ASTM D7309-21b

Standard Test Method for Determining Flammability Characteristics of Plastics and Other Solid Materials Using Microscale Combustion Calorimetry

SIGNIFICANCE AND USE
5.1 This laboratory test method measures thermal combustion properties of materials (1-9).4  
5.2 The test uses controlled thermal and thermal-oxidative decomposition of specimens and thermal oxidation of the specimen gases as they are released from the specimen to simulate the condensed and gas phase processes of flaming combustion, respectively, in a small-scale laboratory test (1-9).  
5.3 The thermal combustion properties measured in the test are related to flammability characteristics of the material (4-9).  
5.4 The amount of heat released in flaming combustion per unit mass of material is the fire load and the potential fire load (complete combustion) is estimated in Method A as hc.  
5.5 The net calorific value of the material (see Test Method D5865) is determined directly using Method B as hco without the need to know the atomic composition of the specimen to correct for the latent heat of evaporation of the water produced by combustion, or to perform titrations to correct for the heat of solution of acid gases. See Table X1.2 for comparison of Microscale Combustion Calorimetry (MCC) data with Test Method D5865.  
5.6 The temperature T5 % of Method A measured at a heating rate β = 1K/s approximates the surface temperature at piloted ignition in accordance with Ref. (8 and 9) for purposes of fire modeling (see Guide E1591).  
5.7 The heat release capacity ηc (J/g-K) is a flammability parameter measured in Method A that is unique to this test method.  
5.8 The fire growth capacity FGC (J/g-K) is a flammability parameter measured in Method A at heating rate β = 1K/s that is unique to this test method.
SCOPE
1.1 This test method, which is similar to thermal analysis techniques, establishes a procedure for determining flammability characteristics of combustible materials such as plastics.  
1.2 The test is conducted in a laboratory environment using controlled heating of milligram specimens and complete thermal oxidation of the specimen gases.  
1.3 Specimens of known mass are thermally decomposed in an oxygen-free (anaerobic) or oxidizing (aerobic) environment at a constant heating rate between 0.2 and 2 K/s.  
1.4 The heat released by the specimen is determined from the mass of oxygen consumed to completely oxidize (combust) the specimen gases.  
1.5 The rate of heat released by combustion of the specimen gases produced during controlled thermal or thermoxidative decomposition of the specimen is computed from the rate of oxygen consumption.  
1.6 The specimen temperatures over which combustion heat is released are measured.  
1.7 The mass of specimen remaining after the test is measured and used to compute the residual mass fraction.  
1.8 The specimen shall be a material or composite material in any form (fiber, film, powder, pellet, droplet). This test method has been developed to facilitate material development and research.  
1.9 This standard is used to measure and describe the response of materials, products, or assemblies to heat and flame under controlled conditions, but does not by itself incorporate all factors required for fire hazard or fire risk assessment of the materials, products, or assemblies under actual fire conditions.  
1.10 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: There is no known ISO equivalent to this test method.  
1.11 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-Sep-2021
• ICS: 13.220.50 - Fire-resistance of building materials and elements
• 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 E176-24 - Standard Terminology of Fire Standards
• Effective Date: 01-Jan-2024
• Refers: ASTM D883-23 - Standard Terminology Relating to Plastics
• Effective Date: 01-Nov-2023
• Refers: ASTM E456-13a(2022)e1 - Standard Terminology Relating to Quality and Statistics
• Effective Date: 01-Apr-2022
• Refers: ASTM E1591-20 - Standard Guide for Obtaining Data for Fire Growth Models
• Effective Date: 01-Apr-2020
• 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 E176-18a - Standard Terminology of Fire Standards
• Effective Date: 15-Dec-2018
• 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 E176-18 - Standard Terminology of Fire Standards
• Effective Date: 01-Mar-2018
• Refers: ASTM E456-13A(2017)e1 - Standard Terminology Relating to Quality and Statistics
• Effective Date: 01-Oct-2017
• Refers: ASTM E456-13A(2017)e3 - Standard Terminology Relating to Quality and Statistics
• Effective Date: 01-Oct-2017

Overview

ASTM D7309-21b is the standard test method developed by ASTM International for determining the flammability characteristics of plastics and other solid materials using microscale combustion calorimetry (MCC). This laboratory-based method provides a controlled and reproducible procedure for assessing key thermal combustion properties that are directly related to the flammability of a wide range of solid materials. Through the use of controlled heating and oxygen consumption calorimetry, this standard supports material development, research, and comparative evaluation in areas where understanding fire behavior is crucial.

Key Topics

• Microscale Combustion Calorimetry: Uses controlled heating of small (milligram) specimens in either inert or oxidizing atmospheres to simulate condensed and gas-phase combustion processes on a laboratory scale.
• Thermal Decomposition Analysis: Determines how materials break down and release gases under heat, simulating real-world flaming combustion scenarios.
• Heat Release Parameters:
  • Fire Load: The amount of heat released per unit mass during flaming combustion.
  • Net Calorific Value: The heat realized by complete combustion, measured directly without chemical analysis.
  • Heat Release Capacity (ηc) and Fire Growth Capacity (FGC): Unique flammability parameters assessed by this method that provide insight into material behavior under fire exposure.
• Test Conditions: Specimens of known mass and form (fiber, film, powder, pellet, etc.) are decomposed under controlled heating rates (0.2 to 2 K/s) in anaerobic (oxygen-free) or aerobic (oxidizing) environments.
• Measurement Techniques: Heat release is calculated from oxygen consumption during combustion, with precise quantification of combustion temperatures and residue.

Applications

• Material Flammability Screening: Ideal for rapid assessment during material research and development, especially for plastics and other polymers.
• Comparative Fire Performance: Enables comparison between different materials or formulations based on standardized flammability metrics.
• Supporting Fire Modeling: Provides critical input data such as ignition temperatures and heat release characteristics for predictive fire growth modeling (referenced in ASTM E1591).
• Regulatory and Compliance Testing: Assists manufacturers and laboratories in meeting regulatory requirements for fire safety by providing standardized data on heat release and combustion behavior.
• Quality Assurance and Control: Useful in quality control settings where consistent fire behavior from batch to batch is required.

Related Standards

• ASTM D5865: Used for determining the gross calorific value of coal and coke, referenced for comparison of net calorific values.
• ASTM E176 & ISO 13943: Provide terminology related to fire standards and fire safety.
• ASTM E1591: Guide for obtaining data for fire growth models, relevant for interpreting test results in the context of fire modeling.
• ASTM D883: Contains relevant terminology relating to plastics.
• ASTM E967: Test method for temperature calibration of calorimetric devices, essential for accurate MCC instrumentation.
• ASTM E2935: Practice for evaluating the equivalence of testing processes.

This method is not intended to replace large-scale fire testing or represent all aspects of fire hazards but delivers invaluable, standardized data for predicting materials' response to heat and flame under controlled laboratory conditions.

Keywords: flammability testing, plastics fire behavior, thermal decomposition, heat release capacity, microscale combustion calorimetry, oxygen consumption, calorimetric analysis, fire load, ASTM D7309-21b standard, polymer fire safety, material development.

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: D7309 − 21b
Standard Test Method for
Determining Flammability Characteristics of Plastics and
Other Solid Materials Using Microscale Combustion
Calorimetry
This standard is issued under the fixed designation D7309; 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.
1. Scope* responsibility of the user of this standard to establish appro-
priate safety, health, and environmental practices and deter-
1.1 This test method, which is similar to thermal analysis
mine the applicability of regulatory limitations prior to use.
techniques, establishes a procedure for determining flamma-
bility characteristics of combustible materials such as plastics.
NOTE 1—There is no known ISO equivalent to this test method.
1.11 This international standard was developed in accor-
1.2 The test is conducted in a laboratory environment using
dance with internationally recognized principles on standard-
controlled heating of milligram specimens and complete ther-
ization established in the Decision on Principles for the
mal oxidation of the specimen gases.
Development of International Standards, Guides and Recom-
1.3 Specimens of known mass are thermally decomposed in
mendations issued by the World Trade Organization Technical
an oxygen-free (anaerobic) or oxidizing (aerobic) environment
Barriers to Trade (TBT) Committee.
at a constant heating rate between 0.2 and 2 K/s.
1.4 The heat released by the specimen is determined from
2. Referenced Documents
themassofoxygenconsumedtocompletelyoxidize(combust)
2.1 ASTM Standards:
the specimen gases.
D883 Terminology Relating to Plastics
1.5 Therateofheatreleasedbycombustionofthespecimen
D5865 Test Method for Gross Calorific Value of Coal and
gases produced during controlled thermal or thermoxidative
Coke
decomposition of the specimen is computed from the rate of
E176 Terminology of Fire Standards
oxygen consumption.
E177 Practice for Use of the Terms Precision and Bias in
ASTM Test Methods
1.6 Thespecimentemperaturesoverwhichcombustionheat
E456 Terminology Relating to Quality and Statistics
is released are measured.
E691 Practice for Conducting an Interlaboratory Study to
1.7 The mass of specimen remaining after the test is
Determine the Precision of a Test Method
measured and used to compute the residual mass fraction.
E967 Test Method for Temperature Calibration of Differen-
1.8 The specimen shall be a material or composite material
tial Scanning Calorimeters and Differential ThermalAna-
in any form (fiber, film, powder, pellet, droplet). This test
lyzers
method has been developed to facilitate material development
E1591 Guide for Obtaining Data for Fire Growth Models
and research.
E2935 Practice for Evaluating Equivalence of Two Testing
Processes
1.9 This standard is used to measure and describe the
response of materials, products, or assemblies to heat and
2.2 ISO Standard:
flame under controlled conditions, but does not by itself ISO 13943 Fire Safety—Vocabulary
incorporate all factors required for fire hazard or fire risk
assessment of the materials, products, or assemblies under 3. Terminology
actual fire conditions.
3.1 Definitions:
1.10 This standard does not purport to address all of the
safety concerns, if any, associated with its use. It is the
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
This test method is under the jurisdiction ofASTM Committee D20 on Plastics contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
and is the direct responsibility of Subcommittee D20.30 on Thermal Properties. Standards volume information, refer to the standard’s Document Summary page on
Current edition approved Oct. 1, 2021. Published October 2021. Originally the ASTM website.
approved in 2007. Last previous edition approved in 2021 as D7309 – 21a. DOI: Available fromAmerican National Standards Institute (ANSI), 25 W. 43rd St.,
10.1520/D7309-21B. 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
D7309 − 21b
3.1.1 Terms used in this standard are defined in accordance 3.2.17 specimen gases, n—the volatile chemical species
with Terminology D883, unless otherwise specified. For terms liberated during controlled thermal (oxidative) decomposition
relating to precision and bias and associated issues, the terms of a specimen.
used in this standard are defined in accordance with Terminol-
3.3 Symbols:
ogy E456. For terms relating to fire, the terms in this standard
are defined in accordance with Terminology E176 and
ISO 13943. In case of conflict, the definitions given in Termi-
β = heating rate, K/s
E = 13.1 kJ/g-O is the average heat released by com-
nology E176 shall prevail.
plete combustion of organic compounds per unit
3.2 Definitions of Terms Specific to This Standard:
mass of oxygen consumed
3.2.1 combustion residue, n—the non-volatile chemical spe-
F = volumetric flow rate of the combustion stream at
cies remaining after controlled thermal oxidative decomposi-
ambient temperature and pressure measured at the
tion of a specimen.
terminal flow meter prior to the start of the test,
3.2.2 combustion temperature, n—the specimen tempera-
cm /s
tureatwhichthespecificcombustionrateisamaximumduring
F = volumetric flow rate of the combustion stream at
controlled thermal oxidative decomposition.
ambient temperature and pressure measured at the
3.2.3 controlled heating, n—a controlled temperature pro- terminal flow meter during the test, cm /s
gramusedtoeffectthermaldecompositionoroxidativethermal FGC = fire growth capacity of sample, J/g-K
h = specific heat release of sample, J/g
decomposition in which the temperature of the specimen is
c
o
h = net calorific value of sample, J/g
uniform throughout and increases with time at a constant rate.
c
h = specific heat of combustion of specimen gases, J/g
c,gas
3.2.4 controlled thermal (or thermal oxidative)
η = heat release capacity, J/g-K
c
decomposition, n—thermal (oxidative) decomposition under
m = initial specimen mass, g
o
controlled heating.
m = residual specimen mass after oxidative pyrolysis, g
c
3.2.5 fire growth capacity, n—a parameter derived from the m = residual specimen mass after the anaerobic
p
temperature dependence of the chemical processes responsible pyrolysis, g
Q(t) = specific heat release rate at time t,W/g
for ignition and burning of combustible materials.
Q = maximum specific heat release rate, W/g
max
3.2.6 heat release capacity, n—the maximum specific heat
Q = maximum specific combustion rate, W/g
max
release rate during a controlled thermal decomposition divided
ρ = density of oxygen at ambient conditions, g/cm
O
by the heating rate in the test.
T = time synchronized to temperature, x - τ,s
3.2.7 heating rate, n—the constant rate of temperature rise
T = standard room temperature, 298K.
of the specimen during the controlled temperature program.
T = temperature at 5 % of h measured at heating rate,
5% c
β = 1 K/s, K
3.2.8 maximum specific combustion rate, n—the maximum
T = temperature at 95 % of h measured at heating rate,
value of the specific combustion rate recorded during the test. 95 % c
β = 1 K/s, K
3.2.9 maximum specific heat release rate, n—the maximum
T = heat release temperature at Q ,K
max max
value of the specific heat release rate recorded during the test. 0 0
T = combustion temperature at Q ,K
max max
3.2.10 net calorific value, n—the net heat of complete
τ = transit time of the gas stream between the specimen
combustion of the specimen measured during controlled ther-
location and the oxygen analyzer, s
mal oxidative decomposition per unit initial specimen mass.
x = time at which the oxygen analyzer signal is
recorded, s
3.2.11 oxidative thermal decomposition, n—a process of
X = volume(mole)fractionofoxygeninthecombustion
extensive chemical species change caused by heat and oxygen O
stream measured at the oxygen sensor prior to the
(thermal oxidation, oxidative pyrolysis).
3 3
start of the test, cm /cm
3.2.12 pyrolysis residue, n—the fraction of the initial speci-
X = volume (mole) fraction of oxygen measured at the
O
menmassremainingaftercontrolledanaerobicthermaldecom-
3 3
oxygen sensor during the test at time, t,cm /cm
position.
Y = combustion residue, g/g
c
3.2.13 specific combustion rate, n—the rate at which com-
Y = pyrolysis residue, g/g
p
bustionheatisreleasedperunitinitialmassofspecimenduring
controlled thermal oxidative decomposition.
4. Summary of Test Method
3.2.14 specificheatofcombustionofspecimengases,n—net
4.1 This test method provides two procedures for determin-
calorific value of gases.
ingflammabilitycharacteristicsofmaterialsinalaboratorytest
3.2.15 specific heat release rate, n—the rate at which
using controlled heating (controlled temperature program-
combustion heat is released per unit initial mass of specimen
ming)andoxygenconsumptioncalorimetry.Thistestmeasures
during controlled thermal decomposition.
flammability characteristics using a controlled temperature
3.2.16 specific heat release, n—the net heat of complete program to force the release of specimen gases, thermal
combustion of the volatiles liberated during controlled thermal oxidation of the specimen gases (and optionally the specimen
decomposition per unit initial specimen mass. residue) in excess oxygen, and measurement of the oxygen
D7309 − 21b
consumed to calculate the amount, rate, and temperature of by combustion, or to perform titrations to correct for the heat
heat released by combustion of a solid specimen during of solution of acid gases. See Table X1.2 for comparison of
controlled heating. Microscale Combustion Calorimetry (MCC) data with Test
Method D5865.
4.2 Controlled Thermal Decomposition, Method A—In this
procedure the specimen is subjected to controlled heating in an 5.6 The temperature T of Method A measured at a
5%
heating rate β = 1K⁄s approximates the surface temperature at
oxygen-free/anaerobic environment, that is, controlled thermal
piloted ignition in accordance with Ref. (8 and 9) for purposes
decomposition. The gases released by the specimen during
of fire modeling (see Guide E1591).
controlledthermaldecompositionaresweptfromthespecimen
chamber by a non-oxidizing/inert purge gas (typically
5.7 The heat release capacity η (J/g-K) is a flammability
c
nitrogen), subsequently mixed with excess oxygen, and com-
parameter measured in Method A that is unique to this test
pletelyoxidizedinahightemperaturecombustionfurnace.The
method.
volumetric flow rate and volumetric oxygen concentration of
5.8 The fire growth capacity FGC (J/g-K) is a flammability
thegasstreamexitingthecombustionfurnacearecontinuously
parameter measured in MethodAat heating rate β = 1K/s that
measured during the test to calculate the rate of heat release by
is unique to this test method.
means of oxygen consumption. In Method A the heat of
combustion of the volatile component of the specimen (speci-
6. Limitations
men gases) is measured but not the heat of combustion of any
6.1 The fire growth capacity (FGC) relates to thermal
solidresidue.TableX1.1ofAppendixX1showsdataforη ,h ,
c c
oxidation of gaseous products generated by anaerobic thermal
Y , and T for 14 different commercial plastics tested in
p max
decomposition of solid fuels in flaming combustion. The
triplicate (n = 3).
temperatures of thermal decomposition in this method depend
on heating rate β (8 and 9), so FGC shall be calculated using
4.3 Controlled Thermal Oxidative Decomposition,
Method B—In this procedure the specimen is subjected to h , T and T measured in Method A at heating rate β =
c 5% 95 %
1K/s.
controlled heating in an oxidizing/aerobic environment, that is,
controlled thermal oxidative decomposition. The specimen
6.2 The heat release capacity (η ) is independent of the
c
gases evolved during the controlled heating program are swept
form, mass, and heating rate of the specimen as long as the
from the specimen chamber by the oxidizing purge gas (for
specimen temperature is uniform at all times during the test
example, dry air) and mixed with additional oxygen, if
(1-5).
necessary, prior to entering a high temperature combustion
6.3 Test results obtained from small (milligram) samples by
furnace where the gases are completely oxidized. The volu-
this method do not include physical behavior such as melting,
metric flow rate and volumetric oxygen concentration of the
dripping, swelling, shrinking, delamination, and char/barrier
gas stream exiting the combustion furnace are continuously
formation that can influence the results of large (decagram/
measured during the test to calculate the specific combustion
kilogram) samples in flame and fire tests.
rate by means of oxygen consumption. In Method B the net
6.4 Test results obtained from small (milligram) samples by
calorific value of the specimen gases and solid residue are
this method do not include extrinsic factors such as thickness,
measured during the test.
sample orientation, external heat flux, ignition source, bound-
ary conditions, and ventilation rate that influence the results of
5. Significance and Use
large (decagram/kilogram) samples in flame and fire tests.
5.1 This laboratory test method measures thermal combus-
6.5 The specific combustion rate and combustion tempera-
tion properties of materials (1-9).
ture of Method B are not generally reproducible because
5.2 The test uses controlled thermal and thermal-oxidative
sample geometry can affect the rate of surface oxidation and
decomposition of specimens and thermal oxidation of the
gas phase ignition can occur in the sample chamber at
specimen gases as they are released from the specimen to
appropriate fuel/oxygen ratios. Reproducibility of Q and
max
simulate the condensed and gas phase processes of flaming
T are improved by using low oxygen concentration in the
max
combustion, respectively, in a small-scale laboratory test (1-9).
purge gas, small samples, and low heating rates in this test.
5.3 The thermal combustion properties measured in the test
7. Apparatus
are related to flammability characteristics of the material (4-9).
7.1 The equipment used in this test method shall be capable
5.4 The amount of heat released in flaming combustion per
of displaying changes in combustion heat release rate as a
unit mass of material is the fire load and the potential fire load
function of specimen temperature during controlled heating
(complete combustion) is estimated in Method A as h .
c
and shall have the capability of subjecting the specimen to
5.5 The net calorific value of the material (see Test Method
different atmospheres of oxygen concentration at ambient
o
D5865) is determined directly using Method B as h without
c
pressure.
the need to know the atomic composition of the specimen to
7.2 Commercial thermogravimetric analyzers, pyrolysis
correct for the latent heat of evaporation of the water produced
probes, and electrically-heated ceramic tubes in thermal con-
tact with a combustor, or attached gas analyzers, or both, have
been found suitable. Detailed apparatus design criteria are
The boldface numbers in parentheses refer to a list of references at the end of
this standard. given in Annex A1.
D7309 − 21b
NOTE 2—In typical materials tests a material is exposed to a particular
7.9 Ameansofintroducingoxygenintothemixingsectionat
set of test conditions and the material’s response to those particular test
a constant flow rate of 0-50 cm /min, such that the concentra-
conditions is measured and reported as the test result. In these tests
tion of oxygen is between 20-50 % (60.1 %) by volume
changing the test conditions has an effect on the result of the test. In this
entering the combustion chamber.
test, the heat release capacity (η ) is independent of the test parameters as
c
it is a material property and not a response of a material to a particular set
7.10 A combustor (combustion chamber) capable of main-
of conditions. Thus, changing the test condition (within certain con-
taining a constant temperature in the range of 1073-1273K
straints) will have no effect on the test result. As such, the apparatus
(800-1000°C). Typically, the residence time of the specimen
required to perform this test shall operate to provide test parameters that
gases in the combustor is 10 seconds and the combustor
remain within certain constraints for each section of the device, for
example, specimen chamber, mixing section, combustor. The diameter,
temperature is 1173K (900°C) in accordance with Ref. (5).
length and shape of each section will have no effect on the test result
7.11 An in-line drier to remove moisture and acid gases
provided the section meets the performance given in Annex A1.
from the combustion stream to a dew point of 273K. Solid
7.3 Figure 1 illustrates the basic components of an
desiccant when used to dry the combustion stream shall be of
apparatus, (1, 5, 10-13), satisfactory for this test method which
an indicating type for visual observation of effectiveness.
include:
Anhydrous calcium sulfate has been found suitable
7.4 A specimen chamber (sample chamber) that is capable
7.12 A flow meter capable of measuring gas flow rates of
of holding and heating a small (milligram sized) specimen in a
50-200 cm /min with a response time of <0.1 s, sensitivity of
continuous flow of purge gas.
0.1 % of full scale, repeatability to 60.2 % of full scale, and
7.5 Temperature controller, capable of executing a tempera-
accuracy of 61 % of the full scale.
ture program that changes the specimen chamber temperature
7.13 An oxygen analyzer capable of measuring oxygen
between ambient and 1123 K at a rate that is constant to within
concentration in the range 0-100 % by volume (v/v) with a
5 % of the nominal value in the range 0.2-2 K/s.
response time of <6 s for 90 % deflection, a sensitivity of
7.6 A means of purging the specimen chamber environment
<0.1 % O (v/v), and a linearity of 61 % of full scale at
withaconstantflowofinert(forexample,nitrogen)orreactive
constant temperature and pressure.
(nitrogen/oxygenmixture)gasatarateof50-100cm /minwith
7.14 Recording device, that is either digital or analog and
an accuracy of 61%.
capable of recording and displaying any portion of the heat
7.7 A temperature sensor, to provide an indication of the
releaserateontheordinateasafunctionoftimeortemperature
specimen temperature to 60.5 K. on the abscissa.
7.8 A mixing chamber, where the specimen and purge gases 7.15 Pressurized gas sources, capable of sustaining a regu-
are mixed with sufficient oxygen to effect complete oxidation lated gas pressure of inert and reactive (oxygen) gas to the
of the specimen gases in the combustion chamber. apparatus. The gas sources shall be greater than 99.5 % purity.
FIG. 1 Schematic Diagram of Apparatus
D7309 − 21b
7.16 Containers, (pans, crucibles, vials, cups, etc.) which rate β that will be used for testing in accordance with 4.2
are inert to the specimen and suitable in shape and structural (MethodA). Note that typically the value of β is 1K/s. Record
integrity to contain the specimen throughout the test in and store the data.
accordance with the specifications of this test method.
8.2.4 Perform the temperature calibration flowing purge gas
under the same conditions that will be used to test the actual
7.17 Balance, with a capacity of 250 mg or greater and a
test specimens (Section 9).
sensitivity of 60.01 mg, to weigh specimens or containers, or
both.
NOTE 5—The heating rate, type of specimen holder, purge gas and the
purge gas flow rate can affect the temperature calibration.
8. Calibration and Standardization
8.2.5 Record the temperature sensor reading at the melting
8.1 The transit time τ of the gas stream between the
temperatureforaminimumoftwocalibrationmaterials,oneof
specimen chamber and the oxygen analyzer shall be deter-
which shall have a melting temperature below the temperature
mined in order to synchronize the sample temperature with the
range of interest and one of which shall have a melting
specific heat release.
temperature above the temperature range of interest.
8.1.1 Calibrate the time delay τ between the specimen
8.2.6 During the calibration, the temperature at which melt-
chamber and the oxygen sensor by recording the time between
ingofthecalibrationmaterialbegins(onsetofmelting)shallbe
a perturbation in the purge gas flow rate and the oxygen sensor
equated to the melting temperature of the calibration material.
response.
See Fig. X1.1 in Appendix for an example of a temperature
8.1.2 After making an initial calibration determination,
calibration using zinc as the calibration material.
recalibration is required only when changes to the system that
NOTE 6—When heat is absorbed during melting it causes a negative
might affect the transit time, that is, the flow volume, or gas
deviation of the heating rate and the temperature history from the
flow rate of the instrument, or both, are changed.
programmed values over the melting temperature range. The initial
deviation of the heating rate or the sensor temperature history from the
8.2 Perform a temperature calibration to correct for tem-
programmed values occurs at the onset of melting (melting temperature).
perature differences between the sample and the sensor caused
by thermal lag during transient heating. This is similar to the 8.2.7 Plot the melting temperature of the reference material
procedure used in Test Method E967. on the ordinate (y-axis) versus the temperature sensor reading
8.2.1 Place 10-20 mg of a high purity (≥99.99 %) calibra- at the onset of melting on the abscissa (x-axis) and fit a straight
tionmaterialwithaknownmeltingtemperatureinthecenterof line to the data using least squares regression as illustrated by
the example shown in Fig. X1.2. In all subsequent tests, the
a clean ceramic sample cup. The sample cup shall be identical
to that used for testing. specimen temperature, T, is calculated from the temperature
sensor reading, the y-axis intercept and the slope of the best-fit
8.2.1.1 The materials shown Table 1 have been shown to be
suitable for the temperature calibration. line using the relationship shown below:
8.2.1.2 Use a different sample cup for each calibration
T 5 Intercept1 Slope 3 Temperature Sensor Reading
~ !
material.
8.3 Perform a system performance test in accordance with
NOTE 3—If the same sample cup is used for two calibration materials,
4.2 (MethodA) by measuring the flammability parameters of a
it is possible that contamination of the calibration materials (including
reference material.
alloying) will occur and that the melting temperatures will be affected.
8.3.1 Use general purpose, crystal-clear, additive-free, food
8.2.2 Insert the sample cup and calibration material into the
gradepolystyrene(CAS#9003-53-6)asthereferencematerial
pyrolyzer and remove the air by purging with nitrogen as
for the system performance test. The flammability characteris-
instructed in 4.2 (Method A) for a minimum of five minutes.
tics of this material are: h = 40.2 6 0.6 kJ/g; η = 1080 6 45
c c
NOTE 4—Removal of the air is intended to prevent oxidation of the J/g-K; T = 445 6 2°C; and Y =0 6 0.01 g/g.
p p
calibration materials during the heating program.
8.3.2 If all systems and components of the instrumentation
8.2.3 Increase the pyrolyzer temperature from a starting have been properly calibrated and are performing correctly, the
temperature of approximately 75°C to the maximum pyrolyzer flammability characteristics of the reference material shall fall
temperature (namely in the range 850-900°C) at the heating within the ranges shown in 8.3.1.
TABLE 1 Melting Temperatures of Calibration Materials
Melting Temperature
Calibration Material Abbreviation
(°C) (K)
Indium In 157 430
Tin Sn 232 505
Bismuth Bi 271 545
Lead Pb 328 601
Zinc Zn 420 693
Antimony Sb 631 904
Aluminum Al 660 934
Sodium Chloride NaCl 801 1074
Silver Ag 962 1235
D7309 − 21b
NOTE 7—The system calibration is intended to show that the specimen
temperature, gas flow rates and oxygen concentration are correct and that
the data acquisition system is functioning properly. Further information
can be found in references (14) and (15).
9. Test Specimens
9.1 The specimens shall be taken from a sample that is
representative of the material.
9.2 Specimens shall be free of residual solvents and mois-
ture.
9.3 Specimens shall be in any form (film, fiber, powder,
pellet, droplet). If liquids are tested the boiling point shall be
above the starting temperature of the sample chamber.
9.4 Specimen mass shall be in the range of 1-10 mg.
Specimen mass is subject to the constraint that oxidation of the
specimen gases consumes less than one half of the available
oxygeninthecombustiongasstreamatanytimeduringthetest
FIG. 2 Sample Mass vs. Heating Rate
and at the heating rate used in the test. Typical specimen mass
is 2-5 mg.
10.1.4 Combustor Temperature—shall be set to completely
oxidize the specimen gases in the time they are in the
10. Test Parameters
combustor. Typically the combustor temperature shall be set to
10.1 Theheatreleasecapacity(η )isindependentofthetest
1173K (900°C).
c
parameters provided test parameters are chosen that r
...

This document is not an ASTM standard and is intended only to provide the user of an ASTM 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: D7309 − 21a D7309 − 21b
Standard Test Method for
Determining Flammability Characteristics of Plastics and
Other Solid Materials Using Microscale Combustion
Calorimetry
This standard is issued under the fixed designation D7309; 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.
1. Scope*
1.1 This test method, which is similar to thermal analysis techniques, establishes a procedure for determining flammability
characteristics of combustible materials such as plastics.
1.2 The test is conducted in a laboratory environment using controlled heating of milligram specimens and complete thermal
oxidation of the specimen gases.
1.3 Specimens of known mass are thermally decomposed in an oxygen-free (anaerobic) or oxidizing (aerobic) environment at a
constant heating rate between 0.2 and 2 K/s.
1.4 The heat released by the specimen is determined from the mass of oxygen consumed to completely oxidize (combust) the
specimen gases.
1.5 The rate of heat released by combustion of the specimen gases produced during controlled thermal or thermoxidative
decomposition of the specimen is computed from the rate of oxygen consumption.
1.6 The specimen temperatures over which combustion heat is released are measured.
1.7 The mass of specimen remaining after the test is measured and used to compute the residual mass fraction.
1.8 The specimen shall be a material or composite material in any form (fiber, film, powder, pellet, droplet). This test method has
been developed to facilitate material development and research.
1.9 This standard is used to measure and describe the response of materials, products, or assemblies to heat and flame under
controlled conditions, but does not by itself incorporate all factors required for fire hazard or fire risk assessment of the materials,
products, or assemblies under actual fire conditions.
1.10 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.
This test method is under the jurisdiction of ASTM Committee D20 on Plastics and is the direct responsibility of Subcommittee D20.30 on Thermal Properties.
Current edition approved May 1, 2021Oct. 1, 2021. Published May 2021October 2021. Originally approved in 2007. Last previous edition approved in 2021 as
D7309 – 21.D7309 – 21a. DOI: 10.1520/D7309-21A.10.1520/D7309-21B.
*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
D7309 − 21b
NOTE 1—There is no known ISO equivalent to this test method.
1.11 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
2.1 ASTM Standards:
D883 Terminology Relating to Plastics
D5865 Test Method for Gross Calorific Value of Coal and Coke
E176 Terminology of Fire Standards
E177 Practice for Use of the Terms Precision and Bias in ASTM Test Methods
E456 Terminology Relating to Quality and Statistics
E691 Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method
E967 Test Method for Temperature Calibration of Differential Scanning Calorimeters and Differential Thermal Analyzers
E1591 Guide for Obtaining Data for Fire Growth Models
E2935 Practice for Evaluating Equivalence of Two Testing Processes
2.2 ISO Standard:
ISO 13943 Fire Safety—Vocabulary
3. Terminology
3.1 Definitions:
3.1.1 Terms used in this standard are defined in accordance with Terminology D883, unless otherwise specified. For terms relating
to precision and bias and associated issues, the terms used in this standard are defined in accordance with Terminology E456. For
terms relating to fire, the terms in this standard are defined in accordance with Terminology E176 and ISO 13943. In case of
conflict, the definitions given in Terminology E176 shall prevail.
3.2 Definitions of Terms Specific to This Standard:
3.2.1 combustion residue, n—the non-volatile chemical species remaining after controlled thermal oxidative decomposition of a
specimen.
3.2.2 combustion temperature, n—the specimen temperature at which the specific combustion rate is a maximum during controlled
thermal oxidative decomposition.
3.2.3 controlled heating, n—a controlled temperature program used to effect thermal decomposition or oxidative thermal
decomposition in which the temperature of the specimen is uniform throughout and increases with time at a constant rate.
3.2.4 controlled thermal (or thermal oxidative) decomposition, n—thermal (oxidative) decomposition under controlled heating.
3.2.5 fire growth capacity, n—a parameter derived quantity representing the potential of a material to ignite, burn and spread
fire.from the temperature dependence of the chemical processes responsible for ignition and burning of combustible materials.
3.2.5.1 Discussion—
FGC is calculated by dividing the specific heat release measured at a constant heating rate of 1 K/s by the temperature at 95 %
of the specific heat release minus the temperature at 5 % of the specific heat release, multiplied by the ratio of the 95 % temperature
interval to the 5 % temperature interval, both referenced to a standard room temperature (298K), J/g-K.
3.2.6 heat release capacity, n—the maximum specific heat release rate during a controlled thermal decomposition divided by the
heating rate in the test.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or 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.
Available from American National Standards Institute (ANSI), 25 W. 43rd St., 4th Floor, New York, NY 10036, http://www.ansi.org.
D7309 − 21b
3.2.7 heating rate, n—the constant rate of temperature rise of the specimen during the controlled temperature program.
3.2.8 maximum specific combustion rate, n—the maximum value of the specific combustion rate recorded during the test.
3.2.9 maximum specific heat release rate, n—the maximum value of the specific heat release rate recorded during the test.
3.2.10 net calorific value, n—the net heat of complete combustion of the specimen measured during controlled thermal oxidative
decomposition per unit initial specimen mass.
3.2.11 oxidative thermal decomposition, n—a process of extensive chemical species change caused by heat and oxygen (thermal
oxidation, oxidative pyrolysis).
3.2.12 pyrolysis residue, n—the fraction of the initial specimen mass remaining after controlled anaerobic thermal decomposition.
3.2.13 specific combustion rate, n—the rate at which combustion heat is released per unit initial mass of specimen during
controlled thermal oxidative decomposition.
3.2.14 specific heat of combustion of specimen gases, n—net calorific value of gases.
3.2.15 specific heat release rate, n—the rate at which combustion heat is released per unit initial mass of specimen during
controlled thermal decomposition.
3.2.16 specific heat release, n—the net heat of complete combustion of the volatiles liberated during controlled thermal
decomposition per unit initial specimen mass.
3.2.17 specimen gases, n—the volatile chemical species liberated during controlled thermal (oxidative) decomposition of a
specimen.
3.3 Symbols:
β = heating rate, K/s
E = 13.1 kJ/g-O is the average heat released by complete combustion of organic compounds per unit mass of oxygen
consumed
F = volumetric flow rate of the combustion stream at ambient temperature and pressure measured at the terminal flow meter
prior to the start of the test, cm /s
F = volumetric flow rate of the combustion stream at ambient temperature and pressure measured at the terminal flow meter
during the test, cm /s
FGC = fire growth capacity of sample, J/g-K
h = specific heat release of sample, J/g
c
o
h = net calorific value of sample, J/g
c
h = specific heat of combustion of specimen gases, J/g
c,gas
η = heat release capacity, J/g-K
c
m = initial specimen mass, g
o
m = residual specimen mass after oxidative pyrolysis, g
c
m = residual specimen mass after the anaerobic pyrolysis, g
p
Q(t) = specific heat release rate at time t, W/g
Q = maximum specific heat release rate, W/g
max
Q = maximum specific combustion rate, W/g
max
ρ = density of oxygen at ambient conditions, g/cm
O
T = time synchronized to temperature, x - τ, s
T = standard room temperature, 298K.
T = temperature at 5 % of h measured at heating rate, β = 1 K/s, K
5 % c
T = temperature at 95 % of h measured at heating rate, β = 1 K/s, K
95 % c
T = heat release temperature at Q , K
max max
D7309 − 21b
0 0
T = combustion temperature at Q , K
max max
τ = transit time of the gas stream between the specimen location and the oxygen analyzer, s
x = time at which the oxygen analyzer signal is recorded, s
X = volume (mole) fraction of oxygen in the combustion stream measured at the oxygen sensor prior to the start of the test,
O
3 3
cm /cm
3 3
X = volume (mole) fraction of oxygen measured at the oxygen sensor during the test at time, t, cm /cm
O
Y = combustion residue, g/g
c
Y = pyrolysis residue, g/g
p
4. Summary of Test Method
4.1 This test method provides two procedures for determining flammability characteristics of materials in a laboratory test using
controlled heating (controlled temperature programming) and oxygen consumption calorimetry. This test measures flammability
characteristics using a controlled temperature program to force the release of specimen gases, thermal oxidation of the specimen
gases (and optionally the specimen residue) in excess oxygen, and measurement of the oxygen consumed to calculate the amount,
rate, and temperature of heat released by combustion of a solid specimen during controlled heating.
4.2 Controlled Thermal Decomposition, Method A—In this procedure the specimen is subjected to controlled heating in an
oxygen-free/anaerobic environment, that is, controlled thermal decomposition. The gases released by the specimen during
controlled thermal decomposition are swept from the specimen chamber by a non-oxidizing/inert purge gas (typically nitrogen),
subsequently mixed with excess oxygen, and completely oxidized in a high temperature combustion furnace. The volumetric flow
rate and volumetric oxygen concentration of the gas stream exiting the combustion furnace are continuously measured during the
test to calculate the rate of heat release by means of oxygen consumption. In Method A the heat of combustion of the volatile
component of the specimen (specimen gases) is measured but not the heat of combustion of any solid residue. Table X1.1 of
Appendix X1 shows data for η ,h ,Y , and T for 14 different commercial plastics tested in triplicate (n = 3).
c c p max
4.3 Controlled Thermal Oxidative Decomposition,
Method B—In this procedure the specimen is subjected to controlled heating in an oxidizing/aerobic environment, that is,
controlled thermal oxidative decomposition. The specimen gases evolved during the controlled heating program are swept from
the specimen chamber by the oxidizing purge gas (for example, dry air) and mixed with additional oxygen, if necessary, prior to
entering a high temperature combustion furnace where the gases are completely oxidized. The volumetric flow rate and volumetric
oxygen concentration of the gas stream exiting the combustion furnace are continuously measured during the test to calculate the
specific combustion rate by means of oxygen consumption. In Method B the net calorific value of the specimen gases and solid
residue are measured during the test.
5. Significance and Use
5.1 This laboratory test method measures thermal combustion properties of materials (1-9).
5.2 The test uses controlled thermal and thermal-oxidative decomposition of specimens and thermal oxidation of the specimen
gases as they are released from the specimen to simulate the condensed and gas phase processes of flaming combustion,
respectively, in a small-scale laboratory test (1-9).
5.3 The thermal combustion properties measured in the test are related to flammability characteristics of the material (4-9).
5.4 The amount of heat released in flaming combustion per unit mass of material is the fire load and the potential fire load
(complete combustion) is estimated in Method A as h .
c
o
5.5 The net calorific value of the material (see Test Method D5865) is determined directly using Method B as h without the need
c
to know the atomic composition of the specimen to correct for the latent heat of evaporation of the water produced by combustion,
or to perform titrations to correct for the heat of solution of acid gases. See Table X1.2 for comparison of Microscale Combustion
Calorimetry (MCC) data with Test Method D5865.
The boldface numbers in parentheses refer to a list of references at the end of this standard.
D7309 − 21b
5.6 The temperature T of Method A measured at a heating rate β = 1K ⁄s approximates the surface temperature at piloted ignition
5 %
in accordance with Ref. (8 and 9) for purposes of fire modeling (see Guide E1591).
5.7 The heat release capacity η (J/g-K) is a flammability parameter measured in Method A that is unique to this test method.
c
5.8 The fire growth capacity FGC (J/g-K) is a flammability parameter measured in Method A at heating rate β = 1K/s that is unique
to this test method.
6. Limitations
6.1 The fire growth capacity (FGC) relates to thermal oxidation of gaseous products generated by anaerobic thermal
decomposition of solid fuels in flaming combustion. The temperatures of thermal decomposition in this method depend on heating
rate β (8 and 9), so FGC shall be calculated using h ,T and T measured in Method A at heating rate β = 1K/s.
c 5 % 95 %
6.2 The heat release capacity (η ) is independent of the form, mass, and heating rate of the specimen as long as the specimen
c
temperature is uniform at all times during the test (1-5).
6.3 Test results obtained from small (milligram) samples by this method do not include physical behavior such as melting,
dripping, swelling, shrinking, delamination, and char/barrier formation that can influence the results of large (decagram/kilogram)
samples in flame and fire tests.
6.4 Test results obtained from small (milligram) samples by this method do not include extrinsic factors such as thickness, sample
orientation, external heat flux, ignition source, boundary conditions, and ventilation rate that influence the results of large
(decagram/kilogram) samples in flame and fire tests.
6.5 The specific combustion rate and combustion temperature of Method B are not generally reproducible because sample
geometry can affect the rate of surface oxidation and gas phase ignition can occur in the sample chamber at appropriate fuel/oxygen
0 0
ratios. Reproducibility of Q and T are improved by using low oxygen concentration in the purge gas, small samples, and
max max
low heating rates in this test.
7. Apparatus
7.1 The equipment used in this test method shall be capable of displaying changes in combustion heat release rate as a function
of specimen temperature during controlled heating and shall have the capability of subjecting the specimen to different
atmospheres of oxygen concentration at ambient pressure.
7.2 Commercial thermogravimetric analyzers, pyrolysis probes, and electrically-heated ceramic tubes in thermal contact with a
combustor, or attached gas analyzers, or both, have been found suitable. Detailed apparatus design criteria are given in Annex A1.
NOTE 2—In typical materials tests a material is exposed to a particular set of test conditions and the material’s response to those particular test conditions
is measured and reported as the test result. In these tests changing the test conditions has an effect on the result of the test. In this test, the heat release
capacity (η ) is independent of the test parameters as it is a material property and not a response of a material to a particular set of conditions. Thus,
c
changing the test condition (within certain constraints) will have no effect on the test result. As such, the apparatus required to perform this test shall
operate to provide test parameters that remain within certain constraints for each section of the device, for example, specimen chamber, mixing section,
combustor. The diameter, length and shape of each section will have no effect on the test result provided the section meets the performance given in Annex
A1.
7.3 Figure 1 illustrates the basic components of an apparatus, (1, 5, 10-13), satisfactory for this test method which include:
7.4 A specimen chamber (sample chamber) that is capable of holding and heating a small (milligram sized) specimen in a
continuous flow of purge gas.
7.5 Temperature controller, capable of executing a temperature program that changes the specimen chamber temperature between
ambient and 1123 K at a rate that is constant to within 5 % of the nominal value in the range 0.2-2 K/s.
D7309 − 21b
FIG. 1 Schematic Diagram of Apparatus
7.6 A means of purging the specimen chamber environment with a constant flow of inert (for example, nitrogen) or reactive
(nitrogen/oxygen mixture) gas at a rate of 50-100 cm /min with an accuracy of 61 %.
7.7 A temperature sensor, to provide an indication of the specimen temperature to 60.5 K.
7.8 A mixing chamber, where the specimen and purge gases are mixed with sufficient oxygen to effect complete oxidation of the
specimen gases in the combustion chamber.
7.9 A means of introducing oxygen into the mixing section at a constant flow rate of 0-50 cm /min, such that the concentration
of oxygen is between 20-50 % (60.1 %) by volume entering the combustion chamber.
7.10 A combustor (combustion chamber) capable of maintaining a constant temperature in the range of 1073-1273K
(800-1000°C). Typically, the residence time of the specimen gases in the combustor is 10 seconds and the combustor temperature
is 1173K (900°C) in accordance with Ref. (5).
7.11 An in-line drier to remove moisture and acid gases from the combustion stream to a dew point of 273K. Solid desiccant when
used to dry the combustion stream shall be of an indicating type for visual observation of effectiveness. Anhydrous calcium sulfate
has been found suitable
7.12 A flow meter capable of measuring gas flow rates of 50-200 cm /min with a response time of <0.1 s, sensitivity of 0.1 % of
full scale, repeatability to 60.2 % of full scale, and accuracy of 61 % of the full scale.
7.13 An oxygen analyzer capable of measuring oxygen concentration in the range 0-100 % by volume (v/v) with a response time
of <6 s for 90 % deflection, a sensitivity of <0.1 % O (v/v), and a linearity of 61 % of full scale at constant temperature and
pressure.
7.14 Recording device, that is either digital or analog and capable of recording and displaying any portion of the heat release rate
on the ordinate as a function of time or temperature on the abscissa.
D7309 − 21b
7.15 Pressurized gas sources, capable of sustaining a regulated gas pressure of inert and reactive (oxygen) gas to the apparatus.
The gas sources shall be greater than 99.5 % purity.
7.16 Containers, (pans, crucibles, vials, cups, etc.) which are inert to the specimen and suitable in shape and structural integrity
to contain the specimen throughout the test in accordance with the specifications of this test method.
7.17 Balance, with a capacity of 250 mg or greater and a sensitivity of 60.01 mg, to weigh specimens or containers, or both.
8. Calibration and Standardization
8.1 The transit time τ of the gas stream between the specimen chamber and the oxygen analyzer shall be determined in order to
synchronize the sample temperature with the specific heat release.
8.1.1 Calibrate the time delay τ between the specimen chamber and the oxygen sensor by recording the time between a
perturbation in the purge gas flow rate and the oxygen sensor response.
8.1.2 After making an initial calibration determination, recalibration is required only when changes to the system that might affect
the transit time, that is, the flow volume, or gas flow rate of the instrument, or both, are changed.
8.2 Perform a temperature calibration to correct for temperature differences between the sample and the sensor caused by thermal
lag during transient heating. This is similar to the procedure used in Test Method E967.
8.2.1 Place 10-20 mg of a high purity (≥99.99 %) calibration material with a known melting temperature in the center of a clean
ceramic sample cup. The sample cup shall be identical to that used for testing.
8.2.1.1 The materials shown Table 1 have been shown to be suitable for the temperature calibration.
8.2.1.2 Use a different sample cup for each calibration material.
NOTE 3—If the same sample cup is used for two calibration materials, it is possible that contamination of the calibration materials (including alloying)
will occur and that the melting temperatures will be affected.
8.2.2 Insert the sample cup and calibration material into the pyrolyzer and remove the air by purging with nitrogen as instructed
in 4.2 (Method A) for a minimum of five minutes.
NOTE 4—Removal of the air is intended to prevent oxidation of the calibration materials during the heating program.
8.2.3 Increase the pyrolyzer temperature from a starting temperature of approximately 75°C to the maximum pyrolyzer
temperature (namely in the range 850-900°C) at the heating rate β that will be used for testing in accordance with 4.2 (Method
A). Note that typically the value of β is 1K/s. Record and store the data.
8.2.4 Perform the temperature calibration flowing purge gas under the same conditions that will be used to test the actual test
specimens (Section 9).
TABLE 1 Melting Temperatures of Calibration Materials
Melting Temperature
Calibration Material Abbreviation
(°C) (K)
Indium In 157 430
Tin Sn 232 505
Bismuth Bi 271 545
Lead Pb 328 601
Zinc Zn 420 693
Antimony Sb 631 904
Aluminum Al 660 934
Sodium Chloride NaCl 801 1074
Silver Ag 962 1235
D7309 − 21b
NOTE 5—The heating rate, type of specimen holder, purge gas and the purge gas flow rate can affect the temperature calibration.
8.2.5 Record the temperature sensor reading at the melting temperature for a minimum of two calibration materials, one of which
shall have a melting temperature below the temperature range of interest and one of which shall have a melting temperature above
the temperature range of interest.
8.2.6 During the calibration, the temperature at which melting of the calibration material begins (onset of melting) shall be equated
to the melting temperature of the calibration material. See Fig. X1.1 in Appendix for an example of a temperature calibration using
zinc as the calibration material.
NOTE 6—When heat is absorbed during melting it causes a negative deviation of the heating rate and the temperature history from the programmed values
over the melting temperature range. The initial deviation of the heating rate or the sensor temperature history from the programmed values occurs at the
onset of melting (melting temperature).
8.2.7 Plot the melting temperature of the reference material on the ordinate (y-axis) versus the temperature sensor reading at the
onset of melting on the abscissa (x-axis) and fit a straight line to the data using least squares regression as illustrated by the example
shown in Fig. X1.2. In all subsequent tests, the specimen temperature, T, is calculated from the temperature sensor reading, the
y-axis intercept and the slope of the best-fit line using the relationship shown below:
T 5 Intercept1 Slope 3 Temperature Sensor Reading
~ !
8.3 Perform a system performance test in accordance with 4.2 (Method A) by measuring the flammability parameters of a
reference material.
8.3.1 Use general purpose, crystal-clear, additive-free, food grade polystyrene (CAS # 9003-53- 6) as the reference material for
the system performance test. The flammability characteristics of this material are: h = 40.2 6 0.6 kJ/g; η = 1080 6 45 J/g-K;
c c
T = 445 6 2°C; and Y = 0 6 0.01 g/g.
p p
8.3.2 If all systems and components of the instrumentation have been properly calibrated and are performing correctly, the
flammability characteristics of the reference material shall fall within the ranges shown in 8.3.1.
NOTE 7—The system calibration is intended to show that the specimen temperature, gas flow rates and oxygen concentration are correct and that the data
acquisition system is functioning properly. Further information can be found in references (14) and (15).
9. Test Specimens
9.1 The specimens shall be taken from a sample that is representative of the material.
9.2 Specimens shall be free of residual solvents and moisture.
9.3 Specimens shall be in any form (film, fiber, powder, pellet, droplet). If liquids are tested the boiling point shall be above the
starting temperature of the sample chamber.
9.4 Specimen mass shall be in the range of 1-10 mg. Specimen mass is subject to the constraint that oxidation of the specimen
gases consumes less than one half of the available oxygen in the combustion gas stream at any time during the test and at the
heating rate used in the test. Typical specimen mass is 2-5 mg.
10. Test Parameters
10.1 The heat release capacity (η ) is independent of the test parameters provided test parameters
...