Plastic Film Characteristics

There are so many plastic resin options and combinations of resins available that the best way to ensure a desirable outcome to your poly bag project is to contact Custom Poly Packaging and communicate your requirements.

Film Clarity or "Gloss" can be achieved with additives like EVA or Metalocene blended into the base polyethylene resin. Shiny / glossy film has better optics for retail packaging with either clear or colored films or in any application where appearance is important. Depending on the purpose for the packaging, it may be necessary to choose between clarity and strength. Most polyethylene films that are tough, strong and resist punctures or tearing are not very clear or glossy. They have a more or less milky appearance. There are resin combinations that can improve the shine / gloss / clarity, but typically, if a bag is very tough, it is also more translucent than transparent.

Low Density Polyethylene (LDPE) can normally be identified by its softer feel, shinier appearance and more muffled sound when it is handled while High Density Polyethylene (HDPE) typically has a matte finish, feels and sounds like slippery tissue paper. This is a very general comparison since both HDPE and LDPE can each be modified to seem to have some of the characteristics of the other.

The compostable and biodegradable films we use to manufacture bags and yard signs is LDPE with an additive that causes it to decompose when buried in the ground. This makes them 'Earth Friendly' and takes about a year for this 'green' process to begin. Until the degradable film is in contact with the Earth, it acts in the same way as any other low density polyethylene. It does not start to break down while it is in normal use and does the same job any poly bag would in the same application.

Polypropylene film used to manufacture custom plastic bags at Custom Poly Packaging is a mono layer, random co-polymer containing ethylene. It does not have superior barrier properties. Although the moisture vapor transmission rate (MVTR) is slower than either high or low density polyethylene films, it does allow moisture and air to migrate through the wall of the film. The clarity of the polypropylene we use is, in general, also better than HDPE or LDPE, but it does not have the crystal clarity of the high barrier type polypropylene or cellophane.

Here is a video showing the general operations involved to manufacture poly bags:

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