Rubber Roller Making Machine Manufacturer

Jinan Power Roller Equipment Co., Ltd.

Effect of vulcanization on rubber structure and properties


Release time:

2022-05-18

In the production process of rubber products, vulcanization is the last processing process. In this process, rubber after a series of complex chemical reactions, from linear structure to body structure, lose the plasticity of the compound, have the high elasticity of cross-linked rubber, and then obtain excellent physical and mechanical properties, heat resistance, solvent resistance and corrosion resistance, improve the use value and application range of rubber products.

Effect of vulcanization on structure and properties:

In the production process of rubber products, vulcanization is the last processing process. In this process, rubber after a series of complex chemical reactions, from linear structure to body structure, lose the plasticity of the compound, have the high elasticity of cross-linked rubber, and then obtain excellent physical and mechanical properties, heat resistance, solvent resistance and corrosion resistance, improve the use value and application range of rubber products.

Before vulcanization: linear structure, molecular interaction with van der Waals forces;
Properties: large plasticity, high elongation, solubility;
When vulcanizing: the molecule is initiated, and a chemical cross-linking reaction occurs;
After vulcanization: network structure, molecular bonding with chemical bonds;
Structure: (1) chemical bonds; (2) the position of the cross-linked bond; (3) the degree of cross-linking; (4) cross-linking; Properties: (1) Mechanical properties (fixed tensile strength. Hardness. Tensile strength. Elongation. elasticity); (2) Physical properties (3) chemically stable after vulcanization;

Changes in rubber properties:
Taking natural rubber as an example, with the increase of the degree of vulcanization;
(1) Changes in mechanical properties (elasticity. Tear off strength. Tensile strength. Tear strength. hardness) increased (elongation. Compression set. fatigue and fever) decreased
(2) The change of physical properties reduces the air permeability and water permeability rate, cannot be dissolved, can only swell, and the heat resistance is improved
(3) Changes in chemical stability

Increased chemical stability, the reason

a. The crosslinking reaction eliminates the presence of chemically active groups or atoms, making the aging reaction difficult
      b . The network structure hinders the diffusion of low molecules, making it difficult for rubber radicals to diffuse 

Selection and determination of rubber vulcanization conditions
  First, vulcanization pressure
(1) Rubber products need to apply pressure when vulcanizing, the purpose of which is:
      a. Prevent bubbles in the rubber material and improve the compactness of the rubber material;
      b. Make the rubber material flow and fill the mold to make products with clear patterns
     c. Improve the adhesion between each layer in the product (rubber layer and cloth layer or metal layer, cloth layer and cloth layer), and optimize the physical properties of vulcanized rubber (such as flex resistance).
(2) In general, the selection of vulcanization pressure should be determined according to factors such as product type, formula, plasticity and so on.
(3) In principle, the following laws should be followed: plasticity is large, and the pressure should be small; The product is thick, the number of layers, the structure is complex, and the pressure should be greater; The pressure of thin products should be smaller, and even atmospheric pressure can be used

There are several ways to vulcanize pressurization:
(1) The hydraulic pump transfers the pressure to the mold through the plate vulcanizing machine, and then the mold is transferred to the rubber material
(2) Direct pressurization by vulcanizing medium (such as steam).
(3) Pressurized by compressed air
(4) Injection by injection machine

Second, vulcanization temperature and vulcanization time
     The vulcanization temperature is the most basic condition for vulcanization reactions. The level of vulcanization temperature can directly affect the vulcanization speed, product quality and economic benefits of the enterprise, high vulcanization temperature, fast vulcanization speed and high production efficiency; Conversely, the production efficiency is low.
Increasing the vulcanization temperature can cause the following problems;
(1) Cause the cracking of rubber molecular chains and vulcanization to return to the original, resulting in the decline of the mechanical properties of the rubber material
(2) Reduce the strength of textiles in rubber products
(3) Shorten the scorching time of the rubber material, reduce the filling time, and cause the local lack of glue in the product
(4) Because thick products will increase the temperature difference between the inside and outside of the product, resulting in uneven vulcanization