What property makes elastomers suitable for applications requiring flexibility?

Elastomers are suitable for applications requiring flexibility primarily due to their low cross-link density. This property allows the polymer chains to move relatively freely in relation to one another. The lower the degree of cross-linking in an elastomer, the more its molecular chains can slide past each other, contributing to the material's ability to stretch and recover, much like rubber. This characteristic is essential in applications such as seals, gaskets, and flexible components in various engineering contexts, where flexibility and resilience under stress are critical.

In contrast, a high cross-link density would restrict the movement of polymer chains, resulting in a more rigid structure that is less suitable for flexible applications. While high thermal resistance and electrical conductivity may be desirable properties in certain contexts, they do not directly contribute to the flexibility of elastomers. Flexibility is fundamentally tied to the arrangement and interaction of molecular chains within the material.