ASTM D8117-21

Standard Test Method for Oxidative Induction Time of Polyolefin Geosynthetics by Differential Scanning Calorimetry

SIGNIFICANCE AND USE
5.1 The OIT is a qualitative assessment of the level (or degree) of stabilization of the material tested. This test has the potential to be used as a quality control measure to monitor the stabilization level in formulated resin as received from a supplier, prior to extrusion.
Note 2: The OIT measurement is an accelerated thermal-aging test, and as such can be misleading. Caution should be exercised in data interpretation since oxidation reaction kinetics are a function of temperature and the inherent properties of the additives contained in the sample. For example, OIT results are often used to select optimum resin formulations. Volatile antioxidants may generate poor OIT results even though they may perform adequately at the intended use temperature of the finished product.
Note 3: There is no accepted sampling procedure, nor have any definitive relationships been established for comparing OIT values on field samples to those on unused products, hence the use of such values for determining life expectancy is uncertain and subjective.
SCOPE
1.1 This test method covers a procedure for the determination of the oxidative induction time (OIT) of polyolefin geosynthetics using differential scanning calorimetry.  
1.2 The focus of the test is on geomembranes, but geogrids, geonets, geotextiles, and other polyolefin-related geosynthetics are also suitable for such evaluation.  
1.3 The values stated in SI units are to be regarded as the standard.
Note 1: This standard and ISO 11357-6 2013 address the same subject matter, but differ in technical content.  
1.4 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.  
1.5 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-Jun-2021
• ICS: 59.080.70 - Geotextiles
• Technical Committee: D35 - Geosynthetics
• Drafting Committee: D35.02 - Endurance Properties

Relations

• Refers: ASTM D4439-24 - Standard Terminology for Geosynthetics
• Effective Date: 01-Feb-2024
• Refers: ASTM E473-23b - Standard Terminology Relating to Thermal Analysis and Rheology
• Effective Date: 01-Oct-2023
• Refers: ASTM D4439-18 - Standard Terminology for Geosynthetics
• Effective Date: 15-Apr-2018
• Refers: ASTM D4439-17 - Standard Terminology for Geosynthetics
• Effective Date: 01-Aug-2017
• Refers: ASTM D4439-15a - Standard Terminology for Geosynthetics
• Effective Date: 01-Sep-2015
• Refers: ASTM D4439-15 - Standard Terminology for Geosynthetics
• Effective Date: 01-Jul-2015
• Refers: ASTM E473-14 - Standard Terminology Relating to Thermal Analysis and Rheology
• Effective Date: 15-Aug-2014
• Refers: ASTM D4439-14 - Standard Terminology for Geosynthetics
• Effective Date: 01-Mar-2014
• 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 E691-11 - Standard Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method
• Effective Date: 01-Nov-2011
• Refers: ASTM D4439-11 - Standard Terminology for Geosynthetics
• Effective Date: 01-Oct-2011
• Refers: ASTM E473-11a - Standard Terminology Relating to Thermal Analysis and Rheology
• Effective Date: 15-Jun-2011
• Refers: ASTM E473-11 - Standard Terminology Relating to Thermal Analysis and Rheology
• Effective Date: 01-Apr-2011
• Refers: ASTM D4703-10 - Standard Practice for Compression Molding Thermoplastic Materials into Test Specimens, Plaques, or Sheets
• Effective Date: 01-Jun-2010
• Refers: ASTM E473-10 - Standard Terminology Relating to Thermal Analysis and Rheology
• Effective Date: 01-Mar-2010

Overview

ASTM D8117-21 is the Standard Test Method for Oxidative Induction Time (OIT) of Polyolefin Geosynthetics by Differential Scanning Calorimetry (DSC). This widely recognized ASTM standard specifies a procedure to assess the level of stabilization of polyolefin-based geosynthetics, such as geomembranes, geogrids, geonets, and geotextiles. The test utilizes differential scanning calorimetry to determine the oxidative induction time, providing critical information about the material’s resistance to oxidative degradation and the efficiency of its stabilization additives.

Proper determination of OIT supports quality control in manufacturing, material formulation assessment, and comparative analysis of polyolefin geosynthetics. This standard is essential for geosynthetic engineers, quality control laboratories, and manufacturers seeking to evaluate material performance and longevity.

Key Topics

• Oxidative Induction Time (OIT): A qualitative metric indicating a material’s resistance to oxidative decomposition, measured as the time until an onset of exothermic oxidation at a specified temperature under oxygen atmosphere.
• Differential Scanning Calorimetry (DSC): The method relies on DSC to observe heat flow changes as the sample shifts from inert (nitrogen) to oxidizing (oxygen) atmospheres.
• Sample Preparation: Guidance on homogenizing, molding, and preparing representative test plaques to ensure precise and repeatable results.
• Quality Control in Polyolefin Geosynthetics:
  • Monitoring stabilization levels in supplied resins before extrusion
  • Evaluating the performance of antioxidant additives in formulations
• Limitations and Interpretation: Cautions that OIT is an accelerated measure; actual field performance may differ due to kinetics and the volatility of stabilization additives. No standard correlation exists between OIT values for aged field samples and unused material.

Applications

ASTM D8117-21 is used across the geosynthetics industry to improve product reliability and consistency. Practical applications include:

• Pre-Production Quality Control: Testing incoming resin batches to verify proper stabilizer content before extrusion or molding.
• Material Formulation Optimization: Comparing OIT results for different resin formulations to select optimal and durable blends for geomembranes, geogrids, and related products.
• Regulatory Compliance: Demonstrating that manufactured geosynthetics meet industry stabilization standards, as may be required by project specifications or regulatory bodies.
• Aging and Durability Studies: Tracking the depletion of antioxidants after laboratory or field aging to assess product longevity (with caution regarding interpretation).
• Product Development: Supporting research and development in new polyolefin geosynthetic materials where oxidative stability is critical for service life.

This standard is vital for manufacturers, test laboratories, and engineers focused on geosynthetics for civil engineering, environmental protection, and construction applications.

Related Standards

ASTM D8117-21 references and relates to several other key standards in geosynthetics and thermal analysis, including:

• ASTM D4439: Terminology for Geosynthetics
• ASTM D4703: Practice for Compression Molding Thermoplastic Materials into Test Specimens, Plaques, or Sheets
• ASTM E473: Terminology Relating to Thermal Analysis and Rheology
• ASTM E691: Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method
• ASTM E967: Test Method for Temperature Calibration of Differential Scanning Calorimeters and Differential Thermal Analyzers
• ISO 11357-6:2013: Plastics-Differential scanning calorimetry (DSC)-Part 6: Determination of oxidation induction time (isothermal OIT) and oxidation induction temperature (dynamic OIT), which addresses the same topic but with different technical requirements

By referencing ASTM D8117-21 in procurement, specification, or QA/QC processes, users ensure a scientifically backed, reproducible approach to measuring polyolefin stabilization vital for the reliable performance of geosynthetics.

Keywords: ASTM D8117-21, oxidative induction time, OIT test, polyolefin geosynthetics, geomembranes, geogrids, differential scanning calorimetry, geotextile stabilization, antioxidant performance, quality control.

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:D8117 −21
Standard Test Method for
Oxidative Induction Time of Polyolefin Geosynthetics by
Differential Scanning Calorimetry
This standard is issued under the fixed designation D8117; 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 E967 Test Method for Temperature Calibration of Differen-
tial Scanning Calorimeters and Differential Thermal Ana-
1.1 This test method covers a procedure for the determina-
lyzers
tion of the oxidative induction time (OIT) of polyolefin
geosynthetics using differential scanning calorimetry.
3. Terminology
1.2 The focus of the test is on geomembranes, but geogrids,
3.1 Definitions:
geonets, geotextiles, and other polyolefin-related geosynthetics
3.1.1 For definitions of terms applying to thermal analysis,
are also suitable for such evaluation.
refer to Terminology E473.
1.3 The values stated in SI units are to be regarded as the
3.1.2 For definitions of terms related to geosynthetics, refer
standard.
to Terminology D4439.
3.2 Definitions of Terms Specific to This Standard:
NOTE1—ThisstandardandISO11357-62013addressthesamesubject
3.2.1 oxidative induction time—a relative measure of a
matter, but differ in technical content.
material’s resistance to oxidative decomposition; it is deter-
1.4 This standard does not purport to address all of the
mined by the thermoanalytical measurement of the time
safety concerns, if any, associated with its use. It is the
interval to onset of exothermic oxidation of a material at a
responsibility of the user of this standard to establish appro-
specified temperature in an oxygen atmosphere.
priate safety, health, and environmental practices and deter-
mine the applicability of regulatory limitations prior to use. 3.3 Abbreviations:
1.5 This international standard was developed in accor- 3.3.1 HDPE—high-density polyethylene.
dance with internationally recognized principles on standard-
3.3.2 LDPE—low-density polyethylene.
ization established in the Decision on Principles for the
3.3.3 LLDPE—linear low-density polyethylene.
Development of International Standards, Guides and Recom-
3.3.4 OIT—oxidative induction time.
mendations issued by the World Trade Organization Technical
Barriers to Trade (TBT) Committee.
4. Summary of Test Method
2. Referenced Documents
4.1 The sample to be tested is heated at a constant rate in an
inert gaseous environment (nitrogen). When the specified
2.1 ASTM Standards:
temperature has been reached, the atmosphere is changed to
D4439 Terminology for Geosynthetics
oxygen maintained at the same flow rate. The specimen is then
D4703 Practice for Compression Molding Thermoplastic
held at constant temperature until the oxidative reaction is
Materials into Test Specimens, Plaques, or Sheets
displayed on the thermal curve. The OIT is determined from
E473 Terminology Relating to Thermal Analysis and Rhe-
the data recorded during the isothermal period. The time
ology
interval from when the oxygen flow is first initiated to the
E691 Practice for Conducting an Interlaboratory Study to
oxidative reaction is referred to as the induction period.
Determine the Precision of a Test Method
4.1.1 The end of the induction period is signaled by an
abrupt increase in the specimen’s evolved heat or temperature
This test method is under the jurisdiction of ASTM Committee D35 on
and will be recorded as an exothermic event by a differential
Geosynthetics and is the direct responsibility of Subcommittee D35.02 on Endur-
ance Properties. scanning calorimeter (DSC).
Current edition approved July 1, 2021. Published July 2021. Originally approved
4.2 The test is conducted in open aluminum pans.
in 2017. Last previous edition approved in 2017 as D8117 – 17. DOI: 10.1520/
D8117-21.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or 5. Significance and Use
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
5.1 The OIT is a qualitative assessment of the level (or
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. degree) of stabilization of the material tested. This test has the
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D8117−21
potential to be used as a quality control measure to monitor the 7.2 Oxygen, ultra-high purity grade (extra dry).
stabilization level in formulated resin as received from a
7.3 Nitrogen, ultra-high purity grade (extra dry).
supplier, prior to extrusion.
7.4 Aluminum Pan Degreasing Solvent.
NOTE 2—The OIT measurement is an accelerated thermal-aging test,
7.5 Indium, 99.999 % purity.
and as such can be misleading. Caution should be exercised in data
interpretation since oxidation reaction kinetics are a function of tempera-
7.6 Tin, 99.999 % purity.
ture and the inherent properties of the additives contained in the sample.
For example, OIT results are often used to select optimum resin
formulations. Volatile antioxidants may generate poor OIT results even
8. Hazards
though they may perform adequately at the intended use temperature of
8.1 Oxygen is a strong oxidizer that vigorously accelerates
the finished product.
combustion. Keep oil and grease away from equipment using
NOTE 3—There is no accepted sampling procedure, nor have any
definitiverelationshipsbeenestablishedforcomparingOITvaluesonfield
or containing oxygen.
samples to those on unused products, hence the use of such values for
8.2 The use of pressurized gas requires safe and proper
determining life expectancy is uncertain and subjective.
handling.
6. Apparatus
9. Sampling
6.1 Differential Scanning Calorimeter—As a minimum
requirement, the thermal analysis equipment shall be capable
9.1 Sample Selection—Select a test sample, at least 0.1 gr
of measuring heat flow of at least 10 mW full scale. The
(forexample,~10mmby~10mmfora1.0-mmgeomembrane,
instrument recorder shall be capable of displaying heat flow or
or~7mmby~7mmfora2.0-mmgeomembrane),representing
temperature differential on the y-axis and time on the x-axis.
the material to be analyzed. For freshly manufactured and
The time base must be accurate to 61 % and be readable to
unaged sample, select a region of the product free of
0.1 min.
contamination, for example, marking or adhesive. For aged
coupons, the selected region should also be free of defects and
NOTE 4—The OIT test is a function of a particular compound’s
located at least 12 mm away from an edge or a discontinuity,
stabilizer system and should not be used as a basis of comparison between
formulations that might contain different resins, stabilizers, additive
clamping areas, etc.
packages, or all of these.
9.1.1 If the sample contains a layer or layers of polymers
6.2 Gas Selector Switch and Regulators, for high-purity
other than polyolefins, the polyolefin may be tested separately
nitrogen and oxygen. The distance between the gas switching
from the entire cross section. A recommended procedure is
point and the instrument cell shall be such that the time
given in Appendix X4.
required to transition to an oxygen environment is less than
9.2 Homogenization—Homogenization of the test sample is
1 min.At a flow rate of 50 mL/min, this equates to a maximum
recommended for freshly manufactured and unaged samples,
switching volume of less than 50 mL.
and mandatory for aged samples. One of the procedures given
6.3 Analytical Balance, 0.1-mg sensitivity.
in Appendix X1, Appendix X2,or Appendix X3 can be used to
homogenize the test sample after aging.After homogenization,
6.4 Bore Hole Cutter, 6.4-mm diameter.
the test sample is compression molded into sheet format
6.5 Specimen-Encapsulating Press.
(thickness of 0.25 6 0.015 mm) prior to analysis, using either
6.6 Forceps, Scalpel, and Cutting Board.
Practice D4703, Annex A1 (Procedure C) or the procedure
presented in Appendix X5.
6.7 Electronic Mass Flow Controller, Rotometer
(Calibrated),orSoap-FilmFlowmeter,forgasflowcalibration.
NOTE 6—The temperature at which molding takes place may be at or
above the test temperature of this test method. Prolonged exposure to air
6.8 Specimen Holders—Degreased aluminum pans (6.0- to
at these temperatures may induce a negative bias into OIT measurement.
7.0-mm diameter, 1.5-mm height).
Molding should be performed at as low a temperature and as quickly as
possible to minimize this bias.
NOTE 5—The material composition of the specimen holder can influ-
ence the OIT test result significantly (that is, including any associated
9.2.1 Testing 5 to 10 mg specimens cut out directly from a
catalytic effects).
product(forexample,samplingageomembraneusingapunch)
6.9 Compression-Molding Device with Heated Platens.
and tested without prior homogenization may be acceptable for
monolithic, freshly manufactured, and unaged products, pro-
6.10 Spacer Plates, Shim Stock, Caul Plates, etc.
vided that they represent the entire thickness of the product,
6.11 Polyethylene Terephthalate Film (PET) or Polytetra-
that is, that there is no over-representation of the skins nor the
fluoroethylene (PTFE)-Coated Cloth, for sample-plaque prepa-
core on the punched specimen. In case of dispute, results
ration.
obtained on specimens homogenized and compression molded
6.12 Thickness Gauge.
to a thickness of 0.25 mm are to be considered as referee.
9.2.2 If this test is used to monitor aging of a material, the
6.13 Forced-Air Oven.
sample must be homogenized and the same preparation tech-
7. Reagents and Materials nique must be used before and after aging.
7.1 All chemical reagents used in this procedure shall be 9.3 Number of Specimens—Cut test specimens from the
analytical grade unless otherwise specified. plaque using a 6.3-mm (0.25-in.) bore hole cutter or punch.
D8117−21
NOTE 9—An inadequate melting thermal curve is occasionally obtained
9.3.1 When testing a product for specification conformance,
due to poor surface contact of the calibrant material to the pan surface. If
that is, on freshly manufactured samples, at least two speci-
this occurs, repeat the calibration step. (After one melting/crystallization
mens must be tested.
cycle the calibrant material should coat the bottom of the pan evenly.)
9.3.2 When evaluating the performance of a material to
10.2 Instrument Operation:
aging, at least three specimens must be tested before and after
10.2.1 Load the specimen and reference pans into the cell.
aging.
10.2.2 Allow 5 min for a nitrogen pre-purge prior to begin-
NOTE 7—Excessive difference between individual results may be
ning the heating cycle to eliminate any residual oxygen.
caused by specimen preparation, for example, from the specimen
Commence programmed heating of the specimen (under nitro-
selection, homogenization, or plaquing process. Should differences be-
gen flow of 50 6 5 mL⁄min) from ambient temperature to
tween individual specimens be greater than the within-lab repeatability,
further investigation could be conducted to assess the significance of each 200 °C (set point) at a rate of 20 °C⁄min.
result, which may eventually lead to the exclusion of a result.
10.2.3 When the set temperature has been reached, discon-
tinueprogrammedheatingandequilibratethesamplefor5 min
10. Procedure
at the set temperature. Turn on the recorder. If the instrument
10.1 Instrument Calibration—This procedure uses a two-
being used does not have an isothermal temperature-control
point calibration step. Indium and tin are used as the calibrants
mode feature, ensure accurate temperature control by monitor-
since their respective melting points encompass the specified
ing and adjusting continually, as required.
analysis temperature range (180 to 220 °C). Calibrate the
10.2.4 Once the equilibrium time has expired, change the
instrument in accordance with the manufacturer’s instructions
gas to oxygen at a flow rate of 50 6 mL⁄min. (Record this
using the following procedure. Calibrate the instrument at least
event.) This changeover point to oxygen flow is considered the
once per month or before use if longer than one month.
zero time of the experiment.
10.1.1 Place 5 6 0.5 mg of indium/tin into an aluminum
10.2.5 Continue isothermal operation until the maximum
sample pan. Place an aluminum cover over the pan, and seal
exotherm has been reached to allow a complete examination of
using the encapsulating press. Prepare an empty sealed pan to
the entire exotherm (see Figs. 2 and 3). At the tester’s
beusedasthereference.Placethespecimenandreferencepans
discretion, it is acceptable to terminate the test at a predeter-
into their respective locations in the instrument cell.
mined heat flow change provided that data are available to
10.1.2 Turn on the nitrogen gas flow at a rate of 50 mL⁄min
supportthealternative.Itisalsoacceptabletoterminatethetest
(with an absolute pressure
...

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: D8117 − 17 D8117 − 21
Standard Test Method for
Oxidative Induction Time of Polyolefin Geosynthetics by
Differential Scanning Calorimetry
This standard is issued under the fixed designation D8117; 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 covers a procedure for the determination of the oxidative induction time (OIT) of polyolefin geosynthetics
using differential scanning calorimetry.
1.2 The focus of the test is on geomembranes, but geogrids, geonets, geotextiles, and other polyolefin-related geosynthetics are
also suitable for such evaluation.
1.3 The values stated in SI units are to be regarded as the standard.
NOTE 1—This standard and ISO 11357-6 2013 address the same subject matter, but differ in technical content.
1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility
of the user of this standard to establish appropriate safety safety, health, and healthenvironmental practices and determine the
applicability of regulatory limitations prior to use.
1.5 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:
D4439 Terminology for Geosynthetics
D4703 Practice for Compression Molding Thermoplastic Materials into Test Specimens, Plaques, or Sheets
E473 Terminology Relating to Thermal Analysis and Rheology
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
3. Terminology
3.1 Definitions:
3.1.1 For definitions of terms applying to thermal analysis, refer to Terminology E473.
This test method is under the jurisdiction of ASTM Committee D35 on Geosynthetics and is the direct responsibility of Subcommittee D35.02 on Endurance Properties.
Current edition approved June 1, 2017July 1, 2021. Published June 2017July 2021. Originally approved in 2017. Last previous edition approved in 2017 as D8117 – 17.
DOI: 10.1520/D8117-17.10.1520/D8117-21.
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.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D8117 − 21
3.1.2 For definitions of terms related to geosynthetics, refer to Terminology D4439.
3.2 Definitions of Terms Specific to This Standard:
3.2.1 oxidative induction time—a relative measure of a material’s resistance to oxidative decomposition; it is determined by the
thermoanalytical measurement of the time interval to onset of exothermic oxidation of a material at a specified temperature in an
oxygen atmosphere.
3.3 Abbreviations:
3.3.1 HDPE—high-density polyethylene.
3.3.2 LDPE—low-density polyethylene.
3.3.3 LLDPE—linear low-density polyethylene.
3.3.4 OIT—oxidative induction time.
4. Summary of Test Method
4.1 The sample to be tested is heated at a constant rate in an inert gaseous environment (nitrogen). When the specified temperature
has been reached, the atmosphere is changed to oxygen maintained at the same flow rate. The specimen is then held at constant
temperature until the oxidative reaction is displayed on the thermal curve. The OIT is determined from the data recorded during
the isothermal period. The time interval from when the oxygen flow is first initiated to the oxidative reaction is referred to as the
induction period.
4.1.1 The end of the induction period is signaled by an abrupt increase in the specimen’s evolved heat or temperature and will
be recorded as an exothermic event by a differential scanning calorimeter (DSC).
4.2 The test is conducted in open aluminum pans.
5. Significance and Use
5.1 The OIT is a qualitative assessment of the level (or degree) of stabilization of the material tested. This test has the potential
to be used as a quality control measure to monitor the stabilization level in formulated resin as received from a supplier, prior to
extrusion.
NOTE 2—The OIT measurement is an accelerated thermal-aging test, and as such can be misleading. Caution should be exercised in data interpretation
since oxidation reaction kinetics are a function of temperature and the inherent properties of the additives contained in the sample. For example, OIT
results are often used to select optimum resin formulations. Volatile antioxidants may generate poor OIT results even though they may perform adequately
at the intended use temperature of the finished product.
NOTE 3—There is no accepted sampling procedure, nor have any definitive relationships been established for comparing OIT values on field samples to
those on unused products, hence the use of such values for determining life expectancy is uncertain and subjective.
6. Apparatus
6.1 Differential Scanning Calorimeter—As a minimum requirement, the thermal analysis equipment shall be capable of measuring
heat flow of at least 10 mW full scale. The instrument recorder shall be capable of displaying heat flow or temperature differential
on the y-axis and time on the x-axis. The time base must be accurate to 61 % and be readable to 0.1 min.
NOTE 4—The OIT test is a function of a particular compound’s stabilizer system and should not be used as a basis of comparison between formulations
that might contain different resins, stabilizers, additive packages, or all of these.
6.2 Gas Selector Switch and Regulators, for high-purity nitrogen and oxygen. The distance between the gas-switching gas
switching point and the instrument cell shall be such that the time required to transition to an oxygen environment is less than
1 min. At a flow rate of 50 mL/min, this equates to a maximum switching volume of less than 50 mL.
D8117 − 21
6.3 Analytical Balance, 0.1-mg sensitivity.
6.4 Bore Hole Cutter, 6.4-mm diameter.
6.5 Specimen-Encapsulating Press.
6.6 Forceps, Scalpel, and Cutting Board.
6.7 Electronic Mass Flow Controller, Rotometer (Calibrated), or Soap-Film Flowmeter, for gas flow calibration.
6.8 Specimen Holders—Degreased aluminum pans (6.0- to 7.0-mm diameter, 1.5-mm height).
NOTE 5—The material composition of the specimen holder can influence the OIT test result significantly (that is, including any associated catalytic
effects).
6.9 Compression-Molding Device with Heated Platens.
6.10 Spacer Plates, Shim Stock, Caul Plates, etc.
6.11 Polyethylene Terephthalate Film (PET) or Polytetrafluoroethylene (PTFE)-Coated Cloth, for sample-plaque preparation.
6.12 Thickness Gauge.
6.13 Forced-Air Oven.
7. Reagents and Materials
7.1 All chemical reagents used in this procedure shall be analytical grade unless otherwise specified.
7.2 Oxygen, ultra-high purity grade (extra dry).
7.3 Nitrogen, ultra-high purity grade (extra dry).
7.4 Aluminum Pan Degreasing Solvent.
7.5 Indium, 99.999 % purity.
7.6 Tin, 99.999 % purity.
8. Hazards
8.1 Oxygen is a strong oxidizer that vigorously accelerates combustion. Keep oil and grease away from equipment using or
containing oxygen.
8.2 The use of pressurized gas requires safe and proper handling.
9. Sampling
9.1 Sample Selection—Compression mold the sample into sheet format (thickness of 250 6 15 μm) prior to analysis and weight.
Specimen disks (6.4-mm diameter) cut from the sheet will have a weight of approximately 5 to 10 mg, depending on sample
density.Select a test sample, at least 0.1 gr (for example, ~10 mm by ~10 mm for a 1.0-mm geomembrane, or ~7 mm by ~7 mm
D8117 − 21
for a 2.0-mm geomembrane), representing the material to be analyzed. For freshly manufactured and unaged sample, select a
region of the product free of contamination, for example, marking or adhesive. For aged coupons, the selected region should also
be free of defects and located at least 12 mm away from an edge or a discontinuity, clamping areas, etc.
NOTE 6—If the sample requires homogenization prior to analysis, one of the procedures given in Appendix X1, Appendix X2, or Appendix X3 is
recommended. Poor sample uniformity will adversely affect test precision.
NOTE 7—If the sample contains a layer or layers of polymers other than polyolefins, the polyolefin may be tested separately from the entire cross-section.
A recommended procedure is given in Appendix X4.
9.1.1 Place the assembly into the compression-molding device. The preheat and pressing temperature is 160 °C for polyethylene
and 190 °C for polypropylene.
9.1.2 Heat the sample with appropriate pressure and time settings to obtain a plaque with uniform thickness.
9.1.3 Remove the plaque assembly and place it between two thick steel plates (heat sink) and cool the plaque to ambient
temperature. Alternatively, quench the plaque in ice water.
9.1.4 Determine the average thickness of the sheet to ensure that it is within the allowable tolerances.
9.1.5 Use the bore hole cutter to punch out a disk from the plaque and record the specimen weight.
9.1.1 Place the specimen disk into the appropriate pan type. Use an identical empty pan as the reference. (Do not crimp or seal
the pans.)If the sample contains a layer or layers of polymers other than polyolefins, the polyolefin may be tested separately from
the entire cross section. A recommended procedure is given in Appendix X4.
NOTE 8—If controlled cooling is not necessary, the option to prepare the test sample using Practice D4703, Annex A1 (Procedure C), is acceptable.
9.2 Homogenization—Homogenization of the test sample is recommended for freshly manufactured and unaged samples, and
mandatory for aged samples. One of the procedures given in Appendix X1, Appendix X2, or Appendix X3 can be used to
homogenize the test sample after aging. After homogenization, the test sample is compression molded into sheet format (thickness
of 0.25 6 0.015 mm) prior to analysis, using either Practice D4703, Annex A1 (Procedure C) or the procedure presented in
Appendix X5.
NOTE 6—The temperature at which molding takes place may be at or above the test temperature of this test method. Prolonged exposure to air at these
temperatures may induce a negative bias into OIT measurement. Molding should be performed at as low a temperature and as quickly as possible to
minimize this bias.
9.2.1 Testing 5 to 10 mg specimens cut out directly from a product (for example, sampling a geomembrane using a punch) and
tested without prior homogenization may be acceptable for monolithic, freshly manufactured, and unaged products, provided that
they represent the entire thickness of the product, that is, that there is no over-representation of the skins nor the core on the
punched specimen. In case of dispute, results obtained on specimens homogenized and compression molded to a thickness of 0.25
mm are to be considered as referee.
9.2.2 If this test is used to monitor aging of a material, the sample must be homogenized and the same preparation technique must
be used before and after aging.
9.3 Number of Specimens—Cut test specimens from the plaque using a 6.3-mm (0.25-in.) bore hole cutter or punch.
9.3.1 When testing a product for specification conformance, that is, on freshly manufactured samples, at least two specimens must
be tested.
9.3.2 When evaluating the performance of a material to aging, at least three specimens must be tested before and after aging.
NOTE 7—Excessive difference between individual results may be caused by specimen preparation, for example, from the specimen selection,
homogenization, or plaquing process. Should differences between individual specimens be greater than the within-lab repeatability, further investigation
could be conducted to assess the significance of each result, which may eventually lead to the exclusion of a result.
D8117 − 21
10. Procedure
10.1 Instrument Calibration—This procedure uses a two-point calibration step. Indium and tin are used as the calibrants since their
respective melting points encompass the specified analysis temperature range (180 to 220 °C). Calibrate the instrument in
accordance with the manufacturer’s instructions using the following procedure. Calibrate the instrument at least once per month
or before use if longer than one month.
10.1.1 Place 5 6 0.5 mg of indium/tin into an aluminum sample pan. Place an aluminum cover over the pan, and seal using the
encapsulating press. Prepare an empty sealed pan to be used as the reference. Place the specimen and reference pans into their
respective locations in the instrument cell.
10.1.2 Turn on the nitrogen gas flow at a rate of 50 mL ⁄min (with an absolute pressure of 140 kPa).
10.1.3 Use the following melting profiles:
Indium – ambient to 145 °C at 10 °C ⁄min, 145 to 165 °C at 1 °C ⁄min
Tin – ambient to 220 °C at 10 °C ⁄min, 220 to 240 °C at 1 °C ⁄min
NOTE 8—The specified heating rates are for calibration use only.
10.1.4 Adjust the temperature-calibration software (or potentiometer) to set the melting point at 156.63 and 231.97 °C (see
Practice E967) for indium and tin, respectively. The melting point of the calibrant is defined as the intercept of the extended
baseline and the extended tangent to the first slope of the endotherm (that is, the onset). See Fig. 1.
FIG. 1 Indium and Tin Melting Thermal Curves
NOTE 9—An inadequate melting thermal curve is occasionally obtained due to poor surface contact of the calibrant material to the pan surface. If this
occurs, repeat the calibration step. (Aft
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