BOPP Films – Its Pros, Cons & Manufacturing Process

BOPP (Biaxially-Oriented Polypropylene) film is a versatile plastic film widely used in packaging, labeling, and laminating. It is created by extruding polypropylene resin into a thin sheet and stretching it in two perpendicular directions, a process that significantly improves its strength and durability, making it resistant to tearing and punctures.

BOPP films are highly favored for food packaging globally due to their excellent moisture barrier properties, sealability, high clarity, superior graphic reproduction, and shelf appeal. They also offer the advantage of enabling a monolayer or homogeneous packaging structure.

These films use BOPP as the base material, offering unique attributes:

- Density close to 0.90 g/m, ensuring higher yield at the same cost compared to polyester films.  

- Excellent gloss and high transparency for a superior look and finish.  

- Superior resistance to moisture, pollution, and harmful chemicals compared to polyester films.  

- Available in various finishes like Matte, Glossy, and Silky Matte.  

- Exceptional clarity and dimensional stability.  

- Low electrostatic charge.  

- Effective water vapor barrier.  

- Optimal performance in high-speed printing.  

- Resistance to oils, grease, punctures, and flex cracks across a wide temperature range.  

- Unaffected by moisture, with no wrinkling or shrinking under environmental changes.  

- Recyclable.  

Benefits of BOPP Films:

- Environmentally friendly and lightweight.  

- Widely accepted worldwide.  

- Reduces product damage during transport and weather exposure.  

- Keeps products dry.  

- No delamination required.  

- High clarity and UV resistance.  

Drawbacks of BOPP Films:

- Poor sealing performance.  

- High crystallinity due to nonpolar surface.  

- Low surface energy reduces ink adherence and printing performance.

Applications of BOPP Films:

- Grade F1 films: Food packaging and sealing.  

- Standard BOPP films: Electrical applications, printing, and lamination.  

- Other uses: Textbook covers, extrusion coating, flower packing, reverse printing, and lamination.  

- Adhesive tapes: Pressure-sensitive and general-purpose tapes.  

- White and opaque films: Printing, pouching, cable overwrap, strip packaging for cough drops, and heat-sealable overwraps.  

More Details about Applications:

Food & Beverage Packaging  

BOPP film is widely used for food and beverage packaging due to its strength, durability, and moisture resistance. It is used in stand-up pouches, vacuum pouches, and side-gusseted bags, protecting products during transportation and storage.  

Labeling and Branding  

BOPP film’s transparency and clarity make it ideal for labeling. Its smooth surface ensures easy printing, enabling the creation of attractive labels that enhance brand recognition and customer loyalty.  

Laminating  

BOPP film is suitable for laminating materials like paper, cardboard, aluminum foil, and prints. It enhances strength and durability, making it ideal for brochures, posters, and other printed materials.  

Tamper-Evident Films  

BOPP film is used in tamper-evident packaging to secure products like pharmaceuticals and electronics. This protects items from unauthorized access and ensures consumer confidence.  

Personal Care Product Packaging  

BOPP film is ideal for packaging personal care products like cosmetics and shampoos. Its durability and moisture resistance protect products while providing attractive packaging that boosts brand loyalty.  

Medical Packaging  

BOPP film is used in medical packaging, including bags, pouches, and blister packs. Its strength, transparency, and durability protect medical products while allowing easy content identification.  

Adhesive Tape  

BOPP film is commonly used for adhesive tapes like packaging and Scotch tape due to its strength and tear resistance.  

Agricultural Films  

BOPP film is used in agricultural applications like greenhouse covers and mulch films. Its transparency allows light penetration, while its weather resistance protects crops.

In the flexible packaging sector, BOPP (Biaxially-Oriented Polypropylene) film has been widely used for many years, known for its affordability, superior optical and mechanical features, and excellent gas barrier properties, especially for water vapor.

BOPP Film Manufacturing Process:

Step 1. Raw Material Feeding System  

Isotactic Polypropylene, a semi-crystalline thermoplastic polymer, forms the center layer, while ethylene-propylene copolymers and/or ethylene-butane-propylene copolymers are used for the outer layers. These materials are fed into the extruders through a hopper system.

Step 2. Extrusion  

The materials are melted and heated to 200–230°C within the extruders before being fed into the extrusion head, where they exit as a foil.

Step 3. Foil Cooling  

The foil is cooled by first coming into contact with a chilled cylinder and then submerged in a water bath to solidify the melt.

Step 4. Machine Direction Orientation (MDO)  

The film is passed over several rollers to raise its temperature, preparing it for longitudinal stretching. The foil is stretched up to five times its original length as it moves between rollers spinning at increasing speeds. This process aligns the polymer chains, enhancing the film's mechanical properties and reducing its thickness. The film is then heated again to relieve tension from the stretching (annealing phase).

Step 5. Transverse Direction Orientation (TDO)  

Once the film exits the longitudinal stretching zone, metal jaws grab it on both edges, and the film is stretched transversely by rails in a heated oven. The film expands up to 9 times its original width. The macromolecules align in the transverse direction, further improving the film's mechanical properties and reducing thickness. After stretching, the film goes through an annealing phase to relieve tension.

Step 6. Thickness Measurement and Flame Treatment  

The thickness of the film is automatically measured across its width. One of the film's faces is treated with flame or corona treatment to prepare it for the next steps, such as printing, laminating, or metallization.

Step 7. Reel Winding  

Finally, the film is wound onto a reel and sliced to the specified measurements.

Step 8. Film Measurements

The final product is evaluated based on the following primary metrics:

- Density, grammage, and thickness  

- Elastic modulus, elongation at break, and tensile strength  

- Haze (opacity) and gloss (sparkling appearance)  

- Friction coefficient between films and between films and metals  

- Sealing strength and threshold temperature (°C)  

- Temperature stability (heat shrinkage)  

The film consists of at least three layers, with a thickness range of 15 to 60 microns. The center layer, being the thickest, primarily provides the mechanical qualities, while the two outer layers contribute different characteristics, such as heat-sealing properties.

Additives may be included to meet the specific requirements of the intended application.