Recently,
a national research firm was commissioned to conduct a comprehensive
study among upholstered furniture decision-makers to assess usage,
attitudes, knowledge and needs related to flexible polyurethane foam
(FPF).
The research
was sponsored by the Alliance for Flexible Polyurethane Foam (AFPF),
a joint program of the Polyurethane Division of The Society of the
Plastics Industry, Inc. (SPI) and the Polyurethane Foam Association
(PFA).
One of the most
significant findings of this research was the discovery that many
in the furniture industry are not fully aware of the range of versatility
of FPF as a cushioning material. In fact, there have been such dramatic
advances in flexible polyurethane foam over the past few years, it
is particularly timely to make this FPF technology relevant to those
involved in the furniture design and manufacturing process.
The Furniture
Industry's Guide to Today's Flexible Polyurethane Foam was developed
as an easy-to-use reference tool to help you work with your FPF supplier
and better understand how FPF can be used most efficiently to improve
the comfort and performance of upholstered furniture.
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FPF
= Flexible Polyurethane Foam
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FPF: A Primer
In Comfort.
Flexible polyurethane
foam (FPF) is one of the most versatile materials ever created.
We're literally surrounded by it in our lives. It's in our cars,
in our beds and under our carpets. It's used as a packaging material
to protect delicate instruments. And it's the cushioning material
of choice in almost all upholstered furniture. Over 2.1 billion
pounds of FPF are produced and used every year in the U.S.
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2.1
Billion pounds of FPF are produced every year in the U.S.
That's enough FPF to make approximately 140 million sofas.
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But, while FPF may appear
to be a simple product, it's actually very complex. And it can be
produced to have an almost infinite variety of properties, which
provide three primary functions in upholstered furniture - durability,
comfort and support.
Durability:
Durability refers to
how well and how long FPF retains its original properties. Typically,
the higher the FPF density, the more durable it is, but only by
working with your FPF supplier can you determine the specific density
needed for your applications.
Comfort:
How comfortable a piece
of furniture is has a lot to do with the properties of the FPF used
to make the furniture. Comfort refers to at least two factors: the
tactile facet, which is the feel when touched by hand; and the sitting
comfort. The assessment of comfort depends on who's judging the
FPF and the furniture it's to be used in. FPF is so versatile it
can meet many, many comfort levels and requirements.
Support:
The dictionary definition
of support is "to carry the weight of, hold up, or keep from falling
or sinking." In upholstery, good support from FPF means that cushions
don't bottom out, fall through or compress to the point where they
no longer hold up a person's weight. It also means the cushion is
capable of distributing the weight of a person for maximum performance.
Selecting
The Right FPF.
Begin With Your
FPF Supplier.
Your FPF
supplier is extremely knowledgeable. To ensure you get the right
FPF for your project, it's best to consult with your FPF supplier
first - rather than after an item of furniture has begun production.
By talking with your FPF supplier as early as the design stage,
many potential problems can be avoided. Consulting with your supplier
early also gives him the time he needs to custom-create any FPF
you may need in a more timely, cost-effective manner.
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Involve
your FPF Supplier early in the design and production process
to get the best value and choose the right FPF.
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Guidelines
for Specifying FPF.
FPF has many different
properties, and these properties are measured and described in different
ways. The industry uses standardized ASTM tests to determine physical
properties.
Density.
Density is a measurement of mass per unit of volume and is expressed
in pounds per cubic foot (pcf). It is a primary measurement used
to gauge FPF durability. The higher the density, the more durable
the FPF, and the more expensive it is to produce due to greater
material content.
FPF is available in a
broad variety of densities, ranging from as low as 0.8 pcf to as
high as 6.0 pcf. Most furniture applications, however, utilize FPF
in the 0.9 pcf to 2.5 pcf density range. Typically, the higher the
density, the longer the FPF and your furniture will retain their
original properties.
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Good,
long term cushion performance is a major benefit of higher -
density FPF.
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Another important aspect
of FPF to remember is that density and firmness are independent
of each other. This means you can actually select a low-density
FPF that's firm, or a high-density FPF 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.
Surface Feel.
There are two aspects to surface feel; one relates to the surface
feel of FPF, the other is the surface feel of the finished cushion.
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Recent
innovations in FPF can deliver a surface feel with an IFD as
low as 7, which is similar in surface feel to many fiber - based
products.
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FPF Surface Feel.
The measurement used to determine FPF surface feel is expressed
in terms of the Indentation Force Deflection at 25%, or IFD25. IFD25
is determined by measuring the pounds of force required to indent
a 4-inch-thick FPF sample 25% of its thickness (1 inch). Depending
on the furniture design, the IFD25 specification may range from
as low as 7 pounds of force (IFD25) to as high as 45 pounds of force
(IFD25). This covers the range from "frumpy" cushions to thin cushions
for commercial bar stools.
When requesting FPF using
the IFD25 value, remember that the surface feel is usually tested
on 4-inch-thick samples. So if you're specifying FPF that is more
or less than 4 inches, the IFD25 value will vary based on cushion
thickness.
Cushion Surface
Feel. One of the principal factors that impacts the cushion
surface feel is the cradling effect. Cradling is the ability of
the cushion or fabric to distribute body weight uniformly over the
seating area. Cushion surface feel is also affected by IFD25, cushion
dimensions, cushion thickness, surface wrap and layered construction,
amount of cushion over-sizing, upholstery fabric, and cover upholstery
technique (tight cushion vs. loose cushion construction). Spring
system, decking construction and cushion design will also impact
the feel of the cushion and must be considered when specifying FPF.
Support Factor.
This is the measurement used to gauge FPF support. Typically, the
support factor (also known as compression modulus) can be found
by indenting the FPF 65% of the cushion thickness, then measuring
the pounds of force required to reach this level of indentation,
then dividing this number by the IFD25. The resulting number is
the support factor, which should range from about 1.8 to 2.6. The
higher the number, the better the ability of the FPF to provide
support.
Why be concerned about
the support factor of your FPF? Because a higher support factor
means your cushions will be more capable of distributing weight
evenly as the cushion is indented beyond 25% for maximum performance.
A high support factor also allows you to specify a softer surface
feel so you get extra surface softness without worrying about your
FPF "bottoming out" when weight is applied.
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In
general, support factor increases as density increases and different
grades of FPF can have different support factors. Consult your
FPF suppliers to determine the support factor that's right for
you.
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For most applications,
the FPF IFD25 and support factor specified should allow a seated
person to sit "into the cushion" rather than on top of it. The objective
is to improve cradling, thus reducing pressure points so body weight
is distributed evenly without allowing the springs and decking system
to be felt underneath. In fact, in some ways the support factor
may be a more valid measurement of FPF's cushioning ability than
other specifications because you sit deeper than 25% into a seat
cushion.
Additional
Factors Affecting FPF Performance.
When selecting an FPF,
you must also keep in mind that there are a number of other factors
that can affect the performance of your FPF. These include:
Surface Wrap.Historically,
FPF cushion cores have been wrapped with fiber and other materials
to help produce an extra-soft feel. Technological advances in FPF
though, have eliminated the
need to rely on these
other, less durable wraps. Today's new, softer FPFs can provide
an extra-soft feel and produce a good "hand" for the cushion, along
with providing support and comfort.
Benefits Of FPF
As A Surface Wrap:
Won't mat or lump.
Retains its shape.
Retains its feel.
Does not percolate through cover material.
Reduces wrinkles and cushion height loss.
Provides support and comfort.
Provides an extra-soft feel.
Upholstery Fabric.
Stiffness, breathability, "hand," thickness of fabric and upholstering
technique (loose wrap or tight wrap) can significantly affect the
feel of any cushion.
Spring Systems.
FPF is not the only material that provides support in furniture.
The spring systems - such as 8-way hand-tied coils, sinuous wire
springs and decking materials - do, too. FPF serves as a bridge
between upholstery fabric and the spring system being used.
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FPF
is used as a bridge between the cushion surface and the spring
system because it's the only material to provide both lasting
comfort and support.
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Thickness.
Cushion thickness affects seating comfort and support. The IFD25
and support factor must be carefully chosen, with respect to thickness,
to give seat cushions proper ride.
Fabrication.
It should be noted that most fabrication processes affect the cost
of FPF pieces, but the only way to truly evaluate the final cost
of a piece is to look at the entire manufacturing process. A fabricated
piece that costs a few cents more from your FPF supplier may actually
save several dollars of expense in product handling or assembly
and produce more consistent shapes in the finished product. The
end cost of the finished furniture may actually be less because
of proper fabrication. Your FPF supplier can help you get the best
value by working with you to evaluate the advantages of different
fabrication processes.
Factors Affecting
Cushion Comfort:
Amount of cushion over-sizing
Cover upholstery
technique (tight cushion vs. loose cushion construction)
Cradling
Cushion design
Cushion dimensions
Cushion thickness
Decking construction
IFD25
Layered construction
Spring system
Support factor
Surface wrap
Type of upholstery fabric and whether or not it has backing
Other
Considerations When Specifying FPF.
Even though durability,
comfort and support are the three primary considerations when selecting
an FPF, there are other factors to keep in mind.
FPF Consistency.
FPF properties are maintained within reasonable ranges. It's always
a good idea to speak with your FPF supplier before establishing
or changing FPF specifications, acceptable characteristics and ranges
of variation.
Flammability.
A wide variety of combustion-modified FPFs are available because
a variety of combustion resistance requirements for furnishings,
transportation, and other uses have evolved which range from moderate
to very stringent. Most require that the finished furniture or components
be tested and approved before they can be used in applications requiring
compliance with a standard. Make sure the FPF you select has been
approved for your use. And work closely with your supplier where
flammability requirements apply.
Safety When Storing.
Proper storage and handling of FPF is an important fire safety precaution.
FPF should not be exposed to open flames or other direct or indirect
high-temperature ignition sources such as burning cigarettes, matches,
fireplaces, space heaters, forklifts, welding sparks or bare light
bulbs. As an added precaution, it is recommended that all areas
where FPF is stored or handled need to be protected by automatic
sprinkler systems. Your FPF supplier, local fire officials and your
insurance handler can provide additional information on safe practices
regarding FPF.
Environmentally-Friendly.
FPF manufacturers have devoted a tremendous amount of capital and
effort to comply with ever-changing environmental regulations, and
have been one of the first industries to virtually eliminate CFC
use well ahead of the mandatory deadlines established by the Montreal
Protocol. Recycling of scrap FPF is also more important than ever,
which is why you'll find rebond materials made from FPF scrap are
now being used for the production of the most widely used carpet
underlay material. These recycled materials are also used in other
specialized applications.
The Five Most Common
Mistakes Made 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 the least expensive FPF is the best value.
5. Not discussing
needs and expectations with FPF suppliers.
