ASTM D955-08

Standard Test Method of Measuring Shrinkage from Mold Dimensions of Thermoplastics

SIGNIFICANCE AND USE
Injection Molding—In injection molding, the difference between the dimensions of a mold cavity and of the molded specimen may vary according to the design of the mold and operation of the molding process. Factors such as mold and melt temperature, fill times, and packing conditions are known to affect shrinkage significantly. Adherence to the specified mold design (see 7.1) and specifications outlined in Practice D 3641 or ISO 294-4 or the appropriate material specification will improve the reproducibility of the test.
Compression Molding—In compression molding, the difference between the dimensions of a mold cavity and of the molded specimen may vary according to the design of the mold and operation of the molding process. Factors, such as the amount of material in charge, cooling time, and pressure application are known to affect shrinkage significantly. Adherence to the specified mold design (see 7.2) and specifications outlined in Practice D 4703 or ISO 293 or the appropriate material specifications will improve the reproducibility of the test.
SCOPE
1.1 This test method is intended to measure shrinkage from mold cavity to molded dimensions of thermoplastics when molded by compression or injection processes with specified process conditions.
1.2 This test method covers shrinkage measurements at 24 and 48 h.
1.3 This method will give comparable data based on standard specimens and can not predict absolute values in actual molded parts with varying flow paths, wall thicknesses, pressure and temperature gradients and process conditions. Differences in mold shrinkage may also be observed among the three specimen geometries described in this test method.
1.4 The values stated in SI units are to be regarded as the standard. The values given in parentheses are given for information only.
1.5 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—This standard and ISO 294-3 are equivalent in the design of specimen D2. This test method is equivalent to ISO 294-4 where Type D2 specimens and the procedure in Appendix X2 are used.

General Information

• Status: Historical
• Publication Date: 31-Oct-2008
• ICS: 83.140.10 - Films and sheets
• Technical Committee: D20 - Plastics
• Drafting Committee: D20.09 - Specimen Preparation

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: D955 − 08
Standard Test Method of
Measuring Shrinkage from Mold Dimensions of
1
Thermoplastics
This standard is issued under the fixed designation D955; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
This standard has been approved for use by agencies of the U.S. Department of Defense.
1. Scope* D3641Practice for Injection Molding Test Specimens of
Thermoplastic Molding and Extrusion Materials
1.1 This test method is intended to measure shrinkage from
D4066Classification System for Nylon Injection and Extru-
mold cavity to molded dimensions of thermoplastics when
sion Materials (PA)
molded by compression or injection processes with specified
D4549Classification System and Basis for Specification for
process conditions.
Polystyrene and Rubber-Modified Polystyrene Molding
1.2 This test method covers shrinkage measurements at 24
and Extrusion Materials (PS)
and 48 h.
D4703Practice for Compression Molding Thermoplastic
1.3 This method will give comparable data based on stan-
Materials into Test Specimens, Plaques, or Sheets
dard specimens and can not predict absolute values in actual D4976Specification for Polyethylene Plastics Molding and
molded parts with varying flow paths, wall thicknesses, pres-
Extrusion Materials
sure and temperature gradients and process conditions. Differ- D5947Test Methods for Physical Dimensions of Solid
encesinmoldshrinkagemayalsobeobservedamongthethree
Plastics Specimens
specimen geometries described in this test method. D6778Classification System and Basis for Specification for
Polyoxymethylene Molding and Extrusion Materials
1.4 The values stated in SI units are to be regarded as the
(POM)
standard. The values given in parentheses are given for
D6779Classification System for and Basis of Specification
information only.
for Polyamide Molding and Extrusion Materials (PA)
1.5 This standard does not purport to address all of the
E691Practice for Conducting an Interlaboratory Study to
safety concerns, if any, associated with its use. It is the
Determine the Precision of a Test Method
responsibility of the user of this standard to establish appro-
3
2.2 ISO Standards:
priate safety and health practices and determine the applica-
ISO 293Plastics—Compression Moulding Test Specimens
bility of regulatory limitations prior to use.
of Thermoplastic Materials
NOTE 1—This standard and ISO 294-3 are equivalent in the design of
ISO 294-1Plastics—Injection Moulding of Test Specimens
specimenD2.ThistestmethodisequivalenttoISO294-4whereTypeD2
of Thermoplastic Materials—Part 1: General Principles,
specimens and the procedure in Appendix X2 are used.
and Moulding of Multipurpose and Bar Test specimens
2. Referenced Documents
ISO 294-3Plastics—Injection Moulding of Test Specimens
2
of Thermoplastic Materials—Part 3: Small Plates
2.1 ASTM Standards:
ISO 294-4 Plastics—Injection Moulding of Test
D618Practice for Conditioning Plastics for Testing
Specimens—Part 4: Determination of Moulding Shrink-
D788Classification System for Poly(Methyl Methacrylate)
age
(PMMA) Molding and Extrusion Compounds
D883Terminology Relating to Plastics
3. Terminology
3.1 Definitions—General definitions of terms applying to
1
ThistestmethodisunderthejurisdictionofASTMCommitteeD20onPlastics
and is the direct responsibility of Subcommittee D20.09 on Specimen Preparation. this test method appear in Terminology D883.
Current edition approved Nov. 1, 2008. Published December 2008. Originally
3.2 Definitions of Terms Specific to This Standard:
approved in 1948. Last previous edition approved in 2000 as D955-00. DOI:
10.1520/D0955-08.
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 Available fromAmerican National Standards Institute (ANSI), 25 W. 43rd St.,
the ASTM website. 4th Floor, New York, NY 10036, http://www.ansi.org.
*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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D955 − 08
3.2.1 jetting, n—non-uniform multi-directional flow front 6. Sample Preparation
apparent on the surface of the mold due to rapid filling of the
6.1 Somematerialsrequirespecialtreatmentbeforetheyare
mold cavity.
molded. For example, thermoplastics, which absorb moisture
must be dried before molding. For required conditions for
4. Summary of Test Method
sample preparation, refer to the a
...

This document is not anASTM standard and is intended only to provide the user of anASTM 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:D955–00 Designation: D 955 – 08
Standard Test Method of
Measuring Shrinkage from Mold Dimensions of
1
Thermoplastics
This standard is issued under the fixed designation D 955; 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.
This standard has been approved for use by agencies of the Department of Defense.
1. Scope*
1.1 This test method is intended to measure shrinkage from mold cavity to molded dimensions of thermoplastics when molded
by compression or injection processes with specified process conditions.
1.2 This test method covers initial shrinkage measurements.The method also accommodates shrinkage measurements at 24 and
48 h, which may be critical for some materials. h.
1.3 This method will give comparable data based on standard specimens and can not predict absolute values in actual molded
parts with varying flow paths, wall thicknesses, pressure and temperature gradients and process conditions. Differences in mold
shrinkage may also be observed betweenamong the three specimen geometries described in this test method.
1.4 The values stated in SI units are to be regarded as the standard. The values given in parentheses are given for information
only.
1.5 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.
NOTE1—This test method is technically identical to ISO 294-4 where Type D2 specimens are used except that pressure transducers are an option in
this test method and required in ISO 294-4. 1—This standard and ISO 294-3 are equivalent in the design of specimen D2.This test method is equivalent
to ISO 294-4 where Type D2 specimens and the procedure in Appendix X2 are used.
2. Referenced Documents
2
2.1 ASTM Standards:D374Test Methods for Thickness of Solid Electrical Insulation
D618Practice for Conditioning Plastics and Electrical Insulating Materials for Testing 618 Practice for Conditioning Plastics
for Testing
D 788 Classification System for Poly(Methyl Methacrylate) (PMMA) Molding and ExtensionExtrusion Compounds
D 883 Terminology Relating to Plastics
D 3641Practice for Injection Molding of Test Specimens of Thermoplastic Molding and Extrusion Materials
4
D4066Specification for Nylon Injection and Extrusion Materials
4
D4181Specification for Acetal (POM) Molding and Extrusion Materials Practice for Injection Molding Test Specimens of
Thermoplastic Molding and Extrusion Materials
D 4066 Classification System for Nylon Injection and Extrusion Materials (PA)
D 4549 Specification for Polystyrene and Rubber-Modified Polystyrene Molding and Extrusion Materials (PS)
D 4703 Practice for Compression Molding of Thermoplastic Materials into Test Specimens, Plaques, or Sheets
5
D 4976Specification for Polyethylene Plastics Molding and Extension Materials
5
D5947TestMethodsforPhysicalDimensionsofSolidPlasticsSpecimens SpecificationforPolyethylenePlasticsMoldingand
Extrusion Materials
D 5947 Test Methods for Physical Dimensions of Solid Plastics Specimens
D 6778 Classification for Polyoxymethylene (POM, Acetal) Molding and Extrusion Materials
D 6779 Classification System for Polyamide Molding and Extrusion Materials (PA)
E 691 Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method
1
This test method is under the jurisdiction of ASTM Committee D20 on Plastics and is the direct responsibility of Subcommittee D20.09 on Specimen Preparation .
Current edition approved Nov. 10, 2000. Published January 2001. Originally published as D955–48T. Last previous edition D955–89 (1996).
Current edition approved Nov. 1, 2008. Published December 2008. Originally approved in 1948. Last previous edition approved in 2000 as D 955 - 00.
2
For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at [e-mail]. For Annual Book of ASTM Standards
, Vol 10.01.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.
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