Introduction
- Blown film extrusion is a complex process where temperature, pressure, airflow, and mechanical setup all must be perfectly aligned. Because if even a small setting goes wrong, some gel formation appears in the film, due to which production downtime increases, production stops, quality issues arise in the film, and then customer complaints are received.
- Keeping all these points in mind, here we will discuss the blown film extrusion problems, their technical reasons, and practical solutions so that you can maintain stable production and consistent quality.
- If you’re in blown film production, you’ve probably faced the nightmare of gel formation — those tiny, annoying hard particles that ruin otherwise perfect film rolls. Whether it’s a visual defect or a mechanical weak point, gel defects are bad news for quality and customer satisfaction.
Gel Formation
Gel” is an unwanted hard spot that appears on the surface of the film. It is generally a small, transparent, or slightly discolored particle that appears to be stuck to the film.
This spot is thicker and harder than normal film — and if you stretch the film, the gel area tends to tear or rupture.
How to recognize gel particles on film?
- They look like small “pimples” or “blobs.”
- If you hold the film towards the light, that area will appear thicker and opaque, which will tell you that it is a gel particle.
- During lamination/printing, that area gets rejected because that part is slightly raised and the ink and adhesive are not able to bond easily.
- When you touch the film, you feel roughness or bumps on the surface
- When you press it with your finger, that area does not feel soft but stiff or hard.
Why does gel formation happen?
This mainly happens due to raw material or processing issues:
1. Incomplete Melting:
- When the material or resin is given a proper temperature and the resin does not melt properly at that temperature.
- Processing too much MFI material at low temperature
2. Polymer Degradation (Burning):
- Overheating of the material
- Dead spots are formed in the screw where the material is stuck for a long time
3. Contamination:
- Foreign particles like dust, paper, metal, etc., or an incompatible polymer blend.
- When recycled material is used, some impurities come in it, due to which gel particles start coming out.
4. Screen Pack Blocked:
- Gel particles start coming out due to the melted material not being properly filtered through the screen mesh.
- Gel particles also start coming out due to the screen pack or breaker plate being clogged
How to control gel formation?
Raw Material Quality
- Use virgin, well-processed resin; avoid dirty regrind.
Proper Melt Temp
- Maintain consistent and optimal barrel zone temperature.
Screen Pack Change
- Regularly clean/replace screen packs for filtration
Screw Cleaning
- Purge system using manual cleaning during shutdown
Avoid Dead Zones
- Barrel, adapter, die design optimized
Material Mixing
- Mix masterbatch or blend well—poor dispersion = gels.
Conclusion
Gel formation is a serious visual and structural defect that directly affects the appearance, strength, printability, and end-use performance of blown film. Its root cause is more common in cases such as raw material contamination, poor melt mixing, or thermal degradation.
To control this, some important points must be kept in mind, such as
- use high-quality resin
- optimize processing zones
- maintain screen pack & die cleaning routineand strictly monitor material handling & blending processes
Regular maintenance and vigilant processing practices make gel-free, high-quality film production possible — a necessity, not a luxury, in today’s competitive market.
Note: Read more about gel formation
Que: Is the gel made from reprocessed material?
Ans: Yes, low-quality or contaminated reprocessed material can be a major source of gel formation — especially if it contains foreign particles or degraded polymer.
