Views:0 Author:Site Editor Publish Time: 2021-05-25 Origin:Site
Sometimes paper product performance test data is always inaccurate, do you know why?
Inaccurate quantitative or strength test data for paper products is the most common problem, which leads to customer feedback of poor instrument accuracy, inaccurate testing, and so on. In addition to the accuracy design of the machine itself, it is most likely to be a problem caused by the hysteresis effect. So what is the hysteresis effect?
Hysteresis effect: The moisture content of paper when it reaches equilibrium by low moisture absorption under a certain relative humidity conditions is lower than that when it reaches equilibrium by high moisture dehumidification under the same relative humidity.
Generally speaking, the absorption rate of the paper can be judged by the Paper Surfaces Absorb Weight Tester
Refer to the TAPPI T402 standard, it clarifies hysteresis effect will have 5%-25% impact on test performance.It can be clearly seen from the graph of humidity and moisture content in the figure below that：
For example, the hysteresis effect of 1% vs. the moisture content of 6% is verified by comparative experiments and it is found that this causes 16% impact of the test results. According to the GB/T10739 standard atmospheric measurement method, under the experimental conditions of 23°C and 50%RH, a sudden change of 1°C will bring about a 3%RH change.
Then how to solve the problem of Hysteresis effect?
--- It is necessary to carry out temperature and humidity preconditioning --- the process of making the sample reach a moisture content balance between the air at a specified temperature and relative to the atmosphere.
Temperature and humidity treatment time: generally 4 hours for good circulation conditions, 5-8 hours for higher quantitative, 48 hours for high quantitative or special materials. The judgment is based on the two weighings for more than 1 hour before and after, and the difference between the weighing of the sample is not more than 0.25% of the sample mass, and the balance is considered to be reached.
For the error in the measurement, repeatability and reproducibility experimental analysis is required, and the main factors can be found to serve the customer to explain the corresponding problem.
PS: The following preconditioning times have usually been found satisfactory for a preconditioning apparatus of ample capacity and air circulation:
< 1 h
Paper of ordinary weight and composition
Boards (linerboard, corrugating medium, chipboard, boxboard)
Corrugated and solid fiberboard in sheet form
Sealed boxes (including shipping containers)
24 h or more
Boards of heavy substances and specially treated water vapor resistant papers and boards