The Stuff Upholstery's Made Of

As flexible polyurethane foam achieves 40 years of industry acceptance, here's a look at how it became the cushioning material of choice.

BY MICHAEL J. HEALEY

The Soviet Union launched Sputnik the year that flexible polyurethane foam hit the upholstered furniture market. The Dow Jones hit a high of 520 that same year, and Ted Williams hit .388 to win the American League batting title. It was 1957.

In the intervening 40 years, flexible polyurethane foam (FPF) has become the cushioning material of choice for furniture manufactures. It is used, in various formulations, in almost all upholstered furniture. FPF has become such a widely used product on its merits; it provides a unique combination of form and function. It is supportive, offers contouring comfort, and provides outstanding durability. Additionally, its physical performance properties can last without much change over time. FPF penetrated the furniture market by displacing latex foam rubber, which had been the industry's premium cushioning material for more than a decade. It did so by virtue of its value, offering performance at a more reasonable price.

The perfect replacement
"It was a real battle to get the furniture people to switch from latex to polyurethane foam, and let's be blunt about it: price is all that made it happen," says Bob Bush Sr., vice president sales, Hickory Springs Mfg. Co. "If things had kept on going like they were going in 1957 and 1958, the average sofa today would retail for $2,000 to $3,000," Bush continues. "A latex cushion - even a cheap latex cushion - was $7 to $8. Urethanes jumped into the market at $2."
Ultimately, this new product replaced nearly everything used previously for cushioning, from latex to seaweed to excelsior to cotton batting. Advancements "came one little bit at a time," recalls Dr. Herman Stone, former director of research and development for General Foam Corp., a Hazelton, PA-based foam manufacturer. "The key development was our ability to make lower-density foam that still had good physical properties," he says. "We were able to make the foam both at lower density and at higher yield, so there was less waste involved, and this kept the economics in good shape."

Sensing the opportunities in the early '60s, many entrepreneurs jumped into the fray. "The market first started with the big chemical companies like General Tire, DuPont, and Union Carbide," says Jerry Pool, technical director for the foam division of Leggett and Platt, Inc. "But it turned out to be something that was a lot more entrepreneurs than those big companies could handle alone." In the early '60s, you wound up with companies like Nopco Chemical, E.R. Carpenter, and United Foam, who could adapt to the individual needs of the furniture people."

One-shot breaks through
The chemical companies provided technology and technical help to the "foamers" in exchange for business, says Stone. "Everything we did was new, and on top of that, the technology for making the raw materials was all new - especially on a large scale."

The major breakthrough that enabled FPF to become a truly viable alternative to latex was the advent of the so-called "one-shot" process. In this process, two chemicals, a polyol and a diisocyanate, were mixed vigorously in water with a new silicone surfactant.

The chemical mix was pumped onto a moving conveyor, where it reacted and expanded. Sides on the conveyor allowed the foam to rise, much like bread, into a "bun" or "slab." This continuous slab was then cut, stored, and allowed to cool, or "cure." When fully cured, the foam could be fabricated into whatever shape or pattern the furniture maker wanted. "Everyone switched over from pre-polymer technology to the one-shot technology as fast as they could," Pool says. "It was much more economical and yielded a more competitive product."
The just-described slabstock production process is one of two basic procedures that the foam industry has used over the years to make foam for cushioning. The second is foam molding, a process by which individual items are produced by pouring foam chemicals into specially shaped molds and allowing the liquid chemicals to solidify into foam in the molds. This process is used primarily for automotive cushioning, although some office/contract furniture also uses molded cushions.

Foamers have continued to improve and refine production techniques and foam quality. One such refinement was the development of equipment and chemical additives that made the buns almost perfectly squared at the top. This led to a more efficient use of raw materials because more of the foam was converted to useful product. "We found out pretty quickly that the trick was to convert the chemicals to foam in the most cost-effective manner possible," says Jim Knight, a senior advisor with ARCO Chemical Co. "You can't waste your chemicals because it's the same as wasting money."

An important innovation in the 1970s was the "supersoft" grades of foam made by using auxiliary blowing agents such as methylene chloride and CFC-11. Auxiliary blowing agents yielded a product whose final properties were much softer and had a lower density than anything foamers had heretofore been able to produce.

With these supersoft foams, furniture makers could achieve a greater variety of softness and comfort levels in upholstery without sacrificing support and durability. (CFCs are no longer used as auxiliary blowing agents; liquid carbon dioxide, acetone, and methylene chloride are now used.)

Some 10 to 15 years ago, foamers began producing high resilience (HR) foams higher-density foams with a unique cell structure that allowed greater support without a firm surface feel. HR foams found their way into top-quality seating and preinium cushioning materials.

Still softer feels

More recently, another important development has been "supersoft" FPFS, which have an Indentation Force Deflection measurement within the seven- to 10-pound range (a softness comparable to the feel of fiber). Supersoft FPFs have given furniture manufacturers an alternative to polyester fiber that can be used to fill backs.

Foamers can now offer upholstery manufacturers many different foam formulations from which to choose, each with its own performance properties. The formulation depends on the specific density, firmness (which is actually independent of foam density), and support factor that the furniture maker needs for its application. In performance tests conducted at Mississippi State University and Detroit Testing Laboratories Inc., cushions made with only flexible polyurethane foam were tested against cushions made with densified fiber only, as well as against cushions made with combinations of FPF and fiber. All cushions were subjected to equal and rigorous durability tests to measure thickness retention and IFD values. The result? FPF-only cushions outperformed all other cushions in the tests. In cushions where FPF was used with different amounts of fiber, performance was directly related to the amount of FPF in the cushion. That is, the greater the percentage of FPF, the better the cushions performed. In this case, the performance manifested itself as greater retention of original properties. "Overall, foams today are probably 30 to 40 percent better in a given density than they were two decades ago," says Bob Simmons, vice president of manufacturing for Hickory Springs. "Now, there were definitely some good foams offered back then, but the market wasn't as educated to their needs as much as it is today." "There have been improvements in the higher-quality foam that's available on the market," says Mark Muffi, executive vice president of PeopLoungers, Nettleton, MS, that uses three or four different grades of foam in its products. "There's more availability of the better quality, but it still comes down to how much you want to pay for it," Muffi adds. "It's always pretty much been a situation where you get what you pay for."

"In the last few years, one of the biggest innovations has been the advent of fast-cooling foams," states ARCO's Knight. "These have provided a narrower IFD distribution in a block of foam. The benefit to the foamers is they're producing foam cushions with less variation in IFD from top to bottom and side to side. And the benefit to the furniture manufacturer is that he will not have as many complaints or cushion returns."

"As our capabilities have improved," Jerry Pool explains, "our targets have narrowed ... forced cooling has allowed us to accomplish a much greater consistency in our foams. It's definitely been one of the foamers' major developments in the last five years."

Protecting the environment

At least as challenging as making products that perform well while still competitively priced is doing so in a way that doesn't harm the environment. FPF manufacturers have devoted much capital and effort to comply with ever-changing regulations, and the FPF industry was one of the first to eliminate CFC use well ahead of the mandatory deadlines established by the Montreal Protocol. Additionally, the FPF industry has made recycling a high priority. In fact, recovered manufacturing waste is used for the production of bonded foam - the most widely used carpet underlay material. "Not only do we use all of our in-house-generated scrap, but we buy scrap back from some of our customers," says Herman Stone.

Another challenge foamers have met and will continue to meet is flammability. A wide variety of combustion-modified FPFs is available because a variety of combustion resistance requirements for furnishings, transportation, and other uses has evolved.

Those standards that address total system fire performance rather than isolated component combustibility have had greatest acceptance among foam producers. Composite testing provides the truest projection of how a finished furniture piece will perform under actual fire conditions. "Meeting anticipated new flammability standards will spawn a whole new round of research in the industry," says Bobby Bush Jr., vice president of Hickory Springs' foam products division. "But, we've had all kinds of challenges thrown at us over the past 40 years, and I guess if the foam industry has proven anything, it's that it's pretty resilient."

Michael J Healey is a freelance writer based in Greensboro, NC.

For more information on flexible polyurethane foam, please call the Alliance for Flexible Polyurethane Foam at (800) 696-AFPF (2373) and ask for "The Furniture Industry's Guide to Today's Flexible Polyurethane Foam.

UDM UPHOLSTERY DESIGN & MANUFACTURING OCTOBER 1997

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Understanding Foam Density

One of the three basic measures that upholstery manufacturers need to know when it comes to FPF, says Lou Peters, executive director of the Polyurethane Foam Assn., is density. Density is used to gauge the durability of flexible polyurethane foam. Generally, the higher the density, the more durable the FPF, and the more expensive it is to produce.

FPF is available in a broad variety of densities, ranging from as low as 0.8 pcf to as high as 6.0 pcf. But most upholstered furniture uses FPF in the 0.9 pct to 2.5 pcf density range.

One more thing: density and firmness are not the same thing. You can actually select a low-density FPF that's firm or a high-density that's soft. So, If your FPF feels too firm, it doesn't necessarily mean you need a lower-density FPF. What you really want to ask for is a softer FPF.

All Seats Need Support

Support factor is another measure that is commonly used to assess FPF performance, says Lou Peters, executive director of the Polyurethane Foam Assn., Sometimes called modulus, compression modulus, or comfort factor, support factor is essentially the relationship of the surface feel of the FPF to its deep down support.

The key is knowing that the higher support factor (which should range from about 1.8 to 2.6), the better the ability of the FPF to provide support. In general, support factor increases as density increases. And as density increases, price also tends to increase.

Early Involvement: A Key to a Productive Relationship

Several basic factors underpin the strong working relationship that many furniture manufacturers have with their foamers. These include the quality and consistency of the product they receive, as well as availability, delivery, and, of course, price.

But, involving a foamer before beginning design and production on a piece of furniture also helps forge strong bonds, because, say two prominent manufacturers, that way they get the exact foam that they need.

"Basically, my folks work out the design and then the foamer gets involved with supplying samples, and changes are made from that point," says Larry Rimel, Berkline's senior manager of purchasing. "Our foamer is involved early in the design stages." Adds Vernon Bigsby, Pennsylvania House's vice president of operations for upholstery, "Our foam supplier is involved from the very beginning, and we like to hear from them from time to time... or them to say, 'Well, with this style, why don't you consider this construction?' And we really appreciate their input."

The 5 Most Common Mistakes

When Selecting FPF

1. Equating firmness with density.
2. Failing to estimate for the effect of over-stuffing.
3. Not realizing that cover materials affect firmness.
4. Believing that the least expensive FPF is the best value.
5. Not discussing needs and expectations with FPF suppliers.

What is IFD25?

Another useful measure for assessing FPF performance is IFD, explains Lou Peters, executive director of the Polyurethane Foam Assn. A foam's surface feel is expressed in terms of the IFD at 25 percent, 25 percent IFD, or IFD25. IFD25 is determined by measuring the pounds of force required to indent a four-inch-thick FPF sample 25 percent of its thickness (1 inch).

Depending on the furniture design, the IFD25 spec may range from as low as 7 lbs. of force (IFD25) to as high as 45 lbs of force (IFD25). This covers the range from frumpy cushions to thin cushions for commercial barstools.