Which category does not belong to the classification of natural rubber?

The classification of natural rubber typically includes categories like soft, semi-hard, and hard based on their physical properties and applications. Natural rubber is known for its high elasticity, which allows it to deform easily and return to its original shape.

The category "elastic" does not fit into the traditional classifications because it describes a property rather than a distinct category itself. While all natural rubber types exhibit elasticity, it is not categorized in the same way as soft, semi-hard, or hard. Those latter classifications refer specifically to the hardness or softness of the rubber material, which can vary based on processing and formulation.

Understanding the properties of natural rubber helps in identifying appropriate applications and further refining its use in various industries, making it critical to distinguish between the classifications and general properties like elasticity.