What are the differences in essence and process between PP film and PE film materials?

2026-06-23

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PP film and PE film belong to the polyolefin family, and both raw materials come from petroleum refining. However, the differences in molecular structure and processing technology fundamentally determine the performance differentiation between the two.

1. Molecular structure: Differences in side chains lead to performance differentiation

PE film (polyethylene film): polymerized from ethylene monomer, with linear saturated molecular chains, good flexibility, and moderate crystallinity. The molecular chain arrangement without side groups is more flexible, endowing PE films with excellent flexibility, impact resistance, and low-temperature toughness, but it also leads to lower melting points and insufficient rigidity.

PP film (polypropylene film): polymerized from propylene monomer, with regular methyl side groups on the molecular chain, more regular molecular arrangement, and higher crystallinity. The additional side groups make the molecular chain more "tough", bringing higher melting points, better rigidity and transparency, but also reducing toughness at low temperatures.

Simply put, the nature of PE is "soft and tough", while the nature of PP is "rigid and transparent", which is the underlying logic of all performance differences.

2. Mainstream processes: stretching and casting, resulting in different product categories

The process is the key to determining the final shape of the film, and the performance of the same raw material can vary greatly with different processes

The two mainstream processes of PP film

Biaxially oriented PP film (BOPP): an absolute mainstay in the industry, accounting for over 70% of the total PP film production. By stretching the molecular chains in both directions, the transparency, glossiness, stiffness, and strength are significantly improved, making it the preferred material for packaging printing surface layers.

Cast PP film (CPP): extruded and cast through a T-shaped die, without stretching, retaining the heat sealing performance and high temperature resistance of native PP, mainly used as the inner heat sealing layer of composite packaging.

The two mainstream processes of PE film

Blow molded PE film (LDPE/LLDPE): The most classic PE film process, extruded and inflated, with low cost and excellent heat sealing properties, is the mainstream substrate for ordinary plastic bags, fresh-keeping bags, and protective films.

Cast PE film (CPE): Produced by the cast method, it has a more uniform thickness, higher transparency, and softer hand feel. It is commonly used in high-end clothing packaging, composite inner layers, winding films, and other scenarios.

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What are the differences in essence and process between PP film and PE film materials?

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