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.

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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.

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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.

In the world of industrial packaging, automation is essential for streamlining operations and boosting efficiency. Among the most commonly used automated systems are glue-based packing machines and tape-based packing machines. While both are designed to seal or secure packages, they use different methods and are suited for various applications. Understanding the differences between glue-based and tape-based packing machines can help businesses select the right solution to meet their specific needs.

1. Introduction to Packing Machines

Packing machines are essential for the final stages of product packaging, delivering the efficiency and consistency needed in high-volume production environments. These machines typically handle tasks such as sealing, bundling, and securing products, using various techniques like gluing or taping. The two most common types of packing machines are:

• Glue-Based Packing Machines: These machines utilize adhesives such as glue, hot melt, or liquid adhesives to seal packages or secure products.
• Tape-Based Packing Machines: These machines employ adhesive tape, usually BOPP or PVC tape, to seal and secure packages.

Each type of machine offers distinct advantages depending on the nature of the packaging materials, the desired sealing strength, and the speed of production.

2. How Glue-Based Packing Machines Work

Glue-based packing machines are designed to apply adhesive to various surfaces, bonding packaging materials together. These systems typically feature a glue application unit that dispenses the adhesive, whether in liquid or solid form, followed by mechanisms that apply pressure to ensure proper adhesion. The adhesive can be applied to materials such as cardboard, paper, plastic, or other substrates, depending on the type of package being produced.

Types of Glue-Based Packing Machines:

• Hot Melt Glue Machines: These machines utilize heated adhesive that is melted and applied to packaging surfaces. The glue solidifies quickly upon contact, creating a strong bond. Hot melt glue is commonly used for carton sealing and product assembly.
• Cold Glue Machines: These machines use an adhesive that does not require heating. Cold glue is often preferred for more delicate applications where heat could damage the materials.
• Spray or Roller Glue Application: Some glue-based machines employ spray nozzles or rollers to apply an even layer of adhesive on packaging surfaces. This method is ideal for applications that require the adhesive to cover a larger area.

Applications:

• Carton Sealing: Glue-based machines are frequently used in industries such as food, pharmaceuticals, and consumer goods, where cartons or boxes must be securely sealed.
• Product Assembly: In some cases, glue-based machines are employed for assembling multi-part packaging, such as folding cartons or displays.
• Security Sealing:For tamper-proof or high-security packaging, glue-based machines can apply strong adhesives that create permanent seals.

3. How Tape-Based Packing Machines Work

Tape-based packing machines, on the other hand, utilize adhesive tape—such as BOPP, PVC, or kraft paper tape—to seal packages. These machines are equipped with tape dispensers that automatically feed tape onto the surface of the package, followed by mechanisms that press the tape into place and cut it to the desired length.

Types of Tape-Based Packing Machines:

• Automatic Tape Sealing Machines: These machines apply adhesive tape to carton seals with high precision, making them ideal for sealing the tops and bottoms of boxes.
• Strapping Machines: While primarily used for bundling items, strapping machines that utilize tape-based strapping also fall under the category of tape-based packing machinery. These machines apply pressure to secure the tape and bundle multiple items together.
• Case Erectors with Taping Units: These machines not only form cartons but also automatically apply tape to seal the cartons.

Applications:

• Carton Sealing: Tape-based machines are especially prevalent in shipping and logistics for sealing boxes and packages. They offer speed and efficiency, making them ideal for high-volume operations.
• Packing and Bundling: Tape-based packing machines are commonly used in warehousing and logistics to bundle multiple items together.
• General Packaging: For smaller or lighter items, tape machines provide a quick and efficient solution for sealing and securing products.

4. Key Differences Between Glue-Based and Tape-Based Packing Machines

While both types of packing machines serve the same fundamental purpose of sealing packages, there are several key differences between glue-based and tape-based systems:

5. Advantages and Disadvantages of Each Type

Glue-Based Packing Machines

Advantages:

• Stronger Seals: Glue offers a more robust and permanent seal, making it ideal for products that require secure packaging or tamper-proof seals.
• Versatility: Glue-based systems can be used on a wider range of materials, including paper, cardboard, and plastics, and they accommodate various types of packages, from small boxes to complex multi-part assemblies.
• Durability: These machines are often preferred for applications requiring packaging that will be handled extensively, such as when shipping heavy or fragile goods.

Disadvantages:

• Slower: The application and drying or curing of glue take more time, which can slow down the packing process.
• Higher Costs: Glue-based systems generally come with higher expenses, both for the machinery itself and for operational costs related to adhesive materials.
• Environmental Concerns: Some adhesives are not biodegradable, although there are eco-friendly options available.

Tape-Based Packing Machines

Advantages:

• Speed: Tape-based machines are generally faster since they don't require curing or drying time, making them ideal for high-volume packaging operations.
• Cost-Effective: Tape is relatively inexpensive, and tape-based machines are typically simpler and more affordable.
• Simplicity: These machines are easy to operate and maintain, requiring less training and reducing maintenance efforts.

Disadvantages:

• Weaker Seals: While tape provides adequate sealing for most shipping needs, it may not deliver the same level of security or strength as glue, especially for heavier or fragile goods.
• Limited Material Use: Tape is best suited for sealing cardboard and paper materials but is less effective on certain types of packaging, such as plastics or specific composites.

6. Which is Best for You?

If there's a need for high volumes, a strong seal, and a professional appearance, a glue-based packing machine would be the better option. However, if you're seeking a lower upfront investment, easier maintenance, or are handling smaller production batches, a tape-based packing machine might be more suitable.

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7. Conclusion

Both glue-based and tape-based packing machines offer unique advantages, making them suitable for various packaging needs. Glue-based machines excel in applications that require a strong, durable seal, particularly in industries with stringent security or shipping requirements. Conversely, tape-based machines are ideal for high-speed, cost-effective packaging tasks where speed and efficiency take precedence.

When selecting between glue-based and tape-based packing machines, businesses should consider factors such as production volume, material types, packaging requirements, and cost constraints. In many cases, a combination of both systems can be utilized across different stages of packaging to maximize efficiency and performance

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