The film exhibits several common issues during the production process, such as poor opening, reduced transparency, wrinkling, and uneven thickness. These problems can be traced back to a combination of material selection, temperature control, and mechanical adjustments.
One major issue is the film being too sticky and having a poor opening. This typically occurs due to incorrect resin types, such as using a non-blowing grade low-density polyethylene (LDPE) or an insufficient amount of opening agent. Additionally, high extrusion temperatures can reduce the resin's viscosity, making it too fluid. An excessive inflation ratio may also lead to poor bubble stability, causing the film to stick together. Slow cooling rates and fast traction speeds further contribute to this problem by allowing the film to bond under pressure. To resolve these issues, the resin should be replaced or an opening agent added. Temperature settings should be adjusted, the inflation ratio reduced, and the cooling rate increased. Traction speed should also be carefully controlled.
Another common issue is poor film transparency. This can result from low extrusion temperatures, which prevent proper plasticization of the resin. A small blow ratio or inadequate cooling can also affect clarity. High moisture content in the resin and fast traction speeds may cause the film to cool unevenly, reducing its transparency. To improve clarity, the extrusion temperature should be raised, the inflation ratio increased, and the cooling system optimized. Resin drying is also important, and traction speed should be slowed down to allow for better cooling.
Wrinkles on the film surface are often caused by uneven thickness, insufficient cooling, or improper inflation ratios. If the bubble becomes unstable due to a large inflation ratio, it can swing and cause wrinkles. The angle of the die head, traction roller pressure, and alignment of guide rolls all play a role in this issue. Adjustments to the die gap, cooling system, and traction mechanism are necessary to eliminate wrinkles and ensure even film formation.
Foggy water ripples on the film surface usually indicate poor resin plasticization or high moisture content. Lower extrusion temperatures and damp resin are common culprits. Increasing the extrusion temperature and ensuring proper drying of the raw materials can help resolve this issue.
Uneven film thickness is often linked to an irregular die gap, inconsistent die temperature distribution, or uneven cooling. The inflation and traction ratios must also be properly balanced. Any variation in traction speed will further exacerbate thickness inconsistencies. Regular checks and adjustments to the die, cooling system, and mechanical components are essential for uniform thickness.
Excessive film thickness can occur when the die gap is too wide or the cooling air ring provides too much airflow, causing rapid cooling. A slow traction speed can also lead to thicker sections. Adjusting the die gap, controlling the air flow, and increasing traction speed can help achieve the desired thickness.
On the other hand, thin film can result from a narrow die gap, insufficient cooling, or an overly fast traction speed. Adjusting the die gap, increasing cooling air volume, and slowing down the traction speed can help correct this issue.
Poor heat sealing properties are often due to excessive stretching of the polymer molecules during inflation and traction. A low dew point or improper inflation and traction ratios can cause molecular orientation, reducing the film’s ability to seal. Adjusting the dew point, reducing inflation and traction ratios, and avoiding excessive stretching can improve heat sealing performance.
Low longitudinal tensile strength can be caused by high extrusion temperatures, slow traction speeds, or an unbalanced inflation ratio. Reducing the extrusion temperature, increasing traction speed, and adjusting the inflation ratio can enhance the film’s strength in the longitudinal direction.
Similarly, poor transverse tensile strength may result from a fast traction speed and an imbalanced inflation ratio. Slowing down the traction speed and matching it with the inflation ratio can help improve lateral strength.
Bubble instability is another common problem, often due to fluctuating extrusion temperatures, unstable air supply, or external airflow interference. Ensuring consistent temperatures, stable cooling, and minimizing external disturbances can help maintain bubble stability.
Surface roughness and unevenness are typically caused by low extrusion temperatures or excessive extrusion speed. Raising the temperature and slowing down the extrusion speed can improve surface quality.
Lastly, odors in the film may come from the resin itself, overheating during extrusion, or insufficient cooling of the bubble. Replacing the resin, adjusting the temperature, and improving cooling efficiency can eliminate unwanted smells.
By addressing these factors through proper material selection, temperature control, and mechanical adjustments, manufacturers can significantly improve the quality and performance of blown films. Loose London Blue Topaz Gems,Natural London Blue Topaz Pear Cut Faceted, high quality London Blue Topaz Guangzhou Qinfa Crafts Company , https://www.qinfastone.com
June 24, 2025