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High thermal cracking characteristics
Apr 28, 2018

The plastic raw material processing process is mainly melted, flow, set after cooling, and becomes the finished product. It is a process of heating and then cooling. It is also the process of changing the plastic from pellets to different shapes. The following will explain processing at different stages. process.

1, melting

The device heater (Heater) allows the raw material particles to gradually melt into a fluid flow, mainly with different raw materials suitable for temperature regulation, the temperature will tend to increase the flow of raw materials to speed up, can increase efficiency but does not necessarily guarantee the yield, must be appropriate Balance.

Another good effect and the high thermal cracking property of PP are that it is best to make the raw material smoothly flow to the die during production to avoid the phenomenon of insufficient charge or reflow. The return flow represents the flow of raw materials is faster than the output rate, and finally it will Increasing the average flow efficiency is equal to the increase in MFR, which is one of the methods available for processing, but it also causes the MFR distribution to be abnormal, which may lead to increased instability, which may increase the rate of defects.

However, because the application of PP products is not a high-precision product, the impact is not significant.

2, screw

Most of the PP processing is driven by the screw fluidity, so the design of the screw is very large, the size of the aperture affects the output, the compression ratio affects the pressure value also affects the output and the effect of the finished product, which also includes a variety of materials (Mix, additive and modifier) mixing effect.

The flow of raw materials mainly depends on the warmer, but the turning of the raw material will also generate frictional heat to promote the flowability, so the screw compression is smaller than the small drive flow, and the rotation speed must be increased. The friction heat energy generated must be more than the screw with large compression ratio.

Therefore, it is often said that there is no master in plastic processing, and the one who knows the machine's performance intentionally is the master. The heating of raw materials is not just a heater, it must be counted as both frictional heat and residence time.

Therefore, this is a practical issue, and experience helps to solve production problems and improve efficiency. If the screw is required to have a particularly good mixing effect, sometimes two-stage different screw or twin-shaft screw will be designed and the different types of screw will be divided to achieve various mixing effects.








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