Standard Test Method for Internal Tearing Resistance
of Paper
ASTM D 689 - 92
Glenna J. Wall
SCOPE: This method measures the force perpendicular to the
plane of the paper required to tear multiple sheets of paper through
a specified distance after the tear has been started, using an
Elmendorf-type tearing tester.
REFERENCE: ASTM D 585 Practice for Sampling & Accepting
a Single Lot of Paper
Paperboard, Fiberboard or Related Products
- ASTM D 685 Practice for Conditioning Paper and Paper products
for Testing
- ASTM D 1749 Practice for Interlaboratory Evaluation of Test
Methods Used with Paper and Paper Products
- ASTM E 178 Practice for Dealing with Outlying Observations
- ISO 1974 Paper Determination of tearing resistance (Elmendorf
method)
SUMMARY OF TEST METHOD:
One or more sheets of sample material are torn together through
a fixed distance by means of the pendulum of an Elmendorf-type
tearing tester. The tearing is measured by loss in potential
energy of thependulum.
SIGNIFICANCE: this method is used within the paper industry,
in conjunction with other tests of strength, as a predictor of
end use performance of a wide range of grades of papers.
 |
APPARATUS: Elmendorf-Type Tearing Tester |
CONDITIONING: Per Method D 685
SAMPLING AND TEST SPECIMENS:
- Obtain the sample to be tested in accordance with Methods
D 585.
- From each test unit sample prepare 10 specimens in each principal
direction of the paper, unless test is in only one direction
is required.
- For each specimen designate one side of the material in some
way.
- For each specimen, keep the designated sides of all the plies
facing the same way.
- Cut each ply for test specimen at least 53mm long x 63.0+/-0.15mm
wide, taking all the plies to be torn together from a single
sheet. If this does not provide sufficient materials take from
adjacent sheets of a unit.
PLIES: From preliminary test or the product specification how
many plies are needed to make up a specimen so when torn together
they give an instrument scale reading nearest 40% of full scale.
PROCEDURE: Precondition, condition and test specimens in accordance
with D 685
- Level and adjust apparatus if necessary, before each set
of tests.
- Pendulum sector is raised to initial position and locked
into place.
- Center specimen in the clamps with the bottom edge set against
the stops
- Secure clamp on specimen using the same pressure on both
clamps.
- Make certain the specimen leans toward and not away from
the pendulum.
- Set pendulum on 100
- Make initial slit.
- Depress the pendulum stop to release the pendulum.
- Hold the stop down until the tear is completed
&
- Catch pendulum on return swing without disturbing position
of pointer.
- Make only one test per specimen, each specimen consisting
of the same number of plies.
- Record the scale readings to the nearest division and the
number of plies used in specimens.
CAUTION:
- If line of tear fails to pass through top edge of specimen
but deviates to one side, note and report this, but do not use
the reading obtained.
- If more than 1/3 of tests show this behavior this method
should not be used for material concerned.
- If sheets split extensively when being torn this should also
be reported.
CALCULATE: The average tearing force in millinewtons and if
desired in grams force required to tear a single ply.
- Average tearing force, mN=(16 x 9.81 x average scale reading)/
number of plies
- Average tearing force, gf=(16 x average scale reading)/number
of piles
REPORT
- Report results with the tear parallel with the machine direction
as resistance to internal tearing in the machine direction.
- Those with the tear perpendicular to the machine direction
as resistance to internal tearing in the cross direction.
- For each principal direction, report the average, maximum
and minimum of accepted test values of the force required to
tear a single ply to 3 significant figures.
- For complete report, state the number of plies torn at one
time
- The number and value of any rejected readings and reason
for rejection
- If an augmenting, weigh was used
- Make and model number of the instrument used.
PRECISION
Repeatability (within a laboratory) = 4.2%
Reproducibility (between laboratories) = 12.5%
Comparability (between materials) = 6.9%
