Not all tie-layer adhesives are created equal

Don't take your barrier packaging for granted. Choosing your tie-layers wisely, not only based on price, is of ultimate importance. Knowing how to process them will define the performance of your multi-layer barrier packaging.

How to select a tie-layer?

Tie-layers are selected based on a combination of factors. We highlight some of them on this article

• SUBSTRATES - Typically tie-layers are used to bond Polyolefins to EVOH, Nylon, PET or Aluminium based on their ability to bond via "covalent bonding" - The reaction of the Maleic Anhydride with polar groups such as Hydroxyl (OH), Amines (NH2), etc. The presence of additives should also be carefully evaluated.
• PROCESSING - Either by coextrusion blown, flat die, bioriented, tubing, extrusion-lamination, blow-molding and more.
• END USE - Tie-layers are used primarily for the purpose of producing multilayer Barrier Packaging and therefore take advantage of the combined properties of each and every layer such as barrier to Oxygen, barrier to water, mechanical and thermal properties and so on.
• ADHESION STRENGHT - Several factors would lead to adhesion strength, such as Maleic Anhydride content, type of base resin, thicknesses, processing conditions, storage and usage temperature, etc. A tie-layer has to withstand all the conditions the packaging will go throughout its shelf life.
• COST - Tie-layers are made with different base polymers, different technologies and regulatory characteristics. As an example, a tie-layer designed for bi-oriented multi-bubble extrusion process for deep-freezing shrink bags will require a very high-performance custom formula.
• REGULATORY - Perhaps the most important requirement when it comes to food-packaging. We can't stress enough how important is to work with a reliable partner.

How to Process a tie-layer?

Adhesion strength is defined not only by the Tie-layer type or its functionality but also by a combination of several processing and post-processing conditions.

"When (tie-layer) thickness increases" .... The adhesion tends to increase giving the higher presence of reactive groups. Thickness should be considered as final only after orientation, thermoforming and mechanical orientation. The lack of reactive groups will cause delamination.

"When temperature increases".... Adhesion strength will increase. Processing temperature, cooling, annealing, storage and cooking are variables that influence on the final adhesion strength.

"When Line Speed increases".... The adhesion may go down. There might not be enough contact time for the reactive groups to bond with the substrates, particularly when temperatures and thicknesses are too low.

"When the Orientation increases".... The adhesion strength may go down, either by increasing the Blow-up Ratio (BUR), Biorientation and thermoforming.

"When the time increases".... The adhesion will increase. It is very important to measure the adhesion strength immediately during production but also after 48 to 72 hours in order to find out a more realistic value. In some instances, when additives are present (such as anti-fog and slip) the adhesion should be re-measured within a few weeks.

There is much more complexity when it comes to Tie-layers than we can ever describe in an online article. Our team will be glad to discuss your barrier packaging needs and work closely with your engineering and procurement any time.

NOVERIN? is a proud partner of MPB (Compounding Division of Industrie Polieco Group) . We represent the (maleic anhydride based) Tie-layer brands Coesive? and Proesive? exclusively in North America and Brazil.

We also represent the high-end extrusion lines from Macro Engineering & Technology Inc. in Brazil, all backed by our decades long expertise on the multi-layer packaging segment and dedication to excellence and customer service.

Learn more about NOVERIN? at www.noverin.com and get in contact with us at [email protected]