ASTM D2838-07
(Test Method)Standard Test Method for Shrink Tension and Orientation Release Stress of Plastic Film and Thin Sheeting
Standard Test Method for Shrink Tension and Orientation Release Stress of Plastic Film and Thin Sheeting
SIGNIFICANCE AND USE
As a result of the manufacturing process, internal stresses are locked into the film and these can be released by heating. For any given type of film or sheeting, the temperatures at which shrinkage will begin are related to processing techniques employed to manufacture the film and also may be related to a phase transition in the base resin.
Shrink tension affects the appearance and performance of a film in a shrink-packaging application. It may also be used to determine the degree and direction of orientation. The orientation exerts a great influence upon important physical characteristics such as tensile strength, stiffness, tear resistance, and impact strength.
Data from Procedure A are most useful for determining the degree and direction of orientation, orientation release stress, and the maximum force that the film can exert at a given temperature.
Since, in actual applications, film is seldom, if ever, totally restrained, data from Procedure B are useful in estimating the force an item to be packaged will actually receive and in predicting the appearance of packaged items.
The characterization of shrink tension as a function of temperature, and the resultant determination of orientation release stress and its corresponding temperature, is usually carried out only for a particular material of specified thickness for a defined fabrication process. For product development purposes, quality control and determination of conformity to specification limits, the measurement of shrink tension at only one or two specified temperatures is normally sufficient.
Before proceeding with this test method, reference shall be made to the specification of the material being tested. Any test specimen preparation, conditioning, dimensions, or testing parameters, or combination thereof, covered in the relevant ASTM material specification shall take precedence over those mentioned in this test method. If there are no relevant ASTM material specifications, then the default ...
SCOPE
1.1 This test method covers the determination of the shrink tension and related characteristics, that is, shrink force and orientation release stress, of heat-shrinkable plastic film and sheeting of less than 1.0 mm (0.04 in.) thickness. Two procedures are described that permit the measurement of shrink forces at predetermined temperatures. They are as follows:
1.1.1 Procedure A is designed to measure the maximum force exerted by a specimen that is totally restrained from shrinking as it is heated rapidly to a specific temperature.
1.1.2 Procedure B is designed to measure the maximum force exerted by a specimen that is permitted to shrink a predetermined amount prior to restraint while being heated rapidly to a specific temperature.
1.2 Orientation release stress can be determined from the data obtained using Procedure A.
1.3 The values stated in SI units are to be regarded as the standard. The values in parentheses are for information only. Note 1
There is no known ISO equivalent to this test method.
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.
General Information
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Standards Content (Sample)
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Designation:D2838–07
Standard Test Method for
Shrink Tension and Orientation Release Stress of Plastic
1
Film and Thin Sheeting
This standard is issued under the fixed designation D 2838; 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 (e) indicates an editorial change since the last revision or reapproval.
1. Scope* D 5947 Test Methods for Physical Dimensions of Solid
Plastics Specimens
1.1 This test method covers the determination of the shrink
D 6287 Practice for Cutting Film and Sheeting Test Speci-
tension and related characteristics, that is, shrink force and
mens
orientation release stress, of heat-shrinkable plastic film and
D 6988 Guide for Determination of Thickness of Plastic
sheeting of less than 1.0 mm (0.04 in.) thickness. Two
Film Test Specimens
proceduresaredescribedthatpermitthemeasurementofshrink
E 2251 Specification for Liquid-in-GlassASTM Thermom-
forces at predetermined temperatures. They are as follows:
eters with Low-Hazard Precision Liquids
1.1.1 Procedure A is designed to measure the maximum
force exerted by a specimen that is totally restrained from
3. Terminology
shrinking as it is heated rapidly to a specific temperature.
3.1 Definitions of Terms Specific to This Standard:
1.1.2 Procedure B is designed to measure the maximum
3.1.1 orientation release stress, n—the maximum shrink
force exerted by a specimen that is permitted to shrink a
tension developed by a film in a specified direction throughout
predetermined amount prior to restraint while being heated
its range of shrink temperatures while totally restrained from
rapidly to a specific temperature.
shrinking.
1.2 Orientation release stress can be determined from the
3.1.2 shrink force, n—the force per original unit width
data obtained using Procedure A.
developed by a film in a specified direction and at a specified
1.3 The values stated in SI units are to be regarded as the
temperature in its attempt to shrink while under restraint.
standard. The values in parentheses are for information only.
3.1.3 shrink tension, n—the force per original average
NOTE 1—There is no known ISO equivalent to this test method.
cross-sectionalareadevelopedbyafilminaspecifieddirection
1.4 This standard does not purport to address all of the and at a specified temperature in its attempt to shrink while
under restraint.
safety concerns, if any, associated with its use. It is the
responsibility of the user of this standard to establish appro- 3.2 Definitions:
3.2.1 For definitions of terms used in this test method, refer
priate safety and health practices and determine the applica-
bility of regulatory limitations prior to use. to Terminology D 883.
4. Summary of Test Method
2. Referenced Documents
2
2.1 ASTM Standards: 4.1 A 25.4-mm (1-in.) wide strip of film or sheeting is
clamped in the arms of a shrink tension holder (see Fig. 1), one
D 618 Practice for Conditioning Plastics for Testing
D 883 Terminology Relating to Plastics arm of which contains a strain gage.The holder is immersed in
a hot bath and the force exerted by the film is measured by the
D 4000 Classification System for Specifying Plastic Mate-
rials strain gage. The data is collected by a data acquisition device.
The tests may be carried out with or without free shrinkage of
the material before restraint.
1
This test method is under the jurisdiction ofASTM Committee D20 on Plastics
and is the direct responsibility of Subcommittee D20.19 on Film and Sheeting.
5. Significance and Use
Current edition approved Sept. 1, 2007. Published September 2007. Originally
approved in 1969. Last previous edition approved in 2002 as D 2838 - 02.
5.1 As a result of the manufacturing process, internal
2
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
stresses are locked into the film and these can be released by
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
heating. For any given type of film or sheeting, the tempera-
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. tures at which shrinkage will begin are related to processing
*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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D2838–07
FIG. 1 Design for Shrink Tension Holder
techniques employed to manufacture the film and also may be test specimen preparation, conditioning, dimensions, or testing
related to a phase transition in the base resin. parameters, or combination thereof, covered in the relevant
5.2 Shrink tension affects the appearance and
...
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