ASTM C581-20

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Designation: C581 − 15 C581 − 20 An American National Standard
Standard Practice for
Determining Chemical Resistance of Thermosetting Resins
Used in Glass-Fiber-Reinforced Structures Intended for
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Liquid Service
This standard is issued under the fixed designation C581; 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 U.S. Department of Defense.
1. Scope Scope*
1.1 This practice is designed to evaluate, in an unstressed state, the chemical resistance of thermosetting resins used in the
fabrication of reinforced thermosetting plastic (RTP) laminates. This practice provides for the determination of changes in the
properties, described as follows, of the test specimens and test reagent after exposure of the specimens to the reagent: hardness
of specimens, weight change thickness, appearance of specimens, appearance of immersion media, and flexural strength and
modulus.
1.1.1 This practice is also useful to evaluate other factors, such as surfacing veils and the effect of resin additives, on the
chemical resistance of the resin.
1.2 The values stated in inch-pound units are to be regarded as standard. The values given in parentheses are mathematical
conversions to SI units that are provided for information only and are not considered standard.
NOTE 1—There is no known ISO equivalent to this standard.
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 safety, health, and healthenvironmental practices and determine the
applicability of regulatory limitations prior to use.
1.4 This international standard was developed in accordance with internationally recognized principles on standardization
established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued
by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
2. Referenced Documents
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2.1 ASTM Standards:
D790 Test Methods for Flexural Properties of Unreinforced and Reinforced Plastics and Electrical Insulating Materials
D883 Terminology Relating to Plastics
D2563 Practice for Classifying Visual Defects in Glass-Reinforced Plastic Laminate Parts
D2583 Test Method for Indentation Hardness of Rigid Plastics by Means of a Barcol Impressor
D2584 Test Method for Ignition Loss of Cured Reinforced Resins
3. Terminology
3.1 Definitions of Terms:
3.1.1 For definitions of terms associated with plastic materials, see Terminology D883.
4. Significance and Use
4.1 The results obtained by this practice shall serve as a guide in, but not as the sole basis for, selection of a thermosetting resin
used in an RTP structure. No attempt has been made to incorporate into the practice all the various factors that will potentially affect
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This practice is under the jurisdiction of ASTM Committee D20 on Plastics and is the direct responsibility of Subcommittee D20.23 on Reinforced Plastic Piping Systems
and Chemical Equipment.
Current edition approved Dec. 1, 2015Feb. 15, 2020. Published January 2016March 2020. Originally approved in 1965. Last previous edition approved in 20082015 as
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C581 – 03C581 – 15.(2008) . DOI: 10.1520/C0581-15.10.1520/C0581-20.
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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
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C581 − 20
the serviceability of an RTP structure when subjected to chemical environments. These factors will potentially include stress,
different resin-to-glass ratios, and multiple veils.
5. Apparatus
5.1 Hardness Testing Instrument—This shall be as described in Test Method D2583.
5.2 Flexural Properties Testing Apparatus, in accordance with Test Methods D790.
5.3 Thickness Measurement—A micrometer suitable for measurement to 0.001 in. (0.025 mm).
5.4 Containers, of sufficient size, capacity, and inertn
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