Overview
The Short Span Compression Test (SCT) is a specialized instrument used to evaluate the ability of materials such as paper, cardboard, and corrugated paper to resist compressive loads over short distances. The test simulates the local compressive stress of materials during actual processing, transportation, and use, and the results have important reference value for predicting the compressive properties and structural integrity of packaging materials. The SCT analyzer is designed to adhere to international standards such as ISO 9895 and TAPPI T826, ensuring consistency in the testing process and comparability of results.
SCT test principle
The core principle of SCT testing is to apply a compressive force to the specimen between two fixtures fixed at a distance until the specimen fails. The test distance is typically set at 0.7 mm or less to focus on the material's intrinsic strength and reduce the impact of factors such as specimen bending. During the test, the instrument records the maximum compressive force (F_max) and calculates the short-range compressive strength (SCT index) using the following formula:
SCT index = F_max / (specimen width × specimen thickness)
Among them, the SCT index is usually measured in kilonewtons per meter (kN/m). The test is performed under standard temperature and humidity conditions to eliminate the impact of environmental fluctuations on the results.
Instrument components
The SCT analyzer is mainly composed of a loading system, a fixture system, a force sensor and a data acquisition unit. The loading system provides a smooth and adjustable compression rate; The clamping system ensures that the specimen is securely clamped over short distances to prevent slippage; force sensors measure real-time loads during compression; The data acquisition unit records and analyzes the force-displacement curve and outputs key parameters. Calibration of instruments should be performed regularly to ensure measurement accuracy.
Analysis of results
The test results are influenced by a variety of parameters, including specimen preparation, fixture distance, compression rate, and temperature and humidity conditions. A typical SCT test report contains the maximum compressive force, SCT index, and stress-strain curve. A higher SCT index usually indicates a material's good resistance to local compression, which can help predict its performance in processes such as stacking, printing, and die-cutting. The following table lists the SCT index reference ranges for common paper types:
| Paper type | SCT index range (kN/m) |
| Corrugated core paper | 1.8 - 3.5 |
| Containerboard | 2.5 - 4.5 |
| White cardboard | 2.0 - 3.8 |
The analysis should be comprehensively evaluated based on factors such as material base weight, fiber orientation and humidity, and a single index is not enough to fully reflect the material properties.
Applications:
SCT assays are widely used in the paper, packaging, and printing industries. In packaging design, SCT data can be used to optimize the structure of cartons and cardboard and improve stacking strength. In quality control, it helps monitor the performance consistency of raw materials and finished products; In R&D, it provides key mechanical data for the development of new papers and composites. Through SCT testing, producers can improve product reliability and reduce transportation losses.
Notes:
To ensure test accuracy, check the alignment and cleaning status of the fixture before operation to avoid improper specimen clamping. The instrument should be placed in a stable environment and the force sensor and displacement system should be calibrated regularly. After the test, clean up the debris in time and lubricate and maintain the moving parts. Operators are trained to familiarize themselves with standard processes and safety specifications.
References
ISO 9895: Paper and cardboard - Determination of compressive strength at short ranges
TAPPI T826: Test Method for Short Range Compressive Strength of Corrugated Paper
Paper Mechanical Properties Test Technical Manual, Paper Industry Press