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Application of polyurethane flexible foams for furniture is a highly economically sensitive segment that follows the overall housing market [11]. The furniture segment uses flexible foams obtained from both slabstock and molded foam operations. However, with furniture manufacturing shifting to low-cost environments and the cost competitive nature of the furniture market, there is a significant concentration of furniture foams made in lower-cost slabstock operations (Fig. 7.3). Examples of simple high-resilience slabstock formulations and properties are shown in Table 7.1.

The indentation force deflection (IFD; Table 7.1, Fig. 7.4) measurement is a test that is unique to the comfort segment. This is not a test with a clear relationship to fundamental aspects of polyurethane structure or chemistry. It is an application test with a direct correlation to how the foam is used (usually sat upon). The test is specified in ASTM D3453 and D5672 [12]. A foam sample that is approximately the size of a furniture cushion is compressed by a standard size circular press as shown in Figure 7.4. Manufacturers of end-use products specify the performance of the foam in this test, and the formulator and foamer will then design the foam to meet the test requirements. The specifications are usually the force measured by the df load cell at a certain compression or several compressions (i.e., 25,40, and 65% compression). The force value is normalized to the foam density. Careful experiment will also normalize the compression response to airflow or at least assure that all compared foams have nearly the same airflow to prevent the measurement being influenced by hydraulic resistance (see Section 4.2.2.2). The foam designer will adjust airflow

Approximate split for the polyurethane flexible slabstock and flexible molded foams in North America for furniture for the year 2010.

FIGURE 7.3 Approximate split for the polyurethane flexible slabstock and flexible molded foams in North America for furniture for the year 2010.

TABLE 7.1 Simplified formulation and representative properties for high-resilience foam for furniture applications at three different foam densities

pphp

pphp

pphp

Sorbitol-initiated polyol

100

100

100

EO-capped OH 29

Water

4.5

4

3

Diethanolamine

2

1.5

1

TDI index

100

105

105

Density

lbs/ft3

1.26

1.56

1.87

IFD 40%

lbs

13.2

15.4

19.3

Resilience

%

60

60

62

Compression set

%

10

8

5

Elongation at break

%

150

135

120

Generally, the higher the foam density, the firmer and more durable is the cushion.

properties by careful balancing of diethanolamine cross-linker, gelation, and blow catalysts within the formulation. An additional industry specification gauged from this test is the so-called "sag" factor or comfort factor calculated from the ratio of IFD at 65 and 25% compression. Some manufacturers will use alternative ratios or limitations when using these terms.

All polyurethane markets are competitive, and the furniture market may be especially so [13]. Producer prices are always critical to market and manufacturer

Test fixture and sample geometry for testing flexible foam indentation force deflection (IFD), a common test for furniture applications. Image courtesy of Instron Corporation.

FIGURE 7.4 Test fixture and sample geometry for testing flexible foam indentation force deflection (IFD), a common test for furniture applications. Image courtesy of Instron Corporation.

success, but intense competition assures that competent players rapidly respond to price changes in the market. Success in the furniture market usually requires an ability to meet all the customer requirements. Successful building block and foam manufacturers are able to produce the range of materials required by the next level in the value chain. The occasionally small-volume demands of particular applications have spawned the development of "system houses." These businesses occupy a middleman position between the large building block producers and foam manufacturers. The system houses rapidly develop formulations that meet the small-volume applications required by the foam manufacturer. From the market perspective, the system application must demand and justify the increased price of specific formulation development. The success of system houses has inspired some large building block manufacturers to invest in or purchase their own system companies.

Success in the furniture market also requires that suppliers within the value chain have credibility and historical position within the market. Intuitively, it is clear that customers prefer suppliers with whom they have prior relationships and have a track record for delivering for the industry. This subjective requirement can act as a barrier to entry for new potential providers of products, as well as causing weakly positioned suppliers to fail when economic factors serve to differentiate among suppliers. In addition, history and position within the market provide the necessary up-to-the-minute intelligence of customers, competitors, and price for a rapid response to market demands and fluctuations. Lack of such information creates the so-called market followers who traditionally exhibit poorer profitability even under the best of circumstances [14].

The furniture industry is not considered one that makes significant demands for new polyurethane technology. Price and regulatory forces are the main drivers of new products for this segment. Development of polyols from seed oil feedstocks has created some adjustment of formulations as furniture producers try to develop a market demand for "green" products. Some producers will substitute 5-10% seed oil-derived polyol for petrochemically derived polyol into their formulation. Larger additions are shown to deteriorate properties using low-cost substitutions [15, 16] or unacceptably raise prices for more capable seed oil-designed products [17].

Another area of technology development is the need for improved environmental health and safety of polyurethane foams. These issues relate to improved fire resistance and inhibited smoke generation from foams without the use of halogenated flame retardants [18, 19]. Second-choice flame retardants based on phosphorus are also potentially under scrutiny by regulators [20]. Reduction of volatile organic compounds from foams when in use is also considered a desirable feature by furniture manufacturers.

 
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