How Does Temperature Affect Extrusion Process?
The material goes through a complex temperature process since materials go into hopper and its extrusion.
How is heat generated?
Temperature is one of the important conditions for the twin-screw extrusion process. The material changes from solid state to viscous flow state, which requires heat. There are two sources of heat in the extrusion process:
A. Heating plates which are assembled on screw barrel.
B. Friction among material flow;friction among material and screw, friction among material and barrel; and heat generated by shear of material.
Temperature Adjustment
Feeding port: In order to ensure the smooth addition of materials, it is necessary to maintain the friction among material, so these related screw barrel not only need to be heated but also need to be cooled. In the downstream of the feeding port, the barrel temperature needs to be increased in order to heat the material and promote its melting.
After melting: barrel should to be kept at a low temperature, so that the material can maintain high viscosity, which is easier to do mixing, and prevent material overheating dispersion at a low temperature extrusion.
The temperature setting of the barrel in the direction of the screw axis is related to the type of the twin-screw extruder, the screw configuration and the characteristics of the extruded material and the performance requirements for the final extrudate.It is carried out through the heating and cooling system nd temperature control.
Temperature rise due to pressure building
When screw pressure is built in melt transport, the melt temperature will rise :
This means that the pressure rises by 1 MPa and the temperature rises by 5 ℃. The temperature rise caused by this pressure is harmful and not beneficial which wastes energy easily causes material decomposition, and is not good for mixing.
The configuration of screw pressure zone must be optimized to reduce the length of screw back pressure zone, so as to minimize the energy input and temperature rise.
