The structural composition of rubber products mainly includes the following three basic structures: branched structure, linear structure and cross-linked structure.
Branched structure: The branched chains of the macromolecular chains of rubber products gather to form gel. Gel is not good for the performance and processing of rubber products, because various compounding agents often cannot enter the gel area, resulting in local blanks, unable to form reinforcement and cross-linking, and becoming the weak part of the product.
Linear structure: This is the common structure of unvulcanized rubber products. Due to the large molecular weight, the macromolecular chain is in the form of a random coil without external force. When the external force is removed, the entanglement of the coil changes, the molecular chain rebounds, and a strong tendency to recover is generated. This is the origin of the high elasticity of rubber products.
Cross-linked structure: Linear molecules are connected to each other by bridging some atoms or atomic groups to form a three-dimensional network structure. As the vulcanization process proceeds, this structure is continuously strengthened, the free activity ability of the chain segment decreases, the plasticity and elongation decrease, but the strength, elasticity and hardness increase, and the compression permanent deformation and swelling degree decrease.
Specific applications and characteristics of different rubber products
· Natural rubber: Made from latex collected from rubber trees, it has good wear resistance, high elasticity and tear strength, but it is easy to age in the air and becomes sticky when heated.
· Hydrogenated nitrile rubber (HNBR): Its temperature resistance and weather resistance are much higher than those of general nitrile rubber, and it is suitable for seals in environmentally friendly refrigerant systems.
· Nitrile rubber (NBR): Made by copolymerization of butadiene and acrylonitrile, it has good oil resistance and aging resistance, and is suitable for seals such as oil seals and O-rings.
· Silicone rubber: The main chain is composed of alternating silicon and oxygen atoms, and has excellent high and low temperature resistance, ozone resistance and electrical insulation.
· Fluororubber (FKM): Contains fluorine atoms in the molecular structure, and has excellent high temperature resistance, oil resistance and chemical corrosion resistance.
These structures and characteristics make rubber products perform well in various applications and are widely used in automobiles, construction, electronics, industry and other fields.
