Applications & Uses of Adhesion Promoters

Polymer Alloys

In order to fulfill the requirements of the polymer industry, many developers usually blend polymers together in order to reach an optimum balance of properties.

This approach allows high flexibility in property adjustment and avoids development of new macromolecules which is generally long and expensive compared to polymer alloying. Many polymer blends like PBT/PC or PC/ABS or PP/PA are commercially available.

As already mentioned, polymers are not naturally miscible and compatibilization is most of the time required to obtain stable materials with good mechanical performance. Compatibilization is also important in polymer recycling. Recovery of multilayer material can be facilitated by addition of compatibilizers.

This topic is further developed in polymer recycling of multilayer structures. As there are so many possible combinations of polymers blends, we cannot disclose them all in details. Table below offers a non-exhaustive list of polymer blends and potential compatibilizers.

Polymer blend	Compatibilizer
PA6/PE	PE-g-MAH or E-MAA (Zn)
PA6/PP	PP-g-MAH
PBT/PP	E-BA-GMA
PBT/PA	E-BA-GMA
PET/Polyolefin	E-BA-GMA

Recycling

For many packaging applications multilayer structures are used. The combination of these layers generally provides to the final material with a mix of the individual performances of the polymers involved, like:

Barrier performance
Sealability
Moisture or chemical resistance and
Stiffness

…that are usually impossible to achieve with one single polymer.

The general structure of a multilayer film is:

Multi-layer Structures for Packaging Applications

The core layer is generally a barrier the external layers are inert or sealable. Adhesive layers allow a good cohesion between layers.

Multilayer film packaging waste has become an important global issue triggered by rising concerns over environmental care issues care and limited landfill space.

In order to render the material used compatible it is required during the recycling process to add a compatibilizer in order to reach much better material performance and stability. Table below shows examples of multilayer structures and recommended compatibilizers.

Multilayer type	Application	Component (Function)
PA/PE	Pasta, Meat, cheese, vegetable, fish	PA6 (Oxygen barrier, strength) LDPE, PELLD (Sealing)
PA/ ionomer	Pasta, Meat, Cheese	PA6 (Oxygen, Moisture barrier, abrasion resistance) Ionomer (sealing, clarity, abrasion)
PA/EVOH/PE	Sausage casings, Pate	PA6 (Oxygen, Moisture barrier, strength) EVOH (Oxygen barrier) LDPE (Sealing, flexibility, moisture barrier)
PE/EVOH/PP	Sausage Casings	PP (Moisture Barrier) EVOH (Oxygen barrier) LDPE, LLDPE (Sealing, flexibility, moisture barrier)
PE/EVOH/PE	Milk, juices, purees, sauces	LDPE, LLDPE (Sealing, flexibility, moisture barrier) EVOH (Oxygen barrier)
PET/PE	Liquid detergents	PET (Oxygen barrier) LDPE, LLDPE (Sealing, flexibility, moisture barrier)

Coupling Agents for FR and Wire and Cable Compounds

In order to meet cable producers needs and standards, many W&C applications require halogen free flame retardants. The most common flame retardant used for this application is Aluminum trihydrate (ATH). For efficient flame retardancy 60 to 65% of ATH needs to be added to the polymer matrix reducing original mechanical performances.

Coupling Agents for FR and W&Cable Compounds

However, mechanical properties are also very critical in cables and particularly elongation at break and tensile stress at break. To optimize mechanical performance a good adhesion between the filler and matrix is needed. This can be obtained by addition of a coupling agent. Silane can be used for this purpose, but functionalized polyolefins are excellent candidates providing also some flexibility to the material and easy handling.

Coupling Agents for Glass Filled Polypropylene

As coupling agents in mineral and glass filled polypropylene, adhesion promoters are capable of reacting with the functional groups at the surface of the filler, while the backbone of the polymer is miscible with the base polypropylene.

In this way it bonds the filler to the polymer matrix.
This also permits better surface wetting of the filler, improved filler dispersion and greater homogeneity for the blend.
The result is significantly enhanced tensile and impact strength of the composite.

The appropriate impact modifier for your application depends upon the desired physical properties of the final compound.

Grades delivering stiffness (flexural modulus) or impact strength (Notched Izod) are available on the market. Some others are useful in situations where die high flow of the base resin combined with the very high graft level is desired - for example in pultrusion applications where good surface wetting of the glass roving is necessary.

The addition level of coupling agent required in order to optimize physical properties is generally in the range of 2-5% but will depend upon the mixing efficiency of your compounding equipment.

Coupling agents for Other Filled TPO

PP/Calcium Carbonate - As coupling agent in mineral filled polypropylene, adhesion promoter is capable of reacting with the functional groups at the surface of the filler, while the backbone of the polymer is miscible with the base polypropylene.

In this way it acts to bond the filler into the polymer matrix. This also permits better surface wetting of the filler, improved filler dispersion and greater homogeneity for the blend. The result is significantly enhanced tensile and impact strength of the composite.

PEHD/Mica - Adhesion promoters can be used in Polyethylene filled systems containing mica talc, calcium carbonate...

» Explore Latest Developments in Surface Modifying Technologies

Coupling Agents for FR and Wire and Cable Compounds

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Applications of Adhesion Promoters

Polymer Alloys

Recycling

Coupling Agents for FR and Wire and Cable Compounds

Coupling Agents for Glass Filled Polypropylene

Coupling agents for Other Filled TPO

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