Blown Film Extrusion: Process, Applications, and Innovations  

Blown film extrusion is a widely used industrial process for manufacturing thin plastic films, particularly for packaging and agricultural applications. This technique involves extruding molten polymer into a tubular bubble, which is then inflated, cooled, and processed into flat or tubular films. Below is a comprehensive overview of its process, applications, and technological advancements.  

I.Process Overview

1. Extrusion and Bubble Formation
The process begins by feeding polymer resin (commonly polyethylene, such as LDPE, LLDPE, or HDPE) into an extruder. The resin is heated to a molten state and forced through a circular die, forming a hollow tube. Air is then injected into the tube, inflating it into a bubble, which stretches the polymer radially and axially to achieve the desired thickness and width.  

2. Cooling and Solidification 
The inflated bubble is cooled using air rings or water quenching systems. The "frost line," where the molten film solidifies, is critical for stability. Factors like airflow, cooling rate, and temperature control influence the film’s crystallinity and mechanical properties. Non-contact infrared temperature sensors are often used to monitor the frost line and ensure uniformity.  

3. Collapsing and Winding 
After cooling, the bubble is flattened by rollers and wound into rolls. The film can be slit into flat sheets or retained as a tube for applications like plastic bags. 

II.Key Process Parameters  

Blow-Up Ratio (BUR):The ratio of the bubble diameter to the die diameter, affecting film thickness and strength. Excessive BUR can destabilize the process.

 
Freeze-Line Height: Optimizing this height maximizes stability and film quality.  

Temperature Control:Precise monitoring of melt temperature at the die and cooling rate ensures consistent film properties.  

III.Applications

Blown film extrusion is versatile, producing films for diverse industries:  

1. Packaging 

Food Packaging: Multi-layer films with barrier properties (e.g., EVOH or PA layers) protect against moisture and oxygen. Davis-Standard’s 11-layer co-extrusion lines are used for high-performance food films.  

Stretch and Shrink Films:LDPE-based films are ideal for wrapping pallets or consumer goods.  

2. Agriculture

Mulching Films:Biodegradable blends (e.g., PBAT/PE) enhance soil health while extending degradation periods. Crosslinking agents like BIBP improve mechanical strength and processability.  

Greenhouse Films:UV-stabilized LDPE films provide durability and light diffusion.  

3. Industrial and Specialty Films

 Barrier Films:Used in medical and hygiene products to prevent contamination.  

 Stretch Hoods and Bags:High-strength HDPE films are common in logistics.  

IV.Technological Advancements

1. Multi-Layer Co-Extrusion
Modern lines can produce up to 11 layers, combining materials like PE, PP, and EVOH for enhanced functionality. For example, Brampton Engineering’s AeroFrost systems enable high-speed production of barrier films.  

2. Eco-Friendly Innovations
Biodegradable Films: Blends of PBAT and PE, supplemented with calcium carbonate, balance performance and environmental sustainability.  

Recycled Material Integration: Lines like Reifenhäuser’s EVO process post-consumer plastic waste directly into new films.

3. Automation and Control
Advanced systems, such as Fluke’s infrared temperature scanners and ITALYCS® 5 control software, optimize process stability and traceability.  

V.Challenges and Future Trends

Process Stability: High BUR or uneven cooling can cause bubble instability, necessitating precise control systems.

 
Material Compatibility: Blending polymers (e.g., PBAT/PE) requires additives to improve compatibility and reduce phase separation.  

Sustainability: Demand for bio-based and compostable films drives research into novel polymer blends and recycling technologies.  

VI.Get customized film blowing machine from Chaoxin

ChaoXin As an innovative leader in the field of film blowing machine manufacturing, we focus on creating high-performance energy-saving solutions. Through core technological breakthroughs, we have achieved a 10-30% reduction in equipment operating energy consumption and a 20-50% increase in production capacity. Our intelligent film blowing unit is equipped with a three-year ultra-long warranty service, and also provides a complete set of customized supporting equipment solutions. It can accurately match the bag making unit and multi-functional printing equipment according to the film production characteristics, creating a one-stop production system from film blowing to finished product packaging.

With a modular design concept, we provide in-depth customization services for customers in the fields of packaging, printing, new materials, etc.: from screw combination configuration, die head specification selection, to temperature control system optimization, all can be adjusted according to production needs. This flexible technical architecture ensures that each device can perfectly adapt to the customer's production process, while improving the yield rate of film products, effectively reducing unit production costs, and helping companies establish sustainable competitive advantages in an industry environment with increasingly stringent environmental protection requirements.

Conclusion

Blown film extrusion remains a cornerstone of plastic film production, adaptable to both traditional and emerging needs. Innovations in multi-layer co-extrusion, biodegradable materials, and automation ensure its relevance in industries prioritizing performance and sustainability.