The source and application characteristics of general-purpose rubber

Update:15-06-2019
Summary:

Natural rubber is made of latex, and a part of the non- […]

Natural rubber is made of latex, and a part of the non-rubber component contained in the latex remains in the solid natural rubber. Generally, natural rubber contains 92%-95% of rubber hydrocarbons, while non-rubber hydrocarbons account for 5%-8%. Due to different manufacturing methods, different origins and even different rubber seasons, the proportions of these ingredients may vary, but they are basically within the range.

Protein can promote the vulcanization of rubber and delay aging. On the other hand, the protein has strong water absorption, which can cause the rubber to absorb moisture and mold, and the insulation is degraded, and the protein has the disadvantage of increasing heat build-up. Acetone extracts are high-grade fatty acids and sterols, some of which act as natural antioxidants and accelerators, and others which help the powdered complexing agent disperse during the mixing process and soften the raw rubber. The ash mainly contains salts such as magnesium phosphate and calcium phosphate, and has a small amount of metal compounds such as copper, manganese, iron, etc., because these variable metal ions can promote rubber aging, so their content should be controlled.

The moisture in the dry glue does not exceed 1%, and it can be volatilized during processing. However, when the moisture content is too much, it will not only cause moldiness during the storage of the raw rubber, but also affect the processing of the rubber. For example, the compounding agent is easy to knead during mixing. Group; bubbles are easily generated during calendering and extrusion, and bubbles or sponges are formed during the vulcanization process. Linear structure: the general structure of unvulcanized rubber. Due to the large molecular weight, the macromolecular chain is in the form of a random coil curve without external force. When the external force acts, the removal force is removed, the entanglement of the coil changes, and the molecular chain rebounds, resulting in a strong tendency to recover. This is the origin of rubber high elasticity.

Branched structure: aggregation of branches of rubber macromolecular chains to form a gel. Gels are detrimental to the performance and processing of rubber. In the rubber mixing, various compounding agents often cannot enter the gel area, forming a partial blank, which cannot form reinforcing and cross-linking, and become a weak part of the product. Crosslinked structure: Linear molecules are connected to each other by bridging of some atoms or groups of atoms to form a three-dimensional network structure. This structure continues to increase as the vulcanization process progresses. Thus, the free mobility of the segments is reduced, the plasticity and elongation are lowered, the strength, elasticity and hardness are increased, and the compression set and the degree of swelling are lowered.

Rubber bellows