TAPPI T489

This test method covers a procedure used to measure the resistance to bending of paper and paperboard.This test method is used to determine the bending moment required to deflect the free end of a 38 mm (1.5 in.) wide vertically clamped specimen 15 from its center line when the load is applied 50 mm (1.97 in.) away from the clamp. The resistance to bending is calculated from the bending moment.TAPPI T (number to be assigned) describes a modification of the instrument described in this test method for measurements in the 0 to 10 Taber stiffness range only, and which requires a smaller test specimen. The modified procedure may be recommended for papers which are low in grammage, highly flexible, or both.Test results obtained using modifications of the basic Taber-type instrument such as that described in TAPPI T (number to be assigned) have been reported to be as much as 40% different from those obtained using this test method, and such modifications must not be used when this test method is specified.Other procedures for measuring bending resistance include TAPPI T 535 "Stiffness of Paperboard (Resonance Length Method), TAPPI T 543 Bending Resistance (Stiffness) of Paper (Gurley-Type Stiffness Tester), and TAPPI T 451 Flexural Properties of Paper (Clark Stiffness). The latter method has been classified as Classical.

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