ASTM D1525-17e1

Standard Test Method for Vicat Softening Temperature of Plastics

SIGNIFICANCE AND USE
5.1 Data obtained by this test method is used to compare the heat-softening qualities of thermoplastic materials.  
5.2 This test method is useful in the areas of quality control, development, and characterization of plastic materials.
SCOPE
1.1 This test method covers determination of the temperature at which a specified needle penetration occurs when specimens are subjected to specified controlled test conditions.  
1.2 This test method is not recommended for ethyl cellulose, nonrigid poly(vinyl chloride), poly(vinylidene chloride), or other materials having a wide Vicat softening range.  
1.3 The values stated in SI units are to be regarded as standard. No other units are included in this standard.  
1.4 Due to the potential safety and environmental hazards associated with mercury-filled thermometers, the use of alternative temperature measuring devices (such as thermocouples and RTDs) is encouraged with liquid-in-glass thermometers containing mercury, the use of alternative measuring devices, such as digital thermometers using thermocouple of RTD sensors is encouraged.  
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, health and environmental practices and determine the applicability of regulatory limitations prior to use.
Note 1: This test method is equivalent to ISO 306 in all sections with the exceptions of the allowance for creep, prior to the beginning of the test and the allowance of the fluidized powder as a heat transfer medium.  
1.6 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: 31-Jul-2017
• ICS: 83.080.01 - Plastics in general
• Technical Committee: D20 - Plastics
• Drafting Committee: D20.30 - Thermal Properties

Relations

• Refers: ASTM D883-24 - Standard Terminology Relating to Plastics
• Effective Date: 01-Feb-2024
• Refers: ASTM D883-23 - Standard Terminology Relating to Plastics
• Effective Date: 01-Nov-2023
• Refers: ASTM D1898-68(1989) - Standard Practice for Sampling of Plastics (Withdrawn 1998)
• Effective Date: 29-Sep-2023
• Refers: ASTM D883-20 - Standard Terminology Relating to Plastics
• Effective Date: 01-Jan-2020
• Refers: ASTM D883-19c - Standard Terminology Relating to Plastics
• Effective Date: 01-Aug-2019
• Refers: ASTM D883-19a - Standard Terminology Relating to Plastics
• Effective Date: 15-Apr-2019
• Refers: ASTM D883-19 - Standard Terminology Relating to Plastics
• Effective Date: 01-Feb-2019
• Refers: ASTM D883-18a - Standard Terminology Relating to Plastics
• Effective Date: 01-Dec-2018
• Refers: ASTM D883-18 - Standard Terminology Relating to Plastics
• Effective Date: 01-Nov-2018
• Refers: ASTM E2935-17 - Standard Practice for Conducting Equivalence Testing in Laboratory Applications
• Effective Date: 01-Oct-2017
• Refers: ASTM D883-17 - Standard Terminology Relating to Plastics
• Effective Date: 15-Aug-2017
• Refers: ASTM E2935-16 - Standard Practice for Conducting Equivalence Testing in Laboratory Applications
• Effective Date: 15-Nov-2016
• Refers: ASTM E2935-15 - Standard Practice for Conducting Equivalence Testing in Laboratory Applications
• Effective Date: 01-Oct-2015
• Refers: ASTM E2935-14 - Standard Practice for Conducting Equivalence Testing in Laboratory Applications
• Effective Date: 01-Oct-2014
• Refers: ASTM E77-14 - Standard Test Method for Inspection and Verification of Thermometers
• Effective Date: 01-May-2014

Overview

ASTM D1525-17e1 is the internationally recognized standard test method for determining the Vicat Softening Temperature (VST) of plastic materials. Developed by ASTM International, this test method provides a consistent procedure for measuring the temperature at which a flat-ended needle penetrates a thermoplastic specimen to a specified depth under controlled load and temperature rise. The Vicat softening temperature is widely used for quality control, material development, and material characterization in the plastics industry.

Key Topics

• Purpose: The method assesses the heat-softening qualities of thermoplastic plastics by measuring the temperature at which the material softens under a defined load.
• Test Principle: A flat-ended needle, loaded to a defined force, is placed on a plastic specimen and heated at a uniform rate. The Vicat softening temperature is recorded when the needle penetrates 1 mm into the specimen.
• Loads and Heating Rates:
  • Two standard loads: 10 N (Loading 1) and 50 N (Loading 2)
  • Two heating rates: 50°C/h (Rate A) and 120°C/h (Rate B)
• Applicability: Suitable for rigid and semi-rigid thermoplastics. Not recommended for materials like ethyl cellulose, nonrigid poly(vinyl chloride), and poly(vinylidene chloride), which have a broad softening range.
• Units: Results are reported using SI units in accordance with international standards.
• Temperature Measurement: The use of mercury-free devices such as thermocouples or resistance thermometers (RTDs) is encouraged for health and environmental safety.

Applications

ASTM D1525-17e1 plays a critical role in various industry sectors where thermoplastic materials are used:

• Quality Control: Manufacturers use the Vicat Softening Temperature test to ensure uniformity and reliability across production batches.
• Material Development: Researchers and product developers rely on VST data to compare different thermoplastic materials and select materials suitable for high-temperature applications.
• Material Selection: The standard helps engineers and designers choose plastics that meet specific thermal requirements for end-use environments, such as automotive components, electrical insulation, and consumer products.
• Compliance and Specification: Test results based on ASTM D1525 are often referenced in contracts, product datasheets, and regulatory documentation, ensuring alignment with international thermal property standards.

Related Standards

• ISO 306: Plastics – Thermoplastic Materials – Determination of Vicat Softening Temperature: This international equivalent provides similar test procedures with minor differences related to pre-test creep and permitted heat transfer media.
• ASTM D618: Conditioning Plastics for Testing: Details the standard practices for preparing plastic specimens for accurate testing.
• ASTM D883: Terminology Relating to Plastics: Provides definitions essential for consistent terminology in plastics testing.
• ASTM E1, E77, E608/E608M, E1137/E1137M, E879, E2251: Standards for temperature measurement equipment used in Vicat testing.
• ASTM E691 and E2935: Guidance on conducting interlaboratory studies and equivalence testing for laboratory methods.

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Keywords: Vicat softening temperature, ASTM D1525, thermoplastics, heat resistance of plastics, plastics testing standards, quality control, material characterization, thermal properties, plastics industry, international standards.

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.
´1
Designation: D1525 − 17
Standard Test Method for
Vicat Softening Temperature of Plastics
This standard is issued under the fixed designation D1525; 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.
ε NOTE—Editorial changes were made throughout the standard in September 2017.
1. Scope* 2. Referenced Documents
2.1 ASTM Standards:
1.1 This test method covers determination of the tempera-
D618Practice for Conditioning Plastics for Testing
ture at which a specified needle penetration occurs when
D883Terminology Relating to Plastics
specimens are subjected to specified controlled test conditions.
D1898Practice for Sampling of Plastics (Withdrawn 1998)
1.2 This test method is not recommended for ethyl
E1Specification for ASTM Liquid-in-Glass Thermometers
cellulose, nonrigid poly(vinyl chloride), poly(vinylidene
E77Test Method for Inspection and Verification of Ther-
chloride), or other materials having a wide Vicat softening
mometers
range.
E608/E608MSpecification for Mineral-Insulated, Metal-
Sheathed Base Metal Thermocouples
1.3 The values stated in SI units are to be regarded as
E691Practice for Conducting an Interlaboratory Study to
standard. No other units are included in this standard.
Determine the Precision of a Test Method
1.4 Due to the potential safety and environmental hazards
E879Specification for Thermistor Sensors for General Pur-
associated with mercury-filled thermometers, the use of alter-
pose and Laboratory Temperature Measurements
native temperature measuring devices (such as thermocouples
E1137/E1137MSpecification for Industrial Platinum Resis-
and RTDs) is encouraged with liquid-in-glass thermometers
tance Thermometers
containing mercury, the use of alternative measuring devices,
E2251Specification for Liquid-in-Glass ASTM Thermom-
such as digital thermometers using thermocouple of RTD
eters with Low-Hazard Precision Liquids
sensors is encouraged.
E2935Practice for Conducting Equivalence Testing in
Laboratory Applications
1.5 This standard does not purport to address all of the
safety concerns, if any, associated with its use. It is the 2.2 ISO Standards:
responsibility of the user of this standard to establish appro- ISO 306Plastics—Thermoplastic Material—Determination
priate safety, health and environmental practices and deter- of Vicat Softening Temperature
mine the applicability of regulatory limitations prior to use.
3. Terminology
NOTE 1—This test method is equivalent to ISO306 in all sections with
theexceptionsoftheallowanceforcreep,priortothebeginningofthetest 3.1 Definitions:
and the allowance of the fluidized powder as a heat transfer medium.
3.1.1 Definitions of plastics used in this test method are in
accordance with those defined in Terminology D883, unless
1.6 This international standard was developed in accor-
otherwise specified.
dance with internationally recognized principles on standard-
3.1.2 Vicat softening temperature—thetemperatureatwhich
ization established in the Decision on Principles for the
a flat-ended needle of 1-mm circular cross section will
Development of International Standards, Guides and Recom-
penetrate a thermoplastic specimen to a depth of 1 mm under
mendations issued by the World Trade Organization Technical
Barriers to Trade (TBT) Committee.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
ThistestmethodisunderthejurisdictionofASTMCommitteeD20onPlastics Standards volume information, refer to the standard’s Document Summary page on
and is the direct responsibility of Subcommittee D20.30 on Thermal Properties the ASTM website.
(Section D20.30.07). The last approved version of this historical standard is referenced on
Current edition approved Aug. 1, 2017. Published August 2017. Originally www.astm.org.
approved in 1958. Last previous edition approved in 2009 as D1525-09. DOI: Available fromAmerican National Standards Institute (ANSI), 25 W. 43rd St.,
10.1520/D1525-17E01. 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
´1
D1525 − 17
FIG. 1 Apparatus for Softening Temperature Determination (Immersion Bath)
a specified load (force) perpendicular to the test specimen
using a selected uniform rate of temperature rise.
4. Summary of Test Method
4.1 A flat-ended needle loaded with a specified mass is
placedindirectcontactwithatestspecimen.Themassapplied
can be one of two accepted loads, as follows:
Loading1 21060.2N
Loading2 25061.0N
The specimen and needle are heated at either of two permis-
sible rates, as follows:
RateA 25065°C/h
RateB 2120610°C/h
The temperature at which the needle has penetrated to a
depth of 1 60.01 mm is recorded as the Vicat softening
temperature.
5. Significance and Use
5.1 Dataobtainedbythistestmethodisusedtocomparethe
heat-softening qualities of thermoplastic materials.
Key
5.2 Thistestmethodisusefulintheareasofqualitycontrol,
1 Weight
2 Displacement-measurement device
development, and characterization of plastic materials.
3 Heater(s) (Note that multiple heaters are placed symmetrically
throughout the instrument and not just in the one location shown.)
6. Apparatus
4 Heating block (contains lower contact plate)
5 Load rod with needle
6.1 Theinstrumentshallhaveaheatingsystemconsistingof
6 Temperature-measuring device
a heated bath (see Fig. 1) or a contact heating system (see Fig.
7 Test specimen
8 Contact plate
2):
The equipment shall be constructed essentially as shown in
FIG. 2 Apparatus for Softening Temperature Determination (Di-
Fig. 2 and shall consist of the following:
rect Contact)
6.1.1 Immersion Bath—An immersion bath containing the
heat-transfer medium shall be equipped with an agitation
system, temperature-measuring device, and heater. The heater
shall have automatic control of the selected bath temperature- specimens to be submerged at least 35 mm below the surface
rise rate (see 4.1). The bath shall be constructed to allow the of the heat-transfer medium.
´1
D1525 − 17
6.1.1.1 Heat-Transfer Medium—Shall be a liquid or fluid-
m = mass of the needle rod assembly, kg, and
r
ized powder. Several liquids, such as silicone oils, glycerine,
m = extra mass applied to attain the desired force, kg.
w
ethylene glycol, and mineral oil have been used successfully
Verificationoftheloadshallbemadeonnewequipmentand
for various plastics. The medium used shall be free from
afterreplacingpenetration-measuringdevices,oratanytimeto
contaminants and shall have no short-time effect at elevated
ensure that the equipment is in calibration. The calibration
temperaturesonthematerialbeingtested,liquidmediumsshall
procedurefordial-gauge-typepenetration-measuringdevicesis
be of low viscosity at room temperature.
described in Appendix X1 and Appendix X2.The methods for
determination of the thrust contributed by dial-gauge-type
NOTE2—Theresultsofthetestcandependonthethermaldiffusivityof
the heat-transfer medium.
penetration-measuring devices are also given in Appendix X1
and Appendix X2.
6.1.2 Contact Heating Unit—Shall consist of heater and
6.1.6 Temperature-MeasuringDevice,consistingofasensor
heater blocks which, through conductive heating, raises the
(for example, thermocouple, resistance thermometer (RTD),
temperature of the specimen at the required controlled rate
thermistor probe (E879), or platinum resistance thermometer
until the VICAT Softening Temperature is reached.
(PRT).
NOTE 3—It is desirable to have a method of cooling or heating the bath
6.1.6.1 Digital Thermometer—A digital indicating device
in order to reduce the time required to change the temperature of the bath
incorporating a sensor (that is, thermocouple probe, thermistor
betweentestsmorequickly.Thismaybeaccomplishedbyusingacooling
probe, or platinum resistance thermometer (PRT)) with asso-
coil installed in the bath or an external heat-transfer system. If the
temperature rise rate is adversely affected by the presence of residual
ciated conditioning, conversion, and readout instrumentation
coolant in the cooling coils, the coolant should be purged prior to
adequate to cover the range being tested. The sensor and
beginning the test.
related electronics shall be accurate to at least 60.5°C.
6.1.3 Specimen Support—Asuitablestandorsupportforthe
Thermocouples shall comply with the requirements of Speci-
specimen to be placed in the bath or be part of the contact
fication E608/E608M. Resistance thermometers shall comply
heating structure. The vertical members that attach the speci-
with the requirements of Specification E1137/E1137M.
men support to the upper plate shall be made of a material
6.1.6.2 Liquid-in-Glass Thermometer—Older systems still
having the same coefficient of expansion as that used for the
inexistenceuseathermometerfortemperaturemeasurementat
rod through which the load is applied in order that the
each individual test station. The thermometer shall be one of
penetration-measuring device reading caused by differential
the following, or its equivalent, as prescribed in Specification
expansionovertheintendedtemperaturerangedoesnotexceed
E1: Thermometer 1C or 2C, having ranges from –20 to 150°C
0.02 mm when the specimen is replaced by a piece of
or –5 to 300°C, respectively, whichever temperature range is
heat-resistant material.
most suitable. Liquid-in-glass thermometers (refer to Specifi-
6.1.4 Penetration-Measuring Device—The device used for
cationE2251)shallbecalibratedforthedepthofimmersionin
measuring the penetration of the specimen shall be capable of
accordance with Test Method E77.
measuring a penetration depth of at least 1 60.01 mm. The
NOTE4—WARNING—MercuryhasbeendesignatedbyEPAandmany
measuring device shall be an analog or digital dial gauge or
state agencies as a hazardous material that can cause central nervous
similar device, including an electronic-displacement sensing
system,kidneyandliverdamage.Mercury,oritsvapor,maybehazardous
apparatus.
to health and corrosive to materials. Caution should be taken when
6.1.5 Masses—A set of masses of suitable sizes shall be handling mercury and mercury containing products. See the applicable
product Material Safety Data Sheet (MSDS) for details and EPA’s
suppliedsothatthenetforceontheneedlepointshallbeequal
website- http://www.epa.gov/mercury/faq.htm - for additional informa-
to10 60.2N(Loading1)or50 61.0N(Loading2)whenthe
tion. Users should be aware that selling mercury and/or mercury contain-
apparatus is assembled. The net force shall consist of the
ing products into your state may be prohibited by state law.
weightoftheneedlerodassembly,theforceattributedtoaction
6.1.7 Needle—A flat-tipped, hardened steel needle with a
of the penetration-measuring device, and the extra weight that
cross-sectional area of 1.000 60.015 mm (diameter of 1.120
is required to balance the system. The required mass is
to 1.137 mm) shall be used. The tip shall be free of burrs and
calculated as follows:
be perpendicular to the axis of the rod. The needle shall
Requiredmass,m 5 ~F 2 F !/9.80665 2 m
w s r protrude at least 2 mm from the end of the rod.
where:
7. Sampling
F = total force to be applied to the specimen, N,
7.1 Unlessotherwiseagreeduponbetweenthesellerandthe
F = force exerted by any penetration-measuring device, N
s
purchaser, sample in accordance with the sections on General
(this is a positive value if the thrust of the spring is
Sampling Procedures and Specific Sampling Procedures of
towards the specimen (downward), a negative value if
Practice D1898. Sampling based on engineering principles,
the thrust of the spring is opposing the descent of the
prior to packaging, shall be considered an acceptable alterna-
rod, or zero if no such device is involved),
tive.
5 8. Test Specimen
Aluminum Oxide has been found satisfactory and safe for short-term heat
cycles up to 500°C.
8.1 Use at least two specimens to test each sample. The
Silicone oils having a room temperature viscosity of 100 cP have been found
specimenshallbeflat,between3and6.5mmthick,andatleast
satisfactory and safe for short-term heat cycles up to 260°C.
Borosilicate glass or Quartz has been found satisfactory for this purpose. 10 by 10 mm in area or 10 mm in diameter. If an individual
´1
D1525 − 17
layer of the specimen is less than 3 mm it is permissible to 10.5 Apply the extra mass required to increase the load on
stack not more than three (3) layers to achieve the minimum the specimen to 10 60.2 N (Loading 1) or 50 61.0 N
thickness. The specimens shall be cut from sheet or molded (Loading 2). After a 5-min waiting period, set the penetration
material. The type of mold and the molding process used to indicator to zero.
produce test specimens will affect the results obtained in the
10.6 Start the temperature rise. The rate of temperature
test. Molding conditions shall be in accordance with the
increase shall be either 50 65°C⁄h (RateA) or 120 610°C⁄h
standard for the material being tested or be agreed upon
(Rate B) and shall be uniform throughout the test. The RateA
between the cooperating laboratories.
heatingrequirementshallbeconsideredtobemetifoverevery
12-min interval during the test, the temperature of the bath or
NOTE 5—Discrepancies in test results due to variations in molding
conditionsoftenareminimizedbyannealingthetestspecimensbeforethe
contact plates rises 10 61°C at each specimen location. The
test. Since different materials require different annealing conditions,
Rate B heating requirement shall be considered to be met if
annealing procedures shall be employed only if required by the material
overevery6-minintervalduringthetest,thetemperatureofthe
standard or if agreed upon between the cooperating laboratories.
bath or contact plates rises 12 61°C at each specimen loca-
tion. The selection of the rate of rise shall be agreed upon
9. Conditioning
between cooperating laboratories. See Annex A1 for calibra-
9.1 If conditioning of the specimens is required, the test
tion of single temperature probe units.
specimens shall be conditioned at 23 62°C and at 50 610%
10.7 Record the temperature of the bath or contact plates
relative humidity for not less than 40 h in accordance with
when the needle has penetrated 1 60.01 mm into the test
Procedure A of Practice D618, unless otherwise specified by
specimen. Make sure that an accurate reading of the tempera-
agreement or the relevant ASTM material specification. In
ture is made since the rate of penetration of the specimen will
casesofdisagreement,thetolerancesshallbe 61°Cand 65%
be increasing rapidly at this point.
relative humidity.
10.8 Express the Vicat softening temperature as the arith-
NOTE 6—Conditioning periods less than the 40 h, as specified by
metic mean of the temperature of penetration of all specimens
Practice D618, may be used when it is shown that the Vicat softening
tested. If the range of penetration temperatures for the indi-
temperature is not affected by the shorter conditioning time. Longer
conditioning times may be required for some materials that take longer to vidual test specimens exceeds 2°C, record the individual
reach temperature and humidity equilibrium. Refer to the applicable
results and repeat the test, using at least two new specimens.
ASTM standards for those materials.
NOTE 7—If a permanent record is desired, either read and record the
penetration for each 5°C rise in temperature until the penetration reaches
10. Procedure
0.4 mm, and at 2°C intervals thereafter, or attach a displacement
transducer, having the same resolution as the gauge, to each rod and
10.1 Prepare the instrument so that the temperature of the
continuously record the rate of penetration by means of a multichannel
heat-transfermediumorcontactplatesisbetween20and23°C
recorder or similar data-acquisition device.
at the start of the test unless previous tests have shown that for
NOTE 8—Some commercially available instruments record the time at
a particular material under test no error is introduced by
which the penetration reaches a set depth. If this type of instrument is
starting at a higher temperature. The immersion bath system
used,makeatime-temperaturecalibrationbeforethespecimensaretested.
This calibration compensates for slight variations in the heating rate.
shall be well agitated.
(Even though the variations may be within the specifications set forth in
10.1.1 If it is not possible to reduce the temperature of the
10.6, the compounded error over the range of the test can produce a
heat-transfermediumto20-23°C,itispermissibletostartwith
substantial error in the Vicat softening temperature.)
the bath temperature at 30°C. The selection of the starting
temperature shall be agreed upon between the cooperating
11. Report
laboratories.
11.1 Report the following information:
10.2 Place the specimen, which is at room temperature, on
11.1.1 Reference to this test method,
thespecimensupportsothatitisapproximatelycenteredunder
11.1.2 Complete identification of the material tested,
the needle. Ensure that the needle is at least 3 mm from the
11.1.3 Method of preparing test specimens, including con-
edgeofthespecimen.Gentlylowertheneedlerod,withoutthe
ditioning and annealing methods used,
extra mass, so that the needle rests on the surface of the
11.1.4 Initial starting temperature,
specimen and holds it in position.
11.1.5 Rate of temperature rise, Rate A (50°C/h) or Rate B
10.3 Position the temperature measuring device so that the
(120°C/h),
sensing end is located within 10 mm from where the load is
11.1.6 Total load applied to the specimen, Loading 1
applied to the surface of the specimen. Ensure that the sensing
(10 60.2 N) or Loading 2 (50 61.0 N),
end does not touch the specimen.
11.1.7 Thickness of the specimen and the number of layers
of the material that were used,
10.4 Lower the assembly into the bath or close the contact
plates, taking care not to jar it in any way that would damage 11.1.8 Type of instrument used: Immersion bath and heat-
or dislodge the specimen. transfer medium used or contact plates,
´1
D1525 − 17
TABLE 1 Vicat Softening Temperature Using Loading 1 and Rate B, Values Expressed in Units of °C
Number of
A B C D
Material Average S S r R Participating
r R
Laboratories
Ethylene vinyl acetate 72.4 1.44 2.29 4.03 6.40 10
Polystyrene 97.3 0.68 2.36 1.91 6.62 10
High-density 127.9 1.04 2.73 2.90 7.63 10
polyethylene
Polypropylene 152.5 1.13 2.83 3.16 7.91 10
Nylon 66 251.2 0.70 5.06 1.96 14.16 7
A
S = within-laboratory standard deviation of the average.
r
B
S = between-laboratories standard deviation of the average.
R
C
r = within-laboratory repeatability limit = 2.8 S.
r
D
R = between-laboratories reproducibility limit + 2.8 S .
R
11.1.9 Vicat softening temperature, expressed as the arith- test method need to apply the principles outlined in Practice
metic mean of the Vicat softening temperatures of the indi- E691togeneratedataspecifictotheirlaboratoryandmaterials,
vidual specimens, and or between specific laboratories. The principles of 12.1.1 –
11.1.10 Any observations relating to the test. 12.1.1.3 would then be valid for such data.)
12.1.1 Concept of r and R—If S and S have been calcu-
r R
12. Precision and Bias
latedfromalargeenoughbodyofdata,andfortestresultsthat
were averages from testing two specimens, the following
12.1 Precision—Tables 1 and 2 have been developed in
applies:
accordance with Practice E691. Table 1, for the case using
Loading1(10 60.2N)andHeatingRateB(120 610°C⁄h)is 12.1.1.1 Repeatability, r—The value that the absolute dif-
ference between two individual test results under repeatability
based on round-robin tests conducted in 1982 involving five
materials and differing numbers of laboratories as noted in the conditions are expected to occur with a probability of approxi-
mately 0.95 (95%).
table. Each laboratory obtained three test results for each
12.1.1.2 Reproducibility, R—The value that the absolute
material. Table 2, for the case using Loading 2 (50.0 61.0 N)
difference between two test results obtained under reproduc-
andHeatingRateA(50 65°C⁄h)isbasedonround-robintests
ibility conditions are expected to occur with a probability of
conducted in 1994 involving 8 materials and six laboratories.
approximately 0.95 (95%).
Each laboratory obtained two test results for each material. In
12.1.1.3 Conducting equivalence testing on numerical data
both cases, for each material, all of the individual specimens
from two sources shall be conducted in accordance with
from all material samples were prepared by one source. Each
Practice E2935 or any known method for judging the equiva-
test result was the average of two individual determinations.
lence of two means.
(Warning—The following explanations of r and R (see 12.1.1
– 12.1.1.3) are intended only to present a meaningful way of
NOTE 9—Example a t-test.
considering the approximate precision of this test method.The
12.2 Bias—There are no recognized standards by which to
data given in Tables 1 and 2 shall not be applied rigorously to
estimate the bias of this test method.
the acceptance or rejection of material, as those data are
NOTE10—Reinforcedmaterialshavebeenshowntosometimesbreakat
specific to the round-robin test and are not representative of
the point of penetration at temperatures above 24°C, which can affect the
other lots, conditions, materials, or laboratories. Users of this
repeatability of the test results.
13. Keywords
Supporting data have been filed atASTM International Headquarters and may
be obtained by requesting Research Report RR: RR:D20-1194. 13.1 plastics; thermoplastics; Vicat softening temperature
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D1525 − 17
TABLE 2
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