ASTM D1896-99(2004)
(Practice)Standard Practice for Transfer Molding Test Specimens of Thermosetting Compounds
Standard Practice for Transfer Molding Test Specimens of Thermosetting Compounds
SCOPE
1.1 This practice covers a general procedure for the transfer molding of mechanical and electrical test specimens of thermosetting molding materials.Note 1The 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 may not be 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.
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.
There is no similar, or equivalent, ISO standard.
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NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information.
Designation:D1896–99 (Reapproved 2004)
Standard Practice for
Transfer Molding Test Specimens of Thermosetting
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 may not be exact equivalents; therefore, each system
essentially the whole mass into a hot mold where it solidifies.
shall be used independently of the other. Combining values
3.2 Definitions of Terms Specific to This Standard:
from the two systems may result in nonconformance with this
3.2.1 breathing, v—theoperationofopeningamoldorpress
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 similar, or equivalent, ISO standard.
3.2.3 clamp pressure, n—thepressureappliedtothemoldto
2. Referenced Documents
keep it closed, in opposition to the fluid pressure of the
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.
This practice is under the jurisdiction ofASTM Committee D20 on Plastics and 4. Significance and Use
is the direct responsibility of Subcommittee D20.09 on Specimen Preparation.
4.1 Transfer molding is particularly suited to thermosetting
Current edition approved Nov. 1, 2004. Published January 2005. Originally
materials of intermediate plasticity. Fixed molding parameters
approved in 1961. Last previous edition approved in 1999 as D1896 - 99. DOI:
10.1520/D1896-99R04.
cannot be specified for each type of material. Molding com-
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
pounds of the same type come in many different plasticities
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
measured in accordance with Test Methods D731, D3123, and
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. D3795. For this reason, a material may mold satisfactorily
*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.
D1896–99 (2004)
under one set of fixed parameters, while the same type of (14in. )(seeNote4).Theclamppressureshallbeatleast20 %
materialwithadifferentplasticitymayrequireadifferentsetof higher than the plunger pressure.
parameters to produce satisfactory test specimens.
NOTE 4—Plunger molding pressure under actual molding conditions is
4.2 The mold shown in this practice provides for a set of
a variable that is difficult to control. Pressure standardization should be
fivespecimens.However,ifonlycertainspecimensaredesired,
carried out on an empty cavity with the plunger against the mold-stop
plate. The speed of the moveable platen is not important as the mold is
the other cavities may be blocked by inserting gate blanks.
closed before the plunger operates. A ram speed of 3.6 m/min (140
4.3 Typically, breathing of the mold may not be required to
in./min) and a plunger speed of 2.2 m/min (85 in./min) have been found
release trapped volatile matter as the gas is free to flow from
satisfactory when the mold is not loaded. The plunger speed is subject to
the vent end of the mold. This is a particular advantage for
the flow properties of the molding material when the plunger cavity is
heat-resistant compounds and reduces the tendency for molded
loaded with molding compound.
specimens to blister at high exposure temperatures.
5.2 Mold—A five-cavity mold similar to that shown in Fig.
4.4 Flow and knit lines in a molded piece are often sites of
1 has been found satisfactory, although molds with fewer
mechanical or electrical weakness. Knit lines may be found in
cavitiesordifferentconfigurationsofthetensionspecimenmay
some degree of severity throughout the molded piece. The
be used. Specimens may be eliminated by blocking the runners
semisolid molding compound passing through the gate is
to particular cavities and reducing injection pressure and shot
subjecttonon-Newtonianflowand,consequently,wrinklesand
size accordingly.The gates for each of the cavities in this mold
folds as it travels down the mold cavity. Fibers and other
are 6.4 mm wide by 1.52 mm deep ( ⁄4 by 0.060 in.). Suitable
reinforcements in the molding compound align with the flow
venting must be provided from each cavity. Surfaces of the
pattern and, consequently, may mold perpendicular to the axis
cavity should be finished to SPI-SPE #2. Chrome plating of
of the bar at the center and parallel at the surface of the bar.
the mold surface is recommended.
Mold temperature, thermal conductivity and plasticity of the
NOTE 5—Althoughthemoldshownisgenerallyuseful,itispreferredto
molding compound, degree of preheat, and plunger pressure
use a multiple-identical-cavity mold with a symmetrical layout of runners
are parameters that influence the time to fill the mold cavities
and cavities. In either case, it is important to describ
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