Guidelines for Using Polyolefin Adhesion Promoters
Polyolefin Adhesion Promoters
Eastman Polyolefin Adhesion Promoters are modified polypropylene polymers that are used to improve the adhesion of coatings, inks, and adhesives to low surface energy plastics such as TPO, polypropylene, and polyethylene. They are often used in primer formulations but can also be added directly to formulation to boost adhesion of one-step systems to untreated surfaces.
Adhesion Failure on Polyolefin Surfaces
Polyolefin substrates are difficult to adhere to for three main reasons:
Low Surface Energy
The surface tension of the polyolefin substrate is often less than the surface tension of the coating. This makes the surface difficult to wet.
Polyolefins are nonpolar. This means that there are no active sites for hydrogen bonding or cross-linking.
Polyolefins plastics are highly resistant to solvent. This prevents the coating from diffusing into the substrate properly.
How Eastman Polyolefin Adhesion Promoters Work
Eastman Polyolefin Adhesion Promoters are polyolefin polymers that have been functionalized with polar groups (typically chlorine or maleic anhydride). When applied to a polyolefin substrate, the non-polar back bone of the Eastman Polyolefin Adhesion Promoter interacts with the non polar surface of the polyolefin substrate via Van Der Wall forces. The polar head groups of the adhesion promoter are then free to interact with polar functional groups in the coating, ink, or adhesive. The image below outlines this process in a simplified manner.
Selecting the Proper Polyolefin Adhesion Promoter
Eastman's Polyolefin Adhesion Promoters come in a variety of grades that each provide unique benefits that are well suited to different end use applications. The table below lays out the various grades of Eastman Polyolefin Adhesion Promoters that are commercially available and highlights which grades are recommended based on application, performance attribute, and regulatory attributes.
When selecting a grade some common things to consider are listed below:
The substrate that must be adhered to
The end use application & how it will be applied to the substrate
Environmental regulations regarding VOC, banned chemicals, and recyclability
The attributes needed to provide optimal performance
ChemPoint has product specialists standing by to help you. Contact us today to discuss your application and find the grade best suited for you.
How to Use Eastman Polyolefin Adhesion Promoters
The successful use of polyolefin adhesion promoters depends on the using the proper combination of adhesion promoter, substrate, film thickness, and coating system that is applied over the adhesion promoter film. The polyolefin adhesion promoter is typically spray applied as a thin mist coating and then allowed to dry thoroughly prior to the application of further coatings. The steps for applying a primer made from Eastman Polyolefin Adhesion Promoters are listed below.
Clean the substrate of all contamination with an appropriate cleaning solution and then dry it completely.
Prepare your primer by diluting the Eastman Polyolefin Adhesion Promoter to 5-10% solids using an appropriate solvent.
Apply the primer to the substrate at 0.1-0.2 mil (dry film thickness) by spraying, wiping, or other means.
Allow the primer to dry. Drying times vary but are typically anywhere from 3-10 minutes at 21°C
Topcoats can be applied once the primer is completely dry.
Typically, the best adhesion is achieved by applying Eastman Polyolefin Adhesion Promoters directly to the substrate as a primer. However, in certain applications it is necessary to avoid this priming step. In these applications it may be possible to Eastman's Polyolefin Adhesion Promoters as an additive to the formulation to improve adhesion. In these cases, formulators must test the compatibility of the adhesion promoter with the other components in the formulation to ensure this approach is feasible. The guidelines for utilizing Eastman Polyolefin Adhesion Promoters as an additive are listed below.
Clean the substrate of all contamination with an appropriate cleaning solution and dry thoroughly.
Add the Eastman Polyolefin Adhesion Promoter to the formulation at 2.5% solids to the unreduced coating, ink, or adhesive and mix thoroughly.
For example, add 10 wt% CP 343 25% Xylene to 100 wt% coating, ink, or adhesive.
Test the formulation for compatibility and effect on dry film properties
If target adhesion is not achieved, increase the amount of adhesion promoter until it is while continuing to monitor the effects on dry film and other properties.