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Understand Standup Pouch Structure

Updated: Aug 9, 2023


Standup Pouch Structure

When we talk about how good pouches are, we are actually talking about their internal structural composition. It has the sturdiness of metal cans and protects the nutrient value of the food. Specifically, each pouch consists of four layers as shown in the image.


1st layer (inner) – propylene which acts as a heat seal surface and provides strength and flexibility.

2nd layer – the nylon layer protects from abrasion.

3rd layer – aluminium layer not only protects from lights, gases, and odour but also extends the product's shelf life.

4th layer (outer) – polyester layer provides excellent strength and is very easy to print on.

The materials that we use to produce of retort pouches are approved and undergo quality processes which increase the durability of the packaging.


Are You Ready for Digital / Flex Printing ?

  1. Pouch packaging uses 75% less plastic than rigid plastics.

  2. Packaging weight is reduced by 70% - which translates into lower shipping costs

  3. Empty pouches occupy up to 95% less space than traditional plastic packaging.

UNDERSTANDING FILM

Standup 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 is 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 millimetre (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. The 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. The film vapour also has a moisture vapor transfer rate (MVTR or WVTR). While LLDPE (Poly) is known as a “screen door” to oxygen.


BARRIER CHARACTERISTICS

BARRIER CHARACTERISTICS of standup pouch structure

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 are limited 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).

RECYCLE CODES of standup pouches

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