ASTM D1693

Test Protocol

Specimen preparation requires precise control over thermal history and notch depth. In this section of the procedure, bent strips of the test material are held in a fixed channel to maintain constant stress. The notched faces are exposed to a liquid reagent, typically an alkyl phenoxy polyethoxy ethanol solution, which accelerates the initiation of fractures.

Fluctuations in the notch geometry or the solution concentration will shift the recorded failure times, making uniform preparation indispensable for reproducible benchmarks.

Stress Acceleration

Chemical environments accelerate the propagation of microscopic voids under constant mechanical strain. The test forces a severe bend in the notched strip, which creates high localized tension at the notch root. Solid parts encounter similar multi-axis strains that lead to failures when exposed to soaps or oils.

Material Limit

Practical application of the resulting data is restricted to comparative analysis of similar polyethylene grades rather than absolute product lifetime prediction. While the test ranks resin grades effectively, a finished molded part introduces complex molded-in stress and varying wall thicknesses that the standard specimen does not replicate. Molders rely on these values to choose between virgin resins, but must conduct separate part-level testing to ensure field performance.

When regrind is added, the crack resistance often drops, making the baseline datasheet value an optimistic upper bound.