ASTM D796-87A

Practice for Compression Molding Test Specimens of Phenolic Molding Compounds (Withdrawn 1992)

General Information

• Status: Withdrawn
• ICS: 71.080.90 - Phenols
• Technical Committee: D20 - Plastics
• Drafting Committee: D20.09 - Specimen Preparation

Standards Content (Sample)

Designation: D 796 - 87a
4sb
Standard Practice for
Compression Molding Test Specimens of Phenolic Molding
Compounds’
This standard is issued under the fixed designation D 796; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last rzvision. A number in parentheses indicates the year of last reapproval. A
superscript epsiion (c) indicates an editorial change since the last revision or reapproval.
to a minimum to avoid precurhg the material in the mold
1. ScQpe
before full pressure is reapplied. Precured material in the
1.1 This practice describes procedures for compression
molded specimen would cause poorly knitted areas that
molding of Izad or Charpy impact, flexure, tension, com-
would not have the potential full strength. This mold
pression, water absorption, modulus in tension or flexure,
reopening, commonly known as a “breathe” step, allows any
heat aging, electrical tests, and heat-deflection temperatures
excess gases to be vented.
(Note).
1.2 The values stated in SI units are to be regarded as the
standard. The values in parentheses are given for informa- 4. Apparatus
tion oniy.
4.1 Molds:
1.3 This standard may involve hazardoits materials, oper-
4.1.1 Chrome plating of compression molding cavities is
ations, and equìpmertt. This standard does not purport to
recommended, but not necessary.
address all of ttie safety problems associated with its use. It is
4.1.2 For molding impact and flexure specimens, use the
the responsibility of ttie user of this standard to establish
single-bar, single-cavity positive mold shown in Practice
appropriate sajèty and health practices and determine the
D 647.
applicability of regirlatoiy liinitations prior to use.
4.1.3 For molding tension specimens, use the positive
mold shown in the Mold for Tension Test Specimen figure
NOTE-The utility of this practice has been demonstrated for the
molding of phenolic molding compounds exhibiting higher-viscosity, in Practice D647 to make specimens required for Test
non-Newtonian flow.
Method D 651. Use the positive mold shown in the Five-
Cavity Transfer Mold figure in Practice D 647 to make
2. Referenced Documenfs
specimens required for Test Method D 638.
4.1.4 For molding water absorption specimens, use the
2.1 ASTM Standards:
50.8-mm (2411.) positive mold shown in the Mold for Disk
D 638 Test Method for Tensile Properties of Plastics2
Test Specimens figure of Practice D 647.
D 647 Practice for Design of Molds for Test Specimens of
4.1.5 For molding specimens for electrical tests, use the
Plastic Molding Materials2
101.6-mm (4411.) positive mold shown in the Mold for Disk
D 65 1 Test Method for Tensile Strength of Molded Elec-
Test Specimens figure of Practice D 647.
trical Insulating Materials3
4.2 Press-The hydraulic press shall be such that the
D 958 Practice for Determining Temperatures of Standard
molding pressure on the specimen can be maintained at 13.8
ASTM Molds for Test Specimens of Plastics’
to 34.5 MPa (2000 to 5000 psi).
4.3 Heating System-Use any convenient method of
3. Significance and Use
heating the press platens or molds, provided the heat source
3.1 The conditions under which samples are molded
is constant enough to maintain the mold temperature within
influence the properties of the specimens. In determining
rC3”C (5°F) across molding surface.
whether a given compound meets the specification require-
4.4 Either a thermometer or pyrometer as specified in
ments, it is important to hold to a standard set of conditions.
Practice D 958 may be used to record mold temperature.
This is also necessary for a valid comparison of properties
obtained with different compounds, or between lots of the
5. Conditioning
same compound.
5.1 Except for referee tests, prior conditioning of phenolic
3.2 If the molded specimens show evidence of lowdensity
molding materials is required only for electrical tests (see
areas due to trapped gases, the specimens should be dis-
5.2). For referee tests, condition a sufficient sample of the
carded. In molding new specimens, the mold should be
molding material, spread to a maximum depth of 12.7 mm
opened slightly just after it is closed. It should be closed again
(Y2 in.) in an open container, for 72 h in a Standard
within 2 to 3 s. It is critical to keep this mold reopening step
f 1”C, 50 f 2 % relative
Laboratory Atmosphere (23
humidity) for flexure, impact, tension, and water-absorption
test specimens.
This practice is under the jurisdiction of ASTM Committee D-20 on Plastics
and is the direct responsibility of Subcommittee D20.09 on Specimen Preparation.
5.2 For molding electrical test specimens, condition a
Current ediíion approved Nov. 27, 1987. Published January 1988. OnginaUy
sufficient sample of the molding material in loose-powder
published as D796-44. Last previous edition D 796 - 87.
form for 30 min at 90 * 3
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