis or where the carpet needs to be wet cleaned regularly. From an environmental standpoint, 4PCH, which is used in latex, is not used in the urethane products. Urethane is applied by the carpet mill in the finishing process. In the heat curing chamber it reacts by bubbling and creates a foam-like texture. This backing encapsulates yarn bases for extra tuft bind and provides an attached cushion.

Polypropylene versus Jute

Both polypropylene and jute have characteristics that are beneficial as a carpet back. Below are a few that you may like to be familiar with:

Polypropylene

• Will not shrink
• Does not hold moisture
• Resistant to mildew, insects, bacteria and rot
• Non allergen
• Odor free
• Does not cause browning
• Strong
• Light weight reducing shipping cost
• Can be used indoor or out .

Jute

• Does not harden in cold temperature

• Easier for the installer to work with

• Less frequent stretching problems

• Good seaming characteristics

• Dyeable

• Absorbent, which gives it good hold on a direct glue down

• Jute is bulky which adds hand and cushioning

Some of the Branded Backing Products and Systems

The information provided for the following products was taken from marketing literature. Amoco Fabrics and Fibers is a polypropylene product. With this product a powdered polypro binder attached to the secondary backing joins the primary and secondary backings through a combination of heat and pressure. As a latex free system it is said to improve indoor air quality during installation and to make for a lighter weight carpet.

Action Bac

The trademark owned by Patchogue Plymouth Division of Amoco Fabrics Company for a leno weave of slit-film and spun polypropylene yarns that form a stretchable, all-synthetic secondary backing fabric. A totally synthetic (woven polypropylene) secondary backing which offers resistance to mold and mildew, flexibility for both stretch-in and direct glue down installations, and the ability to readily absorb and firmly retain adhesive. Atlantis by Arco is an in-house urethane finishing system, and it is expected that more manufacturers will use it in the future. The finishing system requires a space only 20 by 30 feet and cost about the same as a high speed tufting machine. Colback is produced by Akzo Nobel and was previously licensed to BSF. It is a nonwoven composed of a bicomponent fiber with a polyester core and a polyamide (nylon) skin. The dyeable nylon sheath prevents "grinning". The product has excellent dimensional stability, keeping the pattern straighter than a woven backing, a characteristic which is important for patterned commercial carpet. Endure J&J's proprietary attached cushion backing which offers improved appearance retention, excellent acoustical benefits, additional thermal insulation, and superior comfort underfoot. It protects carpet from delamination, edge ravel, and moisture; provides installation flexibility; resists fuzzing and pilling; minimizes restretching; is easy to repair if damaged; and can eliminate carpet removal problems. 

Enhancer

A complete family of commercial carpet backing options from Dow Chemical's VERSABACS Carpet Backing System. The Enhancer backing reduces pilling, fuzzing, and edge ravel. It offers greater dimensional stability and will not delaminate, wrinkle or buckle. Enhancer also prolongs the life of carpet and resists moisture. Antimicrobrial and Antistat treatments can be added for hospitals and computer rooms. ER3 by Collins & Aikman Floorcoverings is a vinyl backing for its Powerbond modular tiles. It is a nylon reinforced, polymeric backing system that's made with 75% recycled content.

Everbond

Philadelphia's own permanent tuftlock unitary backing Flex-Back A resilient quality backing from Shaw which resists crumbling,

deterioration, moisture, and fuzzing. Flex-Back's innovative surface allows easy installation with a variety of adhesives. This backing cushions face fiber for added wearability, along with thermal and acoustical insulation.

Kraftcord

A tightly twisted yarn made from plant fiber or synthetics used as backing yarn in carpet weaving or as the filler on upholstery beading. Needletuft by General Fiber & Fabrics is used with needlepunched products. Performance Plus by Textile Rubber is a polyurethane laminated backing finishing system that can be applied in house with the conversion of existing equipment. It serves as a moisture-proof binder between the primary and secondary backings and can be used with woven and nonwoven secondary backing. Prima-Weave by Wayn-Tex is a primary backing that is designed for enhanced wrinkle resistance through coaters, dye units and dryers.

StatiBac

J&J's proprietary backing system engineered for control of BSD (electrostatic discharge) in computer rooms and electronic offices. Dissipates tracked-in static to a safe level in less than 3 seconds. Supertuft by General Fiber and Fabrics is a primary backing for tufted carpets.

ThermalLock

J&J's proprietary backing system utilizes thermoplastic technology to chemically bond the secondary backing to the carpet face. It carries a lifetime warranty when installed using J&J guidelines. Provides outstanding protection against delamination, excellent resistance to edge ravel and zippering, and 20 Ib. tuft bind. Resists damage from water, contains no PVC or plasticizers, meets or exceeds all flammability requirements, and will not deteriorate with age.

Tufloc

J&J's proprietary unitary backing engineered expressly to provide high tuft bind in direct glue-down installations. An increased

concentration of premium latex protects carpet from delamination and edge ravel and maximizes yarn tuft encapsulation for increased tuft bind to prevent fuzzing and pilling.

Typar

Registered DuPont trademark for backing material made of carded, spun polypropylene fibers that are fused together to create the fabric. This product is primarily used in lower weight printed loop carpet, indoor and outdoor mats, and loose rugs.

Ultrabac

A dense weave white synthetic secondary latex compound that results in a better quality backing system. Ultrabac virtually eliminates delamination problems and helps prevent seam ravel.  Ultra-Graphics by Wayn-Tex is a backing made for high-end commercial and residential graphics styles.

Unibond

A hot-melt resin process that adheres the primary and secondary backing of Lees Commercial Carpet.

U reflex

An exclusive backing system for carpet modules, created by Philadelphia to be the safest, most stable and reliable backing ever made.

Definitions

Backcoat: Adhesive applied to the back side of woven goods. The backcoat serves to add strength and stability to the weave, while increasing its stiffness ("hand," or feel).

Backcoating: The application of latex adhesive to the back of a carpet to anchor the tufts, usually followed immediately by addition of a secondary backing material such as woven jute, woven or nonwoven polypropylene.

Cushion-backed carpet: Carpet having a cushion or padding as an integral part of its backing, such as high density foam or sponge-back carpet.

Filling Yam: In weaving, any yarn running across the width of the fabric perpendicular to the warp yarns. In woven carpet, filling yarns are part of the group of construction yarns which also include chain and stuffer warp and form the backing. Woven carpet fill and chain warp yarns interlace to secure the pile yarns. Filling and other construction yarns usually are fibrillated polypropylene, jute, kraftcord, or similar materials.

Film Yam: Yarn produced by slitting extruded films into narrow strips. Slit film polypropylene yarns are woven into fabrics used as primary backings in tufted carpets. (See slit film).

Foamback: Term used to denote that a fabric has been laminated to a backing of polyurethane foam.

High Density Foam: Applied as a liquid foam, then cured, to form an integral part of the carpet back; made from compounded natural and/or synthetic latex foam having a minimum density of 17 pounds per cubic foot and a minimum weight of 38 to 45 ounces per square yard.

Jute: For many years, the primary secondary-backing material for tufted carpets. Today jute represents a very small percentage of the market.

Jute grows mainly in Bangladesh, India and Pakistan. It is yellowish-brown in color, is coarse and harsh, with good resistance to

microorganisms and insects. The fiber has moderate dry strength but low wet strength. It has good abrasion resistance.

Latex: A water emulsion of synthetic rubber, natural rubber, or other polymer. In carpet, latex is used for laminating secondary backings to tufted carpet, backcoating carpet and rugs, and for manufacturing foamed cushion. Almost all carpet latex consists of styrene butadiene synthetic rubber (SBR) compounded with large quantities of powdered fillers. The latter are most often whiting, which is calcium carbonate. Latex is the raw material from which rubber is made.

Leno Weave: In a leno weave polypropylene secondary backing the slit-film filaments run lengthwise. A woven fabric construction in which paired warp yarns twist around one another between fill yarn picks. It is similar to woven gauze bandage construction. Leno construction renders the yarns relatively immobile within the fabric, making possible very open weaves which are relatively stable. Woven polypropylene secondary backings for tufted carpets are generally of leno weave construction.

Non-woven: An assembly of textile fibers held together by mechanical interlocking in a random web or mat, by fusing of the fiber (in the case of thermoplastic fibers), or by bonding with a cementing medium such as starch, glue casein, rubber, latex, or one of the cellulose derivatives, or synthetic resins. Initially, the fibers may be oriented in one direction or may be deposited in a random manner. This web or sheet of fibers is bonded together by one of the methods described above. Normally, crimped fiber that range in length from 0.75 to 4.5 inches are used. Non-woven refers to any fabric manufactured by a method other than weaving but particularly those fabrics composed of fibers held together by chemical, mechanical, adhesive, or fusion means. In popular usage knitted fabrics are not considered to be non-wovens.

Scrim Back: A secondary back made of light, coarse fabric, cemented to the primary back in tufted construction. If a cushion has one side covered with a scrim fabric, this fabric should be installed face up.

Shrinkage: The widthwise or lengthwise contraction of fiber, yarn or fabric of carpets and rugs after shampooing or washing, redrying or exposure to elevated temperature. It is caused by the swelling of the woven yarns. Shrinkage occurs in carpet backing. Although the increased use of manmade fibers reduces the possibility of shrinkage, extreme caution should be exercised to prevent over-wetting during cleaning.

Slit-Film Yam: Yarn of a flat, tape-like character produced by slitting an extruded film.

Stutters: Extra yarn running in the warp direction through a woven fabric to increase the fabric's strength and weight.

Stutter Yams: Extra yarns, usually jute, running lengthwise through the back of woven carpet, to increase bulk, weight, and thickness of the fabric.

Warp: A weaving term for yarns in woven fabrics and carpets which run lengthwise. Warp yarns are usually delivered to the loom from a beam, a large spool with hundreds of ends wound on it, mounted behind the loom. Woven carpets usually have three sets of warp yarns, which may be wound on three loom beams. These include stuffer warp for lengthwise strength and stiffness, pile warp which forms the carpet surface tufts, and chain warp which interlaces with fill yarn to lock the structure together. On woven polypropylene backing the warp is the thin, shiny, chain-like yarn.

Weft or Woof: The foundation threads of a rug, strung across the width of the loom. After each row of knots is tied, these threads are passed through alternate warp threads. They secure the knots in place and form part of the rug's sides. On woven polypropylene backing the weft is the broad, round wire.

Common Backing Problems

Back of the Carpet is Very Soft Can be due to application of low levels of latex compound during manufacturing.

Back of the Carpet is Very Stiff Can be due to application of excessive levels of latex compound during manufacturing.

Latex on Nap - This is the result of the selvedge edge folding over onto the carpet's face or a hole in the carpet that allows the latex to touch a face roller on the coater.

Mill Soil, Dirty Back Carpet came in contact with dirt or grime. Carpet can normally be installed as is but can sometimes be cleaned. A dirty back is an appearance blemish but will not effect the carpet's performance.

Mill Seam, Secondary This occurs when two rolls of secondary back are seamed together to ensure a continuous run during the latex operation.

Mill Seam, Primary Back - This occurs when two rolls of primary backing have been sewn together to facilitate the continuation of the tufting operation.  This condition will be seen as a widthwise band or void and will look similar to missing tufts or shear bands.

Narrow Selvedge - The carpet was not hooked properly on the tenter pins of the dryer, which caused the unpinned selvedge to be narrower.

Narrow Width Carpet - The carpet is narrower than 12', 13' - 6", 15', etc. The manufacturing tolerance is minus 1%, which equals 11' 10 1/2" for a 12' carpet. If less than the minus 1% it is considered a narrow width.

Pan Streaks (Coating) - A build up in the pans of latex interfered with the proper latex application, resulting in too little or too much latex being applied. 

Small Lumps of Excessive Latex on the Primary Back and Hidden by the Nap This is a coating defect that occurred during application of the backing.

Wrinkled Back (Tufting) - A bad needle on the tufting machine that cuts or damages the primary back. Also rollers out of adjustment can put more tension in one area than another creating shrinkage differences.•

Wrinkled Primary Back (Finishing) - The primary back is wrinkled and the secondary back is smooth. This occurs when the carpet is creased prior to latex application and was not pulled out properly on the tenter during application.

Wrinkled Secondary Back with Flat Primary Back (Finishing)- The wrinkled secondary back was not pulled out properly on the tenter during application.

Wrinkled Primary and Secondary Back - (Final Inspection) (Shipping) The primary and secondary back are properly laminated.  This condition generally occurs while being rolled up during the final inspection or in the case of cut orders at the cut order table.

Dimensional Changes In Synthetic Carpet Backing - When carpet backings were of natural fibers such as jute and cotton, shrinkage from oven/vetting occurred. With synthetic backings we have a different set of circumstances.

Expansion and Contraction - Delamination from expansion and contraction can be a problem in a warm humid climate where air conditioning is raised and lowered nights and weekends. This can effect both carpet over pad and glue down installations.

Air Conditioning - When a carpet is buckled, turning on the air conditioner will normally make the ripples disappear.

Overwetting - Overwetting during cleaning can make a carpet ripple.

Cleaning - Some carpets will ripple during regular cleaning (not over wetting) and flatten out when it dries.

STATEMENT ON LATEX ALLERGIES 1. AND SB LATEX USED IN CARPETS

Many consumers are confused by news reports on allergic reactions to "latex." The allergic reactions are usually stimulated by contact with natural latex (for example, the material used in some medical gloves and condoms). SB latex is different from natural latex and does not cause allergic reactions. "Latex" is a generic term used to describe both natural and synthetic latex, although they have very different properties: ft' Natural latex is produced from the rubber tree Hevea brasilienenesis found in ' 'Africa and Southeast Asia. The latex sap contains a mixture of more than two hundred natural proteins that constitute about 1 % of the sap. It appears that some of these proteins can sensitize some individuals over time and may lead to an allergic reaction. Synthetic SB latex is a water emulsion manufactured by polymerization in chemical plants. Unlike natural latex, synthetic latex is manufactured from high-purity chemicals and does not come from trees like natural latex. It contains no proteins. Allergy to natural rubber proteins should not be called "latex allergy" but rather "natural latex allergy" so as not to implicate the numerous products that contain only synthetic latex. SB latex used to back carpets, and other latex materials used in paints, are examples of products that have been incorrectly associated with natural latex allergies. Synthetic latex products have not been shown to pose any hazards to natural latex-sensitive individuals. > , For additional information on SB latex, contact: Robert J. Fensterheim Executive Director, SBLC Members of the SB Latex Council include BASF Corporation, The Dow Chemical Company, GenCorp Specialty Polymers Division, Goodyear Tire and Rubber Company, Ameripol Synpol/Mallard Creek Polymers Division, and Reichhold Chemicals, Inc. 3/97 SB Latex Council 1350 Eye Street, N.W. • Suite 200 • Washington, DC 20005 202-962-9400 • fax: 202-289-3565

USE OF SB LATEX IN CARPETS

SB latex (synthetic) has been used in carpet for more than four decades. Over ninety percent of all carpet manufactured in the United States uses SB latex as a bonding agent to hold yarn and backings together. SB latex should not be confused with natural latex, which is chemically different and has been associated with allergic reactions. New carpet sometimes has a distinctive odor. This "new carpet" odor is from a chemical identified as 4-phenylcyclohexene (4-PC or 4-PCH), a trace by-product of the SB latex manufacturing process. The small amount of 4-PCH dissipates with adequate fresh air ventilation, but is noticeable because its odor is detectable at extremely low levels, as low as one part per billion. Laboratory research studies, including standard toxicology studies and specific testing for skin sensitization and respiratory irritation, were conducted by the SB Latex Council (SBLC) to determine any possible health effects from 4-PCH. No evidence indicating potential humanhealth effects from 4-PCH emissions was found. The results were made available to both the Environmental Protection Agency (EPA) and the Consumer Product Safety Commission (CPSC) as part of their reviews of indoor air quality issues. The findings from both agencies support those from the SBLC: there is no evidence that emissions from SB latex, at the extremely low levels found in carpet installations, represent a human health hazard. Carpet tested through the Carpet and Rug Institute's Indoor Air Quality Testing Program must meet a maximum allowable 4-PCH emissions level of 0.05 mg/m2/hr. The CRI label shows that the product meets this emission level. Although extensive health effects studies have not shown 4-PCH emissions to be harmful, some people may find the odor unpleasant. In response to this concern, SB latex manufacturers have voluntarily developed and implemented improvements to the SB latex manufacturing process that have reduced 4-PCH emissions from their product by more than 60% since 1989. The SBLC continues to work cooperatively with government agencies and the carpet industry to use sound scientific information to determine the safety of its products, to prevent and/or reduce emissions, and to address consumer questions. For additional information on SB latex, contact: Robert J. Fensterheim Executive Director, SBLC Members of the SB Latex Council include BASF Corporation, The Dow Chemical Company, GenCorp Specialty Polymers Division, Goodyear Tire and Rubber Company, Ameripol Synpol/Mallard Creek Polymers Division, and Reichhold Chemicals, Inc

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ALERGIES

Latex Allergies, VOC Limits and Floor Prep by Ken Knudtzon have participated in many forums , conventions, meetings and other floor covering industry events. At a recent meeting, one of the topics related to a segment pertaining to latex allergies that had appeared on 20/20, and ABC network TV show. The main topic was latex gloves but the reporter also made reference to carpet backings.

The SB Latex Council (SBLC) said that many consumers may be confused by news reports on allergic reactions to "latex." These reactions are usually stimulated by contact with natural latex, not the SB latex used in the coatings on carpet backs or floor covering adhesives. "Latex" is a generic term used to describe both natura l and synthetic latex, although they each have different properties:

• Natural Latex is produced from the rubber tree Havea Brasilienensis found in Africa and South-east Asia. The latex sap contains a mixture of more than 200 natural proteins that constitute about 1% of the sap. It appears that many of these proteins can sensitize some individuals over time, and may lead to an allergic reaction.

• Synthetic SB Latex is a water emulsion manufactured by polymerization in chemical plants. Unlike natural latex, synthetic latex is manufactured from high-purity chemicals, does not come from trees like natural latex, and contains no proteins.

The SBLC went on to say that allergy to natural rubber proteins should not be called "latex allergies," but rather "natural latex allergies," so as not to implicate numerous products that contain only synthetic latex. SB latex used in carpet backings, and other synthetic latex materials found in adhesives or paints, are examples of products that have been incorrectly associated with natural latex allergies. Synthetic latex products have not been known to pose any hazards to natural latex-sensitive individuals.

Another item worth noting is a new proposal for volatile organic compound (VOC) limits for adhesives and sealants used in commercial and manufacturing processes in California. Today, two types of floor covering adhesives are being manufactured: traditional and low VOC. Emissions from "traditional" adhesives are the result of solvents evaporating during spreading, transfer, drying, surface preparation and cleanup operations. Some adhesive products are formulated with "exempt" solvents that are not treated as VOCs under the California calculated method of VOC determination. The proposed limits for floor covering adhesives (effective Jan. 1, 1998) are: Ceramic Tile 130 g/ 1, Cove Base 150 g/L, Indoor Floor Covering Installation 150 g/1, and Outdoor Floor Covering 250 g/1. Emissions from low-VOC adhesives are determined by subjecting an adhesive to a test in a small scale environmental chamber. The Floor Covering Adhesive Manufacturer Committee of the National Association of Floor Covering Distributors (NAFCD) developed a test that exempts no ingredients to measure traditional voc emissions. In order to meet the low-VOC designation, a multipurpose carpet adhesive or modular carpet adhesive must achieve a 48 hour emission integral of 2,000 rng/m2. All low-VOC adhesives tested to date would achieve a calculated rate of 30 g/1 or less. Thus, if a California installation contractor is unsure whether the roduct he/she is buying meets the California limit he should use a product designated as "low-voc."

One of the major other installation problems cited at these meetings is floor preparation. The big complaint is the condition of the subtloor when the installation contractor arrives to install carpet or resilient. New concrete must be cured (90 to 120 days), clean, dry and smooth. It must be free of curing compounds, hardeners, sealers and breakers, or parting compounds that make adhesives prone to slab bonding failures. If any of the above has been used, it must be completely removed by scarifying, sanding, shot blasting or grinding prior to the application of patch, underlayment or adhesives. Cracks, holes, footprints, wheel impressions or score marks should be filled with patch or underlayment to assure a smooth surface. Location of expansion or isolation joints must be specified by the architect and they should have an elastomeric filler in them. Patch or underlayment should never be used to smooth them over, as they will crack or buckle when the slab moves and telegraph thru the floor covering. Crack isolation materials and expansion joint covers are available for use with various floor coverings and should also be specified by the architect. Old concrete must be clean, dry, and free of paint, dirt, oils and any other contaminants. The floor covering contractor should not proceed with the carpet or resilient installation unless he/she has written assurance from the owner or general contractor that moisture and alkali tests have been conducted and the floor is suitable for the installation of floor coverings. As a general guideline, an emission rate of 3 Ibs. or less is acceptable for most carpet. A pH range of 5-9 is considered satisfactory for alkalinity. If any of the above conditions apply to a job you will be working on, and the owner or general contractor or architect says "go ahead" or "don't worry about things like that — the client is moving in on Monday," get it in writing or you could (and probably will) be charged with the failure of the installation. *

AIR EMISSIONS FROM CARPET MANUFACTURING PROCESSES

James A. Mulholland, Melanie C. Pitrolo, Ravindra Bissram, and Srikanth Patury

Environmental Engineering, Georgia Institute of Technology

200 Bobby Dodd Way

Atlanta GA 30332-0512

james.mulholland@ce.gatech.edu

Charlene W. Bayer and Robert J. Hendry

Georgia Tech Research Institute

To better characterize stack emissions from carpet manufacturing processes, volatile organic compound (VOC) emissions were measured and hazardous air pollutants (HAPs) were identified for four processes: suessen heatsetting, beck dyeing, continuous dyeing, and latex coating. The study included field and laboratory investigations performed during the 1996-99 time period.  In nylon 6 fiber heatsetting, caprolactam is the major VOC emitted, released at a rate of 400 mg per pound of fiber. For nylon 66 fiber heatsetting, on the other hand, VOC emissions are predominantly long-chain acids and esters found in yarn spinning lubricant. Total VOC emissions ranged from 240 to 600 mg per pound of fiber processed. Total VOC emissions from beck dyeing ranged from 500 to 1000 mg/yd2 carpet; for continuous dyeing, the VOC emission estimate ranged from 100 to 200 mg/yd2 carpet. VOC emissions included long-chain hydrocarbons at plants using powder dyes, and glycol ethers and other oxygenated compounds at plants using liquid dyes. Alkyl benzenes from stainblock application were also observed.  Laboratory results demonstrate that water-soluble VOCs partition between gas and water effluents. Pure hydrocarbon auxiliary compounds present in the dye applications, on the other hand, were entirely released to the stack gas. VOC emission factors for styrene-butadiene latex coating were estimated to range from 150 to 280 mg/yd2. Laboratory simulation results were in close agreement with the field measurements.  In total, it is estimated that 1-2 g of VOCs are released to the air in the manufacture of one square yard of nylon carpet.

Introduction

Emission source inventories of volatile organic compounds (VOCs) are inadequate in part due to incomplete characterization of a large number of minor sources. The need to better characterize air emissions from carpet manufacturing processes was identified as a research priority by the Consortium on Competitiveness for the Apparel, Carpet, and Textile Industries (CCACTI), a Georgia traditional industries program.1 In July 1996, a three-year project was undertaken to estimate emissions of VOCs and hazardous air pollutants (HAPs) at carpet manufacturing plants. Carpet manufacturing processes that can result in significant air emissions are yarn heatsetting, carpet dyeing, and carpet backing.  Nylon and polyester yarns are prepared in a spinning mill. Staple fibers, which are unaligned, and continuous filament fibers are received with residual lubricant from the fiber manufacturer. More lubricant is added at the spinning plant (“overspray”), particularly to staple fiber. Fibers are drawn out to increase fiber alignment and twisted to form a yarn. The resulting plyed yarns are coarse and thick. Yarns are heatset to stabilize shrinkage which may occur in subsequent thermal processing. Heatsetting typically occurs in an autoclave or superba at elevated temperature and pressure, or in a suessen at higher temperature and atmospheric pressure. After heatsetting, the yarn is attached to a primary backing material (tufting process). Both batch and continuous methods are used to dye carpet. In the batch process, carpet is immersed in dye solution contained in large, enclosed dye becks for about one hour. Batch, or beck, dyeing is followed by carpet rinsing and drying. In the continuous dyeing process, dye is typically sprayed on carpet as it passes through a dye range. The dye is then steam set, rinsed to remove any excess dyes and chemicals, and dried in a gas-fired oven. Anti-soil and anti-staining agents may be applied.

In the final carpet manufacturing step, a foam or woven secondary backing is applied to the carpet. This backing is applied by coating the surface of the primary backing with latex adhesive. The two backings are rolled together to form a tight bond, and the adhesive is cured in a gas-fired oven. The carpet is then ready for distribution to stores and consumers.  Potential stack emissions associated with these carpet manufacturing processes that may be of concern include the following. The high heatset temperatures may result in the release of volatile components of yarn finishing as well as from the yarn itself. Auxiliary chemicals used in dyeing, including oxygenated VOCs and HAPs, may be emitted. In the secondary backing application, free latex constituents, such as styrene and butadiene, may be released. Although much is known about water and solid effluents from carpet manufacturing, little is known about air emissions. Indoor air quality and its impacts on both textile workers within the carpet mills and on end-use consumers have been assessed in numerous studies. While stack emission tests have been performed to address specific concerns, such as caprolactam from nylon 6 heatsetting2 and water soluble VOCs from carpet dyeing,3 these test results are not widely available.  Moreover, comprehensive emissions testing for the carpet industry has not been performed.  The overall goal of this work was to gain a better understanding of air emissions from carpet manufacturing processes through field measurement and laboratory simulation. This collaborative effort involved three industry partners. Field studies were performed at eight plants: two suessen heatsetting plants, two beck dye plants, two continuous dye plants, and two latex coating plants. Laboratory studies were also performed to assess emission of any VOCs that could not be measured in the field due to limitations in sample collection methods, as well as to assess effects of temperature and alternative applications on air emissions.

Analytical Methods

Field tests were performed over two-week periods during April of 1997 (two continuous dye plants and two latex coating plants) and April of 1998 (two suessen heatsetting plants and two beck dye plants). Stack measurements were conducted during normal operation of the process lines; stacks were assumed to operate with constant volume flows. Particularly challenging aspects of the field assessment were the large number of stacks and high moisture content of the stack gas. Access holes were drilled on a straight section of the exhaust stack to minimize disturbances from rain-caps, fan blades, and elbows. Dry and wet-bulb temperatures, relative humidity and velocity were measured with a TSI VelociCalc Plus Meter, Model 8388. At least three locations within each exhaust flow were checked to ensure that even temperature distributions existed. Volume flow rates were determined for each stack by conducting velocity measurements across the traverse plane of the stack. The error in mass flow measurement is estimated to be within 5% of the calculated value for stacks allowing good access for a full traverse flow.  Various methods were used for stack gas collection and analysis, as summarized in Table 1. Non-polar and slightly polar VOCs were trapped on Tenax-GR® and analyzed by gas chromatography with mass spectroscopy (GC/MS). Artifacts associated with these samples were identified.4 For stacks with very high moisture content gas, water impinger samples were taken and VOCs were extracted by solid-phase microextraction (SPME) fibers and analyzed by GC/MS. Aldehydes and ketones were collected in dinitrophenyl hydrazine (DNPH), either coated on extraction tubes or contained in impinger bottles, and analyzed by liquid chromatography with UV detection (LC/UV). Silica gel tubes were used to collect ammonia from latex coating plant stacks, with analysis by ion chromatography with conductivity detector (IC/CD).  

Prior to field testing, samples of chemical applications were analyzed to target potential VOC emissions. These results were also useful in relating the field emissions that were observed to particular chemical applications. After field testing, simple laboratory tests were developed to simulate the time-temperature environment of the carpet during processing. These tests allowed for the assessment of any VOC emissions that could not be measured in the field due to limitations in sample collection methods, as well as the assessment of effects of temperature and alternative applications on air emissions.

Results and Discussion

Air emission factors (mass emission per production unit) for VOCs and HAPs were estimated for four processes: suessen heatsetting, beck dyeing, continuous dyeing, and latex coating. Results, summarized in Table 2, were obtained by studying two plants as follows. First, site visits were conducted to identify process conditions and to collect material and chemical application samples. Second, laboratory analyses of process chemicals were performed to identify potential air emissions. Third, field measurements of stack flow rates and VOC concentrations were taken to determine air emissions. Fourth, laboratory simulation tests were performed to assess effects of process conditions and applications on gas emissions. Emission factors and maximum production capacity were then used in potential-to-emit calculations for the eight plants studied. In total, it is estimated that 1-2 g of VOCs are released to the air in the manufacture of one square yard of nylon carpet. For the maximum production capacity at the plants studied, this translates to an annual VOC emission of 50 to 100 tons. Select results for each process are highlighted in the subsections that follow.

Yarn Heatsetting

Raw staple fiber is delivered to the plant in 550 lb bales; continuous filament fiber is delivered on spools. Approximately 4 gallons of lubricant is added to each 550 lb bale of staple fiber. Tints may be added to differentiate yarn types. Spinning involves the repeated drawing out of fiber along rotating rollers. Heatsetting reintroduces texture to the yarn. In suessen heatsetting, the yarn is exposed to saturated steam at 200°C for 1 minute. The nominal yarn processing rate is 325 lb/hr. Stock lubricants obtained from each plant contained up to 0.8% (wt) VOCs. Major species included diethylene glycol and long-chain esters (most notably butyl hexadecanoate and butyl stearate), acids and alkanes.  Nylon 6 and 66 yarn heatsetting resulted in very different VOC emissions, as evidenced by the GC/MS chromatograms of Tenax samples from suessen stacks shown in Figures 1 and 2.  The major species emitted from nylon 6 processing was caprolactam (peak 9). The release of caprolactam may result from unpolymerized nylon 6 precursor or reaction during heatsetting.5  Laboratory experiments with four different types of nylon 6 fiber resulted in caprolactam emission rates ranging from 0.6 to 1% (wt), with an average of 400 mg per pound of nylon 6 fiber processed. In contrast, major species emitted from nylon 66 processing were spinning lubricant constituents, particularly butyl hexadecanoate (peak 16) and butyl stearate (peak 22).  Over 80% of spinning lubricant VOCs appears to be released. Nylon 66 thermal decomposition products were not observed.6

Carpet Dyeing

The beck dye plants studied used stainless steel, atmospheric dye tanks, with a liquor-to-carpet weight ratio of 25:1. Nominally, there is a 30 minute warm-up period, 30 to 60 minute boil period, and 30 minute cool-down period. After batch dyeing, the carpet is dried in a continuous process. Stainblock may be applied, containing alkyl benzene compounds.  Samples of stock dyeing solutions were obtained prior to field testing. Both powder and liquid dyes are used. The major species detected in the powder dye solution were numerous long-chain hydrocarbons (12-20 carbon length). In contrast, dyebath containing liquid dyes contained oxygenated organics, including butyl hexadecanoate and butyl stearate. The total VOC content of the dyebaths ranged from 0.1% to 0.5% (wt).   In the field study, beck stacks were sampled four to six times during a cycle to allow for an integrated emission assessment. Major VOC emissions detected were C14 – C20 alkanes from becks using powder dyes and oxygenated VOCs from becks using liquid dyes. These results were consistent with laboratory simulation results. The laboratory and experimental results suggest that nearly all of the non-polar VOCs in the dyebath solution are released to the stack, but only a fraction of the oxygenated VOCs are found in the stack gas.  The continuous dye plants studied used only powder dyes. Carpet entering the plant goes through a pre-steamer which stretches the carpet and opens fiber pores to better accept the dye chemicals. The carpet is then prewashed, followed by application of a gumming agent and dyebath solution. The carpet is steamed to set the dye, and then washed and dried. A fluorochemical spray containing a scotchguard chemical and an anti-soiling agent containing stainblock may be applied prior to drying. At the time of the field tests, only the dryer stacks could be sampled. VOC emissions from steamer stacks were estimated from laboratory simulation tests.  Chemical analysis of samples of chemical bath applications applied during continuous dyeing indicated that these aqueous solutions contained less than 1% VOCs. Laboratory simulation tests indicated that the fraction of VOCs released to the exhaust gas during steaming ranged from over 90% for the more volatile, less water-soluble components to about 10% for the more water-soluble components. The gumming agent had the highest VOC content, with 2-ethyl-1-hexanol the major constituent and glycol ethers (e.g. butyl cellosolve and butyl carbitol) minor constituents.   Results of both the beck and continuous dye emission studies indicate that a large fraction of the VOC emissions are released during carpet dyeing and steaming (rather than drying), and that water-soluble VOCs partition between gas and aqueous effluents. Laboratory results illustrating the latter finding are shown in Figure 3 below.

Latex coating

In the carpet finishing process, a secondary backing fabric is bound to a primary backing to provide strength and support. Precoat and adhesive are applied and cured at about 200°C in a gas-fired oven. This process is run on a continuous line. Precoat and adhesive formulations differ only slightly. Components include styrene-butadiene latex, thickener, filler, and water.  Major VOC constituents found in the precoat and adhesive are long-chain hydrocarbons.   In addition, several compounds derived from the latex were observed: styrene and butadiene (unpolymerized), ethyl benzene (styrene precursor), cumene (styrene-butadiene polymer catalyst), and 4-ethyl cyclohexene (4-EC) and 4-phenyl cyclohexene (4-PC), which are Diels-Alder reaction products of styrene and butadiene. Estimated emission factors for these latex-derived compounds are listed in Table 3.

Conclusions

VOC and HAP emission factors were estimated for four carpet manufacturing processes: suessen heatsetting, beck dyeing, continuous dyeing, and latex coating. Field measurements and laboratory simulation experiments were used to estimate total emissions and emission factors. It is estimated that 1-2 g of VOCs are released to the air in the manufacture of one square yard of nylon carpet. For the maximum production capacity at the plants studied, this translates to an annual VOC emission of 50 to 100 tons.  Suessen heatsetting and beck dyeing were found to have the highest VOC emission rates.  In yarn heatsetting, the amount of lubricant, which contains mineral oil alkane constituents, is a controlling factor for VOC emissions, particularly for staple fiber. Caprolactam is the major VOC emitted in nylon 6 heatsetting. In carpet dyeing, VOC emissions are derived from dyebath auxiliary compounds. For powder dyes, these are mostly long-chain hydrocarbons. For liquid dyes, oxygenated VOCs are principle components. HAP emissions from beck and continuous dyeing processes included glycol ethers. Emissions from latex coating included styrene, ethyl benzene, cumene, and two styrene-butadiene Diels-Alder products: 4-phenyl cyclohexene and 4-ethenyl cyclohexene.   These field and laboratory results provide the most complete characterization of VOC emissions from carpet manufacturing to date. Auxiliary compounds in chemical applications were responsible for much of the VOC emissions. Significant emission reduction is possible through reformulating applications and improved process control.

References

1. The Consortium on Competitiveness for the Apparel, Carpet, and Textile Industry (CCACTI), Traditional Industries Program (TIP), State of Georgia, http://www.gatip.org/tcwhatisccacti.html.

2. “Volatile Organic Compound Emissions Characterization – Carpet Yarn Heat Setting and Autoclave Processes.” Prepared by E.I. du Pont de Nemours & Company for World Carpets, Inc., Rome, GA, July 1996.

3. “Carpet Mill Emissions Study.” Prepared by Waterford Compliance Group for Crompton and Knowles Colors Inc., Dalton, GA, September 1997.

4. Clausen, P.A., and Wolkoff, P., “Degradation Products of Tenax TA Formed during Sampling and Thermal Desorption Analysis: Indicators of Reactive Species Indoors,” Atmospheric Environment 1996, 31, 715-725.

5. Czernik, S., Elam, C.C., Evans, R.J., Meglen, R.R., Moens, L., and Tatsumoto, K., “Catalytic Pyrolysis of Nylon-6 to Recover Caprolactam,” J. Anal. Appl. Pyrol. 1998, 46, 51-64. 

6. Ballistreri, A., Garozzo, D., Giuffrida, M., and Montaudo, G., “Mechanism of Themral Decomposition of Nylon 66,” Macromolecules 1987, 20, 2991-2997.

Dyes used in Oriental rugs

In the middle of XIX century chemical rug dyes are spread over all of the oriental countries. The law issued by Persian government that prohibited its import, including the order to stop work on all rugs manufactures that used them, had no effect on the situation. Cruel punishment that was in cutting off right hand of any dyer who was guilty of breaking that law was soon forgotten. After the World War I chemical dyers were used all over the world. Aniline dyes, found by English chemist Perkin (1856), surely, had a fatal effect on the color perception of the oriental rugs, but since that times lots of high quality synthetical dyes were discovered, and nowadays they are used everywhere.
However, other qualities of the plants' pigments cannot be substituted. Although cloth panted with those pigments loose the intensity of color, get old, but thus their colors become milder. Besides that, they are able to give colours so deep and mild that even at high intensity never look irritating. The recepies of dying were considered to be a secret of workshops or clans, being transmitted further on by heritage, as well as all of secrets of a craft. The same is with everything we said about the material. While dying a lot depended on the climate and the type of soil on which the plants grew. Quality of the wool also influenced the tone of a color of a dye - using the same production process the varying quality often gives varying tones of colors. The material ment for dying is first washed in the hot water and degreased, sometimes using even soap, after which it is put in a bath for twelve hours. In the dying bath itself it lies for a very long period of time, after which it is dried in the sun. On manufacture plants every time is dyed a big enough portion of raw material is dyed while the nomads. who can dye only one small portion at a time, do not achieve every time the same color tone of a dye, which is the reason why one can meet various tones of the same color on a single carpet, as, for example, on the background picture, which is quite big solid surface.

Nowadays for dying wool meant for carpet manufacturing they mostly use chrome dyes. Buying a handmade rug, no matter if the dyes are natural or synthetic, you can be sure that it's value will increase as time goes. Even the rugs that have been made at the end of XIX century using anyline dyes are valued very high because of their age.

There is a popular opinion that a rug that has been dyed using natural dyes are unconditionally better than a rug created using chrome dyes. This is a wrong idea. Chrome dyes quite often turn to last longer and be tougher than the natural dyes.

CARPET SPECIFIER'S RESPONSIBILITY

Most claims directly relate back to a specification. Just because a label reads "5-year guarantee, 10 or lifetime guarantee for high traffic areas, or…guaranteed for extra heavy traffic", doesn't mean the carpet is always the right product for the space it will be installed. For example, all parties of a claim were present, including the owner, manager, attorneys, dealer, installer and specifier.  Upon a site examination, carpet installed had a totally loss of appearance retention or an "uglied out" look.  It was noticed that a marble corridor led into the entrance where the carpet was installed. The center of this marble corridor had a traffic pattern with a low depressed area where foot traffic had abraded away the marble stone. The carpet could not live up to the traffic requirements of that area. So the question was who was responsible for recommending this particular style of carpet for this particular installation. Of course fingers started pointing in all directions.  But the ultimate finger of blame pointed directly to the specifier. What was the specifier's reply to this accusation? He answered, "Well, I read on the back of the contract folder that this carpet is rated for heavy traffic. Don't look at me! Something is wrong with the carpet, it should of held up.   In this case, the liability of the installation did go back to the specifier since they assumed this area of responsibility. If the specifier had the proper education, then this problem need not have occurred at all. Keep in mind that carpet may not always be the proper product to specify for certain local traffic conditions.   Events like this happen daily. A number of reasons are behind this type of situation— budget, lack of product knowledge, color, oversell, incorrect information or incompetence—can all be direct causes of this scenario. The specifier must realize their involvement within the floor covering industry. They should act with earnest desire and dedicate themselves toward education and conduct business in a professional manner so that instances like this don't happen...or if they do, then they can be resolved without a lot of time and expense on anyone's part.

The areas of responsibility concerning the Specifier are as follows:

1. Consult with manufacturer to determine proper carpet construction for each installation.
2. Specify the proper carpet, color and cushion for each installation.
3. Consult industry guides such as CRI's Commercial Carpet Installation and

Standard for Installation of Textile Floor Covering Materials.

1. Specify the correct installation system for each job based on manufacturer's specifications.
2. Be responsible for carpet color/construction/specifications as ordered.

For all concerned, in any endeavor involving installations, obligations must be met and taken seriously—from the bottom to the top of the ever changing chain of command. Those who are involved in the carpet industry will seriously look at the specifiers duties when it comes to each and every responsibility and if needed, changes are made.

VIDEO: HOW CAN YOU TELL IF IT HAS BEEN SEAM SEALED



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How to Make An Informed Carpet Quality Comparison

By James Piper - September 2007

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.

Other Options

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.

Beyond 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.

Pile On

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.

Study examines carpet protector chemical in bodies of water

October 22, 2014

Perfluorinated compounds (PFCs) have recently received scientific and regulatory attention due to their broad environmental distribution, persistence, bioaccumulative potential, and toxicity. Studies suggest that fish consumption may be a source of human exposure to perfluorooctane sulfonate (PFOS) or long-chain perfluorocarboxylic acids. Most PFC fish tissue literature focuses on marine fish and waters outside of the United States (U.S.). To broaden assessments in U.S. fish, a characterization of PFCs in freshwater fish was initiated on a national scale using an unequal probability design during the U.S. Environmental Protection Agency's (EPA's) 2008–2009 National Rivers and Streams Assessment (NRSA) and the Great Lakes Human Health Fish Tissue Study component of the 2010 EPA National Coastal Condition Assessment (NCCA/GL). Fish were collected from randomly selected locations—164 urban river sites and 157 nearshore Great Lake sites. The probability design allowed extrapolation to the sampled population of 17,059 km in urban rivers and a nearshore area of 11,091 km² in the Great Lakes. Fillets were analyzed for 13 PFCs using high-performance liquid chromatography tandem mass spectrometry. Results showed that PFOS dominated in frequency of occurrence, followed by three other longer-chain PFCs (perfluorodecanoic acid, perfluoroundecanoic acid, and perfluorododecanoic acid). Maximum PFOS concentrations were 127 and 80 ng/g in urban river samples and Great Lakes samples, respectively. The range of NRSA PFOS detections was similar to literature accounts from targeted riverine fish sampling. NCCA/GL PFOS levels were lower than those reported by other Great Lakes researchers, but generally higher than values in targeted inland lake studies. The probability design allowed development of cumulative distribution functions (CDFs) to quantify PFOS concentrations versus the sampled population, and the application of fish consumption advisory guidance to the CDFs resulted in an estimation of the proportion of urban rivers and the Great Lakes that exceed human health protection thresholds.

STOP THAT CAT!!!!