Elastomers

Definition

Elastomers are a class of polymers characterized by their ability to undergo significant elastic deformation when subjected to stress and return to their original shape when the stress is removed. They are often rubber-like materials that combine flexibility, resilience, and durability, making them suitable for a wide range of applications. Their unique properties stem from their molecular structure, which allows for considerable chain mobility and entanglement.

5 Must Know Facts For Your Next Test

1. Elastomers can undergo large strains of up to 1000% without permanent deformation, making them ideal for applications like seals and gaskets.
2. The main types of elastomers include natural rubber, synthetic rubber (like styrene-butadiene rubber), and thermoplastic elastomers.
3. Temperature affects the performance of elastomers; at low temperatures, they can become brittle, while at high temperatures, they may lose elasticity.
4. Elastomers exhibit viscoelastic behavior, which means they have both viscous and elastic properties, influencing how they respond under different stress conditions.
5. Common applications of elastomers include automotive tires, medical devices, footwear, and various industrial products due to their excellent flexibility and resistance to wear.

Review Questions

• How does the molecular structure of elastomers contribute to their unique elastic properties?
  • The molecular structure of elastomers features long polymer chains that are loosely entangled and exhibit significant flexibility. This allows them to stretch considerably when stressed, as the chains can slide past each other without breaking. When the stress is removed, the chains return to their original arrangement due to the weak intermolecular forces present, resulting in the material's ability to recover its shape.
• Discuss the role of cross-linking in improving the performance characteristics of elastomers.
  • Cross-linking plays a crucial role in enhancing the mechanical properties of elastomers by creating a network structure among polymer chains. This chemical bonding increases the strength and thermal stability of the material while reducing its tendency to flow under stress. As a result, cross-linked elastomers maintain their shape better under various conditions and exhibit improved resistance to deformation, making them suitable for demanding applications.
• Evaluate how oxidative degradation impacts the longevity and performance of elastomers in practical applications.
  • Oxidative degradation significantly impacts the longevity and performance of elastomers by breaking down polymer chains through chemical reactions with oxygen. This process can lead to changes in color, loss of elasticity, and decreased mechanical strength over time. In practical applications, such as automotive tires or medical devices, exposure to oxygen can shorten their lifespan and affect reliability. Understanding oxidative degradation is essential for selecting appropriate additives or protective measures to enhance the durability of elastomeric materials.

Related terms

Thermoplastic elastomers:

A type of elastomer that combines the properties of rubber with the processability of thermoplastics, allowing them to be molded and reshaped upon heating.

Cross-linking: The process of chemically bonding polymer chains together to form a network structure, enhancing the mechanical properties and thermal stability of elastomers.

Polymer blending: A technique that involves mixing two or more polymers to achieve desired physical properties, often used to enhance the performance of elastomers.