Adjusting the temperature of a PP film blower to obtain the best film quality is a complex but crucial process that involves the precise control of multiple temperature zones. Here are some key steps and considerations
First, understand the melting characteristics of PP material
The melting temperature range of PP (polypropylene) is usually between 164-175 ° C. This is the basic basis for adjusting the temperature of the film blowing machine.
2. Setting and adjusting the temperature section
The temperature control of the film blowing machine is usually divided into several key sections, including the feeding section, the melting section and the homogenization section (also known as the metering section), and the die head temperature.
Charging section:
Temperature setting: The temperature of the feeding section should be relatively low to prevent resin viscous flow blocking the feed port. It is usually set between 50-90 ° C, depending on the specific equipment and the fluidity of the resin.
Adjustment principle: Ensure that the resin can successfully enter the melt stage, while avoiding degradation caused by overheating.
Melting section:
Temperature setting: The temperature of the melting section should be gradually increased to the viscous flow temperature of PP, that is, between 164-175℃. At this stage, the resin needs to be completely melted and mixed evenly.
Adjustment principle: Ensure that the resin is sufficiently melted while avoiding degradation and bubble formation caused by overheating. It is possible to determine whether the temperature is appropriate by observing the fluidity and color of the molten resin.
Homogenization segment:
Temperature setting: The temperature of the homogenizing section should be kept stable, or slightly higher than the temperature at the end of the melting section (about 2-5 ° C), to ensure that the melt reaches a uniform temperature and pressure before extrusion.
Adjustment principle: Maintain the steady flow and uniformity of the melt to provide high-quality melt for the subsequent film blowing process.
Die temperature:
Temperature setting: Die head temperature should be lower than the temperature at the end of the homogenization section, but should not be lower than the viscous flow temperature of PP. The specific temperature depends on the thickness and performance requirements of the film.
Adjustment principle: Ensure that the melt has a certain viscosity at the die head in order to form a stable film, while avoiding film breaking and collapsing phenomenon.
3. Optimization of temperature control system
Closed-loop control: The closed-loop temperature control system is used to monitor the current temperature in real time through the sensor and compare it with the preset temperature to automatically adjust the working state of the heater. This can greatly improve the accuracy and stability of temperature control.
High-precision sensor: Select a high-precision temperature sensor and calibrate it regularly to ensure the accuracy of temperature measurement.
Reasonable arrangement of the heater: reasonable arrangement of the heater position, so that the temperature distribution in each area is uniform, to avoid local overheating or undercooling phenomenon.
Iv. Other precautions
The influence of environmental factors: pay attention to the influence of external environmental factors (such as room temperature, humidity, etc.) on the temperature control system, and take corresponding measures to reduce its interference.
Regular maintenance: Regular maintenance and maintenance of the film blowing machine, clean the dust and oil on the surface of the electric heat pipe, and maintain its good heat dissipation performance.
Film quality evaluation: by detecting the film thickness, hardness, transparency and other quality indicators, timely adjustment of temperature parameters, in order to obtain the best film quality.
