What is elasticity?

Elasticity describes the ability of a material to deform under load and return to its original shape when the load is removed. Elasticity is created by the entangled Polymer chains and their lattice-like cross-linking. Under load, the polymer chains are stretched without being permanently damaged. When the load is released, the chains return to their entangled state. In rubber and plastics technology, elasticity is a key parameter for materials that Seals, spring elements or diaphragms.

 

Factors influencing elasticity

  • Polymer base: Different Rubber types have different elasticities (e.g. particularly high flexibility at low temperatures with VMQ, higher rigidity with FKM).
  • Degree of cross-linking: A stronger cross-linking increases the strength, but reduces the maximum elongation and flexibility.
  • Fillers and additives: Reinforcing fillers make the material stronger and less elastic. Plasticiser increase the elasticity, but can reduce the restoring force.
  • Hardness (Shore A): Elasticity decreases with increasing hardness. Softer compounds deform more easily.
  • Temperature: cold makes elastomers stiffer, heat increases flexibility but also causes them to age more quickly
  • Ageing and media contact: UV, ozone, heat or chemicals can reduce elasticity in the long term.
  • Duration of load: Short loads are well restrained. Long or permanent loads lead to permanent deformation.
  • Geometry: Thin or filigree areas deform more easily than solid cross-sections.

 

Types of elasticity

  • Linear elasticity: The deformation is proportional to the load (e.g. with small strains).
  • Non-linear elasticity: Typical for rubber with large deformations (polymer chains align parallel to each other, creating crystalline areas that have a stiffening effect)
  • Time-dependent elasticity (viscoelastic): The recovery behaviour depends on the duration and speed of the load.