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Polyethylene (PE) vs Polypropylene (PP) Poly Bags - Whats the difference?

Posted by Ashley Livengood on

There has been some debate over which material will work best for your bagging applications. Below we list some of the most important differences between Polyethylene and Polypropylene material.

3 mil polyethylene bag 

Polyethylene (PE)

 

Polyethylene is flexible, durable and tear-resistant these three characteristics are extremely important when you want your poly bag to contain heavy items. Industrial companies use polyethylene for storage bags for large heavy items such as industrial machining parts.

  • Inert, translucent and creates a lower static charge
  • Prohibits a the greater amount of light to enter the bag which protects the contents
  • Attracts much less dirt, dust and other foreign, organic elements
  • Soft and pliable
  • Higher purity (100% Virgin)

 

Wikipedia's Definition of Polyethylene:

LDPE is defined by a density range of 0.910–0.940 g/cm3. LDPE has a high degree of short- and long-chain branching, which means that the chains do not pack into the crystal structure as well. It has, therefore, less strong intermolecular forces as the instantaneous-dipole induced-dipole attraction is less. This results in a lower tensile strength and increased ductility. LDPE is created by free-radical polymerization. The high degree of branching with long chains gives molten LDPE unique and desirable flow properties. LDPE is used for both rigid containers and plastic film applications such as plastic bags and film wrap. In 2013, the global LDPE market had a volume of almost US$33 billion.

The radical polymerization process used to make LDPE does not include a catalyst that "supervises" the radical sites on the growing PE chains. (In HDPE synthesis, the radical sites are at the ends of the PE chains, because the catalyst stabilizes their formation at the ends.) Secondary radicals (in the middle of a chain) are more stable than primary radicals (at the end of the chain), and tertiary radicals (at a branch point) are more stable yet. Each time an ethylene monomer is added, it creates a primary radical, but often these will rearrange to form more stable secondary or tertiary radicals. Addition of ethylene monomers to the secondary or tertiary sites creates branching.

polypropylene bags
Polypropylene (PP)

 

A polypropylene bag is a high clarity crystal clear bag which enhances the product’s image. It provides a highly protective barrier against moisture and vapors. Delay evaporation and dehydration to preserve freshness and taste of packaged foods. Polypropylene bags make great ways for storing food, electronics manufacturing, hospitals, agriculture, clean room technology flat poly bags can be used virtually anywhere.

  • Crystal clear for great product presentation
  • Stiff and hard plastic
  • Rough surface has the potential to produce scratches
  • Outstanding vapor and moisture barrier.
  • Meets FDA and USDA specifications.

Wikipedia's Definition of Polypropylene:

Melting process of polypropylene can be achieved via extrusion and molding. Common extrusion methods include production of melt-blown and spun-bond fibers to form long rolls for future conversion into a wide range of useful products, such as face masks, filters, diapers and wipes.

The most common shaping technique is injection molding, which is used for parts such as cups, cutlery, vials, caps, containers, housewares, and automotive parts such as batteries. The related techniques of blow molding and injection-stretch blow molding are also used, which involve both extrusion and molding.

The large number of end-use applications for polypropylene are often possible because of the ability to tailor grades with specific molecular properties and additives during its manufacture. For example, antistatic additives can be added to help polypropylene surfaces resist dust and dirt. Many physical finishing techniques can also be used on polypropylene, such as machining. Surface treatments can be applied to polypropylene parts in order to promote adhesion of printing ink and paints.

If you've made it this far, you should also check out our huge selection of polyethylene and polypropylene poly bags available for your packaging needs.

Feel free to contact us with any questions you may have.


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