What is the Difference Between Blown and Cast Film?

March 14, 2025

What is the Difference Between Blown and Cast Film?

by SmartShield Packaging

When it comes to selecting the right plastic film for packaging, two primary contenders emerge: blown film and cast film.

Both methods produce plastic films, commonly used in stretch wrap and other packaging materials, but they differ in manufacturing processes, characteristics, and applications.

If you’re looking to improve your packaging process, keep reading for a deeper understanding between blown and cast films.

Quick Summary Table: Blown Film vs. Cast Film

Feature/Aspect	Blown Film	Cast Film
Manufacturing Process	Air is blown into extruded molten plastic, creating a bubble that is then flattened.	Molten plastic is extruded through a flat die and cooled quickly on a chill roll.
Texture & Clarity	Rougher texture with less clarity due to the air cooling process.	Smoother texture with higher clarity and gloss due to rapid cooling.
Strength & Durability	Higher puncture resistance and strength, ideal for heavy or irregular loads.	Generally strong but with better stretchability and tear resistance.
Cling Properties	Typically offers two-sided cling, securing loads more effectively.	Usually features one-sided cling, suitable for uniform loads.
Noise During Application	Tends to be noisier, which might be a consideration in certain environments.	Quieter unwind, preferred in noise-sensitive areas.
Cold Weather Performance	Performs better in colder conditions, maintaining flexibility.	Less suited to extreme cold, potentially becoming brittle.
Suitability	Preferred for irregularly shaped, heavy, or sharp-edged items.	Ideal for uniform, rectangular loads requiring high aesthetic appeal.
Technological Aspect	Older, more traditional technology with a focus on durability.	Newer technology allowing for multi-layer films with customized properties.

What is Blown Film?

Blown film extrusion involves feeding plastic pellets into an extruder, where they are melted and pushed through a circular die. Air is then blown into the extruded tube, inflating it like a balloon to the desired size before being cooled and collapsing into a flat double-layer film.

This process imparts unique characteristics to the blown film:

Texture and Strength: The cooling air impacts the film on both sides, leading to a more crystalline structure. This results in a higher puncture resistance and a slightly tacky surface, offering better load-holding capabilities.
Two-Sided Cling: The inherent tackiness provides cling on both sides of the film, enhancing stability for irregularly shaped loads or those requiring extra hold.
Cold Resistance: The molecular structure of blown film remains more flexible at lower temperatures, reducing the risk of cracking in cold environments.

However, the blown film process can produce films with slight variations in thickness and a hazier appearance due to the air-cooling method, which may affect clarity.

What is Cast Film?

Cast film production, conversely, employs a flat die through which the molten polymer is extruded. The film is then drawn onto a chilled roll, rapidly cooling it into a solid state.

This method offers several advantages:

Clarity and Gloss: The quick cooling on the chill roll produces a film with excellent clarity and a glossy finish, suitable for applications where product visibility is key.
Consistent Thickness: The cast film process allows for tighter control over film width and thickness, ensuring uniformity across the entire film.
Quiet Unwind: The single-sided cling and smoother surface result in a quieter release from the roll, an important feature in noise-sensitive environments.

The ability to co-extrude layers in the cast film process enables the incorporation of different resins, each layer tailored to provide specific properties such as enhanced cling, puncture resistance, or barrier qualities.

Specialty Hand Stretch Wraps: Tailored for Specific Needs

There’s also the cast hand stretch wrap, which is also known as stretch film or pallet wrap . This variant of cast film is ideal for its cost-effectiveness and rapid production process, making it a go-to choice for businesses seeking economical stretch wrap solutions.

It can also be provided with additional features, such as:

Anti-static Stretch Wrap: Essential for securing static-sensitive items like electronics, ensuring protection against static discharge.
VCI Stretch Wrap: Ideal for safeguarding large metal components from corrosion, providing a rust-free environment during storage and transport.
Airflow Stretch Wrap: A vented material that allows for air circulation, crucial for moisture or heat dissipation. This wrap is perfect for products like living plants or wood, where breathability is key.

Comparative Applications

Choosing between blown and cast films often depends on the application's specific requirements:

Heavy-Duty Packaging: For items with sharp edges or those needing extra protection during transport, the superior strength and puncture resistance of blown film might be the better choice.
High-Clearance Display Packaging: When packaging aesthetics and product visibility are paramount, the clarity and gloss of cast film make it the ideal option.
Environmental Conditions: For shipments subjected to cold storage or transport in lower temperatures, blown film's resilience to cold conditions offers a significant advantage.

Customization and Innovation

Both blown and cast films can be customized with colours and additives to meet specific needs. Innovations in resin technology have allowed for the development of high-performance films that challenge traditional thickness-to-strength ratios, enabling thinner films to provide the same or superior levels of protection and stability as thicker options.

Key Differences and Considerations

Puncture Resistance: Blown film offers superior puncture resistance, ideal for sharp or irregular loads.
Cling: Blown film provides a two-sided cling, whereas cast film usually has a one-sided cling, influencing load stability.
Noise: Blown film can be louder during application, which might be a consideration in noise-sensitive environments.
Stretchability: Cast film stretches more, allowing for potentially greater material efficiency.
Cold Weather Performance: Blown film performs better in colder conditions, making it suitable for specific environmental needs.
Technology: Blown film technology is older and more traditional compared to the newer methods used in cast film production.

In practice, the choice between blown and cast film often comes down to specific packaging needs. For instance, a 47-gauge high-performance blown film is equivalent to a 60-gauge cast film in terms of puncture strength, but the latter may contain more additives to enhance performance.

Understanding these differences can guide you in selecting the right film for your packaging requirements, ensuring your products are protected while optimizing costs and material use.

SmartShield's Custom Packaging Approach

At SmartShield, we understand that each packaging challenge is unique. By leveraging both blown and cast film technologies, we tailor solutions that not only protect your products but also align with your sustainability goals and budgetary constraints.

Whether optimizing for strength, clarity, environmental resilience, or cost, our team is dedicated to providing the custom packaging solutions that best fit your needs.

Article written by SmartShield

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