Working principle and applications of rubber calenders

A rubber calender is a basic piece of equipment used in the processing of rubber products. It uses mechanical action to extrude and stretch rubber compounds near their viscous flow temperature, producing rubber sheets or cloths with a specific thickness, width, and surface finish.

The working principle of a rubber calender is based on the extrusion and stretching deformation of the rubber compound within the gap between the rollers.

• Core Process: Rubber compound with a certain temperature and plasticity is fed into the gap between two or more counter-rotating rollers. The rotation of the rollers generates friction, pulling the rubber compound into the gap.
• Extrusion and Stretching: The roller gap gradually decreases from the inlet to the outlet (or is achieved by adjusting the roller spacing). During this process, the rubber compound is subjected to strong extrusion, shearing, and stretching actions, its volume is compressed, and its shape is stretched into a thin sheet.
• The Role of Speed ​​Ratio: To meet different process requirements (such as mixing, venting, and permeation), a certain speed ratio is usually maintained between adjacent rollers. For example, a speed ratio (e.g., 1:1.1 to 1:1.5) for the feed rollers helps to remove air bubbles, while a speed ratio (e.g., 1:1.4 to 1:1.5) for the wiping rollers enhances the penetration of the rubber compound into textiles.
• Forming and Output: Finally, the rubber compound is calendered into a sheet of predetermined thickness and width and output from the last set of rollers, cooled, and then wound up.

Rubber calenders are widely used in the rubber industry and are key equipment in the production of tires, hoses, belts, and other products.

• Sheeting: Directly pressing the compounded rubber into sheets of uniform thickness, serving as semi-finished products for subsequent processes.
• Laminating: Covering the surface of textiles (such as cord fabric, canvas) or steel cord fabric with rubber compound to form a rubberized fabric, used to reinforce the skeletal structure of rubber products. This process typically uses constant-speed calendering (speed ratio 1:1).
• Rubbing: Allowing the rubber compound to penetrate into the gaps of the textile, enhancing the bonding strength between the rubber compound and the reinforcing material. This process uses differential-speed calendering (speed ratio greater than 1), utilizing shear force to promote penetration.
• Forming and Bonding: Pressing into sheets with specific cross-sectional shapes or surface patterns, or bonding two layers of rubber sheets together.
• Steel Cord Calendering: Composite steel cords between two layers of rubber sheets to manufacture reinforcing cord fabric for tires.