Air Permeability: The dispersion rate of gas within polymers is related to the thermal activity of polymer molecules. Butyl rubber molecules have a dense arrangement of side methyl groups, restricting the thermal activity of polymer molecules, resulting in low air permeability and good air tightness.
Heat Stabilization: Butyl rubber vulcanizates exhibit excellent heat stability. Sulfur-vulcanized butyl rubber can be used in air for extended periods at 100°C or slightly lower temperatures, while resin-vulcanized butyl rubber can be used at temperatures up to 150°C–200°C. Thermo-oxidative aging of butyl rubber is degradative, with a softening trend.
Energy Absorption: Butyl rubber molecules lack double bonds and have a high density of side methyl groups, giving them excellent characteristics in absorbing vibration and impact energy. Within a wide temperature range (-30°C–-50°C), the rebound rate of butyl rubber is no more than 20%, clearly demonstrating that butyl rubber's ability to absorb mechanical energy is superior to other rubbers. The damping properties of butyl rubber at high deformation rates are inherent to the polyisobutylene chain segments and are largely unaffected by operating temperature, degree of unsaturation, vulcanization pattern, and formulation changes. Therefore, butyl rubber was a relatively ideal sound insulation and vibration damping material at the time.
Low Temperature Properties: The spatial structure of butyl rubber molecules is helical. Although it has a large number of methyl groups, each pair of methyl groups on both sides of the helix is offset from each other by an angle, so the butyl rubber molecular chain is still quite flexible, with a low glass transition temperature and good elasticity.
Ozone and Aging Resistance: The high saturation of the butyl rubber molecular chain gives it excellent ozone resistance and weathering resistance. Its ozone resistance is approximately superior to natural rubber and 10 times that of styrene-butadiene rubber.
Chemical Stability: The high saturation structure of butyl rubber gives it high chemical stability. Butyl rubber exhibits excellent corrosion resistance to most inorganic and organic acids. While it is not resistant to concentrated oxidizing acids, such as nitric acid and sulfuric acid, it is resistant to non-oxidizing acids and moderately concentrated oxidizing acids, as well as alkaline solutions and redox solutions. After immersion in 70% sulfuric acid for 13 weeks, butyl rubber showed virtually no loss in strength and elongation, while the properties of natural rubber and styrene-butadiene rubber were severely degraded.
Electrical Properties: Butyl rubber has better electrical insulation and corona resistance than ordinary synthetic rubbers. Its volume resistivity is 10 to 100 times higher than that of ordinary rubbers, its dielectric constant (1kHz) is 2 to 3, and its power factor (100Hz) is 0.0026.
Water Absorption: Butyl rubber has extremely low water permeability. At room temperature, its water absorption rate is only 1/10 to 1/15 that of other rubbers.
