SCT vs RCT Test: main differences
RCT vs SCT: Two key methods for measuring compression strength in paper and board
In the paper and board packaging industry, accurately measuring compression strength is essential to ensure the performance and quality of the final product. Two of the most widely used methods internationally are the RCT – Ring Crush Test and the SCT – Short-span Compression Test, each with its own particularities and advantages.
Short-span Compression Test (SCT)
The SCT measures the compression strength of a specimen only 0.7 mm in length, in accordance with standards such as ISO 9895, DIN 54518, TAPPI T826 or SCAN P46. Strength is typically expressed in kilonewtons per metre (kN/m) or pounds per inch (lbs/in), as the result is normalised to the specimen’s width.
The short span between clamps virtually eliminates buckling, providing a direct measurement of the intrinsic strength of the fibres. This method is less dependent on basis weight and on the accuracy of sample preparation, making it the preferred choice for quality control and R&D.
Recommended equipment:
- SCT Short-span Compression Tester with high-precision pneumatic clamps and MP-15 manual cutter for specimen preparation.
This method’s low dependence on basis weight and preparation precision makes it the preferred option in quality control laboratories and R&D departments. In addition, its high repeatability and strong correlation with paper density make it ideal for comparing grades and optimising material design to achieve maximum structural performance. la densidad del papel lo hacen ideal para comparar calidades y optimizar el diseño de materiales para obtener el máximo rendimiento estructural.
Ring Crush Test (RCT)
The RCT measures the compression strength of a strip of paper formed into a ring, in accordance with standards such as ISO 12192, TAPPI T822, DIN 53134 or SCAN P34. It is used to evaluate liners and flutings both in the machine direction and cross direction. Strength is typically expressed in newtons (N), kilonewtons per metre (kN/m), pounds (lbs) or pounds per inch (lbs/in).
Its accuracy largely depends on proper sample preparation and perfect parallel alignment between the specimen and the guides. This method reflects not only crush resistance but also the paper’s behaviour under buckling and folding. This makes it useful for simulating certain real structural conditions, such as those found at the corners or walls of a corrugated box, where structural stability is just as important as the material’s intrinsic strength.
Recommended equipment:
- CDM-5 Sample Crush Tester with RCT device, discs and MP-10 manual cutter for specimen preparation.
In summary:
- The SCT is ideal for measuring the material’s pure strength and minimising the effect of buckling, delivering highly consistent results.
- The RCT is useful for assessing paper performance in conditions closer to actual use, where buckling is part of the material’s behaviour.
At TECHLAB SYSTEMS, we design and manufacture equipment for both methods, complying with the main international standards and ensuring reliable results for the paper and board industry.
📩 Want to know more about our RCT and SCT equipment?
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