ASTM D731-10

Standard Test Method for Molding Index of Thermosetting Molding Powder

SIGNIFICANCE AND USE
This test method provides a guide for evaluating the moldability of thermosetting molding powders. This test method does not necessarily denote that the molding behavior of different materials will be alike and trials may be necessary to establish the appropriate molding index for each material in question.
The sensitivity of this test diminishes when the molding pressure is decreased below 5.3 MPa (764 psi), so pressures lower than this are not ordinarily recommended. This is due to the friction of moving parts and the insensitivity of the pressure switch actuating the timer at these low pressures.
SCOPE
1.1 This test method covers the measurement of the molding index (plasticity) of thermosetting plastics ranging in flow from soft to stiff by selection of appropriate molding pressures within the range from 3.7 to 36.5 MPa (530 to 5300 psi).
1.2 The values stated in SI units are to be regarded as the standard. The values given in parentheses are for information only.
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 1—There is no known ISO equivalent to this test method.

General Information

• Status: Historical
• Publication Date: 30-Apr-2010
• ICS: 83.080.10 - Thermosetting materials
• Technical Committee: D20 - Plastics
• Drafting Committee: D20.30 - Thermal Properties

Relations

• Replaces: ASTM D731-08 - Standard Test Method for Molding Index of Thermosetting Molding Powder
• Effective Date: 01-May-2010
• Referred By: ASTM D704-99(2020) - Standard Specification for Melamine-Formaldehyde Molding Compounds
• Effective Date: 01-May-2010

Standards Content (Sample)

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.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: D731 − 10
Standard Test Method for
1
Molding Index of Thermosetting Molding Powder
This standard is issued under the fixed designation D731; 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* 4. Summary of Test Method
1.1 Thistestmethodcoversthemeasurementofthemolding 4.1 A cup mold is mounted in a semi-automatic type press.
index(plasticity)ofthermosettingplasticsranginginflowfrom A predetermined quantity of test sample is charged into the
soft to stiff by selection of appropriate molding pressures mold, controlled at a temperature dependent upon the test
within the range from 3.7 to 36.5 MPa (530 to 5300 psi). material. The minimum force required to mold a cup having a
flashorfinthicknesswithinaspecifiedtoleranceisdetermined.
1.2 The values stated in SI units are to be regarded as the
This force along with the mold closing time is reported as
standard. The values given in parentheses are for information
molding index.
only.
1.3 This standard does not purport to address all of the
5. Significance and Use
safety concerns, if any, associated with its use. It is the
5.1 This test method provides a guide for evaluating the
responsibility of the user of this standard to establish appro-
moldability of thermosetting molding powders. This test
priate safety and health practices and determine the applica-
method does not necessarily denote that the molding behavior
bility of regulatory limitations prior to use.
of different materials will be alike and trials may be necessary
NOTE 1—There is no known ISO equivalent to this test method.
to establish the appropriate molding index for each material in
question.
2. Referenced Documents
5.2 The sensitivity of this test diminishes when the molding
2
2.1 ASTM Standards:
pressure is decreased below 5.3 MPa (764 psi), so pressures
D256 Test Methods for Determining the Izod Pendulum
lower than this are not ordinarily recommended. This is due to
Impact Resistance of Plastics
thefrictionofmovingpartsandtheinsensitivityofthepressure
D883 Terminology Relating to Plastics
switch actuating the timer at these low pressures.
D957 Practice for Determining Surface Temperature of
Molds for Plastics
6. Apparatus
E691 Practice for Conducting an Interlaboratory Study to
3
6.1 Mold—A cup mold of the flash type, to produce a
Determine the Precision of a Test Method
molded cup as shown in Fig. 1, operated under controlled
3. Terminology pressure and temperatures and provided with stops so that flash
or fin thickness cannot be less than 0.14 mm (0.0055 in.). The
3.1 Definitions are in accordance with Terminology D883,
area of the mold casting creating the molded flash shall be
unless otherwise specified.
located on top of the cup, flat, perpendicular to the axis of the
3.2 Definitions of Terms Specific to This Standard:
cup, and in the form of an annular ring 3.17 mm (0.125 in.) in
3.3 plasticity—a measure of the resistance of a molten
width.
thermosetting material to flow under heat and pressure. A
6.2 Pyrometer—A calibrated pyrometer, traceable to a na-
measure of the apparent viscosity of the material.
tional standard (for example, NIST), and accurate to 61°C
shall be used to determine the temperature of the mold
surfaces. For properly measuring mold temperatures, reference
1
This test method is under the jurisdiction ofASTM Committee D20 on Plastics
Practice D957.
and is the direct responsibility of Subcommittee D20.30Thermal Properties.30 on
Thermal Properties (Section D20.30.08).
6.3 Heating System—Any conventional means for heating
Current edition approved May 1, 2010. Published June 2010. Originally
the press platens, provided the heat source is constant enough
approved in 1950. Last previous edition approved in 2008 as D731 - 08. DOI:
10.1520/D0731-10.
2
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
3
Standards volume information, refer to the standard’s Document Summary page on A detailed drawing of the mold design is available from ASTM Headquarters.
the ASTM website. Order Adjunct: ADJD0731.
*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
1

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D731 − 10
FIG. 1 Cup Mold
to maintain the molding temperature within 61°C of the of 0.15 to 0.20 mm (0.006 to 0.008 in.) shall be molded (see
specified temperature (see 9.2). Note 3). The adhering fin shall be removed and the cup
weighed to the
...

This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation:D731–08 Designation:D731–10
Standard Test Method for
1
Molding Index of Thermosetting Molding Powder
This standard is issued under the fixed designation D731; 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*
1.1 This test method covers the measurement of the molding index (plasticity) of thermosetting plastics ranging in flow from
soft to stiff by selection of appropriate molding pressures within the range from 5303.7 to 5300 psi (3.736.5 MPa (530 to 36.5
MPa).5300 psi).
1.2 Thevaluesstatedininch-poundSIunitsaretoberegardedasthestandard.Thevaluesgiveninparenthesesaremathematical
conversions to SI units that are provided for information only and are not considered standard. only.
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 1—There is no ISO standardknown ISO equivalent to this test method.
2. Referenced Documents
2
2.1 ASTM Standards:
D256 Test Methods for Determining the Izod Pendulum Impact Resistance of Plastics
D883 Terminology Relating to Plastics
D957 Practice for Determining Surface Temperature of Molds for Plastics
E691 Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method
3. Terminology
3.1 Definitions are in accordance with Terminology D883, unless otherwise specified.
3.2 Definitions of Terms Specific to This Standard:
3.3 plasticity—a measure of the resistance of a molten thermosetting material to flow under heat and pressure. A measure of
the apparent viscosity of the material.
4. Summary of Test Method
4.1 A cup mold is mounted in a semi-automatic type press. A predetermined quantity of test sample is charged into the mold,
controlled at a temperature dependent upon the test material. The minimum force required to mold a cup having a flash or fin
thickness within a specified tolerance is determined. This force along with the mold closing time is reported as molding index.
5. Significance and Use
5.1 This test method provides a guide for evaluating the moldability of thermosetting molding powders. This test method does
not necessarily denote that the molding behavior of different materials will be alike and trials may be necessary to establish the
appropriate molding index for each material in question.
5.2 The sensitivity of this test diminishes when the molding pressure is decreased below 764 psi (5.3 MPa),5.3 MPa (764 psi),
so pressures lower than this are not ordinarily recommended. This is due to the friction of moving parts and the insensitivity of
the pressure switch actuating the timer at these low pressures.
1
This test method is under the jurisdiction of ASTM Committee D20 on Plastics and is the direct responsibility of Subcommittee D20.30 Thermal Properties (Section
D20.30.08).
Current edition approved Dec. 15, 2008. Published January 2009. Originally approved in 1950. Last previous edition approved in 1999 as D731-95(1999), which was
withdrawn in August 2008 and reinstated in December 2008. DOI: 10.1520/D0731-08.Thermal Properties.30 on Thermal Properties (Section D20.30.08).
Current edition approved May 1, 2010. Published June 2010. Originally approved in 1950. Last previous edition approved in 2008 as D731 - 08. DOI: 10.1520/D0731-10.
2
For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at [e-mail]. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
*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.
1

---------------------- Page: 1 ----------------------
D731–10
6. Apparatus
3
6.1 Mold—Acup mold of the flash type, to produce a molded cup as shown in Fig. 1, operated under controlled pressure and
temperatures and provided with stops so that flash or fin thickness cannot be less than 0.0055 in. (0.14 mm).0.14 mm (0.0055 in.).
The area of the mold casting creating the molded flash shall be located on top of the cup, flat, perpendicular to the axis of the cup
...