Edge Crush Test of corrugated cardboard in Packaging

Corrugated boxes are essential but often under-acknowledged in ensuring the safe transit of goods in the marketplace. Their strength is assessed using widely recognized test methods like the Edge Crush Test (ECT) to measure their ability to carry weight and stack.

ECT correlates well with board strength, helping paperboard and packaging manufacturers maintain quality at the formulation, conversion, and production levels.

Requirement

Introduction

In recent years, changes in global shipping practices and greater use of e-commerce and home delivery have driven an increased focus on packaging quality. Corrugated packaging must now endure more intricate load-bearing requirements, ranging from stacked storage to palletization.

Corrugated boxes are increasingly used to transport goods not only commercially but also in sectors like health care for the safe transportation of products. Meanwhile, increased recycling and lightweighting have created a need to use test methods that are representative of actual performance.

Modern shipping practices, particularly in B2B operations, involve stacked loads where vertical compression is the dominant stress. As a result, assessing edgewise compressive strength has become one of the most practical ways to evaluate packaging durability.

Test Methods

Transition from Mullen Burst Test

Traditionally, the Mullen Burst Test has played an important role in grading corrugated board for puncture strength. But with greater recycling, it became clear that even with the same basis weight, boards did not always perform well in a burst test, although they were good in compression.

Although the Mullen test continues to be useful for certain rupture-resistant applications, it doesn't accurately tell the story of stacking performance. As a result, ECT is more widely used as an application-specific measure.

Edge Crush Test (ECT)

ECT measures the compressive strength of corrugated board when loaded along its edge. A prepared specimen is placed between two rigid platens and compressed perpendicular to the flute direction until structural failure occurs. The maximum load achieved is recorded as force per unit width.

Since box edges and corners carry the majority of stacking loads, ECT provides a realistic assessment of how a carton will perform under vertical compression. So it is well-suited for process and raw material evaluation.

Boards rated by ECT can often be less material-intensive to achieve the same performance as burst-rated boards and can help drive cost and sustainability objectives.

Solution

Standardised ECT testing approaches

International standards provide several methods for performing ECT, promoting international standardization. These, broadly speaking, fall into three types:

• Testing untreated rectangular specimens without edge modification
• Applying wax to specimen edges to minimize localized edge effects
• Using specially shaped samples to ensure failure occurs away from loaded edges

Presto offers advanced mechanical testing instruments designed to perform ECT in accordance with these international methodologies.

Software-controlled compression testing apparatuses with a rigid fixture, an accurate load cell, and parallel flat platens. Guide blocks maintain specimen alignment during testing, ensuring repeatability and accuracy. The system operates at a constant speed until failure, automatically capturing peak load and calculating edge crush resistance in the required units.

High-precision fixtures

Special fixtures keep the ECT specimen aligned and contained. Fixtures for other tests, such as the Flat Crush Test (FCT) and Ring Crush Test (RCT), can be designed similarly to assess a material's performance using a single piece of equipment.

Automatic bench-top testers are available in a range of capacities (2.5-10 kN) to test a broad range of boards.

Test standards

• ISO 3037
• ISO 13821
• TAPPI T 838
• TAPPI T 839