Linear structure: The general structure of unvulcanized rubber. Due to the large molecular weight, without external force, the macromolecular chain is in the shape of a random curly curve. When the external force acts to remove the external force, the degree of entanglement of the coil changes, and the molecular chain rebounds, resulting in a strong tendency to restore. This is the origin of rubber's high elasticity.
Branched chain structure: the aggregation of the branched rubber macromolecular chain to form a gel. Gel is detrimental to rubber performance and processing. During rubber mixing, various compounding agents often fail to enter the gel area, resulting in partial voids, unable to form reinforcement and cross-linking, and become weak parts of the product.
Cross-linked structure: Linear molecules are connected to each other through the bridges of some atoms or groups of atoms to form a three-dimensional network structure. As the vulcanization process progresses, this structure continues to strengthen. In this way, the free movement ability of the chain segment decreases, the plasticity and elongation rate decrease, the strength, elasticity and hardness increase, and the compression set and swelling degree decrease.