ASTM D2659 Standard Test Method for Column Crush Properties of Blown Thermoplastic Containers

ASTM D2659

Standard Test Method for Column Crush Properties of Blown Thermoplastic Containers

What is Top Load Test?

Top load testing, also known as column compression testing, is a method used to evaluate how well packaging components can withstand vertical compressive forces without deforming or failing. The most common form of this test involves applying a controlled load to the top of a specimen, typically a bottle, jar or rigid tray, until it reaches a specified amount of deformation or structural failure.

Although related to other compression tests, such as crate crush tests, the top-load test focuses specifically on column strength rather than surface or edge compression. This makes it particularly relevant for rigid or semi-rigid containers, for which maintaining product integrity and safety through axial load performance is critical.

Why Crush Resistance is a Critical Metric

Unlike tests for leaks or seals, ASTM D2659 examines the mechanical strength of the container itself. It simulates the constant downward pressure experienced during stacking by applying a controlled compressive force at a constant rate. The resulting data is not just a single number; it provides a comprehensive profile of how the container behaves under stress, which is crucial for predicting its performance in the real world.

Decoding the Data: What ASTM D2659 Reveals

This test method generates several key performance indicators, each of which provides information about the strength of the container:

• Crushing yield load is the point at which the container's structure begins to deform permanently. This is often the most critical value for design specifications.
• Deflection at crushing yield load: how much the container compresses before it yields, indicating its ductility or stiffness.
• Crushing load at failure: The maximum load that the container can sustain before it catastrophically collapses.
• Apparent crushing stiffness: A measure of the container's resistance to deformation.

Importantly, D2659 accounts for material behaviour. Containers made from brittle materials may fail suddenly at the yield point, whereas those made from ductile materials may yield and deform significantly without failing immediately and clearly. This distinction is vital for selecting the right material for the right application.

As the standard rightly points out, the results of D2659 are most significant under conditions similar to those of the test. For applications involving vastly different forces, such as high-speed impact or long-term constant load (creep), additional testing is necessary, including impact, creep and fatigue tests. D2659 provides the foundational pillar of compressive data upon which a complete understanding of package performance can be built.