Polypropylene films are everywhere in modern packaging—from the tape sealing your moving boxes to the clear wrapper protecting your snacks. But not all polypropylene films are created equal. The way these films are manufactured determines their properties, performance, and where they work best. We’ll walk you through the three main types—Cast PP (CPP), Biaxially Oriented PP (BOPP), and Oriented PP (OPP)—so you can understand what sets them apart.
What Makes Polypropylene Films Different
Polypropylene film is a general term for plastic films made from polypropylene that are produced through different manufacturing methods, creating films with different characteristics for different applications. The main difference between these films comes down to one word: stretching.
Stretching plastic film improves dimensional stability, mechanical properties, gloss, transparency, and gas barrier properties. Think of it like pulling taffy—when you stretch the polymer molecules, they align in specific directions, making the film stronger and clearer.
Key stretching directions:
– MD (Machine Direction): Longitudinal stretching along the production line
– TD (Transverse Direction): Horizontal stretching across the film width
– No stretching: Film is cast flat without orientation
Cast Polypropylene Film (CPP)
CPP film is an abbreviation for Cast Polypropylene, which refers to a non-stretching, non-directional flat extrusion film. CPP is produced through the cast extrusion process and is a non-oriented film, though strictly speaking, it has some orientation in the longitudinal direction.
The manufacturing process is straightforward. Polypropylene is melted in an extruder, pushed through a T-shaped die, and cast onto a chilled roller for rapid cooling. By rapidly cooling on a chill roll, the film acquires excellent clarity and smoothness.
CPP characteristics:
– Soft and flexible like polyethylene
– Good transparency, high gloss, good stiffness, good moisture resistance, excellent heat resistance and easy heat sealing
– Formula can be customized for different functions
– Can be used in hot filling, retort pouch, aseptic packaging and other fields because the softening point of PP is about 140°C
CPP has higher tear and impact resistance, and better cold temperature performance and heat-sealing properties compared to BOPP. We see this play out in bread bags, vegetable packaging, and clothing wrappers—applications where you need a film that seals easily without special coatings.
Oriented Polypropylene Film (OPP)
OPP film is short for Oriented Polypropylene, uniaxially stretched in the TD direction. This transverse stretching gives OPP films balanced properties that work well for packaging and labeling applications.
OPP film is produced through uniaxial stretching of PP film, allowing the film to extend in the TD direction, resulting in better tensile strength, gloss, gas barrier properties, etc. The stretching process improves what the base material can do, making it stronger and more resistant to moisture.
Common OPP applications:
– Adhesive tapes and packaging tape
– In-mold labels, especially for PP/PE containers where OPP film is the best material
– Product packaging bags
– Self-adhesive labels
OPP tape based on polypropylene film has advantages of high tensile strength, light weight, non-toxic, tasteless, environmental protection, and wide application range. You’ll find OPP in countless everyday products because it hits a sweet spot of performance and cost.
Biaxially Oriented Polypropylene Film (BOPP)
BOPP film is an abbreviation for Biaxially Oriented Polypropylene, stretching in MD and TD directions. This dual-direction stretching creates the strongest and most versatile polypropylene film type.
Production involves extruding molten polypropylene through a narrow die to form a sheet or thick film, which is then stretched in both directions (longitudinally and laterally) in a special stretcher at specific temperatures and speeds. After stretching, the film is cooled or heat-treated and processed (e.g., corona treatment, coating) to achieve its final form.
BOPP makes up about 80% of PP packaging film and has improved mechanical properties, with clarified grades having excellent transparency. This dominance makes sense when you look at what BOPP can do.
BOPP properties:
– Transparent, odorless, tasteless, non-toxic, with high tensile strength, impact strength, rigidity, toughness, and high transparency
– BOPP film can have the best water vapor barrier property among all plastic film materials
– Requires corona treatment before printing or gluing
– Difficult to heat-seal homopolymer BOPP without excessive distortion, so it is often coated for better sealability
BOPP film is used in packaging for biscuits, crisps, baked goods, sweets, bread, pasta; in cigarette wrap, shrink wrap, and shrink labels; in lamination of books and magazines; in office stationery films; in industrial laminates and supports for adhesive tapes; and in films for metallization used in applications such as gift wrapping and snack food packaging.
Comparing CPP, OPP, and BOPP Films
| Feature | CPP Film | OPP Film | BOPP Film |
|---|---|---|---|
| Stretching | None | Uniaxial (TD) | Biaxial (MD + TD) |
| Flexibility | Soft, flexible | Moderate | Stiff, crinkly |
| Heat Sealing | Excellent without coating | Moderate | Requires coating |
| Strength | Lower | Moderate | Highest |
| Transparency | Good | Good | Excellent |
| Cost | Lower | Moderate | Higher |
The biggest difference between CPP film and OPP film is whether the film is stretched, with OPP using a stretching process to enhance the properties of the film. In terms of production methods, OPP and BOPP are products produced by different methods, but from the application point of view, the two are the same commodity because the difference in characteristics is small.
Choosing the Right Film for Your Application
Your application determines which film makes sense. CPP works when you need heat-sealable packaging without extra coatings—think food pouches, textile bags, or retort packaging that handles high temperatures. Although CPP film is not stretched, the formula can be adjusted according to customer needs, so that its application becomes more extensive, allowing for anti-fog, anti-static, or other specialized versions.
OPP fits tape, label, and general packaging applications where you need good strength and clarity at a reasonable price. BOPP is your choice for demanding applications—snack bags that need moisture barriers, cigarette packaging, or any situation where you need the best combination of transparency, strength, and barrier properties.
We’ve worked with packaging manufacturers who initially chose CPP for a frozen food application, only to switch to a specialized retort-grade CPP when they needed to handle higher temperatures during processing. The point is: understanding these differences helps you make better choices from the start.
Conclusion
Polypropylene films—whether Cast (CPP), Oriented (OPP), or Biaxially Oriented (BOPP)—each bring specific strengths to packaging applications. CPP offers flexibility and heat-sealability without coatings. OPP provides balanced properties for tapes and labels. BOPP delivers the highest strength and barrier performance for demanding packaging needs.
The stretching process makes all the difference. No stretching gives you CPP’s flexibility and customization potential. Uniaxial stretching creates OPP’s balanced performance. Biaxial stretching produces BOPP’s superior strength and clarity. Your application requirements—whether it’s heat resistance, barrier properties, or cost considerations—will point you toward the right choice.
Frequently Asked Questions
What’s the main difference between CPP and BOPP film?
CPP is unstretched and soft with excellent heat-sealing properties, while BOPP is stretched in both directions, making it stronger and stiffer with better barrier properties. CPP works great for applications needing easy heat sealing, while BOPP excels when you need high strength and moisture resistance.
Can BOPP film be heat sealed?
Homopolymer BOPP doesn’t heat seal well on its own and typically needs special coatings or co-extrusion with heat-sealable layers. Manufacturers apply coatings like PVDC or EVA latex, or use co-extrusion methods to make BOPP heat-sealable for packaging applications.
Are OPP and BOPP films the same thing?
They’re produced through different stretching methods, but in practical use, the differences are minimal. OPP is stretched transversely while BOPP is stretched in both directions. However, the performance characteristics are so similar that they’re often used interchangeably in applications like packaging and labeling.
Why does BOPP need corona treatment?
BOPP film has low surface energy, which means inks and adhesives don’t stick well without treatment. Corona treatment modifies the surface to improve wettability and adhesion, making the film suitable for printing and lamination. This treatment is standard before any gluing or printing operations.
Which polypropylene film is best for food packaging?
It depends on your specific needs. BOPP works well for dry foods like snacks and baked goods because of its excellent moisture barrier. CPP is better for products requiring heat sealing or retort processing, like ready-to-eat meals. Many food packages actually use laminates combining both—BOPP for the outer layer and CPP for the heat-sealable inner layer.
Ready to find the right polypropylene film for your project? We offer a complete range of PP films tailored to your specific packaging needs. Contact us today to discuss your requirements and get expert guidance on selecting the best film solution for your application.