01 Effect of Film blowing machine temperature on product quality
Whether the plasticization is complete and uniform, and whether the bubble shape is stable, the temperature is one of the main process conditions.
When the film-blowing machine is producing the polyethylene-blown film, different temperatures should be selected according to the melt index (MI) of the raw material and different product specifications. Generally, the larger the melt index, the lower the temperature used for processing, and the reverse then high.
If the temperature of the extruder is low, the viscosity of the plastic is high, the transparency of the film is poor, unplasticized crystal points and clouds are prone to occur, the film is easily broken, and the elongation at the break of the film is reduced.
If the temperature of the extruder is too high, the viscosity of the plastic will decrease, the fluidity will be large, and the opening of the film will be poor, which will easily lead to unstable production, but the transparency will increase.
If the temperature continues to rise, the material will be decomposed by overheating, and the film will turn yellow with a yellow-black focus. Therefore, the unstable temperature of the film-blowing machine will make the bubble shape incorrect, affect the quality of the product, and even cause defective products.
02 Film blowing machine to control the thickness of the blown film
The film thickness of the film-blowing machine is one of the main indicators of quality inspection. The factors that affect the thickness are:
①The design of the machine head has a smooth cavity structure and no dead ends so that the material flow rate is uniform and uniform.
②The gap between the die openings is uniform, not in the middle, and can be adjusted easily to control the uniformity of the output.
③ The blowing flow and flow rate of the cooling air ring should also be stable, otherwise, the part with poor cooling of the film will be extended and thinned, otherwise it will become thicker, and the thickness can be adjusted by using the wind force.
④Heating device of the machine head: The heating distribution of the machine head should be uniform to ensure equal resin flow at the die opening of the Film blowing machine. Otherwise, the high-temperature part of the film stretches, expands, and becomes thinner; otherwise, it becomes thicker.
⑤The main engine is running normally, to ensure the uniformity of the output, and the traction speed of the Film blowing machine should also be uniform.
⑥Influence of external airflow, in the part below the cooling line of the film-blowing tube, airflow interference caused by external wind fluctuations is not allowed, and plastic film can be used to set up a curtain.
03 Influence of screw speed of Film blowing machine on the quality of film production
The rotation speed of the film-blowing machine rod increases, the plastic stays in the barrel for a short time, the plasticization is poor, and the film has incomplete plasticization crystal points, or due to the increase of the extrusion volume, the cooling part is not suitable, and the appearance quality of the film will also deteriorate. not good.
There are also special situations in production. The increase of the screw speed of the Film blowing machine increases the output, but the heater temperature does not continue to rise, and the production is still normal. This is caused by shear heat, but it must be compared with the traction ratio. Matching, product quality can be stable.
The screw speed is reduced, which is beneficial to the cooling of the film tube. In the case of incomplete plasticization of the Film blowing machine, reducing the screw speed is beneficial to improve the product quality, but the speed is low, the plastic stays in the barrel for a long time, and it is easy to decompose. In short, the rotational speed of the screw of the film-blowing machine must match the process conditions such as processing raw materials, finished product specifications, and temperature to ensure product quality.
I hope that the introduction of the above content can help you use the Film blowing machine better. More information about the Film blowing machine will continue to be updated. See you in the next issue.