ACM A70
Hardness band · default condition
A70 = shore A 70
Default automotive oil-seal/gasket compound; best balance of sealing force, tear and set.
Values for the A70 condition
Other ACM grades and fills
ACM is listed in 11 conditions; see the grade overview at ACM.
Compare all 11 grades and fillsHide
| Grade · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness |
|---|---|---|---|---|---|
Shore A 50 | Choose for low-clamp-load gaskets, diaphragms and boots needing high flexibility in hot oil. | — | 8 | 330 | 12 Shore D |
Non-black / mineral-filled coloured ACM | Silica/clay-filled light-coloured compounds for identification-coded or non-marking seals; lower strength than black. | — | 9 | 250 | 70 Shore A |
Low-temperature grade | Pick when seals must stay flexible to −35/−40 °C; trades some hot-oil swell resistance. | — | 10 | 250 | 22 Shore D |
Shore A 60 | Compromise hardness for valve-cover gaskets and moulded boots with moderate sealing loads. | — | 10 | 280 | 16 Shore D |
Active-chlorine cure-site type | Older low-cost type with good processing safety; slower cure, higher set and risk of mould/metal corrosion. | — | 11 | 260 | 68 Shore A |
A70DefaultThis page Shore A 70 | Default automotive oil-seal/gasket compound; best balance of sealing force, tear and set. | — | 11 | 220 | 22 Shore D |
Heat-resistant / high-heat-stabilised grade | Choose for turbo-era powertrain seals seeing 160–175 °C oil sump peaks. | — | 11 | 200 | 23 Shore D |
Epoxy cure-site type | Ammonium-salt/acid cured epoxy type; good hot-oil ageing and moderate set, used in hoses and gaskets. | — | 11 | 240 | 72 Shore A |
Carboxyl cure-site type | Mainstream modern type: fast cure, low compression set, no metal-corroding chlorine residues. | — | 12 | 210 | 22 Shore D |
Shore A 80 | For high-pressure shaft seals and extrusion-resistant O-rings in hot oil. | — | 13 | 170 | 30 Shore D |
Shore A 90 | Back-up rings, bonded-to-metal seal cases and anti-extrusion parts; low elongation. | — | 14 | 110 | 40 Shore D |
What is ACM A70?
ACM A70 is ACM heat treated to A70 — default automotive oil-seal/gasket compound; best balance of sealing force, tear and set. ACM A70 has a tensile strength of 11 MPa (1.6 ksi), weaker than 78% of polymer grades. Elongation at break is 220% and the elastic modulus is 0.01 GPa (8.7×10⁻⁴ Msi). ACM A70 has a density of 1.25 g/cm³ (0.0452 lb/in³), heavier than 64% of polymer grades. Its glass-transition temperature is -25°C (-13 °F).
Advantages
- Good UV / weathering resistance — 85/100, better than 88% of polymer grades
- High service temperature — 150°C (302 °F), better than 79% of polymer grades
- Ductile — tolerates forming and impact — 220%, better than 77% of polymer grades
Limitations
- Difficult to machine — 30/100, worse than 87% of polymer grades
- Low stiffness — 0.01 GPa (8.7×10⁻⁴ Msi), worse than 86% of polymer grades
- Absorbs moisture — dry before molding — 1%, worse than 84% of polymer grades
- High mold shrinkage — 2%, worse than 81% of polymer grades
ACM A70 properties
Typical room-temperature values for ACM A70; 16 are specific to this condition. Other listed values are ACM reference data and may not represent this condition. Bars are the position among polymer grades.
Physical3
ACM A70 has a density of 1.25 g/cm³ (0.0452 lb/in³), heavier than 64% of polymer grades. Its glass-transition temperature is -25°C (-13 °F).
Mechanical10
ACM A70 has a tensile strength of 11 MPa (1.6 ksi), weaker than 78% of polymer grades. Elongation at break is 220% and the elastic modulus is 0.01 GPa (8.7×10⁻⁴ Msi).
Thermal8
ACM A70 is rated for continuous service to 150°C (302 °F). It conducts heat at 0.2 W/m·K (0.116 BTU/hr·ft·°F), worse than 56% of polymer grades. Thermal expansion is 200 µm/m·K (111.1 µin/in·°F).
Electrical5
ACM A70 is an electrical insulator with a dielectric strength of 15 kV/mm (381 V/mil) and a resistivity of 1×10⁸ Ω·m.
Chemical & Environmental3
Corrosion resistance is very good (75/100), worse than 66% of polymer grades. UV resistance is excellent.
Sustainability4
Producing a kilogram of ACM A70 takes about 110 MJ of energy and emits 5 kg of CO₂ — more than 64% of polymer grades. Typical recycled content is 0%.
Manufacturability4
ACM A70's machinability is poor (30/100, worse than 87% of polymer grades); formability very good (70/100).
Common Calculations4
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with ACM A70
Is ACM easy to machine?
Cured ACM is die-cut, waterjet or cryogenically deflashed; conventional machining smears and is avoided.
Can ACM be welded?
Thermoset — cannot be welded; joints are made by adhesive bonding or by co-curing/bonding to metal inserts with phenolic-type primers.
Can ACM be formed, bent or molded?
Compression, transfer or injection moulded; press cure ~170–190 °C for 2–5 min plus 4 h post-cure at 150–175 °C to develop low compression set; mill mixing is sticky and needs cool rolls and processing aids.
What surface finishes work on ACM?
Post-cure removes volatiles and odour; surfaces can be PTFE- or MoS2-coated / plasma-treated on seal lips to cut friction; no painting or plating.
ACM chemical composition (wt %)
Limits by weight percent from the governing specification, written the way the spec states them — a single maximum for impurities, a range for alloying elements, and the base element as balance. Nominal is the typical mid-range value.
| Element | Spec limit (wt %) | Nominal |
|---|---|---|
| cure-site monomer (carboxyl, active chlopart of the base polymer | 0.5 – 5 | 2 |
| carbon black (N550/N774)reinforcing filler; sets hardness | 20 – 45 | 30 |
| plasticizer (ester/ether type)improves low-temperature flexibility | 0 – 15 | 7 |
| curatives + accelerators (diamine/blocke | 0.5 – 3 | 1.5 |
| stearic acid / processing aids / antioxi | 1 – 5 | 3 |
| ethyl acrylate / n-butyl acrylate / methmonomer ratio sets Tg / oil-swell balance | ≥ 45 (balance) | — |
ACM A70 — frequently asked
What is ACM A70 used for?
ACM A70 is typically used for transmission seals, valve stem seals and gaskets in hot oil environments. In short: hot-oil seal workhorse; cheaper than HNBR or FKM; 150 °C continuous in oil.
What is the tensile strength of ACM A70?
ACM A70 has a typical tensile strength of 11 MPa (1.6 ksi) — weaker than 78% of polymer grades. Strength varies by condition: see the 11 listed tempers.
Is ACM A70 easy to machine?
Not especially — machinability is rated poor (30/100, worse than 87% of polymer grades). Cured ACM is die-cut, waterjet or cryogenically deflashed; conventional machining smears and is avoided.
Can ACM A70 be welded?
Thermoset — cannot be welded; joints are made by adhesive bonding or by co-curing/bonding to metal inserts with phenolic-type primers.
What surface finishes work on ACM A70?
Post-cure removes volatiles and odour; surfaces can be PTFE- or MoS2-coated / plasma-treated on seal lips to cut friction; no painting or plating.
Can ACM A70 be formed, bent or molded?
Compression, transfer or injection moulded; press cure ~170–190 °C for 2–5 min plus 4 h post-cure at 150–175 °C to develop low compression set; mill mixing is sticky and needs cool rolls and processing aids.
What is the maximum service temperature of ACM A70?
ACM A70 is rated for continuous use to about 150°C (302 °F), and briefly to 175°C. Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
Sources
- ASTM D1418 — Rubber and rubber lattices: nomenclature — ASTM (2022)
- ASTM D2000 / SAE J200 — Classification system for rubber products in automotive applications — ASTM / SAE (2020)
- Nipol AR acrylic rubber technical data — Zeon Corporation (2022)
- Noxtite ACM / PA acrylic elastomer product guide — Unimatec (Nippon Mektron) (2021)
- Rubber Technology: Compounding and Testing for Performance — Hanser (2009)
- Handbook of Elastomers / specialty heat- and oil-resistant elastomers chapter — CRC Press (2001)
Property data is compiled from published supplier and standards handbooks and normalised for comparison. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.