Understanding Film

BAGS & FILM 101

Are You Flexible?

  • Flexible packaging uses 75% less plastic than rigid plastics.
  • Packaging weight is reduced by 70% - which translates into lower shipping costs.
  • Empty pouches occupy up to 95% less space than traditional plastic packaging.
  • Flexible pouches cost less.

UNDERSTANDING FILM

Stand up pouches are typically made from two or more films laminated together. Films can be laminated by using an adhesive or by heat and pressure.

PET/Ink/LLDPE - Common laminated structure.

PET - Polyester (or Mylar) is the outside layer that provides strength and exhibits a high melting point.

Ink - is the printing that occurs on the inside of the PET layer and will get sandwiched with the next layer of film

LLDPE - Poly - is the inside layer that provides a moisture barrier and exhibits a low melting point. This layer melts together to form the seal.

PRINTING

To protect the ink and to keep it from contacting the product, Reverse Trap Printing is used. This process where the reverse image is printed on the inside of the outer film layer and is then sandwiched between the next layer.

Surface Printing is when printing is done on the outside of the film. This is normally required if the film used is not transparent.

FILM THICKNESS

A typical pouch thickness ranges between 3 Mil and 5 Mil. A ‘Mil’ is sometimes called a ‘Thou’, and should not be confused with a millimeter (Metric).

Mil (Thou) = .001 inch
Gauge (ga) = .00001 inch = .01 Mil
Micron(µ) = .00003937 inch = .03937 Mil

BREAKING ALL THE BARRIERS

Flexible packaging is designed to keep the contents fresh and maximize shelf life by providing a protective barrier from outside elements such as UV light, oxygen and moisture, while containing the aroma and preventing gas and moisture exchange

The air we breathe is 20% oxygen and 78% nitrogen. Film has an oxygen transfer rate (OTR) which is the amount of oxygen that passes through a defined area of film over a 24 hour period. The lower this number, the better the barrier. Foil has the best OTR of 0. Other good barriers are Saran coated polyester (KPET), METPET and EVOH. To increase shelf life, oxygen can be removed by purging with nitrogen before sealing. Film also has a moisture vapor transfer rate (MVTR or WVTR). While LLDPE (Poly) is known as a “screen door” to oxygen.

BARRIER CHARACTERISTICS

CategoryDescriptionOTR (CC/M2)* (Oxygen Transfer Rate)MVTR (g/m)* (Moisture Vapor Transfer Rate)
Foil Aluminum 0 0
EVOH Ethylene Vinyl Alcohol 0.6 100
METPET Metalized Polyester 0.95 1.2
KPET Saran Coated PET 7.8 7.55
PET Polyester 85 55
Nylon Nylon 95 260
OPP Polypropylene 2000 8
LLDPE Polyethylene 2500 17

BIODEGRADABLE

The majority of films have decomposition rates of 100 years or more. It has been discovered that by adding starch to Poly, it will begin to decompose in mere months. While this may sound advantageous, the uses for food packaging arelimited because of the poor barrier and high decomposition rate when exposed to heat, moisture and UV light. These elements exist both in landfills and in the supply chain. Fluorescent lighting, heat and humidity all have to be controlled within the supply chain to ensure and maintain the integrity of the packaging.

RECYCLE CODES

Recycle codes on plastic packaging refer to a resin code that is assigned to a particular plastic (polymer). The majority of laminated pouches do not display resin codes. The individual film layers that make up the laminated structure are assigned codes, however, once they are laminated, the code will become 7 (other).

ResinDescriptionUses
PET, PETE
(Polyester)
Plastic bottles (Water, Juice, Soda, Ketchup, Oven Bags, Microwaveable food trays)
HDPE
(High Density Polyethylene)
Non-food bottles (Shampoo, Cleaners, Motor oil, Plastic Lumber, Flower Pots, Recycling bins)
PVC [Vinyl]
(Polyvinyl Chloride)
Shrink Wrap, Deli & Meat Wrap, Pipe, Siding, Window Frames, Decking, Flooring...
LDPE
(Low Density Polyethylene)
Bags (Bread, Produce, Garbage, Frozen Food, Toys, Squeezable Bottles, Container Lids)
PP
(Polypropylene)
Containers (Yogurt, Margarine, Deli Foods, Medicine Bottles, Bottle Caps, Carpeting)
PS
(Polystyrene)
Cups, Plates, Bowls, Meat Trays, CD Cases, Packing Peanuts, Insulation...
OTHER
(Other or Multi-layer resin)
Reusable water bottles, Barrier Layers, Oven Baking Bags, Custom Packaging...