Integrating Biodegradable Materials into Existing Blown Film Lines

More packaging manufacturers are now switching to biodegradable films. These materials offer a way to reduce landfill waste and to meet environmental targets. But adding them to your existing blown film line can bring challenges, especially if the line was designed for conventional LDPE or similar materials.

We will cover what you need to know. You’ll find out how biodegradable films behave, where the risks lie and how to adapt your setup for smooth production.

Why Biodegradable Films Are Different

Biodegradable films break down under the right conditions, often with heat, moisture or microbial action. This makes them more complex to handle than traditional films.

Some of the most common types include:

• PLA (Polylactic Acid) - plant-based and compostable
  
  
• PBAT (Polybutylene Adipate Terephthalate) - flexible and often blended with starch
  
  
• Starch-Based Films - made from corn or potato starch, often used in short-life bags
  
  

Each material has different mechanical and thermal properties. Most are more sensitive to heat, shear and moisture than standard plastics. That means your line needs tighter control over processing conditions.

Common Challenges When Switching to Biodegradable

1. Processing Temperatures
Biodegradable resins often melt at lower temperatures. If barrel or die zones are too hot, the film may burn or become brittle.

Tip: Lower your heat zones and test gradually. Start at the lower end of the resin’s processing range and increase only if needed.

2. Screw and Die Design
Standard screws may not give enough mixing or may shear the resin too much. PLA, for example, can degrade if it's overworked.

Tip: Use screws with gentle mixing zones. For long-term use, consider screw designs made for biodegradable blends.

3. Cooling Requirements
Some materials cool faster or slower than LDPE. This affects bubble stability and sizing.

Tip: Adjust your air ring settings. Monitor bubble shape closely and allow time for cooling curve tests.

4. Gauge and Film Strength
Biodegradable films are often weaker than LDPE, especially at thinner gauges.

Tip: Run at slightly thicker gauges at first. Test the film’s performance before reducing its thickness.

5. Shelf Life and Storage
Many biodegradable films absorb moisture or degrade over time, even before use.

Tip: Store raw material in sealed containers. Use it on a first-in, first-out basis and avoid long dwell times in hoppers.

Line Adjustments and Best Practices

Start with Small Runs
Trial smaller batches before full production. This gives time to tune settings without risking waste or downtime.

Fine-Tune Line Speeds
Slow down initial runs. Many biodegradable films can’t handle high draw-down speeds. A slower pace will help maintain film strength and avoid breakage.

Monitor Tension and Web Handling
These films often stretch more or behave inconsistently. Tension zones need to be tighter and more responsive.

Use Web Guiding Systems
Biodegradable films are more prone to edge curl or drift. An automated web guide protects against material waste and helps keep film aligned.

Invest in Quality Control Checks
Check seal strength, film clarity, gauge uniformity and print response. These checks help you adapt as you move to new film grades or blends.

Working with Recyclable and Biodegradable Blends

Some film types combine recycled plastic with biodegradable content. These hybrids offer a balance between performance and sustainability but add complexity.

You may need to adjust:

• Extrusion temperatures
  
  
• Cooling rates
  
  
• Sealing profiles
  
  
• Film storage and conversion conditions
  
  

Run extra trials and work closely with material suppliers to get the right blend.

A Step Toward Sustainable Production

Switching to biodegradable materials is not a one-size-fits-all process. But with the right preparation, many existing blown film lines can handle the change. You don’t always need major equipment changes, just smarter control and a willingness to test and adapt.

Manufacturers that get ahead now can offer greener options without sacrificing quality or performance.

How Swallow Can Help

At Swallow, we work with blown film producers across the UK and beyond to optimise film quality, line performance and system control. Whether you’re trialling a new biodegradable resin or planning a long-term switch, we can help you fine-tune your system.

From upgrade advice to web handling and tension control, we’re ready to support you. Get in touch with our team for expert guidance tailored to your setup.