Paper and board - Automated off-line testing of physical properties for CD (cross direction) profiles
1Key Takeaways
This document specifies methods for determining cross-direction profiles of physical properties of paper and board using automated off-line testers. Applicable to most papers and boards, but not to tissue and corrugated board. Agreement is required between the parties to determine which properties are relevant. Results…
2Expert Interpretation
This in-depth analysis of the ISO 18522:2016 standard covers automated, off-line testing methods for the cross-machine direction physical properties of paper and board. This includes test principles, equipment requirements, sampling procedures, and standardized measurement techniques for key parameters (basis weight, thickness, tensile strength, etc.). A comparative analysis with traditional stand-alone instrument testing is provided, along with implementation recommendations.
Standard Overview
ISO 18522:2016 specifies a method for determining the distribution of physical properties of paper and board in the cross direction (CD) using an automated off-line tester. This standard is applicable to most paper grades except tissue paper and corrugated board. Test results can be reported as either average values or CD distributions.
Core Test Parameters
| Test Items | Reference Standards | Typical Module Types |
|---|---|---|
| Quantitative | ISO 536 | Electronic Balance Module |
| Thickness | ISO 534 | Contact Thickness Gauge |
| Tensile Strength | ISO 1924 Series | Double Grip Tensile Module |
Technology Evolution Analysis
Since its introduction in the 1980s, automated offline testing technology has gone through three stages of development:
- Basic stage (1980s): capable of testing only basic parameters such as basis weight and thickness
- Expanded stage (1990s): adding tensile, tear, and flexure test modules
- Optical integration stage (after 2000s): integrating optical measurement systems with C/2°, D50/2°, and D65/10° light sources
Comparison of key test methods
Differences in tensile test methods
The modules used in the automated tester (as shown in Figure 1) differ from the ISO 1924-3 standard method in the following ways:
- Specimen width: 15mm (automated) vs. 25mm (standard)
- Clamp distance: 100mm (automated) vs 180mm (standard)
- Test speed: 20mm/min (automated) vs 100mm/min (standard)
Despite the differences, the test results of the two can still maintain good consistency through correlation coefficient correction (see Appendix C of the standard).
Implementation Recommendations
Equipment Calibration
It is recommended to calibrate key modules at the following frequency:
- Quantitative module: Verify daily with standard weights
- Thickness module: Calibrate weekly with standard gauge blocks
- Optical module: Calibrate monthly with standard white plates
Sample Treatment
For moisture-sensitive parameters (such as tensile strength), the accelerated humidity conditioning method in Appendix A of the standard is recommended:
- Spread the sample flat on a sieve with a vacuum system
- Extract 23°C/50%RH air at a negative pressure of 1.47kPa
- Treatment time: 1-3 minutes for low-weight paper and 5-10 minutes for high-weight board