ASTM D5946 Contact Angle Measurements on corona-treated polymer film surfaces

Use of Water Contact Angle Measurements for Corona-Treated Polymer Films is done by ASTM D5946. The surface characteristics of a polymer film decide how well the polymer films can retain the surface coatings. The contact angle of a water droplet on the polymer film surface indicates its ability to accept and retain surface coatings.

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Introduction

ASTM D5946 uses Water Contact Angle Measurements for Corona-Treated Polymer Films. A polymer film’s surface characteristics decide how well it can retain its surface coatings. The contact angle of a water droplet on the polymer film surface indicates its ability to accept and retain surface coatings.

Scope

Water Contact Angle Measurements by ASTM D5946 for surface-treated polymers. Surface coating substances like inks, paints, adhesives, and clear coats are applied to polymer films to make decorative inscriptions and graphics on automobiles and electronic items. The capability of polymer films to retain these surface-coating substances primarily depends on the surface characteristics of the polymer films. Some surface-treating techniques can improve surface characteristics. One such technique is Corona, an electrical discharge treatment that can increase the wetting tension of a polymer film. The contact angle of a water droplet on the polymer film surface gives a fair idea about its ability to accept and retain surface coatings.

Test Procedure

Take the polymer film sample, approximately 25 mm wide and 300 mm long, and place it on the specimen holder so that it is flat without wrinkles or distortions. If the apparatus has a sample holder, stretch the film using this holder and ensure a flat surface. If no holder is provided, adjust the film manually to remove wrinkles. Fill the liquid dispenser with water and set it to dispense a 5 to 8 µL droplet. Bring the film toward the suspended droplet, taking care to have the droplet transferred onto the film surface without distortion, squirt, or drop.

Once the droplet is placed, use the imaging system or other appropriate measuring tools, such as a protractor, grid, or CCD sensor, to capture and measure the contact angle created by the droplet on the sample surface. Before repeating the process, move the sample to a fresh area without contact with the droplets. Perform this measurement ten times on different sample portions to obtain accurate and reproducible measurements. The values thus obtained for contact angle measurement are helpful for correlating wettability behavior as well as surface properties of corona-treated polymer film.

Test Conditions for Routine and Interlaboratory Measurements:

The table below represents the different conditions for testing, including requirements for routine measurements, interlaboratory measurements, and special test conditions.

Aspect	Description
Conditioning for Routine QA or Process Control	Conditioning is not generally required for routine quality assurance (QA) or process control measurements, as it may affect the measured value and misrepresent actual conditions.
Conditioning for Interlaboratory Measurements	Conditioning is required for interlaboratory measurements that compare results. Condition the test specimens at 23 ± 2°C (73.4 ± 3.6°F) and 50 ± 10% relative humidity for at least 40 hours, by Procedure A of Practice D618, unless specified otherwise. Tolerances: ±1°C (±1.8°F) and ±5% relative humidity.
Test Conditions for Routine QA or Process Control	Routine QA or process control measurements do not generally require special test conditions.

Specimen size

The sample size required for the test is 25 mm wide and 300 mm long. If the sample is taken from a roll, note the orientation relative to the web’s machine direction.

Result

The result represents the value of the film’s wettability and capacity to accept and retain surface coatings; the lower the contact angle, the higher the wettability.

Conclusion

ASTM D5946 provides a standardized procedure for evaluating the surface characteristics of corona-treated polymer films via water contact angle measurements. It helps determine whether films are wettable and can resist coating, which is crucial in applications such as printing coating.

FAQs

What is the purpose of ASTM D5946?

ASTM D5946 is a standardized method for measuring the surface wettability of corona-treated polymer films using water contact angle measurements. It helps determine the film's ability to accept and retain surface coatings like inks, adhesives, and paints.

What does a lower contact angle indicate about the film?

A lower contact angle means the polymer film has greater wettability, which signifies an increased ability to accept and hold coatings. It is essential for its functionality in different coating applications.

What is the required size of the polymer film sample for testing?

The sample size required for the test is 25 mm wide and 300 mm long. If the sample is taken from a roll, note the orientation relative to the web's machine direction.

Why is the contact angle critical in this test?

The contact angle measures the wettability of the polymer film's surface. The lower the contact angle, the higher the wettability, which reflects that the film will better accept and retain coatings. It is an essential factor for printing, coating, or adhesion processes.

What is the required conditioning temperature and humidity for interlaboratory studies?

For interlaboratory studies, specimens should be conditioned at 23 ± 2°C (73.4 ± 3.6°F) and 50 ± 10% relative humidity, unless otherwise specified. The tolerances for temperature and humidity are ±1°C (±1.8°F) and ±5%, respectively.