According to the theory of plastic melting, the extruder screw of the blown film is divided into three sections: the feeding section, the melting section and the homogenizing section. At the end of the feeding section, the temperature of the melt should be a viscous flow temperature, depending on the melting theory. All kinds of blown film resin viscous flow temperature was PP:164-175 degrees Celsius, PE:105-135 degrees Celsius, PA:195-210 degrees celsius. In the feeding section of the inlet, the temperature is low, to prevent the resin viscous flow plug feeding mouth, feeding temperature is about 120-165 degrees. At the end of the feeding section is equal to the melting point or the temperature of viscous flow, in this section can be set as the heating temperature of geometric alignment; melting section starts when the temperature reaches the temperature of viscous flow to melt, for crystalline resin, temperature of viscous flow is equal to the melting point temperature. Then need continuous heating temperature (the temperature is about 150-200 degrees), in order to make the polymer molecular chain length, different heat energy has melting; in homogeneous section, re melting homogenizing and quantitative pressure constant output melt, the temperature can be kept constant, or the ratio of the melting temperature is only slightly at the end of period increased (2-5 degrees).
For blowing film, through the head section of the low temperature, for the film and normal blowing, not rupture of membrane, membrane collapse phenomenon. In general, it is about 10 degrees lower than the equalization section. From the homogenizing section to touch the temperature but also can be regarded as the arithmetic of temperature drop.
The control points of the extrusion temperature is:
Different kinds of resin, blown film process temperature;
The same kind of resin, the type and the melt index are different, the process temperature is different, the melt index is large, the fluidity is good, the temperature is low.
The same resin, blown film thickness is different, the process temperature is also different. Processing of thick film, the process temperature can be a bit higher, the temperature can also touch the mouth a little higher, is conducive to reducing viscosity, resin flow.