Linear structure: the common structure of unvulcanized rubber. Due to its large molecular weight, it is in the form of fine mass without external force. When the external force is applied and removed, the entanglement degree of the fine group changes, and the molecular chain rebounds, resulting in a strong recovery tendency. This is the origin of the high elasticity of rubber.
Branched chain structure: aggregation of branched chains of rubber macromolecules to form gel. Gel is unfavorable to the performance and processing of rubber. During rubber mixing, various compounding agents often improve the gel area and form a local blank, which can not form reinforcement and cross-linking, and become the weak part of the product.
Crosslinking structure: linear molecules are connected to each other by bridging some atoms or atomic groups to form a three-dimensional network structure. With the progress of vulcanization process, this structure is continuously strengthened. In this way, the free movement ability of the chain segment decreases, the plasticity and elongation decrease, the strength, elasticity and hardness increase, and the compression set and swelling degree decrease.