Adhesion Promoters
Adhesion is one of the most critical properties for any coating, ink, adhesive or sealant formulation. Often times to improve the adhesion properties an adhesion promoter additive is used. Adhesion promoters typically will interact with both the substrate and functional groups within the polymer network of the formulation to form a chemical bridge between the formulation and the surface it is being applied to.
Lupasol® Adhesion Promoting Additives
Lupasol® is a family of branched polethyelenimine polymers with a very high cationic charge density. Due to this charge density, Lupasol® polymers will adsorb strongly on negatively charged surfaces and are often used as adhesion promoting additives in adhesive, printing ink, and coating formulations.Adhesives
Lupasol® polymers are commonly used in combination with polyvinyl alcohol, polyvinylbutyral, polyvinyl acetate, and styrene based adhesives to improve adhesion to metal, plastic, and cellulose based substrates. In addition, low molecular weight grades of Lupasol® can be used to cross link polymers in an adhesive to dramatically improve cohesion. Typical Lupasol® addition rates in adhesive formulation range from 0.1% - 1%.
Recommended Grades for Adhesives
| Grade | Function | Recommended Concentration |
|---|---|---|
| Lupasol® P | Increase adhesive strength | 0.1 - 5% |
| Lupasol® PS | Increase adhesive strength | 0.1 - 5% |
| Lupasol® G 20 | Increase cohesive strength | < 1% |
As mentioned above, the addition of a small amount of low molecular weight Lupasol® can significantly improve the cohesive strength of an adhesive by acting as a cross linker between polymers in the formulation. To demonstrate this improved cohesion, the cohesive strength of an acrylic pressure sensitive adhesive was tested with varying levels of Lupasol® G 20 added.
Improvement in Cohesive Strength with Lupasol® G 20
Paints & Coatings
In emulsion paint formulations, the addition of a small amount (typically 0.1%) of a low molecular weight Lupasol® polymer can significantly improve adhesion to wet surfaces. This becomes especially important in kitchen and bathroom painting applications.
Recommended Grades for Paints & Coatings
| Grade | Function | Recommended Concentration |
|---|---|---|
| Lupasol® G 20 | Improve wet adhesion | 0.1% |
The increase in wet adhesion is demonstrated by the testing data below. In this test a commercially available vinyl acrylic latex paint was modified with varying levels of Lupasol® G 35. The paint was then applied to a glossy alkyd substrate and wet adhesion was tested in accordance to ASTM D 3356.
Improvement in Wet Adhesion with Lupasol® G 35
Printing Inks
Lupasol® is commonly used as an adhesion promoting additive in printing inks for laminated films. It is particularly effective for sandwich-printed laminated films where ink adhesion is needed to two different types of film. It is important to note that Lupasol® is strongly basic and should only be used with binders and pigments that are stable in alkaline environments.
Recommended Grades for Printing Inks
| Grade | Function | Recommended Concentration |
|---|---|---|
| Lupasol® WF | Improve adhesion to laminated films | 0.5% - 1% |