ASTM D7028-07

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
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Designation:D7028–07
Standard Test Method for
Glass Transition Temperature (DMA Tg) of Polymer Matrix
Composites by Dynamic Mechanical Analysis (DMA)
This standard is issued under the fixed designation D 7028; 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 (e) indicates an editorial change since the last revision or reapproval.
1. Scope D 4092 Terminology for Plastics: Dynamic Mechanical
Properties
1.1 This test method covers the procedure for the determi-
D 5229/D 5229M Test Method for Moisture Absorption
nation of the dry or wet (moisture conditioned) glass transition
Properties and Equilibrium Conditioning of Polymer Ma-
temperature (T ) of polymer matrix composites containing
g
trix Composite Materials
high-modulus, 20 GPa (> 3 3 10 psi), fibers using a dynamic
E 177 Practice for Use of the Terms Precision and Bias in
mechanical analyzer (DMA) under flexural oscillation mode,
ASTM Test Methods
which is a specific subset of the Dynamic MechanicalAnalysis
E 691 Practice for Conducting an Interlaboratory Study to
(DMA) method.
Determine the Precision of a Test Method
1.2 The glass transition temperature is dependent upon the
E 1309 Guide for Identification of Fiber-Reinforced
physical property measured, the type of measuring apparatus
Polymer-Matrix Composite Materials in Databases
and the experimental parameters used. The glass transition
E 1434 GuideforRecordingMechanicalTestDataofFiber-
temperature determined by this test method (referred to as
Reinforced Composite Materials in Databases
“DMA Tg”) may not be the same as that reported by other
E 1471 Guide for Identification of Fibers, Fillers, and Core
measurement techniques on the same test specimen.
Materials in Computerized Material Property Databases
1.3 This test method is primarily intended for polymer
E 1640 Test Method forAssignment of the Glass Transition
matrix composites reinforced by continuous, oriented, high-
Temperature By Dynamic Mechanical Analysis
modulusfibers.Othermaterials,suchasneatresin,mayrequire
E 1867 Test Method for Temperature Calibration of Dy-
non-standard deviations from this test method to achieve
namic Mechanical Analyzers
meaningful results.
1.4 The values stated in SI units are standard. The values
3. Terminology
given in parentheses are non-standard mathematical conver-
3.1 Definitions—TerminologyD 3878definestermsrelating
sions to common units that are provided for information only.
to polymer matrix composites. Terminology D 4092 defines
1.5 This standard does not purport to address all of the
terms relating to dynamic mechanical property measurements
safety concerns, if any, associated with its use. It is the
on polymeric materials.
responsibility of the user of this standard to establish appro-
3.2 Symbols:
priate safety and health practices and determine the applica-
E’ = storage modulus
bility of regulatory limitations prior to use.
E” = loss modulus
2. Referenced Documents tan d = E”/E’ = tangent delta
2 DMA Tg = glass transition temperature defined from dy-
2.1 ASTM Standards:
namic mechanical analysis measurement
D 3878 Terminology for Composite Materials
L = length of specimen
D 4065 Practice for Plastics: Dynamic Mechanical Proper-
W = width of specimen
ties: Determination and Report of Procedures
T = thickness of specimen
T = peak temperature from tangent delta curve
t
This test method is under the jurisdiction of ASTM Committee D30 on
4. Summary of Test Method
Composite Materials and is the direct responsibility of Subcommittee D30.04 on
4.1 Aflat rectangular strip of laminate is placed in the DMA
Lamina and Laminate Test Methods.
Current edition approved Dec. 15, 2007. Published January 2008.
equipment and oscillated at a nominal frequency of 1 Hz. The
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
specimen is heated at a rate of 5°C/min (9°F/min). The same
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
loading frequency and heating rate is used for both dry and wet
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. specimens (moisture conditioned) to allow for comparison.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
D7028–07
The temperature at which a significant drop in storage modulus sequence of a specimen with respect to the testing fixture have
(E’) begins is assigned as the glass transition temperature a profound effect on the DMA Tg result. A meaningful
(DMA Tg). The peak temperature of the tangent delta curve comparison of data requires that the specimen configuration be
(T) is identified along with DMATg for comparison purposes. the same. A non-standard specimen configuration shall be
t
described in the report and the result recorded as non-standard.
5. Significance and Use 6.6 The standard definition in this test method for DMATg
is based on intersecting two tangent lines from a semi-
5.1 This test method is designed to determine the glass
logarithmic plot of the storage modulus versus temperature.
transition temperature of continuous fiber reinforced polymer
OtherT definitions typically produce different test results. For
g
composites using the DMA method. The DMA Tg value is
example,alinearplotscalewillresultinalowervalueofDMA
frequently used to indicate the upper use temperature of
Tg. A non-standard DMA Tg definition shall be described in
compositematerials,aswellasforqualitycontrolofcomposite
the report and the result recorded as non-standard. For com-
materials.
parison purposes the peak temperature of the tangent delta
curve (T) is identified along with DMA Tg.
t
6. Interferences
6.1 The standard testing machine shall be of the Dynamic
7. Apparatus
Mechanical Analysis (DMA) type of instrument that operates
7.1 Micrometer,suitableforreadingto0.025mm(0.001in.)
with forced oscillation and applies a flexural loading mode
accuracy for measuring the specimen thickness and width.
(eitherthree-pointbendordualcantilever)tothetestspecimen.
7.2 Caliper, suitable for reading to 0.025 mm (0.001 in.)
Refer to Practice D 4065 for a summary of various other DMA
accuracy for measuring the specimen length and instrument
practices. Other loading modes (such as tensile, torsion or
clamping distance.
shear) may produce different test results. If another equipment
7.3 Dynamic Mechanical Analyzer (DMA), with oven ca-
type or loading mode is used the non-standard approach shall
pable of heating to above the glass transition temperature and
be described in the report and the test result recorded as
of controlling the heating rate to the specified value.
non-standard.
6.2 Afixedfrequencyof1Hzisstandardinthistestmethod.
8. Sampling and Test Specimens
In general, for a given material, a higher testing frequency
produces a higher DMATg value than this standard, while use 8.1 Two specimens shall be tested for each sample. If the
of the resonance mode will yield a different DMATg that may
testing is part of a designed experiment, other sampling
be either higher or lower than the standard. If a non-standard techniques may be used if described in the test plan.
frequency, or the resonance mode, is used, the non-standard
8.2 Consulttheinstrumentmanufacturer’smanualforspeci-
approach shall be described in the report and the test result men size. A span-to-thickness ratio greater than ten is recom-
recorded as non-standard. mended. Specimen absolute size is not fixed by this method as
6.3 Aheatingrateof5 61°C/min(9 62°F/min)isstandard various dynamic mechanical analyzers require different sizes.
inthistestmethod.Achangeinheatingratewillaffecttheglass Depending on the analyzer, typical specimen size can range
transition temperature result; the standard heating rate is the from 56 6 4 3 12 6 1 3 2.0 6 0.5 mm (2.21 6 0.16 3 0.47
best available compromise for comparing DMA Tg results of 6 0.04 3 0.08 6 0.02 in.) (L 3 W 3 T) to 22 6 1 3 3 6 1
dry and wet laminates. If a different heating rate is used it shall 3 1.0 6 0.5 mm (0.9 6 0.04 3 0.12 6 0.04 3 0.04 6 0.02
be described in the report and the result recorded as non- in.).
standard. 8.3 One of the major fiber directions in the specimen shall
be oriented along the length axis of the specimen. It is standard
NOTE 1—Users should be advised that a heating rate of 5°C/min
that one of the major fiber directions shall be parallel to the
represents a compromise between various issues related to Tg measure-
length of the specimen, and specimens containing only off-axis
ment precision and bias. It is widely known that heat transfer limitations
are more pronounced in DMA apparatus compared to other thermal plies shall not be used. Any deviations from the standard
analysis techniques, such as differential scanning calorimetry (DSC) and
orientation shall be reported and the test results noted as
thermomechanical analysis (TMA). For greatest precision, it has been
non-standard.
recommended that heating rates be 2°C/min or less. Test Method E 1640
8.4 The specimen surfaces shall be flat, clean, straight, and
specifies a heating rate of 1°C/min. However, in many cases 5°C/min is
drytopreventslippageinthegripsandmitigateanyeffectsdue
recommended as a compromise between Tg measurement accuracy and
to moisture. Opposite surfaces must be essentially parallel and
test method convenience, especially for wet laminate measurements, since
intersectingsurfacesperpendicular.Tolerancesinthicknessand
the slower heating rate will cause specimen drying that will itself bias the
results. width must be better than 62%.
8.5 Theselectedsampleshallbetakenfromarepresentative
6.4 Purge gas type and flow rate and the position of the
portion of the laminate. Laminate edges or other irregularities
thermocouple can affect the DMA Tg test result and shall be
created in the laminate by mold or bagging techniques should
noted and reported. The same conditions shall be used for both
be avoided.
calibration and testing runs. Instrumentation manufacturer
recommendations should be followed.
9. Calibration
6.5 It is standard in this test method that one of the major
fiber directions shall be parallel to the length of the specimen. 9.1 The DMA equipment shall be calibrated in accordance
The span-to-depth ratio, ply orientation, and ply stacking with Test Method E 1867 for temperature signals and in
D7028–07
accordance with the equipment manufacturer’s recommenda- 11.6 Strain Amplitude—The maximum strain amplitude
tionforthestoragemodulus.Theequipmentmustbecalibrated should be kept within the linear viscoelastic range of the
inthesameloadingmodeaswillbeusedfortesting,eitherdual material. Strains of less than 0.1 % are standard.
cantilever or three-point bending. The temperature calibration 11.7 Temperature Range—Programtheruntobeginatroom
points must span the DMA Tg result. temperature or a temperature at least 50°C (90°F) below the
estimated DMA Tg and to end at a temperature at least 50°C
(90°F) above DMATg, but below decomposition temperature.
10. Conditioning
11.8 Purge Gas Flow Rate—Follow the manufacturer’s
10.1 Moisture has significant effect on DMATg. Therefore,
manualorrecommendationstosetthepurgegasflowrate.Five
it is recommended that the test specimens should be weighed
litres/minute (0.2 CFM) is a typical purge gas flow rate setting.
before and after DMA Tg testing to quantify the moisture
For some types of dynamic mechanical analyzers, a purge gas
change in the specimen resulting from the DMA Tg test.
flow setting is not required.
10.2 Dry Specimens—Tominimizethepresenceofmoisture
11.9 Thermocouple Positioning—Follow the manufactur-
in the specimens, dry specimens must be conditioned prior to
er’s manual or recommendations to position the thermocouple.
testing by using either of the following techniques:
Typically the thermocouple should be as close to the sample as
10.2.1 Dry the specimens in an oven in accordance with
possible.
Test Method D 5229/D 5229M, Procedure D, then stored until
3 11.10 Test—Conduct DMA Tg measurements using the
test in a desiccator or sealed MIL-PRF-131 (or equivalent)
instrument settings specified and record the load and displace-
aluminized bag, or
ment data as a function of temperature.Allow the oven to cool
10.2.2 Store the material in a desiccator or sealed alumi-
before removing the specimen. Weigh the specimen after the
nized bag immediately after material curing (lamination),
test to the nearest milligram (0.001 g) after the removal from
where the material shall remain except for the minimum time
the oven and record.
required for removal during specimen preparation and testing.
11.11 Specimen Examination—Examine the specimen after
Themaximumtimebetweencure(lamination)andtestingshall
the test and inspect for any visual anomalies (that is, delami-
be 30 days, after which, prior to testing, specimens shall be
nation, blisters, cracks, etc.). Record any visual anomalies
oven-dried in accordance with 10.2.1.
observed.
10.3 Wet Specimens—Condition in accordance with Test
Method D 5229/D 5229M, Procedure B. The conditioned
12. Interpretation of Results
specimensshallbetestedwithin30minutesafterremovalfrom
12.1 Glass Transition Temperature (DMA Tg)—Plot the
theconditioningchamber,orstoredinsealedMIL-PRF-131(or
logarithm of storage modulus (E’) and linear tangent delta (tan
equivalent) aluminized bag until test.
d) versus the linear temperature (Fig. 1). During the glass
transition, the storage modulus of the composite material is
11. Procedure
significantly reduced. The DMA Tg is determined to be the
11.1 Test Specimen—Measure the specimen thickness and
intersection of two tangent lines from the storage modulus by
width to 0.025 mm (0.001 in.) and record. Measure the
this test method. The first tangent line (Line A, Fig. 1)is
specimenlengthto0.025mm(0.001in.)andrecord.Weighthe
selected at a temperature before the transition. This tempera-
specimen to the nearest milligram (0.001 g) and record.
ture is designated as TA. The second tangent line (Line B, Fig.
11.2 Specimen Installation—Install the specimen in the
1) is constructed at the inflection point to approximately the
DMA test equipment oven based upon clamping method to be
midpoint of the storage modulus drop. This temperature is
employed.
designated as TB. The two tangent lines are intersected, and
11.3 Positioning of Specimen—Follow the manufacturer’s
temperaturecorrespondingtothisintersectionpointisrecorded
procedure for positioning the specimen in the clamps. Gener-
as the DMATg. SeeAppendix X1 for additional guidelines to
ally, the spec
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