Complete Guide to Pull-Off Adhesion Testing – ASTM D4541
Pull-off adhesion testing is a way to help you work out how durable and lasting your coatings will be once your product is out in the real world. That’s why it’s an essential part of a solid QA process and one that’s well worth learning about. Ready to find out more about how pull-off adhesion testing works and how it can comply to industry standard ASTM D4541? Dive on in.
What is pull-off adhesion testing?
Pull-off adhesion testing is a method of measuring the resistance of a coating to separation from a substrate when a perpendicular tensile force is applied. There are range of substrate materials that the testing is usually performed on, including metals, plastics, concrete, wood and glass.
What kind of coatings can be tested?
There are a huge range of coatings, finishing and linings that can be tested, including and paint films and powder coatings, UV cured, ceramics, epoxies, bitumens (tar enamel, asphalt mastics), thermoplastic resins (polyethylene, vinyl and plastisols), laminates, lacquers, varnishes, specialty resins (urethanes, fluorocarbons, phenolics and polyesters), elastomerics, and inorganics like glass, zinc, and lead.
How does pull-off adhesion testing work?
Pull-off adhesion testing works by applying a perpendicular tensile force to a coating and substrate. Typically, a test will involve a digital or manual pull-off adhesion testing machine with a dolly. Before staring the test, both the dolly and coating need to be cleaned. The adhesive is then prepared and added to the dolly, which is then adhered to the coated surface. The adhesive is the left to cure.
The machine’s actuator is then placed over the dolly and pressure is applied until the point that the adhesion fails. The pressure may be achieved using a hydraulic pump.
Ready to find a test and inspect solution for your lab or shop floor? Check out our great adhesion testing solutions.
Why test adhesion?
Need to know how well a coating adheres to a substrate applies to a huge range of applications and industries? From being confident that a protective film stays put on flexible packaging to knowing that the exterior paint of a vehicle will stay intact through exposure to the elements, adhesion testing can help with it all.
It is not only a cosmetic concern, can also have some significant safety implications. For example, in construction and maintenance work, the epoxy coatings used to protect steel require strong bonds to prevent wear and corrosion. If the adhesion fails and the epoxy peels, then the steel may rust and cause very expensive damage that could ultimately impact safety.
What industry standards are there for pull-off adhesion testing?
Unlike many other tests, there are a very few industry or application specific standards for assessing whether a particular coating and substrate passes or fails a pull-off adhesion test. It is typically up to you to determine the required level of adhesion you require when carrying out testing and deciding whether a sample meets your requirements.
Variations to watch out for
When it comes to adhesion, there are some variations that can make a huge difference to the bond between coating and substrate – even when you’re looking at very well-established coating application processes. These variations, which can seem very small but which can have big impacts, include:
- Thickness of the applied coating
- Climatic conditions during painting
- Cure times and temperatures
- Substrate and coating moisture contents
- Inadequate surface preparation methods
- Surface contamination
- Substrate densities
- Coating formulation
- Preparation and mixing parameters
These factors just underline how important it is to make sure you carry out thorough adhesion testing that takes into account the kind of substrate, coating and the product’s eventual use, every time any one of those factors changes.
To lessen the variations between results, it is important to use an adhesion tester that minimizes shear forces (forces acting parallel as opposed to perpendicular to the coating), such as those in the The PosiTest AT series. These feature self-aligning aluminum dollies which enable accurate measurements on smooth or uneven surfaces and ensures the minimization of variations.
Pull-off adhesion testing machines at Industrial Physics
We offer a number of reliable adhesion testing machines, such as:
Our range of PosiTest machines have hydraulic pumps and conform to a wide range of international standards, including ASTM D4541/D7234, ISO 4624/16276-1, AS/NZS 1580.408.5 and others. The pressure system of every PosiTest adhesion machine is calibrated and certified to ± 1% accuracy using a NIST traceable load cel.
Complying with the requirements of ISO 4624, this is a sturdy hydraulic tensile tester. It comes with a hand-pump equipped with a precision manometer and the actual adhesion pull off testing head. Different testing heads are available.
Looking for more inspiration? Browse our full range of adhesion testing solutions.
Help for all of your adhesion testing requirements
Hoping to add a new pull-off adhesion testing machine to your existing setup? Just getting started with coating testing and need some help figuring out what you need? Our experts are here to help. Check out ‘The Evolution of Inks & Coatings’ for more quality insights!