Carpet Cushion Tests Methods for Evaluating Carpet Pad

Carpet cushion tests methods are used for the evaluation of carpet pad (cushion). The industry has developed a number of carpet cushion tests methods for evaluating carpet cushion. These evaluations have resulted in a better carpet pad being offered to the consumer.

Many wall to wall carpets will experience premature failure as a result of cushion (pad) failure. Unfortunately a large percent of those in the carpet industry that call themselves “professional” do not recognize when it is the cushion that has failed and not the carpet. When it is believed that a pad has failed there are carpet cushion tests methods for on-site evaluation. Expert-professional inspectors such as the Oregon based Weinheimer Group will be able to determine if it is the carpet or the pad that has failed.

Manufacturing Carpet Cushion Tests Methods

Evaluation of Cushion Density of Foam Style Cushion

To determine density, a one cubic foot (12″ x 12″ x 12″) of foam is weighed. The weight of this cubic foot is reported as (x) pounds per cubic foot.  This is a reasonably accurate test that is reporting the material’s actual substance, in this case the substance being the density.  The higher the density the better the support characteristics of the product.

Cushion Thickness

With cushion, thickness does not mean density.  Thickness is the measurement of the product from one side to the other as the product has been manufactured for use. Thickness is shown as a fraction of an inch or in its decimal equivalent, i.e., 5/32″,  3/8″, 7/16″, 1/2″, 9/16″.

CFD (Compression Force Deflection)

A measure of the load bearing ability of a foam.  It is the force exerted against a flat compression foot larger than the specimen to be tested.  The value can be expressed at 25%, 40%, 50% and/or 65% compression (ASTM D3574).  Note: Previously called “CLD” (Compression Load Deflection)

IFD (Indentation Force Deflection)

A measure of the load bearing capacity of flexible polyurethane foam.  IFD is generally measured as the force (in pounds) required to compress a 50 square inch circular indentor foot into a four inch thick sample, typically 15 inches square or larger, to a stated percentage of the sample’s initial height.  Common IFD values are generated at 25 and 65 percent of initial height. (ASTM D3574.) Note: Previously called “ILD” (Indentation Load Deflection).

Walk-on Testing

This is a standardized testing procedure that can be used by any segment of the industry from carpet manufacturers and cushion producers to distributors and retailers.  This test is used to evaluate installed residential carpet system performance. While this test can be used to evaluate different styles of carpet over a particular control system it can also be used to compare the effects of different types of carpet cushion on the composite floorcovering system.  The complete protocol for this test is available through the Polyurethane Foam Association.

Onsite Carpet Cushion Tests Methods (Field Evaluation)

Discoloration

The gradual yellowing of foam due to a photochemical reaction.  It is faster in sunlight than in artificial light, although it occurs in both.  Fresh foam may discolor in the center of the block as a result of thermal or chemical events.  Discoloration does not affect the physical properties of the foam.

Hard Spots – Resin

Spots that are hard like a marble are generally from the resin used in the bonding process. A spot that is hard enough to be felt is generally considered a defect.  The proper correction is to remove the spot.  A pad should not require replacement unless the spots are excessive.

Hard Spots – Skin

These are shiny, narrow, hard pieces that come from the outside of some foam buns. An inexpensive pad will likely contain more skin than a better variety.  Skin spots are a characteristic of many bonded urethane cushions and it is common for manufacturers not to consider them a defect unless they are large enough and hard enough to cause discomfort when walking in bare foot.

Mildew Problems

Slow seepage or flood that goes undetected or uncured for several days may result in mildew.  Fiber pads suffer this problem.  Rubber & foam are impervious, but they must still be removed because they retain water and the carpet backings are also liable to suffer from mildew.

Oxidation Problems

Rubber & foam pads depend on the sealing off of floor & carpet surfaces to prevent undue oxidation.  Areas with bad air pollution (NO2, O3) intensify problems.  Fiber pads are impervious to this problem.

Thickness

A cushion that is too thick will protrude above the tack strip and will not allow for a good grip of the carpet against the pins, and may also cause a valley to appear along the edges which can lead to excessive restretch problems.

CRI 104 states that cushion thickness should not exceed 3/8 inch (9.5 mm) for commercial installations, and CRI 105 states that cushion thickness should not exceed 7/16 inch (11 mm) for residential installations.  Whenever performing a claim where cushion failure or specification is in question, a sample of the cushion needs to be selected.

CRI Carpet Installations Standards 2011 states, Separate Cushion Selection: It is required that the cushion conform to carpet manufacturer recommendations for the specific product being installed. Failure to follow these recommendations for cushion may void manufacturer warranties. These recommendations may differ, depending on the style and construction of specific carpet. Cushion thickness for commercial carpet installations should not exceed ⅜ inch (10 mm.)

Weight or Density Problems

Rubber pads over 75 oz., or bonded urethane and foam pads of greater than 7/16″, especially less than 5.5 lb. density, while adding comfort to some customers, also lessen the life of the carpet by intensifying problems of delamination.

CRI Green Label Cushion Testing Program uses a variety of carpet cushion tests methods to evaluate carpet pad.
Carpet Cushion Consumer Guidelines, Carpet Cushion Council