Designation:D3418−15
Standard Test Method for
Transition Temperatures and Enthalpies of Fusion and Crystallization of Polymers by Differential Scanning Calorimetry1
This standard is issued under thefixed designation D3418;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.
This standard has been approved for use by agencies of the U.S.Department of Defense.
1.Scope*
1.1This test method covers determination of transition temperatures and enthalpies of fusion and crystallization of polymers by differential scanning calorimetry.
N OTE1—True heats of fusion are to be determined in conjunction with structure investigation,and frequently,specialized crystallization tech-niques are needed.
1.2This test method is applicable to polymers in granular form or to any fabricated shape from which it is possible to cut appropriate specimens.
1.3The normal operating temperature range is from the cryogenic region to600°C.Certain equipment allows the temperature range to be extended.
1.4The values stated in SI units are the standard.
N OTE2—This test method does not apply to all types of polymers as written(see6.8).
1.5This 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 appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.
N OTE3—This standard is similar but not equivalent to ISO11357-1,-2, -3.The ISO procedures provide additional information not supplied by this test method.
2.Referenced Documents
2.1ASTM Standards:2
E473Terminology Relating to Thermal Analysis and Rhe-ology
E691Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method
E967Test Method for Temperature Calibration of Differen-tial Scanning Calorimeters and Differential Thermal Ana-lyzers
E968Practice for Heat Flow Calibration of Differential Scanning Calorimeters
E1142Terminology Relating to Thermophysical Properties E1953Practice for Description of Thermal Analysis and Rheology Apparatus
2.2ISO Standards:3
ISO11357-1Plastics—Differential Scanning Calorimetry (DSC)—Part1:General Principles
ISO11357-2Plastics—Differential Scanning Calorimetry (DSC)—Part2:Determination of Glass Transition Tem-perature
ISO11357-3Plastics—Differential Scanning Calorimetry (DSC)—Part3:Determination of Temperature and En-thalpy of Melting and Crystallization
3.Terminology
3.1Specialized terms used in this test method are defined in Terminologies E473and E1142.
4.Summary of Test Method
4.1This test method consists of heating or cooling the test material at a controlled rate under a specified purge gas at a controlledflow rate and continuously monitoring with a suitable sensing device the difference in heat input between a reference material and a test material due to energy changes in the material.A transition is marked by absorption or release of energy by the specimen resulting in a corresponding endother-mic or exothermic peak or baseline shift in the heating or cooling curve.Areas under the crystallization exotherm or fusion endotherm of the test materials are
compared against the respective areas obtained by the treatment of a well-characterized standard.
1This test method is under the jurisdiction of ASTM Committee D20on Plastics and is the direct responsibility of Subcommittee D20.30on Thermal Properties (Section D20.30.07).
Current edition approved May1,2015.Published June2015.Originally approved in1975.Last previous edition approved in2012as D3418-12ε1.DOI: 10.1520/D3418-15.
2For referenced ASTM standards,visit the ASTM website,,or contact ASTM Customer Service at For Annual Book of ASTM
Standards volume information,refer to the standard’s Document Summary page on the ASTM website.
3Available from American National Standards Institute(ANSI),25W.43rd St., 4th Floor,New York,NY10036,
*A Summary of Changes section appears at the end of this standard Copyright©ASTM International,100Barr Harbor Drive,PO Box C700,West Conshohocken,PA19428-2959.United States
5.Significance and Use
5.1Thermal analysis provides a rapid method for measuring transitions due to morphological or chemical changes,in a polymer as it is heated/cooled through a specified temperature range.Change in specific heat capacity,heat flow and tempera-ture values are determined for these transitions.Differential scanning calorimetry is used to assist in identifying specific polymers,polymer alloys,and certain polymer additives,which exhibit thermal transitions.Chemical reactions that cause or affect certain transitions have been measured with the aid of this technique;such reactions include oxidation,curing of thermosetting resins,and thermal decomposition.5.2This test method is useful for specification acceptance,process control,and research.
6.Interferences
6.1Differences in heating or cooling rate as well as the final heating and cooling temperature have an effect on the mea-sured results,especially on the enthalpy of fusion or crystalli-zation.Therefore,departure from conditions specified for a given polymer is not permitted.
degrade6.2The presence of impurities is known to affect the transition temperature,particularly if an impurity tends to form solid solutions,or to be miscible in the melt phase.
6.3Uncertain radiation losses at temperatures higher than 400°C have been known to affect the accuracy of results at times.
6.4Since particle size has an effect upon detected transition temperatures,the specimens to be compared shall be approxi-mately the same particle size (1-5).4
6.5In cases that specimens react with air during the temperature cycle,provision shall be made for running the test under an inert gas blanket to avoid any incorrect measurement.Since some materials degrade near the melting region,care must be used to distinguish between degradation and transition.6.6Since milligram quantities of a specimen are used,it is essential to ensure that specimens are homogeneous and representative.
6.7It is possible that toxic or corrosive effluents are released when heating the material,and be harmful to the personnel or to the apparatus.
6.8Not all polymers lend themselves to the exact terms of this test method.For some polymers such
as polyarylamides,crystallization is only possible from solution.For other poly-mers such as crystallizable polystyrene,annealing is only possible above their glass transition temperatures.When this test method is used for polymers of this type,carefully annealed samples must be tested without conditioning.
7.Apparatus
7.1Differential Scanning Calorimeter (DSC)—The essential instrumentation required to provide the minimum differential scanning calorimetric capability for this test method includes:
7.1.1DSC Test Chamber—This chamber is composed of the following:
7.1.1.1Furnace(s),to provide uniform controlled heating (cooling)of a specimen and reference to a constant temperature or at a constant rate within the applicable cryogenic to 600°C temperature range of this test method.
7.1.1.2Temperature Sensor,to provide an indication of the specimen temperature to 60.01°C.
7.1.1.3Differential Sensor,to detect heat flow difference between the specimen and reference equivalent to 1mW.7.1.1.4Means of Sustaining a Test Chamber Environment of purge gas at a purge
flow rate of 10to 5065mL/min.
N OTE 4—Typically,99+%pure nitrogen,argon or helium are employed when oxidation in air is a concern.Unless effects of moisture are to be studied,use of dry purge gas is recommended and is essential for operation at sub-ambient temperatures.
7.1.2Temperature Controller,capable of executing a spe-cific temperature program by operating the furnace(s)between selected temperature limits at a rate of temperature change of 0.5to 20°C/min constant to 60.1°C/min or at an isothermal temperature constant to 60.1°C.
7.1.3Recording Device,capable of recording and display-ing any fraction of the heat flow signal (DSC curve)including the signal noise as a function of temperature.
7.1.4Software,for integrating areas under endothermic valleys or exothermic peaks,or both.
7.1.5Containers (pans,crucibles,and so forth)that are inert to the specimen and reference materials;and that are of suitable structural shape and integrity to contain the specimen and reference in accordance with the specific requirements of this test method.
7.1.6Cooling capability to hasten cool down from elevated temperatures,to provide constant cooling r
ates of 0.5-20ºC/min to obtain repeatable crystallization temperatures,to achieve sub-ambient operation,or to sustain an isothermal sub-ambient temperature,or combination thereof.
7.2Balance,capable of weighing to 60.0001grams for transition temperatures and to 60.00001grams for determin-ing enthalpies.8.Sample
8.1Powdered or Granular Specimens—Avoid grinding if the preliminary thermal cycle as outlined in 10.1.3is not performed.Grinding or similar techniques for size reduction often introduce thermal effects because of friction or orientation,or both,and thereby change the thermal history of the specimen.
8.2Molded or Pelleted Specimens—Cut the specimens with a microtome,razor blade,hypodermic punch,paper punch,or cork borer (Size No.2or 3)or other appropriate means to appropriate size,in thickness or diameter and length that will best fit the specimen containers as in 7.1.5and will approxi-mately meet the desired weight in the subsequent procedure.8.3Film or Sheet Specimens—For films thicker than 40µm,see 8.2.For thinner films,cut slivers to fit in the specimen capsules or punch disks,if the circular specimen capsules are used.
4
The boldface numbers in parentheses refer to the list of references at the end of this test
method.
8.4Use any shape or form listed in 8.1–8.3except when conducting referee tests that shall be performed on films as specified in 8.3.9.Calibration
9.1The purge gas shall be used during calibration.9.2Calibrate the DSC temperature signal using Practice E967and the same heating rate to be used in this test method preferably 10°C/min or 20°C/min (see Note 5).(See Section 10for details.)
9.3Calibrate the DSC heat flow signal using Practice E968and the same heating rate as in 9.2(see Note 5).
9.4Some instruments allow for the temperature and heat flow calibration to be performed simultaneously.In such cases,use the same heating rate for this method and follow the manufacturer’s instruction.Report the heating rate.(See 12.1.3.)
N OTE 5—Use of other heating rates is permitted.However,test results are affected by the heating rate.See Table 1.It is the responsibility of the user of other rates to demonstrate equivalency to this te
st method.
10.Procedure
10.1For First-Order Transition (melting and crystalliza-tion):
10.1.1The purge gas shall be used during testing.The flow rate of the gas shall be the same as used in the calibration (9.1).10.1.2Use a specimen mass appropriate for the material to be tested.In most cases a 5-mg specimen mass is satisfactory.Avoid overloading.Weigh the specimen to an accuracy of 610µg.
10.1.2.1Intimate thermal contact between the pan and specimen is essential for reproducible results.Crimp a metal cover against the pan with the sample sandwiched in between to ensure good heat transfer.Take care to ensure flat pan bottoms.
10.1.3Perform and record a preliminary thermal cycle by heating the sample at the same rate used for testing from at least 50°C below to 30°C above the melting temperature to erase previous thermal history.
10.1.4When the effect of annealing is studied,selection of temperature and time are critical.Minimize
the time of exposure to high temperature to avoid sublimation or decom-position.In some cases it is possible that the preliminary thermal cycle will interfere with the transition of interest,causing an incorrect transition or eliminating a transition.Where it has been shown that this effect is present,omit the preliminary thermal cycle.
10.1.5Hold the temperature for 5min (10.1.3).
N OTE 6—In cases that high-temperature annealing cause polymer degradation,the use of shorter annealing times is permitted but shall be reported.
10.1.6Cool to at least 50°C below the peak crystallization temperature using the same rate that was used for heating and record the cooling curve.
10.1.7Hold the temperature for 5min.
10.1.8Repeat heating at the same rate used in 10.1.3(10°C/min or 20°C/min)and record the heating curve.Use this curve to calculate the enthalpies of transition.
10.1.9Measure the temperatures for the desired points on the curves:T eim ,T pm ,T efm ,T eic ,T pc ,and T eic (see Fig.1).Report two T pm ’s or T pc ’s if observed.
10.1.10In case of dispute determine T m and T c at a heating rate of 10°C/min.where:T eim =melting extrapolated onset temperature,°C,T efm =melting extrapolated end temperature,°C,T pm =melting peak temperature,°C,
T eic =crystallization extrapolated onset temperature,°C,T pc =crystallization peak temperature,°C,and
T efc =
crystallization extrapolated end temperature,°C.
N OTE 7—The actual temperature displayed on the temperature axis depends upon the instrument type (for example,specimen temperature,program temperature,or specimen-program temperature average).Follow any recommended procedures or guidelines of the instrument manufac-turer to obtain specimen temperature at the point of interest.
10.2For Glass Transition:
10.2.1The purge gas shall be used during testing.The flow rate of the gas shall be the same as used in the calibration (9.1).10.2.2Use a specimen mass appropriate for the material to be tested.In most c
ases,a 10-mg specimen mass is satisfactory.Weigh the specimen to an accuracy of 610µg.
10.2.3Perform and record a preliminary thermal cycle by heating the sample at a rate of 20°C/min from at least 50°C below to 30°C above the melting temperature to erase previous thermal history.
10.2.4Hold the temperature for 5min.(See Note 6.)
10.2.5Quench cool to at least 50°C below the transition temperature of interest.
10.2.6Hold the temperature for 5min.
10.2.7Repeat heating at a rate of 20°C/min,and record the heating curve until all desired transitions have been completed.(See Note 5.)
10.2.8The glass transition is more pronounced at faster heating rates.A heating rate of 20°C/min is the preferred
TABLE 1Effect of Rate of Temperature Rise on Transition Temperatures
Material Rate of Temperature Rise (°C /Min.)
T g Second Heat (°C)T c (°C)T m First Heat (°C)
T m Second Heat (°C)
PEEK 5Too Weak 298.1342.2341.7PEEK 10Too Weak 293.4339.4340.2PEEK 20150.6287.2339.0338.7PEEK
40156.0
277.7341.4338.2Syndiotactic PP 5Non Observed 75.0131.1130.7Syndiotactic PP 10Non Observed 70.0129.4129.8Syndiotactic PP 20Non Observed 64.9127.9129.1Syndiotactic
PP
40
Non Observed
58.8
130.1
130.4
heating rate for T g measurements.The instrument shall be calibrated at the same heating rate used for testing.If both first-and second-order transitions (T m and T g ,respectively)are to be determined in the same run,use the same heating rate as used in 10.1.8for both transitions and determine results from the second heating step (10.1.8).Report the heating rate.(See 12.1.3.)
N OTE 8—T g obtained using Procedure 10.1will be different from T g measured using procedures 10.2.3–10.2.7.Therefore,the heating rate must be reported as described in 12.1.3.
10.2.9In case of dispute determine T g at a heating rate of 20°C/min.
10.2.10Measure temperatures T eig ,T mg ,and T efg (see Fig.2):
where:
T eig =extrapolated onset temperature,°C,T mg =midpoint temperature,°C,and T efg =extrapolated e
nd temperature,°C.
A new baseline will likely be established after the transition,rather than a peak (see Note 9).For most applications,the T mg temperature is more meaningful.In those cases,designate T mg as the glass transition temperature (T g )in place of the extrapo-lated onset for the glass transition curve.
N OTE 9—Stress relaxation peaks,caused by annealing,that appear in
some polymers above the glass transition are normally eliminated by the preliminary thermal cycle and a new baseline will be established after the transition.
11.Calculation for Heat of Fusion and Crystallization 11.1Construct a baseline by connecting the two points at which the melting endotherm or freezing exotherm deviate from the relatively straight baseline,caused by a signal that is proportional to the difference in heat flow between the refer-ence and specimen capsules (Fig.3and Fig.4).
11.2The method described in 11.1is not applicable for certain materials.In such cases,other graphical means must be developed for enclosing the peak areas as agreed upon between the manufacturer and the purchaser (4-8).
11.3Integrate the area under the fusion heat flow endotherm or crystallization exotherm as a function of time to yield enthalpy or heat (mJ)of the transition.
11.4Calculate the mass normalized enthalpy or heat of transition by dividing the enthalpy obtained in 11.3by the mass of the test specimen.Report this mass normalized enthalpy of transition (J/g).12.Report
12.1Report the following
information:
FIG.1First-Order Transition of
Nylon
12.1.1Complete identification and description of the mate-rial tested,including source,manufacturer’s code,12.1.2Description of instrument used for the test,
12.1.3Statement of the mass,dimensions,geometry,and materials of the specimen container,and the heating rate.12.1.4Description of temperature calibration procedure,
12.1.5Identification of the sample atmosphere by purge gas flow rate,purity,and composition,including humidity,if applicable,
12.1.6Results of the transition measurements using the temperature parameters cited in Fig.1,or any combination of parameters suitable for the purpose in hand.T pm and T eic
that
FIG.2Assignment of Glass Transition of Poly(Methyl Methacrylate)
(PMMA)
FIG.3Typical Heating Curve for
Polyethylene
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