Although several fundamental differences exist between ASTM D 638 Standard Test Method of Tensile Properties of Plastics and ISO 527 Plastics Determination of Tensile Properties, the actual test results can be quite similar. Test data for both test methods have been gathered by an interlaboratory testing provider and the summary statistics of the two groups were compared. The thermoplastic resins tested in this study included polycarbonate (PC), polybutylene terephthalate (PBT), acrylonitrile-butadiene-styrene (ABS) and high impact polystyrene (HIPS). All resins were unfilled, unreinforced, and uncolored. The following properties were analyzed: Tensile Stress at Yield, Tensile Stress at Break, Elongation at Yield, and Modulus of Elasticity. After removing outliers, the data from the remaining labs were analyzed. The strength of agreement between ISO data and ASTM data varied depending on the property and material used. Then were surprising similarities for modulus of elasticity since different speeds of testing and calculation methods were used.
