Rationale
The zero-pitch tensile strength meter is a precision instrument specifically designed to measure the tensile strength of materials at extremely short clamping distances. The core design concept is that when the fixture spacing approaches zero, the stress on the specimen during fracture is almost entirely concentrated in the fibers themselves, rather than the bonding bonds between the fibers. This allows the measurement results to directly reflect the intrinsic strength of a single fiber or fiber network itself, effectively eliminating the interference of fiber length, interweaving degree and bonding area to the test results. This technology offers a unique perspective on assessing the intrinsic strength of pulp fibers.
Its working principle is based on classical formulas for material mechanics. The instrument records the applied force (F) versus the resulting displacement during the test and calculates the tensile strength (σ). For zero-distance testing, the calculation of strength can be simplified to:
σ = F / w
where σ is the zero-distance tensile strength (usually in kN/m or N/m), F is the maximum force value recorded at fracture (N), and w is the width of the specimen (m). The data obtained in this way is directly related to the intrinsic strength properties of the fibers.
Specific applications:
In the pulp and paper industry, the strength characteristics of pulp are a key factor in determining the final paper performance. The traditional tensile strength test reflects the comprehensive effect of fiber bonding and fiber strength, while the zero-distance tensile strength test can strip away the single index of "fiber intrinsic strength". This distinction is of great value.
The application is mainly reflected in the following aspects: First, it is used to evaluate the degree of damage caused by different pulping processes (such as chemical pulp, mechanical pulp, waste pulp) to the fiber itself. The decrease in strength values can directly indicate keratinization or microfiber breakage that occurs during pulping. Secondly, it is used to study the effect of pulping or pulping treatment. Although taping mainly enhances fiber bonding, excessive beating will weaken the fiber itself, and zero-distance tensile strength data can provide a quantitative basis for this. Finally, the method can provide basic intrinsic strength data for evaluating the quality of raw material fibers of different tree species and different growth years.
Test methodology
Zero-pitch tensile strength testing requires the preparation of specific sheets or cutting specimens directly from the slurry plate to ensure uniform specimens. Testing is typically performed under standard temperature and humidity conditions to eliminate the effects of environmental fluctuations. Key operating points include: precise alignment of the fixture to the "zero distance" state, ensuring that the specimen is clamped without pre-damage, and controlling a constant loading rate.
Relevant domestic and foreign technical standards provide a normative framework for this method. For example, ISO standards and national standards involve zero-distance tensile testing, which specify in detail instrument calibration, sample preparation, test procedures and result calculation methods to ensure data comparability and repeatability. Following the criteria is a prerequisite for reliable assessment results.
Data interpretation
When interpreting the zero-distance tensile strength data, it is necessary to combine it with other pulp evaluation indicators for comprehensive analysis. A higher zero-distance tensile strength value indicates that the pulp fiber itself is strong and has the potential to produce high-strength paper. However, if the traditional tensile strength is low, it may indicate that the bonding between the fibers is a weak link and needs to be optimized in pulping or wet part chemistry. Conversely, a lower zero-pitch tensile strength indicates that the fiber has been damaged during processing and may require adjustment of the pulping or bleaching process parameters.
The application of this technology has brought clear benefits to the paper industry. It enables R&D personnel and production engineers to more accurately diagnose the root cause of strength issues, making it an effective tool for process optimization and product quality control. By monitoring this indicator, enterprises can select raw materials and adjust processes in a more targeted manner, so as to achieve efficient use of resources while ensuring product quality.
Technical parameters
| Measurement principle | Determination of intrinsic strength of fibers under zero clamping distance |
| Main output parameters | Zero-distance tensile strength, fracture energy |
| Typical specimens | Standard handwritten or pulp |
| Key Criteria Reference | ISO 15754, TAPPI T 231 |
| Main application scenarios | Pulping process evaluation, fiber quality analysis, R&D and quality control |
References
1. International Organization for Standardization. Paper and cardboard—determination of zero-distance tensile strength. ISO 15754.
2. Pulp and Paper Industry Technology Association. Test method of pulp zero-distance tensile strength. TAPPI T 231.
3. Papers in Journal of Papermaking Science and Technology, Research on the Relationship between Fiber Strength and Paper Properties.