Overview
The scratch resistance of inks is one of the key indicators for evaluating their adhesion fastness and durability, especially in industries such as packaging and printing, label manufacturing, and surface decoration. The friction resistance tester provides a standardized test method for quantitatively evaluating the wear resistance of ink coatings by simulating the friction and scratching effects that may be encountered in actual use. The purpose of this test is to determine the degree of appearance change of the ink layer after undergoing reciprocating or unidirectional friction under specific conditions, and to evaluate the scratch resistance level accordingly.
Test Principle:
The friction resistance tester is usually composed of a friction head, a load system, a reciprocating motion mechanism and a sample fixing platform. During testing, the prepared printed sample is fixed on the platform, and the friction head (usually wrapped in a standard friction cloth or made of a specific material) rubs the ink surface back and forth at a set speed and stroke under the condition of applying a specified vertical pressure. After a predetermined number of cycles, the ink layer is evaluated for wear, shedding, or color transfer through visual observation or instrumental measurements. The relationship between frictional resistance and wear degree can be described in the following simplified model:
F = μ × N
where F represents friction, μ is the coefficient of friction, and N is the applied vertical load. This model helps to understand the impact of load and friction materials on test results.
Test methodology
The testing process strictly follows standard procedures to ensure comparability and accuracy of results. The main steps include: sample preparation, equipment calibration, parameter setting, test execution and result evaluation. The sample should be flat and wrinkle-free, and the ink should be completely dry. Test parameters such as load, speed, friction stroke and number of cycles are determined according to specific application standards or customer requirements. For example, common test conditions may include a load of 500 grams, a friction stroke of 100 mm, a speed of 30 cycles per minute, and a total friction of more than 200 times. Immediately after the test, the sample surface is inspected under a standard light source.
Outcome evaluation
The assessment is usually based on the degree of damage to the ink layer. Types of damage include, but are not limited to: ink peeling, substrate exposure, visible scratches, or fading color. Grading can be either numerical or descriptive. A common grading method is shown in the table below:
| grade | Description |
| 5 | There is no visible change on the surface |
| 4 | Slight marks, visible only at certain angles |
| 3 | Obvious marks, but no ink peoffing |
| 2 | Some of the ink comes off and the substrate is slightly exposed |
| 1 | Severe shedding and extensive exposure of the substrate |
During the evaluation, attention should be paid to the consistency of ambient light, and if necessary, magnifying equipment can be used to assist observation. For color inks, the colorimeter can also be used to measure the ΔE value of color change before and after friction as supplementary quantification data.
Notes:
Test results are influenced by a variety of factors. Ink composition, curing degree, substrate type and surface treatment process are intrinsic factors. External factors include test load, friction head material, friction frequency, and ambient temperature and humidity. For example, higher ambient humidity can soften certain inks, leading to reduced scratch resistance. To ensure the reliability of the test, it is recommended to conduct it under standard temperature and humidity conditions, and to conduct regular maintenance and calibration of the equipment to ensure load accuracy and movement stability. Use a new friction cloth or check the condition of the rubbing head for each test to avoid deviations caused by contamination or wear.
Application:
This test method is widely used in quality control, product development, and compliance verification. With scratch rating data, manufacturers can optimize ink formulations and printing processes to improve product durability in transportation, stacking, and everyday use. At the same time, the test provides a common language for technical specification confirmation in the supply chain, helping to reduce disputes caused by insufficient wear resistance. Different industries may refer to different domestic and foreign standards, and the test conditions need to be adjusted accordingly to be close to actual usage scenarios.
References
ASTM D5264 - Standard Test Method for Evaluating Abrasion Resistance of Printed Materials
ISO 28360 - Printing technology - Determination of friction resistance of printed materials and printing inks
GB/T 7706 - Lithography - Printed materials