Ionomer INJ (Injection-molding grade)
Grade
High-flow pellets for thin-wall caps, closures and cosmetic parts.
Values for the INJ 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 |
|---|---|---|---|---|---|
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 |
INJThis page 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 INJ?
Ionomer INJ is Ionomer in the INJ grade — high-flow pellets for thin-wall caps, closures and cosmetic parts. Ionomer INJ has a yield strength of 13 MPa (1.89 ksi) and a tensile strength of 26 MPa (3.77 ksi) — weaker than 86% of polymer grades. Elongation at break is 330% and the elastic modulus is 0.24 GPa (0.0348 Msi). Ionomer INJ 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
- Readily welded — 92/100, better than 97% of polymer grades
- Forms and bends easily — 88/100, better than 85% of polymer grades
- Ductile — tolerates forming and impact — 330%, better than 83% 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
- Limited service temperature — 60°C (140 °F), worse than 87% of polymer grades
- Low strength — 13 MPa (1.89 ksi), worse than 86% of polymer grades
- Difficult to machine — 33/100, worse than 85% of polymer grades
- Absorbs moisture — dry before molding — 0.6%, worse than 75% of polymer grades
Ionomer INJ properties
Typical room-temperature values for Ionomer INJ; 28 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 INJ 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 INJ has a yield strength of 13 MPa (1.89 ksi) and a tensile strength of 26 MPa (3.77 ksi) — weaker than 86% of polymer grades. Elongation at break is 330% and the elastic modulus is 0.24 GPa (0.0348 Msi).
Thermal11
Ionomer INJ is rated for continuous service to 60°C (140 °F). It conducts heat at 0.24 W/m·K (0.139 BTU/hr·ft·°F), better than 67% of polymer grades. Thermal expansion is 140 µm/m·K (77.8 µin/in·°F).
Electrical6
Ionomer INJ 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 INJ 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 INJ's machinability is poor (33/100, worse than 85% of polymer grades); weldability excellent (92/100); formability excellent (88/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with Ionomer INJ
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 INJ — frequently asked
What is Ionomer INJ used for?
Ionomer INJ 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 INJ?
Ionomer INJ has a typical yield strength of 13 MPa (1.89 ksi) and a tensile strength of 26 MPa (3.77 ksi) — weaker than 86% of polymer grades. Strength varies by condition: see the 5 listed tempers.
Is Ionomer INJ easy to machine?
Not especially — machinability is rated poor (33/100, worse than 85% 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 INJ be welded?
Yes — weldability is rated excellent (92/100). 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 INJ?
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 INJ 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 INJ?
Ionomer INJ is rated for continuous use to about 60°C (140 °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.