Rubber is a versatile material, an ideal choice for industries ranging from aerospace to manufacturing. Its unique combination of properties—including elasticity, durability, and resistance to abrasion and impact—contribute greatly to that versatility, as well as its overall cost-effectiveness and ease of processing. However, one set of characteristics stands out: the thermal properties of rubber. These properties are crucial to how rubber performs in various temperature conditions.
There are several thermal properties that are relevant to various types of rubber:
- Thermal Conductivity: This is the material’s ability to transfer heat. Materials with high thermal conductivity can conduct heat efficiently, while those with low thermal conductivity are good insulators, resisting the flow of heat.
- Thermal Expansion: Most materials expand when heated and contract when cooled. This is relevant when dimensional stability is significant to product outcomes.
- Specific Heat Capacity: This is the amount of heat energy required to raise the temperature of a unit mass of a material by one degree Celsius. It’s relevant for understanding how materials respond to changes in temperature.
- Melting Point: While rubber doesn’t have a distinct melting point like metals, it softens and deforms at high temperatures, known as the softening point.
- Glass Transition Temperature (Tg): This is the temperature at which rubber transitions from a hard, glassy state to a rubbery, viscous state. It’s important for determining the temperature range over which a material can be used effectively.
- Thermal Stability: This refers to the ability of a material to maintain its properties when exposed to high temperatures over time, without significant degradation.
- Heat Resistance: This is a broader term that encompasses all the above properties and indicates how well materials can withstand exposure to high temperatures without degrading or losing its functionality.
Thermal Properties of Butyl Rubber
Butyl rubber, a synthetic rubber, is predominantly made up of isobutylene and a small amount of isoprene. This composition grants butyl rubber its distinctive properties, such as exceptional impermeability to gasses, strong resistance to weathering, and high damping capabilities. In terms of thermal conductivity, butyl rubber is considered a low-conductivity material, meaning it is a good insulator and can help reduce heat transfer.
The melting point of butyl rubber falls within the range of -54°C to -12°C (-65°F to 10°F), making it well-suited for applications requiring flexibility at low temperatures. The glass transition temperature, which is the temperature at which the rubber transitions from a hard, glassy state to a softer, rubbery state, is around -50°C (-58°F) for butyl rubber.
Butyl rubber’s unique properties make it a popular choice for thermal insulation, especially in applications requiring resistance to air, water, and steam. It is also used extensively in the production of seals and gaskets, as well as caps and septa for vials and bottles, thanks to its low thermal conductivity and flexibility.
Thermal Properties of Natural Rubber
Natural rubber is sourced from the latex of the Hevea brasiliensis tree and primarily consists of polyisoprene molecules. This molecular arrangement is responsible for natural rubber’s elasticity, resilience, and strength. Like butyl rubber, natural rubber also exhibits low thermal conductivity, making it a proficient insulator against heat transfer.
Natural rubber exhibits a relatively low melting point, typically ranging from 60°C to 70°C (140°F to 158°F), resulting in increased pliability at relatively moderate temperatures. In contrast, the glass transition temperature of natural rubber ranges from -70°C to -60°C (-94°F to -76°F), signifying its transition from a rigid, glassy state to a more flexible, rubbery state within this temperature range.
In contrast, natural rubber is favored for its heat resistance and flexibility, making it a choice material for high-temperature environments. Its applications include automotive hoses, belts, and seals, where it can withstand the heat generated by engines and machinery. Natural rubber is also used in the manufacturing of gloves and other protective equipment for workers in such environments.
Read more about rubber and silicone on our blog page or learn more about ILT, the world leader in manufacturing seals and septa here.
