ASTM D5224-00

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Designation:D5224–00
Standard Practice for
Compression Molding Test Specimens of Thermosetting
Molding Compounds
This standard is issued under the fixed designation D 5224; 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 * 3.2 Definitions of Terms Specific to This Standard:
3.2.1 breathe step, n—in plastics molding, the part of the
1.1 This practice covers the general principles to be fol-
molding cycle in which the mold halves are opened momen-
lowed when compression molding test specimens of thermo-
tarily, prior to curing, to release volatiles from the molded part.
setting molding compounds, such as phenolics, aminoplastics,
3.2.2 skin, n—in plastics molding, the thin resin-rich layer
melamine phenolics, epoxies, and unsaturated polyesters.
(skin) on the surface of the molded part.
NOTE 1—This standard is similar in content (but not technically
3.2.3 skin effect, n—in plastics testing, the positive or
equivalent) to ISO 295-1974 (E).
negative effect the skin may have on the results of some
1.2 Molding conditions are given for amino, phenolic, and
standard tests.
allyl molding compounds. Materials specification standards
4. Summary of Practice
should always be consulted to determine whether the material
to be molded has any special requirements.
4.1 Compression molded test specimens are produced by
1.3 The values stated in SI units are to be regarded as the
loading a mold cavity with some form of the molding material,
standard. The values in parentheses are given for information
applying a specified pressure to the mating surface for a
only.
specified time and at a specified temperature, and then remov-
1.4 This standard does not purport to address all of the
ing the part from the cavity.
safety concerns, if any, associated with its use. It is the
5. Significance and Use
responsibility of the user of this standard to establish appro-
priate safety and health practices and determine the applica-
5.1 The conditions at which compounds are molded are
bility of regulatory limitations prior to use. known to influence the properties of the specimens.The degree
of cure, elimination of knit-lines between particles, density of
2. Referenced Documents
the part, and degradation of the polymer are among those
2.1 ASTM Standards:
factors which will be affected by the molding conditions. Thus
D 638 Test Method for Tensile Properties of Plastics
it is important to hold to a standard set of conditions in order
D 883 Terminology Relating to Plastics
to have a valid comparison of properties between different
D 958 Practice for Determining Temperatures of Standard
compounds and different batches of the same compound.
ASTM Molds for Test Specimens of Plastics
5.2 If the molded specimens show evidence of low-density
2.2 ISO Standard:
areas due to trapped gases, they should be discarded.Abreathe
ISO 295 Plastics—Compression Molding Test Specimens
step may be necessary to eliminate this situation. It is critical
of Thermosetting Materials
that the breathe step be as brief as possible to avoid precuring
ISO 3167 Plastics—Multipurpose—Test Specimens
of the compound before full pressure is applied. This would
lead to poorly “knitted” areas and lower strength in the molded
3. Terminology
specimen.
3.1 Definitions—For definitions of terms pertaining to plas-
6. Apparatus
tics used in this practice, see Terminology D 883.
6.1 Molds:
6.1.1 The mold shall be made of steel, able to withstand the
ThispracticeisunderthejurisdictionofASTMCommitteeD20onPlasticsand
molding temperatures and pressures. The mold shall be de-
is the direct responsibility of Subcommittee D20.09 on Specimen Preparation.
Current edition approved Nov. 10, 2000. Published February 2001. Originally signed such that the compressive mold force is transferred to
published as D 5224 – 92. Last previous edition D 5224 – 93.
the molding material with no appreciable loss. The molds
Annual Book of ASTM Standards, Vol 08.01.
shown in Figs. 1 and 2 are recommended for maintaining the
Discontinued 1995; see 1994 Annual Book of ASTM Standards, Vol 08.01.
maximum force on the material. They are of the three-plate
ISO Standards Handbook 21,Vol 2, Plastics, 2nd Ed., 1990, available fromThe
AmericanNationalStandardsInstitute,11West42ndSt.,13thFloor,NewYork,NY
10036.
*A Summary of Changes section appears at the end of this standard.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
D5224
to 12.5 mm (0.5 in.). If the specimens are to be used for flame
testing, even thinner specimens may be needed. In all cases the
ASTM Standard Test Procedure to be used shall be consulted
for the dimensions of the required test specimens.
NOTE 3—If at all possible, specimens shall be molded directly to
dimension, rather than machined from a plaque. This maintains the
integrity of any skin effect.
NOTE 4—If specimens are to be machined from plates or plaques, they
should not be taken from the edge of the plaque.Aminimum margin of 10
mm (0.5 in.) is recommended.
6.1.3 A cavity draft angle not exceeding 3° may be used to
facilitate specimen removal.
6.1.4 The clearance between the vertical wall of the cavity
and that of the force shall not exceed 0.1 mm (0.004 in.).
6.1.5 Mold surfaces should be finished to a roughness of 0.4
um to 0.8 um (SPI-SPE #2 or equivalent ), unless it is known
thattheparticulartestisnotaffectedbyacoarsersurfacefinish.
FIG. 1 Single-Cavity Positive-Compression Mold for Bar Test
Chrome plating is recommended but not necessary. All cavity
Specimens
surfacesshouldbedrawpolishedinthedirectionparalleltothe
force to facilitate specimen removal.
6.1.6 If ejector pins are used, they shall not deform the
specimens and their placement shall be such that the pin marks
are not in the area of test.
6.1.7 The mold shall have a loading chamber of sufficient
volume to allow the introduction of the entire charge of
material in a single loading. Preforms may be used to decrease
the required loading volume of high bulk materials. The
conditions of such preforming shall be included in the report.
6.1.8 As the specimen surface facing the lower die is heated
for a longer time and at a higher temperature in the time
interval between filling and compression, it is recommended
that a mark be placed on one cavity face in such a position that
it will not interfere with the testing. When reporting the results
of tests that affect the surfaces unequally, the tested surface
shall be indicated.
6.2 Press—The hydraulic press shall have a range of
pressures sufficient to insure that the specified pressure is
applied and maintained during the entire molding operation,
and of maintaining that pressure within 61.5 MPa (6218 psi).
6.2.1 In order to prevent precure, the press shall be capable
of closing within 15 s after the placement of the material in the
mold.Atwo-speed press is preferred for this purpose. The fast
approach speed can be in the range of 200 to 400 mm/s (8 to
16 in./s) while the slow closing speed of 5 mm/s (0.2 in./s) is
FIG. 2 Compression Mold for Disk Test Specimens
used to prevent gas entrapment.
6.3 Heating System—The molds may be heated by conduc-
tion from heated platens, heaters inserted into the mold itself,
design; consisting of a shell or floating plate, with upper and
or by hot fluids circulated through passageways in the mold.
lower compression plates. Molds may be of single or multiple
The heating system shall be capable of controlling the mold
cavity design.
temperature to 63°C (65°F) from point-to-point on the mold
NOTE 2—Semi-positive molds may be used, and for materials such as
and for the duration of the molding time.
amino compounds, may even be preferred.
6.3.1 Ifthemoldisheateddirectly,itshallbeinsulatedfrom
6.1.2 Although the actual mold cavity may have various
the press platens with a sheet of insulating material.
forms, the majority of tests will use bars 12.7 mm (0.5 in.) in
NOTE 5—It is generally preferable to heat the mold electrically.
width by 127 mm (5 in.) or 64 mm (2.5 in.) in length, discs 51
mm (2 in.) or 102 mm (4 in.) in diameter or an appropriate
tensile bar as described in Test Method D
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