ASTM D6289-98
(Test Method)Standard Test Method for Measuring Shrinkage from Mold Dimensions of Molded Thermosetting Plastics
Standard Test Method for Measuring Shrinkage from Mold Dimensions of Molded Thermosetting Plastics
SCOPE
1.1 This test method is intended to measure batch-to-batch uniformity in initial shrinkage from mold to molded dimensions of thermosetting materials when molded by compression, injection, or transfer under specified conditions.
1.2 This test method provides for the measurement of shrinkage of thermosetting plastics from their molds both initially (within 16 to 72 h of molding) and as they age (post-shrinkage at elevated temperatures).
1.3 Knowledge of the initial shrinkage of plastics is important for the construction of molds and knowledge of post molding shrinkage is important for determining the suitability of the molding material for manufacturing thermosetting plastic components with accurate dimensions.
1.4 The values stated in SI units are to be regarded as the standard. The values given in parentheses are for information only.
1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
Note 1-This test method and ISO 2577-1984 are equivalent when bars of 120 mm length, 15 mm width, and 10 mm thickness are used for compression molding; or flat, square plaques approximately 120 by 120 by 4 mm are used for injection molding.
General Information
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Standards Content (Sample)
NOTICE: This standard has either been superceded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
Designation: D 6289 – 98
Standard Test Method for
Measuring Shrinkage from Mold Dimensions of Molded
Thermosetting Plastics
This standard is issued under the fixed designation D 6289; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
1. Scope D 1898 Practice for Sampling of Plastics
D 3419 Practice for In-line Screw-Injection Molding of Test
1.1 This test method is intended to measure batch-to-batch
Specimens from Thermosetting Compounds
uniformity in initial shrinkage from mold to molded dimen-
E 691 Practice for Conducting an Interlaboratory Study to
sions of thermosetting materials when molded by compression,
Determine the Precision of a Test Method
injection, or transfer under specified conditions.
2.2 ISO Standards:
1.2 This test method provides for the measurement of
ISO 291 Plastics—Standard Atmospheres for Conditioning
shrinkage of thermosetting plastics from their molds both
and Testing
initially (within 16 to 72 h of molding) and as they age
ISO 295 Plastics—Compression Molding Test Specimens
(post–shrinkage at elevated temperatures).
of Thermosetting Materials
1.3 Knowledge of the initial shrinkage of plastics is impor-
ISO 10724 Plastics—Thermosetting Molding Materials—
tant for the construction of molds and knowledge of post
Injection Molding of Multipurpose Test Specimens
molding shrinkage is important for determining the suitability
ISO 2577-1984 Plastics—Thermosetting Moulding
of the molding material for manufacturing thermosetting plas-
Materials—Determination of Shrinkage
tic components with accurate dimensions.
1.4 The values stated in SI units are to be regarded as the
3. Terminology
standard. The values given in parentheses are for information
3.1 General—Definitions of terms applying to this test
only.
method appear in Terminology D 883.
1.5 This standard does not purport to address all of the
3.2 Definitions—For the purpose of this test method, the
safety concerns, if any, associated with its use. It is the
following definitions apply:
responsibility of the user of this standard to establish appro-
3.2.1 molding shrinkage—the difference in dimensions be-
priate safety and health practices and determine the applica-
tween a molding and the mold cavity in which it was molded,
bility of regulatory limitations prior to use.
both the mold and the molding being at 23 6 2°C when
NOTE 1—This test method and ISO 2577-1984 are equivalent when
measured.
bars of 120 mm length, 15 mm width, and 10 mm thickness are used for
3.2.2 post-shrinkage—shrinkage of a plastic product after
compression molding; or flat, square plaques approximately 120 by 120
molding, during post-treatment, storage or use.
by 4 mm are used for injection molding.
4. Significance and Use
2. Referenced Documents
4.1 Compression Molding—In compression molding, the
2.1 ASTM Standards:
difference between the dimensions of a mold and of the molded
D 618 Practice for Conditioning Plastics and Electrical
2 article produced therein from a given material may vary
Insulating Materials for Testing
according to the design and operation of the mold. It is
D 796 Practice for Compression Molding Test Specimens of
2 probable that shrinkage will approach a minimum where
Phenolic Molding Compounds
2 design and operation are such that a maximum of material is
D 883 Terminology Relating to Plastics
forced solidly into the mold cavity or some part of it, or where
D 956 Practice for Compression Molding Specimens of
3 the molded article is hardened to a maximum while still under
Amino Molding Compounds
pressure, particularly by cooling. In contrast, shrinkages may
D 1896 Practice for Transfer Molding Test Specimens of
2 be much higher where the charge must flow in the mold cavity
Thermosetting Compounds
but does not receive and transmit enough pressure to be forced
This test method is under the jurisdiction of ASTM Committee D-20 on Plastics
and is the direct responsibility of Subcommittee D20.09 on Specimen Preparation. Annual Book of ASTM Standards, Vol 08.02.
Current edition approved July 10, 1998. Published February 1999. Annual Book of ASTM Standards, Vol 14.02.
2 6 nd th
Annual Book of ASTM Standards, Vol 08.01. Available from American National Standards Institute, 11 West 42 Street, 13
Discontinued. Replaced by Practice D 5224. Floor, New York, NY 10036.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
NOTICE: This standard has either been superceded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
D 6289
variations in test specimen density may be sufficient to produce inconsis-
firmly into all its recesses, or where the molded article is not
tent shrinkage.
fully hardened when discharged. The plasticity of the material
used may affect shrinkage insofar as it affects the retention and
6.2 Equipment, suitable for measuring the lengths of the test
compression of the charge.
specimen and the corresponding cavity of the mold to within
4.2 Injection Molding—In injection molding, as in com-
0.02 mm.
pression molding, the difference between the dimensions of the
6.3 Oven, for post-shrinkage only.
mold and of the molded article produced therein from a given
material may vary according to the design and operation of the 7. Sampling
mold. The difference may vary with the type and size of
7.1 A representative sample shall be taken from the molding
molding machine, the thickness of molded sections, the degree
material and be kept at room temperature in airtight containers,
and direction of flow or movement of material in the mold, the
without any conditioning, until molded into test specimens (see
size of the nozzle, sprue, runner, and gate, the cycle on which
Practice D 1898).
the machine is operated, the temperature of the mold, and the
length of time that follow-up pressure is maintained. As in the
8. Test Specimen
case of compression molding, shrinkages will approach a
8.1 Compression-Molding Materials—For mold shrinkages
minimum where design and operation are such that a maximum
of compression-molding materials, the test specimens shall be
of material is forced solidly into the mold cavity and where the
bars 120 by 15 by 10 mm, bars 12.7 by 12.7 by 127 mm ( ⁄2 by
molded article is hardened to a maximum while still under
1 1
⁄2 by 5 in.), or disks 3.2 mm ( ⁄8 in.) in thickness and 102 mm
pressure as a result of the use of a runner, sprue, and nozzle of
(4 in.) in diameter made in a positive mold in such a way as to
proper size, along with proper dwell. As in compression
minimize laterial movement of the plastic during the molding.
molding, shrinkages may be much higher where the charge
8.2 Injection-Molding Materials—For mold shrinkage of
must flow in the mold cavity but does not receive and transmit
injection-molding materials, the test specimens shall be bars
enough pressure to be forced firmly into all of the recesses of
1 1
12.7 by 3.2 by 127 mm ( ⁄2 by ⁄8by 5 in.) gated at the end, bars
the mold. The plasticity of the material used may affect
1 1 1
12.7 by 12.7 by 127 mm ( ⁄2 by ⁄2 by 5 in.) disks 3.2 mm ( ⁄8in.)
shrinkage indirectly, in that the more readily plasticized mate-
in thickness and 102 mm (4 in.) in diameter grated radially at
rial will require a lower molding temperature.
a single point in the edge, plaques 120 by 120 by 4 mm or
4.3 Transfer Molding—In transfer molding, as in compres-
plaques 60 by 60 by 2 mm gated with a full edge gate.
sion or injection molding, the difference between the dimen-
8.3 Transfer-Molding Materials—For shrinkage of transfer-
sions of the mold and of the molded article produced therein
molding materials, specimens 12.7 by 12.7 by 127 mm ( ⁄2 by
from a given material may vary according to the design and
⁄2 by 5 in.) gated at the end or at the top near one end, so as
operation of the mold. It is affected by the size and temperature
to provide flow throughout their entire length or disk specimen
of the pot or cylinder and the pressure on it, as well as on mold
3.2 mm ( ⁄8 in.) in thickness and 102 mm (4 in.) in diameter
temperature and molding cycle. Direction of flow is not as
gated radically at a single point in the edge.
important a factor as might be expected, although it can have
8.4 The specimens shall be molded to shape by compres-
some bearing on results.
sion, transfer or injection molding using a mold with single or
4.4 Materials Standards—Always refer to material stan-
multiple cavities.
dards for special treatment prior to molding, molding condi-
tions and special handling of the test specimens after molding.
9. Procedure
In the event the material standard is unavailable, contact the
9.1 If not already known, measure the lengths of the cavities
manufacturer for these recommendations.
(or the distances between the engraved marks in the mold) to
the nearest
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