Definition
A dyne pen, also known as a surface tension test pen or corona treatment test pen, is a portable tool used to quickly assess the free energy or surface wettability of solid materials. In printing, coating, lamination and other processes, it is mainly used to qualitatively judge whether the surface of the material has been properly treated (such as corona, flame treatment) to achieve the adhesion requirements required by subsequent inks, coatings or adhesives.
Principle
The working principle of dyne pens is based on the phenomenon of the spread of liquids on solid surfaces. The pen contains a test solution with a specific surface tension, and its tension value is usually measured in millinewtons per meter (mN/m) or dynes per centimeter (dyn/cm). When the test solution is painted on the surface of the material, if the liquid remains in a continuous liquid film state for 2-3 seconds, it indicates that the free energy of the material surface is equal to or higher than the tension of the test liquid. If the liquid shrinks into droplets or breaks, it indicates that the free energy of the material surface is lower than the test liquid tension. By using a range of test pens with different tension values, the critical surface tension range of the material surface can be approximated.
Measurement method
Measurements should be performed on a clean, flat sample surface. A test pen with a nominal value close to the expected tension range was selected and a stroke of about 25 mm long was drawn on the surface of the sample at moderate speed and pressure. Observe the state change of handwriting within 2-3 seconds. If the handwriting remains intact, replace the test pen with a higher tension value and repeat the test. If the handwriting shrinks, replace the test pen with a lower tension value. Finally, the highest tension value that can maintain the intact liquid film will be used as a reference value for the surface tension range of the material. The test should be performed at multiple points to ensure representative results.
Influencing factors
Test results are influenced by a variety of factors. The chemical composition, microscopic roughness and cleanliness of the material itself are the basic factors. Environmental conditions such as temperature and humidity may affect the volatilization and spread of the test fluid. Consistency in testing operations, including line drawing speed, angle, and pressure, can also introduce bias. In addition, if the material is treated with corona, its effect may decay over time, so the timing of the test is important. The stability and shelf life of the test solution itself also need to be paid attention to.
Applications
This tool is primarily used in areas where process control of surface wettability is required. In the printing industry, it is used to check the surface treatment of substrates such as plastic films, metal foils, and paper to ensure ink adhesion. In the plastics processing and packaging industry, it is used to evaluate the surface condition of polyethylene, polypropylene and other materials before compounding and gluing. In the coatings and adhesives industry, it can be used to quickly screen substrates or evaluate the consistency of surface treatment processes. It serves as a rapid qualitative or semi-quantitative tool and is often used with more sophisticated laboratory instruments.
Selection considerations
The measurement range should be considered when selecting. Common test pens typically have a tension value range of between 30 and 60 mN/m, and users should choose a series of pen sets that cover this range based on the expected tension value of the material to be tested. The formulation type of the test solution needs to match industry practice or relevant standards. The structure of the pen, such as the tip material, sealing, and writing fluency, affects the service life and test consistency. In addition, it is necessary to confirm whether the test fluid provided by the supplier meets the relevant safety and environmental protection requirements. For cases where quality control is strict, a matching standard test solution should be considered for regular calibration.