Complete Analysis of Packaging Film Classification
In the field of food flexible packaging, packaging films are the most fundamental and essential components. Different film materials have significantly different physical properties and application scenarios. Understanding their characteristics is the prerequisite for selecting the correct packaging solution. This article will systematically review common films such as PE film, PP film, PET film, and CPP film.Packaging FilmCore features, manufacturing processes, and application areas help procurement personnel and technical staff quickly understand key selection criteria.
The primary functions of packaging film include protecting products, extending shelf life, providing a printable surface, and enhancing shelf appeal. Different application scenarios have varying requirements for film properties such as strength, transparency, heat resistance, and barrier performance. Therefore, understanding the differences in characteristics among various films is essential.
PE Film (Polyethylene Film): The most commonly used packaging film
Classification of PE Film
Polyethylene (PE) is the most produced type of plastic. PE films can be classified into several main types based on their density:
- LDPE (Low Density Polyethylene Film):Soft and transparent with good heat-sealing properties, it is a commonly used material for the inner layer of packaging bags. Suitable for general food packaging such as bread bags and vegetable bags.
- LLDPE (Linear Low Density Polyethylene Film):Higher in strength than LDPE, with better puncture resistance, commonly used for heavy-duty packaging bags and frozen food packaging.
- HDPE (High-Density Polyethylene Film):High rigidity, low transparency, commonly used as the outer layer for shopping bags and some composite packaging.
Core Advantages of PE Film
PE film’s main advantage is its high cost-effectiveness, excellent heat-sealing performance, and good chemical stability. It can be almost combined with all other packaging materials, making it a versatile choice for various packaging applications.Composite Packaging MaterialsThe most commonly used inner layer material. PE film is also one of the most important materials in the concept of single-material packaging, as products with a full PE structure are easier to recycle and reuse.
The temperature resistance range of PE film is generally between -50℃ and 80℃. It is not suitable for high-temperature steaming, but it fully meets the packaging requirements for refrigerated and ambient temperature food.PE BagIn applications, LDPE is widely used in bag-making processes due to its excellent heat-sealing properties, making it one of the most commonly used film materials in flexible packaging factories.
PP Film (Polypropylene Film): A Heat-Resistant Packaging Option
CPP Film (Cast Polypropylene Film)
CPP film is a polypropylene film produced by the cast extrusion process, featuring excellent transparency and gloss. It has better heat-sealing properties than BOPP film and is commonly used as the inner layer material for composite bags. CPP film has superior high-temperature resistance compared to PE film, maintaining stability around 120°C, making it widely used in high-temperature sterilization bags, instant noodle packaging, and packaging for products requiring thermal filling.
BOPP Film (Biaxially Oriented Polypropylene Film)
BOPP film undergoes biaxial stretching, significantly enhancing its strength and rigidity while maintaining high transparency. It is commonly used as the outer layer material in composite packaging, offering excellent printability and scratch resistance. BOPP film is widely applied in snack packaging, candy packaging, and gift packaging, among other fields.PP plastic bagOne of the most widely used types.
PP film has better chemical resistance and oil resistance compared to PE film, making it more suitable for packaging oily foods. However, PP film has lower toughness at low temperatures and is more prone to becoming brittle in cold environments. This characteristic requires special attention when used for frozen food packaging.
PET Film (Polyester Film): The King of High-Strength Packaging
PET film (polyethylene terephthalate film) is one of the most outstanding film materials in the flexible packaging industry. Its core advantages include:
- High mechanical strength:Far superior tensile strength and tear resistance compared to PE and PP films
- Excellent Dimensional Stability:Resistant to deformation under high temperature and tension conditions
- Excellent barrier performance:Good barrier properties against oxygen and aroma, second only to EVOH and PVDC
- Excellent heat resistance:Maintains performance over a wide temperature range of -70℃ to 150℃
- Excellent printability:High surface energy, excellent ink adhesion, and exquisite printing results
PET film is commonly used as the outer layer material in composite packaging, with typical structures such as PET/AL/PE (used for premium coffee bags) or PET/PE (used for general food packaging).PET MaterialWidely used in beverage bottle packaging and food packaging bags, it is a premium material.Aluminum Foil BagAn important component of vacuum bags.
CPP Film (Cast Polypropylene Film): The Champion of Heat Sealing Performance
CPP film is a polypropylene film specially developed for heat-sealing applications. Unlike BOPP film, CPP film is not subjected to biaxial stretching, retaining excellent heat-sealing properties. In multi-layer composite packaging structures, CPP film is typically used as the innermost layer (heat-sealing layer), responsible for sealing the packaging bag.
The main applications of CPP film include three-side sealed bags, eight-side sealed bags, high-temperature steam sterilization bags, and roll film for automatic packaging machines. Based on different heat resistance requirements, CPP film can be further classified into standard CPP, steam-resistant CPP (capable of withstanding 121°C sterilization), and ultra-high-temperature CPP (capable of withstanding 135°C).Multi-layer compositeThe combination of CPP film with PA film or PET film is commonly used in packaging.
Comprehensive Selection Guide for Packaging Films
| Film Type | Transparency | Heat Sealing Property | Temperature Resistance Range | Barrier Properties | Cost | Typical Applications |
|---|---|---|---|---|---|---|
| LDPE Film | Good | Superior | -50~80℃ | Difference | Low | Inner heat-sealed, vegetable bag |
| CPP Film | Superior | Superior | -20~120℃ | Difference | Chinese | Inner heat-seal, steam-sterilizable bag |
| BOPP Film | Superior | Difference | -20~120℃ | Difference | Chinese | Outer printing, snack bag |
| PET Film | Superior | Difference | -70~150℃ | Good | Mid to High | Outer composite, coffee bag |
| PA Film | Good | Difference | -60~200℃ | Good | High | High-temperature sterilization, puncture resistance |
In actual practice,Custom Soft PackagingIn most projects, few packaging films can independently meet all requirements. Most food packaging bags adopt multi-layer composite structures, complementing the advantages and disadvantages of different films to achieve the optimal balance between performance and cost.
Key Points of Thin Film Composite Technology
Combining different types of films requires selecting the appropriate composite process and adhesive materials. The mainstream composite processes currently include:
- Dry Lamination:The most classic composite method, bonding two layers of film with adhesive, suitable for various material combinations
- Solvent-free lamination:Upgrade Solution in Response to Environmental Trends: No Solvent Required, More Friendly to Operator Health
- Extrusion Coating:Melted PE and other materials are extruded between two layers of film, resulting in high production efficiency.
Regardless of the chosen composite method, key indicators such as composite strength (peel strength), residual solvent content, and appearance quality must be monitored to ensure the quality and safety of the final product.
Need help choosing the right packaging film solution for your product?Contact Huashu PackagingOur technical team has 20 years of experience in the flexible packaging industry and can provide full technical support from film selection to composite processes.