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IIR
Material Type
Rubber
Material Full Name
Isobutylene-Isoprene Copolymer
Process Compatibility
Injection Molding, Compression Molding
Basic Properties
Property |
Parameter/Performance |
Remarks |
|---|---|---|
| Chemical Name | Isobutylene-Isoprene Copolymer | Main chain: isobutylene (97-99.5%), isoprene (0.5-3%) provides crosslinking sites |
| Molecular Structure | Saturated hydrocarbon elastomer | Low unsaturation (0.5-3%) enables ultra-low gas permeability |
| Density | 0.91~0.93 g/cm³ | One of the lightest commercial rubbers (10% lighter than NR) |
| Color | Translucent to off-white (colorable) | Pure gum is colorless; industrial grades contain antioxidants (light yellow) |
| Mechanical Properties | ||
| – Tensile Strength | 10-20 MPa (reinforced) | Requires carbon black/mineral fillers (e.g., N550) |
| – Elongation at Break | 300-800% | Lower elasticity than NR (rebound: 40-60%) |
| – Tear Strength | 20-40 kN/m | Poor self-adhesion (requires adhesives for laminates) |
| Thermal Properties | ||
| – Service Temperature | -50℃~150℃ (short-term 180℃) | Moderate heat resistance but better low-temp performance than FKM |
| – Heat Aging Resistance | ＞80% strength retention after 150℃×72h | Excellent oxidation resistance (saturated backbone) |
| Chemical Properties | ||
| – Gas Impermeability | N₂ permeability: 0.03×10⁻¹² cm³·cm/cm²·s·Pa | 1/20 of NR, 1/8 of EPDM (ideal for tire inner tubes) |
| – Chemical Resistance | Resists acids/alkalis/alcohols; swells in hydrocarbons | ＞200% volume swell in gasoline after 24h |
Processing Characteristics
Mooney Viscosity
- ML(1+8)125℃ 40-70 (requires high-temperature mastication)
Curing Systems
- Sulfur curing (slow; needs activators like ZnO/stearic acid)
- Resin curing (phenolic resin, long high-temperature cure)
Processing Challenges:
- High mixing heat (require staged feeding, roll temp <50℃)
- Severe mill sticking (PE release film recommended)
Common Application Areas
-
Tires: Tubeless tire innertliners, inner tubes (90% market share)
-
Medical: Injection vial stoppers (halogenated IIR, USP Class VI compliant)
-
Industrial: Vibration dampers, pipe linings (damping properties)
IIR Modified Types
Type |
Isoprene Content |
Characteristics |
Typical Applications |
|---|---|---|---|
| Standard IIR | 1.5-2.2% | Balanced properties | Tire inner tubes, sports bladders |
| Halogenated IIR (XIIR/CIIR) | – | Faster curing (2× speed) | Pharmaceutical stoppers, tire innertliners |
| Star-Branched IIR | 0.5-1.0% | Improved flow (30% lower Mooney) | Complex injection-molded parts |
Advantages & Disadvantages
Advantages |
Disadvantages |
|---|---|
| Best gas impermeability (among rubbers) | Slow curing (1/3 of NR speed) |
| Excellent damping (tanδ＞0.3) | Poor oil resistance |
| Ozone/aging resistance (20+ years outdoor) | High heat buildup (unsuitable for high-speed tires) |
Other Elastomer & Rubber Material Selection
NR Rubber
PU Rubber
TPE Rubber
FKM Rubber
TPU Rubber
FAQ Of IIR Materials
Visit our FAQ center for more questions.
What is IIR rubber's most irreplaceable property?
IIR (Isobutylene-Isoprene Rubber) exhibits the lowest gas permeability among all rubbers:
• Air permeability only 1/20 of NR, ideal for ultra-high airtightness applications
• Damping coefficient 10x NR (tan δ＞0.3 at 25℃)
• Resists acids/alkalis/ozone but has poor oil resistance (non-oil media only)
What are the advantages and disadvantages of NR rubber compared to synthetic rubber?
Complies with USP＜87＞/＜88＞ biocompatibility standards:
- Water vapor transmission rate <0.1 g/(m²·day) (moisture protection)
- Withstands repeated 121℃ steam sterilization
- Zero interaction with drug components (non-leachable)
How does IIR enhance tire innerliner performance?
Brominated modification (BIIR) enables:
• 50% higher cord adhesion strength (post-RFL treatment)
• Maintains airtightness at 0.5mm thickness with 15% weight reduction
• Dynamic fatigue life >1 million cycles (ISO 6943 test)