Must-Know Common Flexible Packaging Material Categories for Beginners

Polyethylene (PE):

LDPE (Low-Density Polyethylene): Soft, tough, high transparency, good heat sealability, good moisture resistance.

LLDPE (Linear Low-Density Polyethylene): Higher strength, toughness, puncture resistance, and heat seal strength than LDPE.
HDPE (High-Density Polyethylene): High strength, high hardness, good moisture resistance, good chemical resistance, but low transparency.

Polypropylene (PP):
CPP (Cast Polypropylene): High transparency, good gloss, good heat sealability, better heat resistance than PE, commonly used as the heat-seal layer in laminated films.
BOPP (Biaxially Oriented Polypropylene): Extremely high transparency, gloss, rigidity, and strength, excellent printability, good moisture resistance, but moderate gas barrier properties.

PET (Biaxially Oriented Polyester): Extremely high strength, rigidity, excellent dimensional stability, high-temperature resistance, high transparency, good gloss, excellent gas and moisture barrier properties (compared to ordinary plastics), excellent printability.

Nylon (PA):
BOPA (Biaxially Oriented Nylon): Extremely high toughness, puncture resistance, cold resistance, good gas barrier properties (especially for oxygen), high and low-temperature resistance.

Aluminum Foil:
Characteristics: Perfect barrier properties (light, gas, and moisture resistance), high-temperature resistance, strong decorative appeal. Disadvantages: Opaque, prone to creasing and breakage, non-heat-sealable, relatively high cost. Application: Almost always used as an intermediate layer in composite structures for packaging requiring the highest level of barrier protection.

Metalized Film:
Principle: A very thin layer of aluminum is vacuum-deposited onto the surface of a plastic film (usually PET, BOPP, CPP).
Characteristics: Provides a metallic luster and decorative effect similar to aluminum foil, as well as good light resistance and certain gas/moisture barrier properties (though not as strong as aluminum foil), while maintaining the flexibility of the plastic film, heat sealability (depending on the substrate), and relatively low cost. Application: Often used to replace aluminum foil in some applications. Common types include VMPET (metalized polyester) and VMCPP (metalized cast polypropylene).

Kraft Paper:
High Strength: Tear-resistant and puncture-resistant, making it ideal for heavy-duty packaging (e.g., 50-80g yellow kraft paper, natural kraft paper).
Moisture and Water Resistance: Can be enhanced with coating (e.g., PE) to improve moisture barrier properties.
Eco-friendly and Degradable: Made from wood pulp, it can naturally degrade or be recycled, aligning with the trend toward plastic reduction.

Glassine Paper:
Glassine paper is a high-density, semi-transparent, greaseproof paper produced through supercalendering. Due to its unique physical properties and chemical stability, it plays an irreplaceable role in fields such as medical, food, and labeling.
Glassine paper is irreplaceable in scenarios requiring biodegradability (e.g., food packaging), static control (electronics industry), and cost-sensitive release liners (large-scale label production), making it the optimal choice.

FSC-Certified Paper:
FSC-certified paper is an eco-friendly paper product that meets international sustainable forest management standards. Its core principle is to adhere to environmentally friendly, socially equitable, and economically viable practices throughout the entire process, from raw material procurement to production. Driven by the EU Plastics Directive, Amazon's Climate Pledge, and similar initiatives, the demand for FSC-certified packaging paper is growing at an annual rate of 15%.