Common problems with plastic blown film blown film include film being too sticky, poor tooth opening, poor film transparency, film showing wrinkles, film with misty water marks, uneven film thickness, thicker film thickness, thinner film thickness, The film has poor heat sealability, poor longitudinal tensile strength of the film, poor transverse tensile strength of the film, unstable film bubbles, rough appearance of the film, unevenness, and abnormal smell of the film.
1. The film is too sticky and has poor tooth opening
Reasons: ① Resin raw material is not the right type, it is not blown film-grade low-density polyethylene resin particles, which contains no dentifier or low content of dentifier; ② The temperature of the molten resin is too high and the activity is too large; ③ Blow If the ratio is too large, the tooth opening performance of the film becomes worse; ④ The cooling speed is too slow and the film cooling is lacking, and the adhesion of each other occurs under the action of the traction roller pressure; ⑤ The traction speed is too fast.
Treatment method: ① change the resin raw material, or add a certain amount of teething agent to the bucket; ② properly reduce the extrusion temperature and the temperature of the resin; ③ properly reduce the inflation ratio; ④ increase the air volume, improve the cooling effect, and speed up the film cooling Speed; ⑤ Reduce the traction speed appropriately.
2. Poor film transparency
Causes: ① Extrusion temperature is low, resin is not plasticized, and the transparency of the film after blow molding is poor; ② The inflation ratio is too small; ③ The cooling effect is not good, which affects the transparency of the film; ④ In the resin raw material The moisture content is too large; ⑤ The traction speed is too fast, and the film cooling is lacking.
Treatment methods: ① Properly increase the extrusion temperature so that the resin can be averagely plasticized; ② Properly increase the inflation ratio; ③ Increase the air volume to improve the cooling effect; Stop drying and processing the raw materials; ⑤ Reduce the traction speed appropriately.
3. Film appears wrinkled
Causes: ① the thickness of the film is uneven; ② the cooling effect is not enough; ③ the inflation ratio is too large, the formation of membrane bubbles is unstable, swinging back and forth, and it is easy to show wrinkles; The gap is flattened, so the film is also prone to wrinkle; ⑤ The pressure on the two sides of the traction roller is not different, and the side is high and the side is low; Crumpled.
Treatment methods: ① Adjust the thickness of the film to ensure that the thicknesses are evenly divided; ② Improve the cooling effect to ensure that the film can be adequately cooled; ③ Reduce the inflation ratio appropriately; ④ Reduce the included angle of the herringbone plywood properly; ⑤ Adjust the pressure of the traction roller, Ensure that the film is evenly stressed; ⑥ Check the axis of each guide shaft and make them parallel to each other
4.Misty water pattern on the film
Causes: ① The extrusion temperature is too low and the resin is not plasticized; ② The resin is damp and the water content is too high.
Treatment method: ① Adjust the temperature setting of the extruder and increase the extrusion temperature appropriately. ② Dry the resin raw materials, and the water content of the commonly requested resin cannot exceed 0.3%.
5. Uneven film thickness
Reasons: ① The average of the gap of the die directly affects the average of the thickness of the film. If the gap of the die is not uniform, some parts have larger gaps, and some have smaller gaps. , The thickness of the formed film is not different, some parts are thin, some parts are thick; ② the temperature of the die is unevenly distributed, there are high and low, so that the thickness of the film after blow molding is uneven; ③ around the cooling air ring The amount of air supply is not different, and the cooling effect is uneven, so that the thickness of the film is uneven. ④ The inflation ratio and traction ratio are not suitable, which makes it difficult to control the thickness of the film bubble. ⑤ The traction speed is not constant and occurs from time to time. Changes, of course, will affect the thickness of the film.
Handling method: ① Adjust the die mouth clearance to ensure that there is an average divergence everywhere; ② Adjust the die mouth temperature so that the local temperature of the die mouth is evenly divided; ③ Condition the cooling installation to ensure the average air volume at the air outlet; ④ Adjust the inflation Ratio and traction ratio; ⑤ Check the installation of mechanical transmission to keep the traction speed constant.
6. The thickness of the film is too thick
Causes: ① The die gap and extrusion volume are too large, so the film thickness is too thick; ② The air volume of the cooling air ring is too large, and the film is cooled too quickly; ③ The traction speed is too slow.
Treatment methods: ① Adjust the die clearance; ② Properly reduce the air volume of the air ring to further inflate the film to make it thinner; ③ Properly increase the traction speed
7. Thin film thickness
Causes: ① The die gap is too small and the resistance is too large, so the thickness of the film is thin; ② The air volume of the cooling air ring is too small, and the film is cooled too slowly; ③ The traction speed is too fast, and the film is stretched too much to make the thickness thin .
Treatment methods: ① Adjust the die clearance; ② Properly increase the air volume of the air ring to speed up the cooling of the film; ③ Properly reduce the traction speed.
8. Poor heat sealability of the film
The reasons are: ① the dew point is too low, the polymer molecules are oriented, so that the performance of the film is close to the oriented film, which reduces the heat seal performance; ② the inflation ratio and traction ratio are inappropriate (too large), the film is stretched and oriented, As a result, the heat-sealing performance of the film was affected.
Treatment method: ① adjust the amount of wind in the wind ring to make the dew point higher, and stop inflation and traction as much as possible at the melting point of the plastic to reduce the molecular stretching orientation caused by inflation and traction; ② the inflation ratio and The traction ratio should be appropriately small. If the inflation ratio is too large, the traction speed is too fast, and the film is stretched excessively in the transverse and longitudinal directions, then the performance of the film will tend to stretch in both directions, and the heat sealability of the film will be reduced. Will worsen.
9. Poor longitudinal tensile strength of film
Causes: ① The temperature of the molten resin is too high, which will reduce the longitudinal tensile strength of the film; ② The traction speed is slow, and the longitudinal orientation of the film is not enough, so that the longitudinal tensile strength is deteriorated; ③ The inflation ratio is too large The mismatch with the traction ratio improves the transverse orientation and tensile strength of the film, while the tensile strength in the longitudinal direction becomes worse; ④ The cooling rate of the film is too fast.
Treatment methods: ① appropriately reduce the temperature of the molten resin; ② appropriately increase the traction speed; ③ adjust the inflation ratio to conform to the traction ratio; ④ appropriately reduce the cooling speed.
10. Poor transverse tensile strength of film
Causes: ① The traction speed is too fast, which is too different from the inflation ratio, which causes fibrosis in the longitudinal direction, and the transverse strength becomes worse; ② The cooling speed of the cooling air ring is too slow.
Treatment method: ① Reduce the traction speed appropriately to match the inflation ratio; ② Increase the air volume of the wind ring to quickly cool the inflation film to prevent it from being stretched and oriented in a high elastic state at a relatively high temperature.
11. Membrane instability
Causes: ① Extrusion temperature is too high, the activity of the molten resin is too high, the viscosity is too small, and it is easy to shake; ② Extrusion temperature is too low, the output is small; ③ The air volume of the cooling air ring is unstable, Membrane cooling was uneven; ④ was disturbed and affected by strong external airflow.
Treatment methods: ① adjust the extrusion temperature; ② adjust the extrusion temperature; ③ check the cooling air ring to ensure that the surrounding air supply volume is evenly divided; ④ prevent and reduce the interference of external airflow.
12. The appearance of the film is rough and uneven
Causes: ① Extrusion temperature is too low, resin is not plasticized; ② Extrusion speed is too fast.
Treatment methods: ① Adjust the temperature setting of extrusion, and appropriately increase the extrusion temperature to ensure that the resin is well plasticized; ② Reduce the extrusion speed appropriately.
13. The film has an odor
The reasons are: ① the resin raw material has an odor; ② the extrusion temperature of the molten resin is too high, forming a resin synthesis, resulting in odor; ③ the lack of cooling of the film bubble, the hot air in the film bubble is not cleaned.
Treatment methods: ① change the resin raw material; ② adjust the extrusion temperature; ③ improve the cooling efficiency of the cooling air ring, so that the film bubble is sufficiently cooled.
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