ASTM D1896-09
(Practice)Standard Practice for Transfer Molding Test Specimens of Thermosetting Compounds
Standard Practice for Transfer Molding Test Specimens of Thermosetting Compounds
SIGNIFICANCE AND USE
Transfer molding is particularly suited to thermosetting materials of intermediate plasticity. Fixed molding parameters cannot be specified for each type of material. Molding compounds of the same type come in many different plasticities measured in accordance with Test Methods D731, D3123, and D3795. Consequently, for a given material type, the molding parameters required to produce satisfactory test specimens will often vary dependent on the plasticity of the specific material grade.
The mold shown in this practice provides for a set of five specimens. However, if only certain specimens are desired, the other cavities can be blocked by inserting gate blanks.
Typically, breathing of the mold is not required to release trapped volatile matter as the gas is free to flow from the vent end of the mold. This is a particular advantage for heat-resistant compounds and reduces the tendency for molded specimens to blister at high exposure temperatures.
Flow and knit lines in a molded piece are often sites of mechanical or electrical weakness and can be found in some degree of severity throughout the molded piece. The semisolid molding compound passing through the gate is subject to non-Newtonian flow and, consequently, wrinkles and folds as it travels down the mold cavity. Fibers and other reinforcements in the molding compound align with the flow pattern and, consequently, can orient perpendicular to the axis of the bar at the center and parallel at the surface of the bar. Mold temperature, thermal conductivity and plasticity of the molding compound, degree of preheat, and plunger pressure are parameters that influence the time to fill the mold cavities and the formation of knit lines.
Note 3—If the temperature of the mold is held constant and the plunger pressure varied for a designated thermosetting molding compound, two extreme characteristic conditions can be obtained. If the pressure is low, then the vent end of the cavity will not fully fill, and weld lines ...
SCOPE
1.1 This practice covers a general procedure for the transfer molding of mechanical and electrical test specimens of thermosetting molding materials.
Note 1—The utility of this practice has been demonstrated for the molding of thermosetting molding compounds exhibiting intermediate viscosity non-Newtonian flow.
1.2 The values stated in either SI or inch-pound units are to be regarded separately as standard. The values stated in each system are not always exact equivalents; therefore, each system shall be used independently of the other. Combining values from the two systems may result in nonconformance with this practice.
1.3 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 2—There is no known ISO equivalent to this standard.
General Information
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Standards Content (Sample)
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Designation:D1896–09
Standard Practice for
Transfer Molding Test Specimens of Thermosetting
1
Compounds
This standard is issued under the fixed designation D1896; 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* D3795 Test Method for Thermal Flow, Cure, and Behavior
Properties of Pourable Thermosetting Materials by Torque
1.1 This practice covers a general procedure for the transfer
Rheometer
molding of mechanical and electrical test specimens of ther-
mosetting molding materials.
3. Terminology
NOTE 1—The utility of this practice has been demonstrated for the
3.1 Definitions:
molding of thermosetting molding compounds exhibiting intermediate
3.1.1 General—Definitions of terms applying to this prac-
viscosity non-Newtonian flow.
tice appear in Terminology D883.
1.2 The values stated in either SI or inch-pound units are to
3.1.2 transfer molding, n—a method of forming articles by
be regarded separately as standard. The values stated in each
fusing a plastic material in a chamber and then forcing
system are not always exact equivalents; therefore, each
essentially the whole mass into a hot mold where it solidifies.
system shall be used independently of the other. Combining
3.2 Definitions of Terms Specific to This Standard:
values from the two systems may result in nonconformance
3.2.1 breathing, v—theoperationofopeningamoldorpress
with this practice.
for a very short period of time at an early stage in the process
1.3 This standard does not purport to address all of the
of cure.
safety concerns, if any, associated with its use. It is the
3.2.1.1 Discussion—Breathing allows the escape of gas or
responsibility of the user of this standard to establish appro-
vapor from the molding material and reduces the tendency of
priate safety and health practices and determine the applica-
thick moldings to blister.
bility of regulatory limitations prior to use.
3.2.2 cavity (of a mold), n—the space within a mold to be
filled to form the molded product.
NOTE 2—There is no known ISO equivalent to this standard.
3.2.3 clamp pressure, n—thepressureappliedtothemoldto
2. Referenced Documents
keep it closed, in opposition to the fluid pressure of the
2
compressed molding material.
2.1 ASTM Standards:
3.2.4 fill time, n—the time required to fill each cavity used
D731 Test Method for Molding Index of Thermosetting
in the mold. Fill times can be critical to well molded parts (see
Molding Powder
Note 3 under 4.4).
D883 Terminology Relating to Plastics
3.2.5 minimum plunger pressure, n—theminimumpressure,
D957 Practice for Determining Surface Temperature of
on the ram, required to just fill each cavity used in the mold at
Molds for Plastics
a specified temperature and reasonable fill time.
D3123 Test Method for Spiral Flow of Low-Pressure Ther-
3.2.6 vent, n—a hole, slot, or groove provided in a mold or
mosetting Molding Compounds
machine to allow air and gas to escape during molding,
extrusion, or forming.
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ThispracticeisunderthejurisdictionofASTMCommitteeD20onPlasticsand
is the direct responsibility of Subcommittee D20.09 on Specimen Preparation.
4. Significance and Use
Current edition approved Dec. 1, 2009. Published December 2009. Originally
4.1 Transfer molding is particularly suited to thermosetting
approved in 1961. Last previous edition approved in 2004 as D1896 - 99(2004).
DOI: 10.1520/D1896-09.
materials of intermediate plasticity. Fixed molding parameters
2
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
cannot be specified for each type of material. Molding com-
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
pounds of the same type come in many different plasticities
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. measured in accordance with Test Methods D731, D3123, and
*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.
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D1896–09
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D3795. Consequently, for a given material type, the molding (14in. )(seeNote4).Theclamppressureshallbeatleast20 %
parameters required to produce satisfactory test specimens will higher than the plunger pressure.
often vary dependent on the plasticity of the specific material
NOTE 4—Plunger molding pressure under actual molding conditions is
grade.
a variable that is difficult to control. Pressure standardization should be
4.2 The mold shown in this practice provides for a set of
carried out on an empty
...
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