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Material Decisions: Polyethylene (PE) vs Polypropylene (PP)

by Greiner Packaging

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© Greiner Packaging

Much like comparing apples and oranges, no two materials are created equal when it comes to your packaging needs.  The right material for your project is dependent upon a number of variables including the product itself, as well as considerations such as durability, recyclability and method of transport. When examining the differences between polyethylene and polypropylene materials, it can be summed up in a difference of structure that results in varying physical, thermal and chemical properties. These, in turn, translate to varying limits on temperature exposure, rigidity, permeability, sustainability, and optical properties.

The world’s most common plastic, polyethylene (PE) is an ideal fit for a number of applications and products. It’s both flexible and durable, making it work especially well in packaging for heavier items. However, within the polyethylene family, there are different kinds of polyethylene available — high-density polyethylene (HDPE) and low-density polyethylene (LDPE). While they share some similarities, there are also notable differences between the two types.

  • High-density Polyethylene is a popular choice due to the high quality and inexpensive nature of the material. Its light weight makes it an excellent choice for those wary of supply chain and transportation costs. And, its extreme resistance to chemicals makes it well suited for healthcare and laboratory environments. Moreover, HDPE is one of the easiest plastic materials to recycle in the United States, as it is accepted at most recycling centers across the nation, making it an ideal solution for environmentally conscious companies that are focusing on sustainability.
  • Low-density Polyethylene is much more pliable than its high-density counterpart. While this exceptional “formability” comes at the cost of significantly less tensile strength, it is still suited for a number of applications, perhaps most commonly in the form of plastic margarine tubs, water bottles, and plastic bags.
  • Polypropylene (PP) is generally much more rigid and harder than PE, and tends to hold up well under repeated use. PP is visually appealing and can be made optically clear, making it ideal for situations when it is necessary to see the product inside the packaging in detail. It provides a highly protective barrier against moisture and vapors, while also delaying evaporation and dehydration in order to better preserve the freshness and taste of packaged foods. Unlike, PE, polypropylene has a high melting point, making it pliable when heated above a certain temperature, yet returning to a solid state once cooled.

While some plastics may work interchangeably in a number of applications, there are some inherent differences between them and noting those distinctions will prove to be invaluable when deciding whether or not they are appropriate for your needs. For example, while the rate of recycling PE is outpacing that of PP, the material is softer and thus may be less suitable for some applications unless the introduction of a rigid material like cardboard is used to help reinforce its structure.

At Greiner Packaging, our solutions experts will work with you to carefully review the unique product features and specifications in order to find the best plastic material for your particular project.

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Forward thinking packaging for today's dairy-product companies