Foam designed to be attenuated (dampen
sounds), or be non-attenuated (transmit sound as in loud speakers).
Additive
A
material used to modify the properties, processing, or end use of a base
polymer. The amount of additive used is usually expressed in parts per
hundred (by weight) of the total resin in the polymer formulation.
Air
Flow
Amount
of air expressed in cubic feet per minute, that can be drawn through a
2"x 2"x 1" foam sample at .5-inch water pressure
differential. Air Flow is measured by a test (ASTM D3574).
Air
Traps
Voids
in molded foam parts caused by encapsulation of air pockets during mold
fill-out. These voids have smooth, shiny surfaces.
Amine
A
class of compounds used as catalysts in polyurethane foam reactions.
Amines are characterized by having N, NH or NH2 groups in the molecule.
Antioxidants
Materials
which when added to a flexible polyurethane foam formulation improve the
resistance of the foam to oxidative type reactions, such as scorch
resulting from high exothermic temperatures.
Anti-Static
Flexible Polyurethane Foam
Foam
that contains electrically conductive materials to prevent static
electricity buildup or promote static discharge. It is used primarily in
packaging applications, such as for electronic components.
A-Side
(T)
The
isocyanate portion of a foam formulation.The opposite applies in Europe.
ASTM
– American Society for Testing and Materials
n
organization devoted to the establishment of standard methods and
procedures for testing materials.
Auxiliary
Blowing
Agent (ABA)
An
additive used in the production of foam which supplements the primary
blowing agent (water), and can be used to make foam softer or lighter.
Compounds used to produce gases to expand, or blow, flexible polyurethane
foam during production.Auxiliary
blowing agents are low temperature boiling solvents, such as methylene
chloride, acetone, hydrochlorofluorocarbons, and isopentane.
Back
Rind
Encountered
with the soft rubber compounds.When
this occurs it appears as a slight undercut on the part at the mold
parting line.
Ball
Rebound
A
test procedure (ASTM D3574) used to measure the surface resilience of
flexible polyurethane foam. The test involves dropping a steel ball of
known mass from a predetermined height onto a foam sample.The rebound height attained by the steel ball, expressed as a
percentage of the original drop height, is the ball rebound resilience
value.
Blowing
The
process by which flexible polyurethane is foamed during production.In all cases, blowing occurs when water and TDI (or MDI) react to
form CO2.(Also see Auxiliary
Blowing Agent (ABA)).
Blowing
Agent
A
gas or substance capable of producing a gas, used in making foamed
materials.
Board
Foot
A
unit of foam measurement equal to a square foot of material one inch in
thickness.
Bonded
Foam
Flexible
polyurethane foam particles or shredded flexible polyurethane foam (often
manufacturing scrap) that has been glued to form a useful product. The
resultant foam block is "peeled" into the desired thickness.
Largest use is for carpet cushion. (Also see Rebonded Foam.)
Bonding
The
combination of two or more components into a composite. Foam is often
adhered to other foam grades or to polyester fiber.
Bottom
Out
Lack
of support under full weight load. This characteristic is often found in
low-density foam.This term
is very subjective, as a foam may bottom out with a heavy person, and be
very comfortable to a lighter-weight individual.The problem can be reduced by specifying foam with higher density
and/or greater compression modulus value.
B-Side
(R)
In
North America, the active hydrogen (polyol, water, amine, etc.) portion of
a foam formulation.(In
Europe, the isocyanate portion of a foam formulation).
Buffed
Flexible
polyurethane foam pieces that have been shaped or contoured by removal of
foam using abrasives.
Bun
A
segment of foam cut off from continuously produced slab stock type of
foam.
Calibration
The
weighing of carefully timed dispenses of chemicals from the metering ports
of the mixing head in order to set an exact component ratio or an exact
throughput of all chemicals
Catalyst
A
chemical that changes the rate of reaction of a chemical process, but is
not consumed or produced during the reaction. (Catalysts are required for
foam production to balance rates of competing reactions and to attain
desired physical properties.)
Cell
The
cavity remaining in the structure of flexible polyurethane foam surrounded
by polymer membranes or the polymer skeleton after blowing is complete.
Cell
Count
The
number of cells per linear inch or centimeter, expressed as pores per inch
or pores per centimeter.
Cell
Opening
In
foamed materials, the breaking of membranes within the cell structure,
permitting flow of air through the material.
Cell
Size
The
average diameter of the cells in the final flexible polyurethane foam
product, often measured in micron units.
CFC-Free
Foam
Flexible
polyurethane foams that have been made without the use of
chlorofluorocarbons as auxiliary blowing agents.
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)"
Chain
Extenders
Short-chain
reactive molecules joining diisocyanates in a linear fashion to form
crystalline hard segments that modify the properties of a polyurethane.
Clickability
The
ability of a flexible polyurethane foam to recover from the pinching
effects of die-cutting.
Closed
Cells
Foam
cells having intact cell membranes thereby reducing or eliminating
passageways for airflow.
Closed
Pour
The
case in molded foam production in which the mold lid is closed and locked
and the foaming mixture is introduced through one or more special ports in
the lid of the mold.
CO2
Blown Foam
Foam
in which all the gas for expanding the reaction mix comes from the
reaction of water with isocyanate. Sometimes called an all-water blown
foam.
Cold
Molding
Molding
process for the production of high-resiliency foam in which the foam is
cured at or near room (ambient) temperature. Pouring is carried out
without adding heat.
Colorant
Dyes
or pigments added to impart color to the final foam.
Combustion
Modified Foam
Flexible
polyurethane foams manufactured by using additives based on chlorine,
bromine, phosphorus chemistry to reduce ease of ignition. Hydrated alumina
or melamine is also used.
Combustion
Modifying Additives
A
material that, when added to flexible polyurethane foam, will cause the
foam to be more difficult to ignite or burn less rapidly or lose less
weight during a fire than without that material. (Also known as Fire
Retardants.)
Comfort
The
ability of the cushioning structure to deflect at the surface and to
conform to body shape, preventing a concentration of pressure on the body
without bottoming out.
Compression
Set
A
permanent partial loss of initial height of a flexible polyurethane foam
sample after compression due to a bending or collapse of the cell
framework within the foam sample. A high value of compression set will
cause a flexible polyurethane foam cushion to quickly lose its original
appearance with use, leaving its surface depressed or "hollowed
out." Compression set is measured in the lab by compressing a foam
sample 90% of its thickness (or down to 10% of its original thickness) and
holding it at 70 degrees C (or 158 degrees F) for 22 hours. Compression
set is most commonly expressed as a percentage of original compression.
Other deflections, times and temperatures can be used.
Compression
Set - ASTM D 395
The
amount in percent by which a standard test piece fails to return to its
original thickness after being subjected to a standard compressive load
for a fixed period of time and temperature. It is sometimes referred to as
the elastomer's memory.
Core
The
internal portion of foam, free of any skin.
Core
Density
The
density of the foam sampled without skin, glue lines or compressed
sections at or near the center of the final foamed shape.
Cream
Time (Rise Initiation)
The
time between the discharge of the foam ingredients from the mixing head
and the beginning of the foam rise.At
this point, the surface of the liquid will change color, usually turning
lighter as a result of saturation of the liquid with evolving gas.
Crushing
Usually
a mechanical or vacuum-assisted procedure to open the closed cells of a
high resilience slab stock or molded foam (see degassing.)
Cure
A
term referring to the process whereby chemical reactions approach
completion.At 100% completion, a foam should have 100% of the physical
properties attainable with that particular formulation.
Cure
Time
The
length of time required for sufficient reaction completion to develop a
desired level of polymer strength and dimensional stability and to attain
ultimate physical properties.
Dead
Foam
Foam
that has a low resiliency and only slowly regains its original shape after
deformation.
Deflect
To
compress, usually by a specified amount or percentage.
Degas
To
release molding pressure on tools.Allows
breaking of foam cell windows and relieves internal gas pressures.
Demold
Time
The
time between the discharge of the foam ingredients from the mixing head
and the time at which a molded object may be removed readily from the mold
without tearing or altering its shape and without post-expansion.
Density
A
measurement of the mass per unit volume. It is measured and expressed in
pounds per cubic foot (pcf) or kilograms per cubic meter (kg/m3). (Test
Method ASTM D3547) Also see www.pfa.org/jifsg/jifsgs1.html
Die
Cutting
The
"stamping out" of foam into parts, useful for long runs of cut
parts requiring consistency in size.Also method of trimming polyurethane parts.
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. (Does not affect physical properties.)
Durability
As
applied to flexible foams, the term refers to how well a foam retains its
load bearing capacity and shape with use. Most measures of durability are
done with laboratory-scale tests.
Durometer
(Hardness)
The
resistance to indentation under conditions which do not puncture the
elastomer surface. The most frequently used device is the spring loaded
Shore Durometer. The scale runs from zero hardness for a liquid, to 100
for a hard plane surface such as glass.
Elastomer
Polymers
which resist and recover from deformation produced by force, similar in
behavior to natural rubber. Commonly called rubber, polymer, co-polymer
and vulcanizates.
Elongation
The
percent that a specially shaped sample will stretch from its original
length before breaking. (Test Method ASTM D3574)
Exotherm
The
heat released as a by product of some chemical reactions.All flexible polyurethane foam production reactions are exothermic.
Fatigue
(Flex Fatigue)
A
softening or loss of firmness.Fatigue
can be measured in the laboratory by repeatedly compressing a foam sample
and measuring the change in IFD.
Filled
Foam
The
addition of inorganic materials such as marble dust, barium sulfate,
silica or clay, in foam to increase the density. Fillers are often added
to increase the Support Factor.Filled
polyurethane foam may be inappropriate for some applications, if the
polymer content of the filled foam is not sufficient for the intended
application before fillers are added.Fillers are not chemically bonded into the foam polymer. They are
instead mechanically trapped within the molecular structure of the
polymer. Filled foams with low polymer content or a high percentage of
filler material tend to have less strength and durability.
Fire
Retardants
A
material that, when added to flexible polyurethane foam, will cause the
foam to be more difficult to ignite, burn less rapidly or lose less weight
during a fire. (Also known as "Combustion Modifying Additives".)
Flame
Lamination
The
practice of bonding flexible foam to a fabric or other material (film,
etc.) by melting one surface of the foam with a flame source and quickly
pressing it to the other substrate before the melted material
re-solidifies. (Also called Flame Bonding.)
Flash
A
rubber residue that clings to the part at the mold parting line. Also
frequently encountered as an axial flash bead on the end of parts with
small inside diameters.
Flex
Fatigue
The
loss of foam firmness after flexing the foam a predetermined number of
cycles.
Flow
Marks
A
surface pattern on the part. Commonly found with the harder rubber
compounds.
Foam
A
lightweight cellular material resulting from the introduction of gas
bubbles into a reacting polymer.
Formulation
The
list of chemicals and their relative amounts to be used in the preparation
of a foam.
Free
NCO
Isocyanate
content of a substance that is available for further reaction.This can be either free monomer, as TDI or MDI or as
un-reacted isocyanate groups in a polymer or prepolymer.
Frothing
A
foaming technique in which air or other gases that are mechanically
whipped into the polyurethane mixture using a high-shear mixer prior to
the foam reaction.
Gate
or Sprue
A
mark on the surface of a part where material was fed into the mold cavity.
It may be raised or depressed into the surface. On materials of 60
durometer hardness and harder - will be up to .055 inch in diameter - .007
height or depth.
Gel
Hysteresis
The
ability of foam to maintain original support characteristics after
flexing. Hysteresis is the percent of 25% IFD loss measured as a
compression tester returns to the normal (25% IFD) position after
measuring 65% compression. Lower hysteresis values, or less IFD loss are
desirable. Current research indicates that hysteresis values may provide a
good indication of overall flexible foam durability. Low hysteresis in
conventional foam is equal to less IFD loss.
Hand
The
feel of the foam as the hand is rubbed lightly over the surface. For most
furniture, bedding and textile applications, foam having a stiff or hard
feel to the touch is described as having poor hand. In home furnishings,
foam with a good hand has a springy, velvet feel, while abrasive pads,
firm filler, and some packaging require a hand that is quite the opposite.
Heat
Aging Test
Samples
that are aged at an elevated temperature and retested for deterioration of
original properties.
High
Resilience (HR) Foam
A
variety of polyurethane foam produced using a blend of polymer or graft
polyols. High resilience foam has a less uniform (more random) cell
structure different from conventional products. The different cell
structure helps add support, comfort, and resilience or bounce. High
resilience foams have a high support factor and greater surface resilience
than conventional foams and are defined in ASTM D3770.
Hot
Molding
A
flexible molded foam production process in which high oven temperatures
are used to drive the curing reaction in foams made from relatively
low-reactivity polyols.
Humid
Aging
An
accelerated aging test method under conditions of high humidity and
temperature. (ASTM D3547)
Hydrophilic
An
affinity for water.
Hydrophobic
A
repellency for water.
Hydroxyl
Group
The
combined oxygen and hydrogen radical (ľOH) that forms the reactive group
on polyol molecules.
Immersion
Test
A
test used to measure the resistance to a fluid.The test specimen is immersed into specific fluid for a specific
time and temperature.Properties
are then retested for volume change or swelling.
Indentation
Force Deflection (IFD)
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.(Test Method ASTM D3574)Note:Previously
called "ILD – Indentation Load Deflection".
Integral
Skin Foam
A
molded foam having a dense, tough outer skin and a relatively lower
density core. The product is achieved in a single pour using a combination
of chemical and mechanical aids.
Isocyanate
A
shorthand name for the family of diisocyanates which are one of the two
major ingredients in the chemical process by which polyurethane foam is
made.
Knit
Line
Sometimes
confused with flow marks. Most often found at the two points where
material was fed into the mold cavity.
Laminating
The
bonding of layers of foam and/or other materials together into a single
composite. This may be accomplished through adhesives or through heat
processes like flame lamination.
MDI
In
the United States, usually the abbreviation for pure diphenylmethane
diisocyanate.In other
countries, it can be the un-distilled mixture of diphenylmethane
diisocyanate and higher molecular weight fractions.
Mixing
Head
The
device that mixes two or more component streams before dispensing the
foam-producing mixture to the foam production surface or mold.
Modulus
The
force required in pounds per square inch to stretch the test piece to a
given elongation. It expresses resistance to extension in the vulcanizates.
Mold
Packing
The
practice of purposely adding more material to the mold than is actually
required to just fill it. The extra material serves to accommodate slight
changes in material temperatures, mold temperatures and pour patterns.It is also a way to improve load-bearing properties without
changing the foam formulation.
Mold
Release Agent
Any
material which when applied to the mold surface serves to prevent sticking
of the foamed part to the mold.
Molded
Foam
A
cellular foam product having the shape of the mold cavity in which it was
produced.
Open
Cell Structure
A
permeable structure in flexible foam in which there is no barrier between
cells, and gases or liquids can pass through the foam. Most cell walls
have been ruptured to varying extents.
Parting
Line
A
ridge on the part where mold plates meet. On 0-rings and similar molded
parts parting line will be .003 inch thick extending out from the part
.010 inch. For compression molded parts, parting line ridge will be .004 x
.015 inch.
Pockets
he
undesirable formation of large cavities or pockets in the foam structure.
Pocketing is usually caused by rapid formation and/or release of the
blowing agent before the polymer structure has gained sufficient strength
to contain the gas.
Polyester
A
polymeric polyol containing ester groups in the main molecular chain or in
side chains.
Polyether
A
polymeric polyol containing ether linkages (carbon-oxygen-carbon links) in
the main molecular chain or in side chains.
Polymer
An
organic substance composed of repeating chemical units built up into large
molecules.
Polymer
Density
The
density of the material made up strictly by the foam chemistry without
fillers or reinforcements included.
Polyol
A
key chemical in foam formulation which, when mixed with diisocyanates and
other specific ingredients, produces the reaction that causes flexible
polyurethane foam to form.
Polyurethane
Generally,
a polymer connected by urethane groups. Urethane linkage and its
supplements result from the reaction of polyol with isocyanate.
Pore
Size
The
number of cells per linear inch.
Prepolymer
A
reacted, but not completely polymerized product. In the polyurethane
industry, this is usually a pre-reacted product formed by reacting
polyol(s) or water with diisocyanate(s). The materials normally contain
residual free isocyanate groups for further reaction with more polyol(s)
or water to produce the final polymer.
Pressure
Release Collapse
Shallow
surface voids and/or shear collapse on molded foam parts caused by the
sudden release of internal mold pressure or failure of the mold to seal.
Usually seen with shiny surfaces and a thin surface skin similar to cold
collapse.
PU
Short
for polyurethane
Rebonded
Foam
That
foam resulting from a process of adhering small particles of foam back
together again to make a usable cushioning product. Various adhesives and
bonding processes are used. A typical application for rebonded foam is as
carpet underlay.(Also see
Bonded Foam.)
Recovery
The
return to original dimension and properties of a flexible polyurethane
foam sample after a deforming force is removed.
Resilience
An
indicator of the surface elasticity or "springiness" of foam. It
is measured by dropping a steel ball onto the foam cushion and measuring
how high the ball rebounds.
Resiliency
- ASTM D 945
The
ratio of returned energy to impressed energy. A number of tests have been
devised for comparing these and related properties.
Reticulated
Foam
Flexible
polyurethane foams characterized by a three-dimensional skeletal structure
with few or no membranes between strands. Reticulated foams are generally
used as filters, acoustical panels, and for controlled liquid delivery.
Shrink
The
dimensional change in a rubber part as it cures in the molding operations.
May also refer to a specific section of the part which changes dimension
more radically than other part sections.
Skin
The
higher-density outer surface of a foam usually occurring when the foam
surface cools more rapidly than the core.
Slab
A
section of foam cut from the interior of a large bun.
Slab
Stock
Flexible
polyurethane foam made by the continuous pouring of mixed liquids onto a
conveyor, creating a continuous loaf of foam.
Slab
Stock Production Process
One
of the two basic procedures used to manufacture foam. A continuous process
in which the reacting foam chemical mix is dispensed on to a moving
conveyor belt where the foaming process is completed. This foam is
subsequently fabricated into useful shapes.
Static
Fatigue
The
loss in load bearing properties of a flexible polyurethane foam sample
under constant compression of 75% for 17 hours at room temperature.(ASTM D3574)
Struts
The
structural members of a foam material. These roughly triangular features
contain most of the solid polymer and form the cell shape.
Supersoft
Foam
Foams
that have an IFD measurement within the 4 to 10 pound range having a
comparable feel to fiber.
Surface
Firmness
The
number of pounds of force necessary to indent a foam sample by 25% of its
original height.
Surfactants
A
term to describe substances that provide resiliency and stability to thin
films and that markedly lower the surface tension of liquids, thus
permitting easier bubble formation. An integral part of the foam
manufacturing chemistry.
System
In
polyurethane or polyisocyanurate technology, the two or more substances or
materials which, when mixed together, react to form a polyurethane or
polyisocyanurate polymer.
TDI
Toluene
Diissocyanate.
Tear
Strength
A
measure of the force required to continue a tear in a foam after a split
or break has been started and expressed in pounds per inch (lbs./in.)This property is important in determining suitability of foam in
applications where the material is sewn, stapled, or otherwise anchored to
a solid substrate.Also
important in demoldability (ASTM D3574).
Tensile
Strength
The
pounds per square inch of force required to stretch a material to the
breaking point. (Reference ASTM D3574.)
Tensile
Strength - ASTM D412
The
force required to break a dumbbell test specimen. It is calculated by
dividing the breaking force in pounds by the cross section of the
unstressed specimen in square inches.
Tension
Set
The
increase in length expressed as a percent of the original length, when a
vulcanizate is stretched and released. It depends on time, load and
temperature defined for the test.
Thermoset
A
material that is cured by temperature and decomposes rather than melts
upon application of elevated temperatures.Most PUs are thermoset materials.
Tight
Foam
Flexible
polyurethane foam with many closed cells, resulting in low air flow
measurements.
Total
Vertical Motion (TVM)
The
deflection of a seating system during sitting.
Urethane
Actually
a misnomer as applied to polyurethane foam. A colorless, crystalline
substance used primarily in medicines, pesticides, and fungicides.
Urethane is not used in the production of urethane polymers or foams. The
urethanes of the plastics industry are so named because the repeating
units of their structures resemble the chemical urethane.
Vapor
Pressure
The
pressure of a vapor above the liquid from which it formed.Vapor pressure is temperature dependent.
Virgin
Foam
Unfilled
flexible slab stock foam that has not been processed in any manner other
than cutting to shape.
Voids
The
undesirable formation of large cavities or pockets in a foam structure.
Voids are usually caused by poor moldability or incorrect mold filling.
Water
Blown Foam
Flexible
polyurethane foam in which the gas for expansion is carbon dioxide
generated by the reaction between water and an isocyanate material.All flexible polyurethane foam is water blown, although auxiliary
blowing agents are often used to obtain special physical properties.
Windows
The
thin membranes formed between cell struts. Windows may be present (a
closed-cell foam) or absent (an open-cell foam) depending on the
particular foam chemistry used.
