Secondary Backing Systems for Carpet

Image of Secondary Carpet Backing

Once dyed, the carpet goes into the finishing department, where the secondary backing is applied and the surface is sheared smooth.

The secondary backing is any material laminated to the primary backing in a “marriage roller” for dimensional stability while locking individual tufts in place.

The secondary backing is glued to the primary backing with latex. The latex is a milky, rubbery fluid, usually styrene-butadiene synthetic rubber (SBR) compounded with large quantities of powdered filler such as chalk. The new carpet odor is from the chemical 4-PC, a by-product of the latex.

Latex is applied to the back of the carpet. As the carpet passes under the puddle of latex, a blade forces the latex down and around all the yarn on the back of the carpet, which locks the yarn into the backing. A second coat of latex is applied to hold the secondary backing onto the tufted material, which gives the carpet its dimensional stability.

After the primary and secondary backings are glued together at the marriage roller, the carpet is sent to an oven to cure the latex.

Dimensional stability, primarily imparted by the secondary backing, is the ability of carpet to retain its size and shape after installation.

Action Bac Carpet Backing

Most secondary backing today is woven polypropylene, such as Propex’s, Action Bac®, which is a backing made of a leno weave of slit film and spun olefin yarns that forms a stretchable, all synthetic secondary backing fabric. It is shredded and spun into yarn, which is then used.

The secondary backing might be made of jute, a material high in lignin content derived from a fibrous plant native to India, Bangladesh, and the Far East. Jute backing has several major problems, such as potential for browning and rotting.

There are several other backing systems, including:

  • AdBac®: A composite backing system whose key component is an extruded polyethylene that’s processed into a spun-bonded fabric. That fabric is sandwiched between the PolyBac® primary and the Action Bac secondary backing. When heat is applied, the fabric melts to adhere the primary and secondary backings. By eliminating the latex, this system eliminates delamination and gives carpet lighter in weight, greater flexibility, easier installation, and more easily recycled. Additionally, by eliminating the latex, the “new carpet odor” is also eliminated. AdBac, PolyBac and ActionBac are registered trademarks of Propex® Fabrics.
  • Attached cushion or cushion-backed carpet: Carpet having a cushion or padding as an integral part of its backing.
  • Attached Polyurethane Carpet Backing
    KangaBack®, a trademark of Textile Rubber & Chemical, is an attached 100% polyurethane cushion product for residential use.
  • Moisture barrier carpet backings: Most moisture barrier backings are solid vinyl or urethane. Their purpose is to keep water-based spills from penetrating through the carpet, affecting both the carpet and the surface under the carpet. However, they can also have the disadvantage of trapping any moisture trapped under them from evaporating. This can be especially damaging to the concrete itself and to the glue if the carpet is glued down. It can lead to failure of the carpet installation. Also, because the pad does not absorb a spill, or pet urine, the material tends to spread outward more, making wicking over a larger area more likely.
  • Pet-Agree® Wear-Dated® carpet from Solutia comes with a soft impervious polyethylene backing that traps liquids (pet urine in particular) where they can be found and cleaned thoroughly before soaking into the padding and through to the floor. Pet-Agree keeps liquid from seeping through the carpet into the cushion.
  • Shaw’s LifeGuard® Waterproof Backing Barrier “provides complete, clean-up protection by keeping spills and odor-causing pet accidents from soaking through to the pad and subfloor. Carpet made with LifeGuard® waterproof backing is engineered for life’s little messes, keeping 100% of all spills, splatters and accidents contained for complete clean-up protection. Carpets featuring LifeGuard are treated with Shaw’s patented R2X Stain and Soil Resistance Protection, while a patented 100% thermoplastic commercial-grade backing provides a moisture barrier that is highly resistant to liquids soaking into the carpet padding and subfloor.”
    Attached Polyurethane Carpet Backing
     
  • Shaw’s SoftBac® is a woven/non-woven combination backing system that eliminates the harsh surface of the backing that can scuff up walls and banisters. Additionally, it results in a carpet that is more flexible and lighter. SoftBac provides up to 3 times the delamination strength of ordinary backings.
  • Powerbond® ER3, made by Collins & Aikman Floorcoverings, is a secondary backing that’s made from reclaimed carpet tile (which includes the nylon tufted surface and vinyl backing).”
  • Polyurethane systems: A polymeric resin applied by the mill in the finishing process. In the heat and curing chamber it reacts and creates a foam-like texture. This backing encapsulates the yarn for extra tuft bind (the force required to pull a tuft from the carpet) with a cushion attached and also gives water repellency to provide a moisture barrier. Additionally, urethane does not degrade the way latex can and it does not give off the 4-PC “new carpet odor”.
  • Dow’s Enhancer® system is the best-known urethane system. The Enhancer system functions as both the adhesive and the secondary backing and adheres to the back of the carpet by reacting with it. This system provides a moisture barrier protection that protects sub-floors and reduces wicking from spills. The Enhancer system protects the carpet against edge ravel, pilling and fuzzing. It also provides a cushioned alternative in direct glue down situations and increases the life of the carpet.

    • Dow Enhancer Urethane Backing
     
  • PVC backing: Poly Vinyl Chloride. Sometimes used as a secondary backing on carpet tiles and six-foot wide carpets because of its weight and stiffness.
  • Sponge rubber cushion: Rubber carpet cushion backing that is laminated to the back of a carpet.
  • Unibond® backing: A hot-melt resin process that adheres the primary and secondary backing offered by Lees Commercial Carpets.
  • Unitary backing: A heavy application of back coating applied to the carpets back without a secondary back. Used primarily with loop pile carpet.
     
    Unitary Backing

Related Carpet Manufacturing and Fibers Information:

VIDEO: Chemistry of Carpet Fibers by Bane-Clene’s Chemist

The starting point of carpet is the fiber.

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