Softest compound, most stable seal line.
Aperflu 3275 pairs the family's lowest hardness (68 Shore A) with an 8% compression set — a rare combination. Soft compounds usually take a set quickly; this one does not.
That makes it the right choice where the mating surface is delicate or the available sealing force is limited: glass-lined reactors, ceramic-faced fittings, lightweight alloy housings. With 19 MPa tensile and 145% elongation it still has enough body for reliable handling and installation.
A close matchup: both are carbon-black filled, general-purpose FFKM compounds rated to the 316 °C class. Aperflu 3275 runs softer (68 Shore A) with more strength and roughly half the compression set; Kalrez 4079 is harder and stays flexible 9 °C lower.
| Property | Aperflu 3275 | Kalrez 4079 |
|---|---|---|
| Hardness | 68 Shore A | 75 Shore A |
| 100 % modulus | 9.0 MPa | 7.24 MPa |
| Tensile strength at break | 19.0 MPa | 16.88 MPa |
| Elongation at break | 145 % | 150 % |
| Compression set, 70 h | 8 % @ 200 °C | 14 % @ 204 °C |
| Set test specimen | O-ring #214 | Pellet |
| Max. service temperature | 315 °C | 316 °C |
| Lowest service temperature | −10 °C | −19 °C |
Highlighted cells indicate the more favourable published value.
13% higher tensile strength (19.0 vs 16.88 MPa), 24% higher 100% modulus — more sealing force at low strain — and about 40% lower compression set (8% vs 14% at 200–204 °C / 70 h).
Five points more elongation and a service floor 9 °C lower (−19 °C vs −10 °C), useful for cold-start or outdoor service. Both sit in the same 316 °C class, so maximum temperature is not a differentiator.
Soft, low-set sealing of glass-lined and low-load joints up to 315 °C: 3275. Harder general-purpose parts that need extrusion resistance and −19 °C flexibility: 4079.
Kalrez® is a trademark of DuPont de Nemours, Inc. Kalrez 4079 values are taken from DuPont published technical information (Rev. 1, July 2019); Aperflu 3275 values are taken from its compound technical data sheet (rev. 06/2016). All figures are typical values, not specifications. The two datasets use different specimens (O-ring #214 vs pellet) and set temperatures (200 °C vs 204 °C) — confirm selection with immersion testing in the actual process fluid.
68 Shore A seals without over-stressing fragile mating surfaces.
Seals reliably where bolt torque or spring force is limited by design.
Soft, low-set sealing for hygienic clamp and tri-clover connections.
Send us your media, temperature and pressure profile — we will recommend the grade.