Definition
Paper absorbency tester is a specialized laboratory equipment used to quantify the absorption capacity of paper and its related materials to liquids. The instrument measures the rate or total amount of liquid absorbed by paper by simulating the liquid contact process under specific conditions, and the result is usually expressed as the amount of liquid absorbed per unit area or per mass. This assay has a fundamental role in the paper industry, packaging material evaluation and printing quality control.
Principle
The working principle of paper absorbency tester is mainly based on the theory of capillary action and surface infiltration. When the paper comes into contact with the liquid, the liquid penetrates into the material driven by the capillary force of the pores between the fibers. The instrument records the process of liquid absorption by controlling conditions such as contact time, liquid type and pressure. Common determination principles include the Krem method (Cobb method), the basic relationship of which can be expressed as:
U = (W2 - W1) / A
Among themUis water absorption (usually measured in g/m²),W1WithW2The mass of the sample before and after absorption of liquid,AThe effective contact area of the specimen. This formula reflects the mass of the paper absorbing liquid per unit area within a specified amount of time.
Measurement method
According to different standard systems, there are certain differences in the measurement methods of paper water absorption. Common standards include ISO 535 (Krem method), TAPPI T441, and GB/T 1540. A typical procedure is as follows: first place the specimen of the specified size in the instrument test area and apply appropriate pressure to ensure a seal; The specimen is then exposed to a specified volume or depth of liquid (usually water) for a standard period of time; Excess liquid is quickly removed after contact and the change in specimen mass is weighed. Part of the method also involves the use of colored liquids or electronic sensors to record the liquid front rise altitude to assess the absorption rate. The measurement process should be carried out in a constant temperature and humidity environment to minimize the impact of environmental fluctuations on the results.
Influencing factors
The measurement of paper absorbency is influenced by a variety of factors. Material factors include the type of fiber of the paper, the degree of beating, the content of fillers, the degree of sizing and the pore structure, etc., which directly affect the size and distribution of the capillary. In terms of liquid properties, the surface tension, viscosity, and pH of the liquid may alter the infiltration kinetics. Operating conditions such as contact time, liquid temperature, applied pressure, and ambient temperature and humidity also play a role in the measurement results. In addition, the specimen's pretreatment history, such as whether it has been dried or moisture balanced, also needs to be taken into account. Therefore, these variables are specified in the standard methodology to ensure comparability of results.
Application
The application range of paper absorbency tester is wide. In the paper industry, it is used to evaluate sizing effects and control the water resistance of base paper and lined cardboard. The packaging sector relies on this test to ensure the strength retention of cartons and bags in wet environments. The printing industry is concerned about the impact of paper absorbency on ink absorption, drying time, and print clarity. In addition, the instrument provides critical data in the development and quality control of hygiene materials (e.g., paper towels, filter paper) and specialty papers (e.g., photo paper, label paper). The results of the tests help optimize the production process and meet the requirements of product specifications or industry standards.
Selection
When choosing a paper absorbency tester, it is necessary to consider many aspects. First of all, the standard system (such as ISO, TAPPI, GB, etc.) should be clearly followed to ensure that the instrument design complies with the corresponding methods for contact area, time control, pressure application and liquid supply mode. Second, evaluate the automation of the instrument based on common test needs, such as automatic timing, liquid dosing, or direct data calculation, which can improve test efficiency and repeatability. In addition, the durability of the instrument's material, the user-friendly design of the user interface, and the after-sales technical support are also considerations in the selection process. Users can choose based on their lab's sample throughput, budget range, and long-term R&D needs, based on basic measurement accuracy.