Standard Test Methods for Flexible Cellular Materials—Slab, Bonded, and Molded Urethane Foam - PDF

ASTM D3574 Compression Platens – Universal Grip Data Sheet (PDF)

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ASTM D3574 is the family of test methods for flexible polyurethane foam: slab, bonded and molded foams used in seating, mattresses, furniture, automotive interiors and packaging. Each property has its own lettered test. The ones run on a universal testing machine are indentation force deflection (IFD), compression force deflection (CFD), tensile, tear and dynamic fatigue.

Main D3574 Tests

• Test A: density

• Test B1 – Indentation Force Deflection (IFD): the force to indent a full-size pad 25% and 65% with a round foot; the standard firmness number for seating and bedding

• Test C – Compression Force Deflection (CFD): the stress to compress a small specimen 50% between flat platens

• Test D – constant deflection compression set: thickness lost after 22 h at 70 °C under 50%, 75% or 90% compression

• Test E – tensile strength and elongation with a dumbbell specimen

• Test F – tear resistance with a slit block specimen

• Test H – resilience: ball rebound

• Tests I1–I5 – dynamic and static fatigue (roller shear and constant-force pounding)

D3574 does not include a flammability test; burn rate for automotive foam is tested separately (for example, FMVSS 302).

IFD Test (Test B1) Setup

• Specimen: 380 × 380 × 100 mm (15 × 15 × 4 in) is the reference size; full parts can also be tested

• Indentor foot: 203 mm (8 in) diameter, 323 cm² (50 in²) area, with a rounded edge

• Support plate: perforated so air can escape from under the foam

• Preflex the specimen twice to 75–80% of its thickness, then rest

• Indent at 50 mm/min (2 in/min) to 25% of thickness, hold 60 s and read the force; continue to 65%, hold 60 s and read again

Confirm preflex speed, rest time and tolerances against your copy of D3574.

Calculations

• IFD 25% and IFD 65%: forces in N (or lbf) per 323 cm² after the 60 s hold

• Support factor = IFD 65% ÷ IFD 25% (also called sag factor); higher means more bottom-out support

• CFD 50% = force ÷ specimen area (kPa)

• Compression set = (t0 − tf) ÷ t0 × 100, based on the original thickness

Example: a seat foam reads 150 N at 25% and 400 N at 65%. Support factor = 400 ÷ 150 = 2.67.

Equipment

• Universal testing machine with a 1–5 kN load cell and enough daylight for a 100 mm pad

• IFD fixture: 203 mm indentor foot and a perforated support plate larger than the specimen

• CFD platens at least as large as the 50 × 50 mm specimen

• Tensile grips and a die-cut dumbbell for Test E; tear grips for Test F

• Environmental chamber for heat-aged or humid-aged properties

Related Standards

• ASTM D1056 – flexible cellular sponge and expanded rubber

• ISO 2439 – indentation hardness of flexible foam

• ISO 3386 – compression stress-strain of flexible foam

• ASTM D3767 – rubber dimensions

ASTM D3574 FAQ

What is IFD in ASTM D3574?

Indentation force deflection (Test B1): the force needed to push a 323 cm² (50 in²) round foot 25% or 65% into a foam pad, read after a 60-second hold. It is the standard firmness rating for seat and mattress foam.

What is the difference between IFD and CFD?

IFD indents a large pad with a smaller round foot and reports force. CFD compresses a small specimen between flat platens larger than the specimen and reports stress, usually at 50% compression.

What is support factor?

IFD 65% divided by IFD 25%. A higher ratio means the foam stiffens more as it is compressed, giving more support before bottoming out.

Does ASTM D3574 include a flammability test?

No. D3574 covers physical properties such as density, IFD, CFD, compression set, tensile, tear, resilience and fatigue. Burn tests such as FMVSS 302 are separate standards.