ASTM E28-18(2022)

Standard Test Methods for Softening Point of Resins Derived from Pine Chemicals and Hydrocarbons, by Ring-and-Ball Apparatus

SIGNIFICANCE AND USE
3.1 In general, with materials of these types, softening does not take place at a definite temperature. As the temperature rises, these materials gradually change from brittle or exceedingly thick and slow-flowing materials to softer and less viscous liquids. For this reason, the determination of the softening point must be made by a fixed, arbitrary, and closely defined method if the results obtained are to be comparable.  
3.2 In these test methods, the softening point is defined as the temperature at which a disk of the sample held within a horizontal ring is forced downward a distance of 25.4 mm (1 in.) under the weight of a steel ball as the sample is heated at 5 °C/min in a water, glycerin, silicone oil, ethylene glycol/water or glycerin/water bath.  
3.3 The automatic method was chosen to be the reference method because a round robin demonstrated that it gave more precise results than the manual method.
SCOPE
1.1 These test methods are intended for determining the softening point of resins (including rosin and terpene resins) and similar materials by means of the ring-and-ball apparatus.  
Note 1: For testing asphalts, tars, and pitches, see Test Method D36.  
1.1.1 Test method using the automated ring and ball softening point apparatus is the reference method and the test method using the manual ring and ball method is an alternative method.  
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, health, and environmental 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.

General Information

• Status: Published
• Publication Date: 30-Nov-2022
• ICS: 87.060.20 - Binders
• Technical Committee: D01 - Paint and Related Coatings, Materials, and Applications
• Drafting Committee: D01.34 - Pine Chemicals and Hydrocarbon Resins

Relations

• Refers: ASTM E177-14 - Standard Practice for Use of the Terms Precision and Bias in ASTM Test Methods
• Effective Date: 01-May-2014
• Refers: ASTM E177-13 - Standard Practice for Use of the Terms Precision and Bias in ASTM Test Methods
• Effective Date: 01-May-2013
• Refers: ASTM E691-13 - Standard Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method
• Effective Date: 01-May-2013
• Refers: ASTM E1-13 - Standard Specification for ASTM Liquid-in-Glass Thermometers
• Effective Date: 01-May-2013
• Refers: ASTM E691-11 - Standard Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method
• Effective Date: 01-Nov-2011
• Refers: ASTM E177-10 - Standard Practice for Use of the Terms Precision and Bias in ASTM Test Methods
• Effective Date: 01-Oct-2010
• Refers: ASTM E177-08 - Standard Practice for Use of the Terms Precision and Bias in ASTM Test Methods
• Effective Date: 01-Oct-2008
• Refers: ASTM E691-08 - Standard Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method
• Effective Date: 01-Oct-2008
• Refers: ASTM E1-07 - Standard Specification for ASTM Liquid-in-Glass Thermometers
• Effective Date: 01-Nov-2007
• Refers: ASTM D36-06 - Standard Test Method for Softening Point of Bitumen (Ring-and-Ball Apparatus)
• Effective Date: 01-Dec-2006
• Refers: ASTM E177-06b - Standard Practice for Use of the Terms Precision and Bias in ASTM Test Methods
• Effective Date: 15-Nov-2006
• Refers: ASTM E177-06a - Standard Practice for Use of the Terms Precision and Bias in ASTM Test Methods
• Effective Date: 01-Nov-2006
• Refers: ASTM E1-05 - Standard Specification for ASTM Liquid-in-Glass Thermometers
• Effective Date: 01-Nov-2005
• Refers: ASTM E691-05 - Standard Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method
• Effective Date: 01-Nov-2005
• Refers: ASTM E177-06 - Standard Practice for Use of the Terms Precision and Bias in ASTM Test Methods
• Effective Date: 01-Nov-2004

Overview

ASTM E28-18(2022), "Standard Test Methods for Softening Point of Resins Derived from Pine Chemicals and Hydrocarbons by Ring-and-Ball Apparatus," defines procedures for determining the softening point of resins-such as rosin and terpene resins-using a ring-and-ball apparatus. The standard, issued by ASTM International, establishes both a reference automated method and an alternative manual method to provide accurate, comparable results when characterizing resins and similar materials. As resins transition from a brittle, hard state to a viscous liquid over a temperature range rather than at a distinct point, a standardized method such as ASTM E28 is essential for reliable measurement and comparison.

Key Topics

• Scope and Applicability: The standard covers determination of the softening point for resins derived from pine chemicals and hydrocarbons using automated and manual ring-and-ball test methods. Materials specifically addressed include rosin, terpene resins, and similar substances. For asphalts, tars, and pitches, users should reference ASTM D36.
• Definition of Softening Point: The softening point is defined as the temperature at which a resin sample disk, held in a horizontal ring, is forced down by a steel ball to a fixed distance under controlled heating in a prescribed bath liquid.
• Instrumentation: Describes requirements for the automated ring-and-ball apparatus (reference method), the manual apparatus, and associated components, including rings, balls, centering guides, and suitable beakers for various temperature ranges.
• Bath Liquids: Specifies appropriate bath mediums-water, glycerin, silicone oil, or ethylene glycol/water mixtures-based on the softening point range of the test material.
• Precision and Repeatability: Provides data on repeatability and reproducibility for both automated and manual methods, emphasizing the greater precision achieved with the automated reference method.

Applications

The procedures in ASTM E28-18(2022) are widely used in quality control, specification compliance, and research for producers and users of industrial resins. Key applications include:

• Raw Material Characterization: Determining the softening point of natural and synthetic resins to assess processing and performance suitability.
• Quality Assurance: Ensuring batch-to-batch consistency in manufacturing and verifying product properties meet procurement specifications.
• Formulation Development: Supporting research and development of adhesives, varnishes, coatings, and sealants that rely on resin softening behavior for processing or application characteristics.
• Regulatory and Contractual Compliance: Providing standardized reporting necessary for supplier agreements and meeting regulatory requirements involving material thermal properties.
• Comparison Across Markets: Allowing consistent comparison of resin products from different sources globally due to adherence to internationally recognized test methods.

Related Standards

• ASTM D36 - Standard Test Method for Softening Point of Bitumen (Ring-and-Ball Apparatus): For testing asphalts, tars, and pitches.
• ASTM E1 - Specification for ASTM Liquid-in-Glass Thermometers: Requirements for thermometers used in these tests.
• ASTM E177 - Practice for Use of the Terms Precision and Bias in ASTM Test Methods.
• ASTM E691 - Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method.

By following ASTM E28-18(2022), laboratories and manufacturers can accurately determine the softening point of resins, ensuring reliable and reproducible results critical to product quality, formulation, and regulatory compliance. This standard supports consistent resin testing practices worldwide, facilitating international trade and benchmarking.

Keywords: ASTM E28, ring-and-ball apparatus, resin softening point, rosin, terpene resins, pine chemical resins, hydrocarbons, quality control, industrial resins testing, standard methods.

Standards Content (Sample)

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.
Designation: E28 − 18 (Reapproved 2022)
Standard Test Methods for
Softening Point of Resins Derived from Pine Chemicals and
Hydrocarbons, by Ring-and-Ball Apparatus
ThisstandardisissuedunderthefixeddesignationE28;thenumberimmediatelyfollowingthedesignationindicatestheyearoforiginal
adoptionor,inthecaseofrevision,theyearoflastrevision.Anumberinparenthesesindicatestheyearoflastreapproval.Asuperscript
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 ASTM Test Methods
E691Practice for Conducting an Interlaboratory Study to
1.1 These test methods are intended for determining the
Determine the Precision of a Test Method
softening point of resins (including rosin and terpene resins)
and similar materials by means of the ring-and-ball apparatus.
3. Significance and Use
NOTE 1—For testing asphalts, tars, and pitches, see Test Method D36.
3.1 In general, with materials of these types, softening does
1.1.1 Test method using the automated ring and ball soften- not take place at a definite temperature. As the temperature
ingpointapparatusisthereferencemethodandthetestmethod rises, these materials gradually change from brittle or exceed-
usingthemanualringandballmethodisanalternativemethod. ingly thick and slow-flowing materials to softer and less
viscous liquids. For this reason, the determination of the
1.2 The values stated in SI units are to be regarded as the
softening point must be made by a fixed, arbitrary, and closely
standard. The values given in parentheses are for information
defined method if the results obtained are to be comparable.
only.
3.2 In these test methods, the softening point is defined as
1.3 This standard does not purport to address all of the
the temperature at which a disk of the sample held within a
safety concerns, if any, associated with its use. It is the
horizontal ring is forced downward a distance of 25.4 mm
responsibility of the user of this standard to establish appro-
(1in.) under the weight of a steel ball as the sample is heated
priate safety, health, and environmental practices and deter-
at 5°C⁄min in a water, glycerin, silicone oil, ethylene glycol/
mine the applicability of regulatory limitations prior to use.
water or glycerin/water bath.
1.4 This international standard was developed in accor-
dance with internationally recognized principles on standard-
3.3 The automatic method was chosen to be the reference
ization established in the Decision on Principles for the
method because a round robin demonstrated that it gave more
Development of International Standards, Guides and Recom-
precise results than the manual method.
mendations issued by the World Trade Organization Technical
4. Sample Preparation
Barriers to Trade (TBT) Committee.
4.1 Preparation of Sample by the Pour Method:
2. Referenced Documents
4.1.1 This procedure is suitable for materials that can be
heated and poured without adverse effects on the softening
2.1 ASTM Standards:
point.
D36TestMethodforSofteningPointofBitumen(Ring-and-
4.1.2 Select a sample representative of the material to be
Ball Apparatus)
tested.Thesampleshouldconsistofflakes,pastilles,orfreshly
E1Specification for ASTM Liquid-in-Glass Thermometers
broken lumps free of oxidized surfaces. Avoid inclusion of
E177Practice for Use of the Terms Precision and Bias in
finely divided material or dust.
4.1.3 Selectaquantityatleasttwicethatnecessarytofillthe
These test methods are under the jurisdiction of ASTM Committee D01 on desired number of rings, and melt it immediately in a clean
Paint and Related Coatings, Materials, and Applications and are the direct
container, using an oven, hot plate, sand bath or oil bath to
responsibility of Subcommittee D01.34 on Pine Chemicals and Hydrocarbon
prevent local overheating. Take care to avoid incorporating air
Resins.
bubbles in the sample. Melt the sample completely, but do not
Current edition approved Dec. 1, 2022. Published December 2022. Originally
approved in 1936. Last previous edition approved in 2018 as E28– 18. DOI:
heat it above a temperature necessary to pour the material
10.1520/E0028-18R22.
readily. The time from the beginning of heating to the pouring
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
of the sample should not exceed 15 min.
contact ASTM 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.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E28 − 18 (2022)
NOTE 2—For materials that may be heat sensitive, continuously inert
6.2 Ring—A brass, shouldered ring conforming to the di-
the flask containing the test specimen with nitrogen (N ) during the
mensions shown in Fig. 1(a).
remelting procedure.
6.3 Ball—A steel ball, 9.53mm 6 0.1 mm ( ⁄8 in.) in
4.1.4 Formaterialsthattendtocrackorshrinkintheringon
diameter, weighing between 3.45g and 3.55 g.
cooling, immediately before filling the ring, preheat the ring to
approximately the temperature at which the material is to be
6.4 Beaker, 600 mL or what is recommended by the manu-
poured. The ring, while being filled, should rest bottom down
facturer. Ensure that the dimensions will properly fit the
on a suitable metal surface. Pour the sample into the ring so as
heating unit.
to leave an excess on cooling. After cooling a minimum of
6.5 Stir Bar—The dimensions must be such that the bar
30min, trim off the excess resin on the periphery of the ring.
spins freely under the test stand. It is recommended that the
Toremoveexcessresinfromthetop,cuttheexcessmaterialoff
stirringbarsuppliedwiththeinstrumentbeusedoronethathas
cleanlywithaslightlyheatedknifeorspatula,orgraspthering
been shown to give the same result as the one supplied.
in a pair of tongs and draw the top surface quickly and firmly
over the surface of a heated metal plate. In case the test is
7. Procedure for Materials Having a Softening Point
repeated, use a clean container and fresh sample.
Between 35 °C (95 °F) and <80 °C (176 °F)
5. Reagents and Materials
7.1 Add a stir bar to the 600–mL beaker and fill with
5.1 Bath Liquids:
approximately 500 mL of distilled or deionized water, con-
5.1.1 Distilled or Deionized Water, Freshly Boiled—For
forming to the requirements in 5.1.1. Ensure that the beaker is
softening points between 35°C (95°F) and 80°C (176°F).
properly positioned on the heater in the test unit. Place the
5.1.1.1 Usedistilledordeionizedwaterthathasbeencooled
preparedsampleringsinthetestinsert.Placetheball-centering
to at least 27°C (81°F) below the anticipated softening point,
guideandballontopofthesamplering.Placethetestinsertin
but in no case lower than 5°C (41°F).
the beaker of water, suspending it from the support pins. Place
5.1.2 USP Glycerin—For softening points between 80°C
the temperature measuring device in the test insert. Verify that
(176°F) and 150°C (302°F). Repeated use of glycerin will
the control unit is set for the correct bath liquid.
increase the moisture content over time and may affect results.
7.2 Heating—Heat the bath so that the temperature of the
Replace with fresh glycerin if any change in appearance is
water is raised uniformly at a rate of 5°C (10°F)⁄min. Protect
noted.
the bath from drafts, using shields if necessary. The maximum
NOTE 3—Glycerin should not be used for softening points greater than
permissible variation for any one min. period after the first
150°C (302°F) due to the 160°C (320°F) flash point of glycerin.
threemin.is 60.5°C(61°F).Rejectanytestinwhichtherate
5.1.3 Silicone Oil (Polydimethylsiloxane)—For softening
of temperature rise does not fall within these limits.The test is
points above 80°C (176°F). The silicone oil must have a
complete when the light beam has been interrupted by the
temperature range of 200°C+(392°F), remain clear within
falling ball and material.
thetemperaturerange,havenoapparentreactivitywiththetest
specimen, have a high water repellency, and maintain a NOTE5—Rigidadherencetotheprescribedrateofheatingisabsolutely
essential for reproducibility of results.
uniform viscosity and stirring rate within the temperature
range.
7.3 Softening Point—Record as the softening point the
temperaturedisplayedontheunitafterthelightbeamhasbeen
NOTE 4—Replace with fresh silicone oil if any change in appearance is
noted. Do not use silicone oil that contains any gels; gels are an indicator interrupted by the falling ball and material.
that degradation has occurred.
7.4 Start the cooling process in the instrument. Remove the
5.1.4 Ethylene Glycol/Water—For softening points up to
temperaturemeasuringdevicefromthetestinsert,thenremove
35°C (95°F).
the test insert from the beakers. Thoroughly clean the test
5.1.4.1 Prepareafresh50/50(v/v)mixtureofdistilledwater
insert, ball, and ring in a suitable solvent.
and ethylene glycol prior to sample analysis. For softening
points between 0°C and 35°C, a 50/50 (v/v) mixture of
8. Calibration
glycerin and water may be used.
8.1 Thecalibrationofanyautomatedringandball-softening
REFERENCE METHOD
point apparatus must be performed on a regular basis since
AUTOMATED RING AND BALL SOFTENING POINT
accurate temperature control is required. Follow the manufac-
METHOD
turer’s instructions for calibration of the instrument.
6. Apparatus
9. Procedure for Materials Having Softening Points
6.1 Automated Ring and Ball-Softening Point Instrument
Between 80 °C (176 °F) and 150 °C (302 °F)
with Control Unit, test units, and test inserts.
9.1 Use the same procedure as described in Section 7,
except fill the bath with glycerin or silicone oil.
The sole source of supply of silicone oil, 200 fluid, 50 cSt viscosity known to
the committee at this time is Dow Corning Corp., Midland, MI 48686. If you are
NOTE6—Formaterialssofteningaround80°C(176°F),reportthebath
aware of alternative suppliers, please provide this information to ASTM Interna-
tional Headquarters.Your comments will receive careful consideration at a meeting liquidsinceaglycerinorsiliconeoilbathwillyieldaslightlyhigherresult
of the responsible technical committee, which you may attend. than a water bath.
E28 − 18 (2022)
FIG. 1 Shouldered Ring, Ring Holder, Ball-Centering Guide, and Assembly of Apparatus Showing Two Rings
10. Procedure for Materials Having Softening Points ALTERNATE METHOD
Above 150 °C (302 °F) MANUAL RING AND BALL SOFTENING POINT
METHOD
10.1 Use the same procedure as described in Section 7,
except fill the bath with silicone oil (Note 3).
13. Apparatus
13.1 Ring and Ball Apparatus, consisting of the following:
11. Procedure for Materials Having Softening Points
13.1.1 Ring—A brass, shouldered ring conforming to the
Below 35 °C (95 °F)
dimensions shown in Fig. 1(a).
11.1 Apparatus:
13.1.2 Ball—A steel ball, 9.53mm 6 0.1 mm ( ⁄8 in.) in
11.1.1 Freezer or Isopropyl Alcohol Dry-Ice Bath.
diameter, weighing between 3.45g and 3.55 g.
11.2 Procedure:
13.1.3 Ball-Centering Guide—A brass guide for centering
11.2.1 Cool the bath, described in 5.1.4.1, to −25 °C
theballconformingtothegeneralshapeanddimensionsshown
(−13°F) in the precooled freezer or an isopropyl alcohol
in Fig. 1(c), the use of which is optional.
dry-ice bath.
13.2 Support for Ring and Thermometer—Any convenient
11.2.2 Use the same procedure as in Section 7.Take care to
method for supporting the ring and thermometer may be used,
immediately begin heating as directed once the test specimen
provided it meets the fo
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