Elastomers are a class of polymers characterized by their high elasticity, meaning they can undergo significant deformation and then return to their original shape when the stress is removed. They are widely used in various applications due to their flexibility, resilience, and strength. Elastomers are essential in many industries, including automotive, construction, and healthcare.

Key Properties of Elastomers

  1. Elasticity: Elastomers can stretch up to several times their original length and return to their initial shape once the stress is released.
  2. Amorphous Structure: Elastomers have an amorphous molecular structure, which contributes to their elasticity. They have long polymer chains that are loosely cross-linked, allowing them to be flexible.
  3. Low Young's Modulus: They possess a low Young’s modulus, meaning they require less force to deform.
  4. Thermoelastic Behavior: At low temperatures, elastomers are glassy and brittle, while at higher temperatures, they exhibit a rubbery, elastic behavior.

Types of Elastomers

  1. Natural Elastomers: Derived from natural sources such as rubber trees. Example: natural rubber (polyisoprene).
  2. Synthetic Elastomers: Produced through polymerization of petrochemicals. Examples include:
    • Styrene-Butadiene Rubber (SBR): Commonly used in tires.
    • Nitrile Rubber (NBR): Used in oil-resistant applications.
    • Silicone Rubber: Known for heat resistance and used in medical and cooking applications.
    • Neoprene: Used in wet suits and gaskets due to its weather resistance.

Structure of Elastomers

Elastomers have long, flexible polymer chains with a low degree of cross-linking, allowing for free movement when stress is applied. These chains uncoil and straighten under tension but return to their coiled state when the stress is released. The cross-links between the chains are crucial for maintaining the integrity and preventing permanent deformation.

Applications of Elastomers

  1. Automotive: Tires, seals, hoses, and belts.
  2. Consumer Goods: Footwear soles, elastic bands, and toys.
  3. Healthcare: Gloves, medical tubing, and seals.
  4. Construction: Sealants and insulation materials.

Advantages of Elastomers

  • High Flexibility: Elastomers can endure large deformations without permanent damage.
  • Good Impact Resistance: Due to their flexibility, they absorb impact well, making them ideal for shock absorbers.
  • Chemical Resistance: Some elastomers (like nitrile rubber) are resistant to oils and chemicals, making them suitable for industrial applications.

Disadvantages of Elastomers

  • Thermal Sensitivity: Elastomers tend to degrade at high temperatures.
  • Aging: Exposure to UV light, oxygen, and ozone can cause elastomers to become brittle over time.
  • Limited Load-Bearing Capacity: Due to their softness, elastomers are not suitable for applications requiring high mechanical strength.

Curing or Vulcanization

To enhance the properties of elastomers, they are often vulcanized—a process involving heating with sulfur to create additional cross-links between the polymer chains. This increases their strength, elasticity, and resistance to chemicals.

Summary

Elastomers are versatile materials that combine flexibility, durability, and resilience. They play a critical role in countless applications due to their unique properties. However, they have limitations regarding thermal stability and aging, which can be mitigated through modifications like vulcanization.