Extrusion is one of the basic processes in the rubber process. The extrusion expansion rate is a common process problem in the extrusion process. For example, when extruding an inner tube, the diameter of the tire blank is larger than the diameter of the die; the thickness of the semi-finished product of the extruded tread increases, shortened length, etc. When using reclaimed rubber to produce rubber products, the manufacturer of reclaimed rubber products must fully consider the process performance, that is, the expansion-shrinkage phenomenon, when designing the extrusion rubber formula.
1. Molecular structure of reclaimed rubber and extrusion performance of rubber
In theory, the molecular chain is flexible, the intermolecular force is small, the rubber viscosity is small, the relaxation time end, and the expansion ratio are small, otherwise the expansion ratio is large. The reclaimed rubber has large molecular weight, high viscosity and poor fluidity. The elastic deformation generated during the flow process requires a long relaxation time, and the extrusion expansion ratio is large; the molecular chain is small, the extrusion expansion ratio is small. The molecular chain distribution of reclaimed rubber becomes wider and the expansion ratio increases. Butterfly rubber is prone to molecular chain entanglement, increasing the intermolecular force, prolonging the relaxation time and increasing the expansion ratio.
When using reclaimed rubber to produce rubber products, the larger the rubber content, the greater the elastic deformation, and the larger the extrusion expansion ratio; but the rubber content is too small, and it is not easy to extrude, it is recommended to control it at 30%-50%, which is better for the extrusion performance. favorable.
2. Reclaimed rubber product formula to reinforce filling system and rubber extrusion performance
In the production process of reclaimed rubber products, the addition of fillers will reduce the rubber content of the rubber, thereby reducing the elastic deformation of the rubber and reducing the extrusion expansion rate. The reclaimed rubber 2ELYY77 product formula uses high-structure carbon black, and the expansion rate is small; appropriately increasing the amount of carbon black and the structure degree can significantly reduce the extrusion expansion rate of the reclaimed rubber. It should be noted that when the amount of high-structure carbon black or activated carbon black is too large, it is difficult to extrude, and the amount of carbon black needs to be reasonably controlled.
3. Reclaimed rubber product formula softening plasticizing system and rubber extrusion performance
Adding an appropriate amount of softener in the production of reclaimed rubber extrusion rubber can reduce the extrusion expansion rate of the rubber compound, reduce the expansion rate, and make the specifications of the extruded semi-finished products more accurate. It is necessary to avoid the use of softeners and plasticizers that are easy to spray.
To improve the extrusion performance of reclaimed rubber products through formula design, rubber product manufacturers also need to properly adjust the vulcanization system to give the rubber a long enough scorch time to avoid early vulcanization during extrusion; try to avoid the use of volatilization or moisture content When preparing low-strength or sticky soft rubber, adding an appropriate amount of reinforcing agent can increase the strength and Mooney viscosity of the rubber to avoid air entrapment during extrusion and poor stiffness after extrusion. There was a problem. Later, the editor will continue to share with you other measures to improve the extrusion performance of reclaimed rubber products.
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