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Standard: |
TAPPI |
Method: |
TAPPI T 414 |
Title: |
Internal tearing resistance of Paper(Elmendorf-type method) |
TAPPI T 414 measures the force perpendicular to the plane of the paper required to tear multiple plies through a specified distance after the tear has been started using an Elmendorf-type tearing tester. It does not measure edge-tear resistance. The measured results may be used to calculate the approximate tearing resistance of a single sheet. It is not suitable for single-ply tear testing. For highly directional boards and papers, prepare specimens according to T 496 “Specimen Preparation for Cross Directional Internal Tearing Resistance for Paper, Paperboard and Related Materials.” See section 8.5. Caution is recommended in interpreting results from weakly bonded sheets, especially those containing lightly refined long-fibered chemical pulps. The low rate of tear when multiple plies are torn simultaneously may produce erroneously high results.
Multiple sheets of the sample material are torn together through a fixed distance by means of the pendulum of an Elmendorf-type tearing tester. The work done in tearing is measured by the loss in potential energy of the pendulum. The instrument scale is calibrated to indicate the average force exerted when a certain number of plies are torn together (work done divided by the total distance torn).
The amount of sample necessary for tear testing is highly dependent on the tear properties of the sample — (i.e. a sample with low tear strength will require more sample than a sample with a higher tear strength.) For most samples ten, 8.5″ x 11″ sheets of paper should be adequate. For newsprint or other paper with a low tear strength twenty, 8.5″ x 11″ sheets are necessary. Ten replicates will be performed in both the MD and CD directions. If additional testing is requested, twenty, 8.5″ x 11″ sheets of paper are required. If sample quantity is limited, testing can be done by sampling fewer sheets and/or performing fewer replicates.
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