Ionomer SOFT
Hardness band
SOFT = soft / flexible low-modulus ionomer
Very low stiffness, rubber-like ionomer for soft-touch overmolds, ski boots and impact-absorbing layers.
Values for the SOFT condition
Other Ionomer grades and fills
Ionomer is listed in 5 conditions; see the grade overview at Ionomer.
Compare all 5 grades and fillsHide
| Grade · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness |
|---|---|---|---|---|---|
SOFTThis page Soft / flexible low-modulus ionomer | Very low stiffness, rubber-like ionomer for soft-touch overmolds, ski boots and impact-absorbing layers. | 6 | 20 | 550 | 33 Shore D |
Injection-molding grade | High-flow pellets for thin-wall caps, closures and cosmetic parts. | 13 | 26 | 330 | 55 Shore D |
Sodium-neutralized ionomer | Pick for maximum clarity, hot-tack, abrasion resistance and stiffness; more moisture-sensitive, dry before molding. | 17 | 33 | 350 | 62 Shore D |
Lithium-neutralized ionomer | Specialty high-stiffness, high-resilience grade used in golf-ball and high-performance sports applications. | 19 | 36 | 300 | 65 Shore D |
Hard / high-modulus golf-cover grade | Highly neutralized, stiff and cut-resistant — the classic golf-ball cover and ski-base ionomer. | 20 | 38 | 260 | 66 Shore D |
What is Ionomer SOFT?
Ionomer SOFT is Ionomer heat treated to SOFT — very low stiffness, rubber-like ionomer for soft-touch overmolds, ski boots and impact-absorbing layers. Ionomer SOFT has a yield strength of 6 MPa (0.87 ksi) and a tensile strength of 20 MPa (2.9 ksi) — weaker than 94% of polymer grades. Elongation at break is 550% and the elastic modulus is 0.05 GPa (0.0065 Msi). Ionomer SOFT has a density of 0.95 g/cm³ (0.0343 lb/in³), lighter than 75% of polymer grades. Its glass-transition temperature is -25°C (-13 °F).
Advantages
- Forms and bends easily — 95/100, better than 99% of polymer grades
- Readily welded — 93/100, better than 98% of polymer grades
- Ductile — tolerates forming and impact — 550%, better than 92% of polymer grades
- Low embodied carbon — 3 kg CO₂/kg, better than 83% of polymer grades
- Polishes to a fine finish — 70/100, better than 77% of polymer grades
Limitations
- Difficult to machine — 20/100, worse than 97% of polymer grades
- Low strength — 6 MPa (0.87 ksi), worse than 94% of polymer grades
- Limited service temperature — 55°C (131 °F), worse than 91% of polymer grades
- Absorbs moisture — dry before molding — 0.6%, worse than 75% of polymer grades
Ionomer SOFT properties
Typical room-temperature values for Ionomer SOFT; 26 are specific to this condition. Other listed values are Ionomer reference data and may not represent this condition. Bars are the position among polymer grades.
Physical7
Ionomer SOFT has a density of 0.95 g/cm³ (0.0343 lb/in³), lighter than 75% of polymer grades. Its glass-transition temperature is -25°C (-13 °F).
Mechanical12
Ionomer SOFT has a yield strength of 6 MPa (0.87 ksi) and a tensile strength of 20 MPa (2.9 ksi) — weaker than 94% of polymer grades. Elongation at break is 550% and the elastic modulus is 0.05 GPa (0.0065 Msi).
Thermal11
Ionomer SOFT is rated for continuous service to 55°C (131 °F). It conducts heat at 0.23 W/m·K (0.133 BTU/hr·ft·°F), better than 65% of polymer grades. Thermal expansion is 140 µm/m·K (77.8 µin/in·°F).
Electrical6
Ionomer SOFT is an electrical insulator with a dielectric strength of 32 kV/mm (812.8 V/mil) and a resistivity of 1×10¹⁴ Ω·m.
Chemical & Environmental3
Corrosion resistance is very good (78/100), worse than 61% of polymer grades. UV resistance is fair.
Sustainability4
Producing a kilogram of Ionomer SOFT takes about 88 MJ of energy and emits 3 kg of CO₂ — less than 76% of polymer grades. Typical recycled content is 0%.
Manufacturability8
Ionomer SOFT's machinability is poor (20/100, worse than 97% of polymer grades); weldability excellent (93/100); formability excellent (95/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with Ionomer SOFT
Is Ionomer easy to machine?
Machinable but gummy and elastic — use sharp positive-rake tools, high speed, low feed and air/mist cooling; expect poor dimensional accuracy on thin sections.
Can Ionomer be welded?
Excellent heat-sealing, hot-tack, impulse, ultrasonic and hot-plate welding; bonds well to aluminum foil, nylon and PET in coextrusion/extrusion-coating.
Can Ionomer be formed, bent or molded?
Dry 3–4 h at 50–60 °C, melt 190–250 °C (never above ~260 °C to avoid ionic degradation/gel), cold mold 10–30 °C for gloss; blown/cast film and thermoforming run easily.
What surface finishes work on Ionomer?
Molds to a very high natural gloss; paints and inks need corona/flame treatment; not suitable for plating, and printing over the sealant layer should be reverse-printed on the carrier film.
Ionomer 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 |
|---|---|---|
| methacrylic acid (or acrylic acid)acid comonomer providing ionic sites | 8 – 20 | 12 |
| Zn or Na (or Li) neutralizing cation20–70 % of acid groups neutralized; ion type defines the grade family | 0.3 – 3 | 1.2 |
| additives (slip, antiblock, UV, antioxidgrade dependent | 0 – 1.5 | 0.3 |
| ethylenebackbone comonomer | ≥ 78 (balance) | — |
Ionomer SOFT — frequently asked
What is Ionomer SOFT used for?
Ionomer SOFT is typically used for golf ball covers, skin/blister packaging film, heat-seal layers for food packaging, ski boot shells and sporting goods, foam laminates and metal adhesion coatings. In short: toughest clear ethylene copolymer; best hot-tack seal layer; high-gloss abrasion resistance.
What is the yield strength of Ionomer SOFT?
Ionomer SOFT has a typical yield strength of 6 MPa (0.87 ksi) and a tensile strength of 20 MPa (2.9 ksi) — weaker than 94% of polymer grades. Strength varies by condition: see the 5 listed tempers.
Is Ionomer SOFT easy to machine?
Not especially — machinability is rated poor (20/100, worse than 97% of polymer grades). Machinable but gummy and elastic — use sharp positive-rake tools, high speed, low feed and air/mist cooling; expect poor dimensional accuracy on thin sections.
Can Ionomer SOFT be welded?
Yes — weldability is rated excellent (93/100). Excellent heat-sealing, hot-tack, impulse, ultrasonic and hot-plate welding; bonds well to aluminum foil, nylon and PET in coextrusion/extrusion-coating.
What surface finishes work on Ionomer SOFT?
Molds to a very high natural gloss; paints and inks need corona/flame treatment; not suitable for plating, and printing over the sealant layer should be reverse-printed on the carrier film.
Can Ionomer SOFT be formed, bent or molded?
Dry 3–4 h at 50–60 °C, melt 190–250 °C (never above ~260 °C to avoid ionic degradation/gel), cold mold 10–30 °C for gloss; blown/cast film and thermoforming run easily.
What is the maximum service temperature of Ionomer SOFT?
Ionomer SOFT is rated for continuous use to about 55°C (131 °F), and briefly to 90°C. Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
Sources
- Surlyn ionomer resin product and processing datasheets — DuPont / Dow Packaging & Specialty Plastics (2022)
- CAMPUS plastics property database — ethylene ionomers — CAMPUS/CWFG (2023)
- Engineering Plastics, ASM Engineered Materials Handbook Vol. 2 — ASM International (1988)
- ASTM D638 / D790 / D256 / D1238 test methods for plastics — ASTM International (2022)
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.