ASTM D5224-00(2006)

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
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Designation:D5224–00 (Reapproved 2006)
Standard Practice for
Compression Molding Test Specimens of Thermosetting
Molding Compounds
This standard is issued under the fixed designation D5224; 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 (´) indicates an editorial change since the last revision or reapproval.
1. Scope 3. Terminology
1.1 This practice covers the general principles to be fol- 3.1 Definitions—For definitions of terms pertaining to plas-
lowed when compression molding test specimens of thermo- tics used in this practice, see Terminology D883.
setting molding compounds, such as phenolics, aminoplastics, 3.2 Definitions of Terms Specific to This Standard:
melamine phenolics, epoxies, and unsaturated polyesters. 3.2.1 breathe step, n—in plastics molding, the part of the
molding cycle in which the mold halves are opened momen-
NOTE 1—This standard is similar in content (but not technically
tarily, prior to curing, to release volatiles from the molded part.
equivalent) to ISO 295-1974 (E).
3.2.2 skin, n—in plastics molding, the thin resin-rich layer
1.2 Molding conditions are given for amino, phenolic, and
(skin) on the surface of the molded part.
allyl molding compounds. Materials specification standards
3.2.3 skin effect, n—in plastics testing, the positive or
should always be consulted to determine whether the material
negative effect the skin may have on the results of some
to be molded has any special requirements.
standard tests.
1.3 The values stated in SI units are to be regarded as
standard.Thevaluesinbracketsaregivenforinformationonly.
4. Summary of Practice
1.4 This standard does not purport to address all of the
4.1 Compression molded test specimens are produced by
safety concerns, if any, associated with its use. It is the
loading a mold cavity with some form of the molding material,
responsibility of the user of this standard to establish appro-
applying a specified pressure to the mating surface for a
priate safety and health practices and determine the applica-
specified time and at a specified temperature, and then remov-
bility of regulatory limitations prior to use.
ing the part from the cavity.
2. Referenced Documents
5. Significance and Use
2.1 ASTM Standards:
5.1 The conditions at which compounds are molded are
D638 Test Method for Tensile Properties of Plastics
known to influence the properties of the specimens.The degree
D883 Terminology Relating to Plastics
of cure, elimination of knit-lines between particles, density of
D958 Practice for Determining Temperatures of Standard
the part, and degradation of the polymer are among those
ASTM Molds for Test Specimens of Plastics
factors which will be affected by the molding conditions. Thus
2.2 ISO Standard:
it is important to hold to a standard set of conditions in order
ISO 295 Plastics—Compression Molding Test Specimens
to have a valid comparison of properties between different
of Thermosetting Materials
compounds and different batches of the same compound.
ISO 3167 Plastics—Multipurpose—Test Specimens
5.2 If the molded specimens show evidence of low-density
areas due to trapped gases, they should be discarded.Abreathe
step may be necessary to eliminate this situation. It is critical
ThispracticeisunderthejurisdictionofASTMCommitteeD20onPlasticsand
is the direct responsibility of Subcommittee D20.09 on Specimen Preparation. that the breathe step be as brief as possible to avoid precuring
Current edition approved March 15, 2006. Published March 2006. Originally
of the compound before full pressure is applied. This would
approved in 1992. Last previous edition approved in 2000 as D5224 - 00. DOI:
lead to poorly “knitted” areas and lower strength in the molded
10.1520/D5224-00R06.
specimen.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Standards volume information, refer to the standard’s Document Summary page on 6. Apparatus
the ASTM website.
3 6.1 Molds:
Withdrawn. The last approved version of this historical standard is referenced
on www.astm.org. 6.1.1 The mold shall be made of steel, able to withstand the
ISO Standards Handbook 21, Vol 2, Plastics, 2nd Ed., 1990, available from
molding temperatures and pressures. The mold shall be de-
AmericanNationalStandardsInstitute(ANSI),25W.43rdSt.,4thFloor,NewYork,
signed such that the compressive mold force is transferred to
NY 10036.
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D5224–00 (2006)
FIG. 1 Single-Cavity Positive-Compression Mold for Bar Test
Specimens
the molding material with no appreciable loss. The molds
shown in Figs. 1 and 2 are recommended for maintaining the
maximum force on the material. They are of the three-plate
design; consisting of a shell or floating plate, with upper and
lower compression plates. Molds may be of single or multiple
cavity design. FIG. 2 Compression Mold for Disk Test Specimens
NOTE 2—Semi-positive molds may be used, and for materials such as
amino compounds, may even be preferred.
6.1.6 If ejector pins are used, they shall not deform the
6.1.2 Although the actual mold cavity may have various
specimens and their placement shall be such that the pin marks
forms, the majority of tests will use bars 12.7 mm [0.5 in.] in
are not in the area of test.
width by 127 mm [5 in.] or 64 mm [2.5 in.] in length, discs 51
6.1.7 The mold shall have a loading chamber of sufficient
mm [2 in.] or 102 mm [4 in.] in diameter or an appropriate
volume to allow the introduction of the entire charge of
tensile bar as described in Test Method D638. The multi-
material in a single loading. Preforms may be used to decrease
purpose design from ISO 3167 may also be used. The mold
the required loading volume of high bulk materials. The
shall be capable of molding thickness from 1.5 mm [0.06 in.]
conditions of such preforming shall be included in the report.
to 12.5 mm [0.5 in.]. If the specimens are to be used for flame
6.1.8 As the specimen surface facing the lower die is heated
testing, even thinner specimens may be needed. In all cases the
for a longer time and at a higher temperature in the time
ASTM Standard Test Procedure to be used shall be consulted
interval between filling and compression, it is recommended
for the dimensions of the required test specimens.
that a mark be placed on one cavity face in such a position that
NOTE 3—If at all possible, specimens shall be molded directly to
it will not interfere with the testing. When reporting the results
dimension, rather than machined from a plaque. This maintains the
of tests that affect the surfaces unequally, the tested surface
integrity of any skin effect.
shall be indicated.
NOTE 4—If specimens are to be machined from plates or plaques, they
6.2 Press—The hydraulic press shall have a range of
should not be taken from the edge of the plaque.Aminimum margin of 10
pressures sufficient to insure that the specified pressure is
mm [0.5 in.] is recommended.
applied and maintained during the entire molding operation,
6.1.3 A cavity draft angle not exceeding 3° may be used to
and of maintaining that pressure within 61.5 MPa (6218 psi).
facilitate specimen removal.
6.2.1 In order to prevent precure, the press shall be capable
6.1.4 The clearance between the vertical wall of the cavity
of closing within 15 s after the placement of the material in the
and that of the force shall not exceed 0.1 mm [0.004 in.].
mold.Atwo-speed press is preferred for this purpose. The fast
6.1.5 Mold surfaces should be finished to a roughness of 0.4
approach speed can be in the range of 200 to 400 mm/s [8 to
to 0.8 µm (SPI-SPE #2 or equivalent ), unless it is known that
16 in./s] while the slow closing speed of 5 mm/s [0.2 in./s] is
the particular test is not affected by a coarser surface finish.
used to prevent gas entrapment.
Chrome plating is recommended but not necessary. All cavity
6.3 Heating System—The molds may be heated by conduc-
surfacesshouldbedrawpolishe
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