Polymers generally exist in the glassy state, high elastic and viscous flow states three physical state, plastic extruder under certain conditions, the three physical state transformation will occur.
This is the internal basis of the plastic forming process, which is made by plastic extruder through the viscous flow, not the glass state and the high elastic state.
The plastic is moved by the hopper into the cylinder, which is gradually pushed towards the head in the direction of the screw.
The following are the characteristics of the physical state of plastics in the extrusion process.
This process actually reveals the polymer from charging period to the nose of a motion path, in this kind of passive movement, high polymer under the influence of temperature, from the glassy state to the high elastic state, and then to viscous flow is made into a fixed shape, and then back to the high elastic state, glassy state mechanics state change process.
Decomposition of the plastic extrusion process
Loading segment -- delivers and starts pressing the material
The snails are filled with loose solid particles (or powder), and the material begins to be compacted.
2, compression section
1) due to the resistance, the material being compacted: because the spiral groove becomes shallow gradually, and mesh, shunt plate and the nose, the resistance of the high pressure formed in the course of plastic, the material is very dense.
2) external heat, internal heat and material melting
At the same time, the temperature of the plastic is gradually rising with the heat and the internal friction heat generated by the mixing and shearing of the material.
For conventional three full thread screw, about a third of the compression section, with one point of contact for a material wall plastic temperature of viscous flow temperature, began to melt.
3) all the materials melt and become viscous
As the materials move forward, the amount of molten material increases.
While not molten material quantity to gradually reduce, about at the end of the compression section, and all the molten material into a viscous flow state, the temperature at every point but then it is not very evenly.
The homogenization segment - homogenization, extrusion
After the homogenization of the homogenized section, it is more uniform, and finally the screw will be used for the quantitative, constant pressure and temperature of the melting material.
4, the machine head - - shape, shape
The mouth mold is a forming part, and the material is obtained through it to obtain the geometrical shape and dimension of the section.
After cooling and other processes, the finished products are formed.
