Embed Size (px)
Citation preview
S p r i n g 2 0 0 2
Featured Technical Articles
How Tzero™ Technology Improves DSC Performance – Part III. The Measurement of
Specific Heat CapacityDr. B. Cassel
Specific heat capacity (Cp) measurement
by traditional DSC using the ASTM E1269
method is a time consuming procedure for
determining structure change. Advanced
Tzero™ technology, available
only in the Q1000 DSC, offers
significant advantages in
ease and reliability of the
measurement. Full Article
Characteristics of Tg Detection Using Micro
Thermomechanical AnalysisCarlton G. Slough
Glass transition (Tg) detection is an
important measurement in the thermal
analysis of polymers. This paper
discusses how a new technique, Micro
Thermomechanical Analysis
(µTMA™) can make Tg
measurements on very
small (cubic micrometer)
sections of a sample.Full Article
One lucky attendee will win a FREE Portable DVD Player! Offer valid until 5/30/02.
Space is limited, so visit www.tainst.com/new/showcases.htmlfor course details and register today!
18 MONTHS...18 NEW PRODUCTSLearn about the latest thermal analysis and rheology innovations in a convenient web-based format. Each topic is a separate course and youcan attend only the one that interests you.
Tzero™ DSC Technology
Tzero™ DSC and Pharmaceutical Applications
New Q800 Dynamic Mechanical Analyzer
New Rheometer Technology
New Q Series™ Thermal Analysis Technology
New 2990 µThermal Analyzer
e-Product Showcases!
Full Article
TA Instruments is proud to introduce our NEWQuickStart e-Training Courses. These internet based courses are designed to teach a new
user how to set up and run samples on their thermal analysis and rheology instrument.
Quick Start e-Training Courses
TECH Talk
New ProductBrochures
Training Courses
New Staff atTA Instruments
Conferences &Exhibitions
FREE Posters –Rheology
Thermal Analysis
FREE PolymerReference Card
2002 Parts andAccessories Price Guide
DEMODEALS
P R O M O T I O N S
Trade-In
HOTLINE P1 Spring 02 5/13/02 8:40 AM Page 1
Tech TalkThis section will provide technical notes, helpful hints, and service advice, and specific information on thermal analysis and
rheology instrumentation and use. The goal is to help you get maximum value from your TA Instruments equipment.
Technical DocumentsTwo excellent technical articles are available for easy download. The first, written by Sujan Bin Wadud of our rheology
staff, has a dynamic mechanical analysis (DMA) focus. It describes the application of the Time Temperature Superposition
principle to creep data on films or fibers that are wound on spools at high speed and then stored for a period
of time. (DMA creep data.pdf)
The second is written by software engineer, Ben Crowe, and relates to optimization of heater PID settings during
the execution of any thermal method (Q Series™ instruments only). This can be done by the user and has significant value
in “tuning” the furnace for high performance special applications such as in DSC isothermal crystallization studies.
(heater PID.pdf)
HINTSLosing a TGA pan in a vertical furnace rarely happens, but if it does, here’s a hint for retrieving it. Wrap the tip and end of
a 30 cm piece of 6.3 mm (1/4 inch) diameter Tygon‚ tubing with double-sided tape. Carpet tape, available from your local
hardware store, work best. This forms a flexible finger with a tacky end that may be put into a COLD TGA furnace to pull
out a lost pan.
Once you have prepared a sample and reference pan for a DSC experiment, it is often difficult to tell which pan is which.
One may identify the reference pan by scratching an “X” on the top with tweezers as soon as the pan is crimped. One may
collect a series of different reference pans (Al, Cu, Pt, AU, etc.) in a small box (such as that for
sample pans). Then the appropriate reference pan may be selected from your collection when needed.
HOME
REWARDS FOR HINTSIn the summer 2001, a new HINTS feature was added to the Hotline. These suggestions on how to do better or
easier thermal analysis were very popular. So we are looking for more to pass along. Do you have such a hint that
you would like to offer? Send it to us and if we use it, we’ll send to you a certificate worth $50 on your next purchase
of supplies, services or equipment. Send your hints to [email protected].
HOME
NEWBROCHURES –
Click on the cover to download abrochure
OVERVIEW
DMATGADSC
RHEOLOGY
Training Courses
HOME
2002 U.S. COURSE SCHEDULEThermal Analysis and Rheology Training Courses
Monday Tuesday Wednesday Thursday Friday
TGA DSC MDSC DMA RheologyFebruary 18 February 19 February 20 February 21 February 22
TGA DSC MDSC DMAApril 15 April 16 April 17 April 18
DSC TGA DMA RheologyJune 10 June 11 June 12 June 13
TGA DSC MDSC DMAAugust 12 August 13 August 14 August 15
DSC TGA DMA RheologyOctober 7 October 8 October 9 October 10
TGA DSC MDSC DMA RHEOLOGYDecember 9 December 10 December 11 December 12 December 13
The TMA training course will be taught over the Internet in 2002.
TMA Part I TMA Part IIMarch 25 March 26 1:00 - 3:00 PM (Eastern Time)
April 8 April 9 1:00 - 3:00 PM (Eastern Time)
More Information and Course Outlines
We are pleased to introduce Jeremy Smith, as our new Technical Representative for
Delaware, Maryland, Washington DC, and parts of Northern Virginia and West Virginia
(see www.tainst.com; “Contact Us” section of our website for details). Jeremy has
completed an extensive training program, and is now actively involved in selling our
thermal and rheology products. He holds a BS degree in Chemical Engineering and has
several years experience in sales of laboratory equipment. Jeremy will be based
in Delaware. He replaces Chris Kleespies, who has been promoted to Eastern District
Sales Manager.
New Staff at TA Instruments
TA Instruments continues to grow and add staff worldwide. Some of our new employees are detailed below.
We are also are pleased to introduce David Jacobson, as Territory Manager
responsible for thermal and rheology product sales in Minnesota, Iowa, Wisconsin,
North and South Dakota, and parts of Michigan. (see www.tainst.com; “Contact Us”
for details). David resides in Shakopee (MN), holds a BS degree in Chemistry from the
University of Wisconsin (Madison), and has extensive experience in sales of analytical
instrumentation. He replaces Tim Sadowski, who is now Western District Sales Manager.
HOME
Conferences and Exhibitions
Pittsburgh Conference 2002The recent Pittsburgh Conference, held in New Orleans (March 18-22, 2002), was very successful for TA Instruments.
Displayed for the first time was the new Q600 Simultaneous DSC / TGA and the new Q800 Dynamic Mechanical Analyzer.
An enhanced Polymer Library, containing MWD capability, was also introduced as an option for Rheology Advantage
software (RA4).
As a joint 2002 Pittcon / Analytica customer promotion, TA Instruments offered a
new Q100 with Tzero™ technology to a lucky customer who visited our booths.
We are pleased to announce that Mr. Joachim Trick of Daimler Chrysler, Stuttgart,
Germany is the winner. The picture shows him receiving the award from
Wolfgang Künze, our country manager. Mr. Trick comments that "this award will
be used for the quality control of polymers used in our passenger cars
and trucks, and will greatly assist our high quality approach. Daimler Chrysler
greatly appreciates the generosity of TA Instruments in making this award."
30th Annual Conference — North American Thermal Analysis SocietyConference: September 23-25, 2002 Short Course: September 21-22, 2002
Pittsburgh Marriott City Center, Pittsburgh, Pennsylvania
Register or join on-line: please visit www.natasinfo.org
For more information call: 916-922-7032
Additional EventsA listing of other national conferences / exhibitions being held during the 2Q / 3Q of 2002, where TA Instruments thermal
analysis and rheology equipment will be displayed are is follows:
HOME
2002 EUROPEAN EVENT SCHEDULEDate Meeting Location Country
May 15th Laborama Liege Belgium
May 16 – 17 Belgium Polymer GroupUniversity of Mons
Belgium(organizers)
May 29 – 31 Thermal Analysis Congress Massy France
May 30 Laborama Gent Belgium
June 11 – 14 Kemiforum Stockholm University Sweden
June 11 - 14 IWPCPS Pharm. Workshop Oxford University UK
June 12 – 14 Nordic Rheology Conference Gothenburg Sweden
June 26 – 27 Surfex Manchester UK
More Information: [email protected] [email protected] [email protected]
[email protected] [email protected] [email protected]
2002 NORTH AMERICAN EVENT SCHEDULEDate Meeting Location
May 5 – 9 SPE ANTEC San Francisco, CA
May 13 – 15 SAMPE Long Beach, CA
May 14 – 15Canadian Thermal Analysis
Mississauga, Ont, CanadaSociety Meeting
June 16 – 19Inst. Food Technologists
Anaheim, CAMeeting
August 19-21 ACS National Boston, MA
QuickStart e-TrainingTA Instruments is proud to introduce our NEW QuickStart e-Training Courses. These internet
based courses are designed to teach a new user how to set up and run samples on their
thermal analysis and rheology instrument. These courses, starting in June 2002, will be offered
at $250 per class and will run 60-75 minutes in length. New purchasers of covered instruments
will get a waiver for one free class per instrument purchased. These courses are in addition to
the installation &training provided by our service engineers, and our Application & Theory course
given every other month in Delaware.
The QuickStart e-Training presentations will cover our DSC, TGA, DMA, & Rheology
instruments and Universal Analysis (data analysis) software. (See specific instruments covered
below). These courses will be taught at regular intervals starting June 2002. We’ve made these
courses easy to attend by bringing them to you, via the Internet. You will be able to log-in
from your office or home and see the presentations on your computer. You will call in to a
teleconference number and be able to hear the instructor, and be able to ask questions.
As always with TA Instruments, every course is presented by an experienced thermal analyst,
who has the knowledge to answer your questions.
HOME
Instruments covered:
• Q10, Q100, & Q1000 DSC’s
• Q50 & Q500 TGA’s
• Q800 & 2980 DMA
• AR500, AR1000, & AR2000 Rheometers
Attendees will receive:
• A basic understanding of the instrument
• Instruction on calibration and routine maintenance
• Tips on how to prepare samples
• Instructions on setting up experimental runs and method development
• How to run samples
• Steps for analyzing data collected
Register Now!
COURSE LOCATION:DELAWARE TECHNICAL & COMMUNITY COLLEGE
400 Stanton-Christiana Road
Newark, Delaware 19713-1260
COURSE DESCRIPTION:The TA Instruments Thermal Analysis and Rheology training courses (lecture based) are designed to familiarize the
user with applications, method development, and operating techniques of the TAI thermal analysis and rheology
instrumentation. Each course day is specific to a particular technique so users receive the maximum instructional benefit
by attending only those course days applicable to their instrumentation. You should only attend course days for which you
already have instruments. The course start time is 8:30 a.m. The length varies depending on the instrument (see attached
outlines).
The full training course includes instruction on the following thermal analysis and rheology products:
2000, 2900 and Q Series Thermal Analysis modules (DSC, MDSC, TGA, TMA, DMA); and AR500, AR1000 and AR2000
Rheology instruments.
WHO SHOULD ATTEND?This course is designed for the scientist, engineer, or technician who desires a more comprehensive understanding of
Thermal Analysis and Rheology techniques. The course is lecture based and includes a balance between theory and
practical applications. Attendees should have a minimum of two months of hands-on instrument operating experience to
obtain the maximum benefit from this course.
Registrants with arrangement questions about this course should contact Cathy Palopoli, course registrar,
at (302) 427-4107 or e-mail [email protected].
MEALS AND HOUSINGFollowing is a list of convenient hotels within walking distance of the course site. You will need to make your own
reservations. Rates are subject to change without notice.
Fairfield Inn Christiana Hilton Homestead Studio Suites65 Geoffrey Drive 100 Continental Drive 333 Continental Drive
Newark, DE 19713 Newark, DE 19713 Newark, DE 19713
(302) 292-1500 (302) 454-1500 (302) 283-0800
$76.00 + Tax $199.00 + Tax $65.00 + Tax
Marriott Courtyard Shoney’s Inn48 Geoffrey Drive 900 Churchmans Road
Newark, DE 19713 Newark, DE 19713
(302) 456-3800 (302) 368-2400
$145.00 + Tax $60.00 + Tax
Breakfast and lunch during the course will be provided. You will be on your own for dinner.
(continue)
TRANSPORTATIONThe college and hotels are approximately a 40-minute drive from the Philadelphia International Airport. Car rentals are
available at the airport or at the Wilmington Amtrak Train Station.
REGISTRATIONThe tuition fee for each module course date is $400.00. Tuition is waived for one individual with the purchase of your
module(s) and is valid for one year. The tuition fee for additional attendees is $400.00 per module. Payment should be
made by check or credit card (Mastercard, Visa or American Express) at the time of registration.
The training course is offered 4-6 times per year (depending on module). Registration for a particular session closes
four weeks prior to the course. Applicants for a filled session will be rescheduled by telephone for the first mutually
acceptable date.
Registrations should be sent to:Cathy Palopoli
TA Instruments
109 Lukens Drive
New Castle, DE 19720
FAX: (302) 427-4164
Checks should be made payable to TA Instruments - Waters LLC and sent to Cathy Palopoli at the above address.
A confirmation of enrollment and a map/directions to the training course facility and hotels will be mailed when payment or
tuition waiver form is received.
(View Training Course Outlines)
(Registration Form)
DIFFERENTIAL SCANNING CALORIMETRY (DSC)Training Course Outline
(Length: Full Day - approximately 4:30 pm)
I. Theory & Operation• Calorimeter Theory
• Heat Flux Dsc Design
• Purge Rates
ll. Calibration & Sample Preparation• Baseline Calibration
• Temperature Calibration
• Sample Preparation
lll. Glass Transition• What Is It?
• How Is It Observed and Measured?
• What Affects The Glass Transition?
IV. Melt• What Is It?
• How Is It Observed and Measured?
• What Affects The Melting?
V. Crystallization• What Is It?
• How Is It Observed And Measured?
• What Affects The Crystallization?
Vl. Heat Capacity/Mdsc• What Is It?
• How Is It Observed and Measured?
• What Affects The Heat Capacity?
MODULATED DIFFERENTIAL SCANNING CALORIMETRY (MDSC)Training Course Outline
(Length: Full Day - approximately 4:30 pm)
Special Note to MDSC UsersIf you are a new MDSC user, you should plan to attend the DSC course prior to attending the MDSC course.
The MDSC course assumes a knowledge of general DSC principles.
I. Theory
Il. Calibration and sample preparation
Ill. Application of MDSC to characterization of heat Capacity including the glass transition
lV. Application of MDSC to characterizationof melting and crystallization.
V. Theoretical problems associated withmeasurements over the melting region
Vl. Selecting optimum conditions
Vll. Interpreting results
Vlll. Typical applications where MDSC provides a benefit over DSC
(continue)
(continue)
THERMOMECHANICAL ANALYSIS (TMA)Training Course Outline
(Length: 3/4 day - approximately 2:30 pm)
I. Theory & Operation• Theory
• Experimental Parameters
• Operating Suggestions
ll. Calibration• Mass
• Temperature
• Baseline
lll. Maintenance• Changing Hang Down Wire
• Thermocouple Replacement
• Maintaining Heat Exchanger
• Cleaning Furnace Housing
IV. Software• Software
• Instrument Control for Windows NT
• Universal Analysis
V. Applications• Thermal Stability
• Compositional Analysis
• Oxidative Stability
• High Resolution TGA
• Simultaneous TGA-DTA (SDT 2960)
• Evolved Gas Analysis
THERMOMECHANICAL ANALYSIS (TMA)Training Course Outline
(Internet Course / 1:00-3:00 PM Eastern Time)
I. Introduction• Theory
• Hardware
ll. Sample Preparation and Operating Conditions
lll. Calibration
IV. Applications• Expansion
• Penetration
• Flexure
• Tension
(continue)
DYNAMIC MECHANICAL ANALYSIS (DMA)Training Course Outline
(Length: Full Day - approximately 4:00 pm)
I. Theory• Linear Viscoelasticity
• Transient Testing (Creep and Stress Relaxation)
• Dynamic Mechanical Analysis
• TMA Controlled Force Mode
ll. DMA 2980 - The Instrument• Instrument Design
• Experimental Considerations
• Sample Considerations and Clamp Selection
• Instrument Parameters
lll. Calibration• Clamp Calibrations
• Position Calibration
• Instrument Calibration
IV. Applications of DMA• Transitions
• Crystallinity
• Crosslinking
• Curing
• Aging
• Effect of Fillers
• Blends/Copolymers
V. Time-Temperature Superposition• Theory
• Guidelines for Tts
• Running TTS Experiment
RHEOLOGY TRAINING COURSE(Length: Full Day - approximately 4:00 pm)
This lecture based course is designed to familiarize the novice user of the Rheometer with its potential as a problem
solver in product formulation and evaluation. It is also hoped that elements of procedure optimization will be
demonstrated for a variety of samples. The three main techniques that will be covered are as follows:
A. FlowThis section will deal with the measurement of shear viscosity by controlled stress and rate methodologies, and using
ramped and equilibrium shear regimes to access complete flow curves. Flow curve modeling via the software will be
discussed.
B. CreepThis section of the course will familiarize the attendees with the measurement of low shear flow measurement as well
as the use of viscoelastic modeling and the significance of the Voigt unit.
C. Oscillation/Dynamic TestingHere, further aspects of linear viscoelastic behavior will be explored, including the mathematical significance of
mechanical moduli in samples, the measurement of thixotropy and thermal changes in materials and the more tradi-
tional frequency/time domain probes.
The course will cover theoretical background and the basics of sample evaluation.
NAME:
COMPANY:
ADDRESS:
PHONE: Fax:
Email:
Please check below the portion of class you are attending and enclose payment with the application.
Remember to include course date(s) at the top of this form. Course outlines are attached.
DSC Course TGA/SDT Course DMA Course
Date Date Date
Modulated DSC TMA Internet Course Rheology Course
Date Date Date
Checks should be made payable to Credit Card Payments - Amount $
TA Instruments - Waters LLC and should be
sent, along with this application form, to: Credit Card
Cathy Palopoli Account #
TA Instruments
109 Lukens Drive Expiration Date
New Castle, DE 19720
Fax: (302) 427-4164 Cardholder Name
Note: Please return this form as soon as possible to ensure acceptance and the date of Your choice.
Enrollment is on a first come basis.
• Applicants may cancel up to 10 days prior to the course for a full refund.
• Applicants who have not canceled reservations 10 working days prior to the course are subject to the entire tuition
charge or forfeit of tuition waiver.
THERMAL ANALYSIS / RHEOLOGY TRAINING COURSE
Application for Enrollment
FREE Rheology Poster FREE Thermal Analysis Poster HOME
For your FREE Polymer Reference Card email – [email protected]
w w w . t a i n s t . c o m
i n f o @ t a i n s t . c o m e - m a i l
i n t e r n e t
TA Instruments109 Lukens Drive, New Castle, DE 19720
(302) 427-4000
compliments of
Common PolymersReference Card
Symbol Reference Standard Tm(˚C) Hm(J/g)
In Indium 156.61 28.71Sn Tin 231.95 60.6Pb Lead 327.46 23.1Zn Zinc 419.53 108.0Ag Silver 961.93 –Au Gold 1064.43 –
C a l i b r a t i o n s t a n d a r d s
w w w . t a i n s t . c o m
U s e f u l C o n v e r s i o n s1 Pa = 10 dynes/cm2
1 psi = 6895 Pa1 psi = 6.895 x 10-3 MPa
1 Pa = 0.000145 psi1 MPa = 1,000,000 Pa
1 GPa = 1,000 MPa1 Newton = 101.97 g force
1 Joule = 0.239 calories1 calorie = 4.184 Joules
˚F = 9/5 (˚C) + 32˚C = 5/9 (˚F - 32)
10 Poise = 1 Pa sec
C o m m o n P o l y m e r s R e f e r e n c e
ABS Acrylonitrile 110 – 125 – 375 65 – 95 2070 – 4140Butadiene styrene
PMMA Polymethylmethacrylate 85 – 110 160 313 50 – 90 2240 – 3170Acrylonitrille 95 135 – 66 3450 – 4070
PTFE Polytetrafluoroethylene 126* 327 525 70-120 525PVDF Polyvinylidene fluoride -60 – -20 170 – 178 470 70-142 1724 – 2896Nylon 6 Nylon 6 40 – 87* 210 – 220 400 80 – 83 2690Nylon 6,6 Nylon 6,6 50* 255 – 265 426 80 2830 – 3240PC Polycarbonate 140 – 150 – 473 68 2350PBT Polybutylene terephthalate – 220 – 287 386 60 – 95 2280 – 2760PET Polyethylene terephthalate 73 – 80 245 – 265 414 65 2410 – 3100PEEK Polyetheretherketone 150 334 575 40 – 108 3860PEI Polyetherimide 215 – 217 – – 47 – 56 3310LDPE Low density Polyethylene -25 98 – 115 459 100 – 220 240 – 330HDPE High Density Polyethylene 60 – 80 130 – 137 469 59 – 110 1000 – 1550PI Polyimide – 310 – 365 – 45 – 56 3100 – 3450PPO Polyphenylene Oxide 100 – 142 – 400 38 – 70 2250 – 2760PPS Polyphenylene Sulfide 88 285 – 290 508 49 3790PP Polypropylene -20 160 – 175 417 81 – 100 1170 – 1720PS Polystyrene 74 – 109 240 – 250 351 50 – 83 2620 – 3380PSO Polysulfone 190 – 510 56 2690PES Polyethersulfone 220 – 230 – – 55 2400 – 2620PVC Polyvinyl Chloride 75 – 105 – 265 50 – 100 2070 – 3450
Acronym Polymer Tg(˚C) Tm(˚C) TGA** Linear CTE FlexuralDecomp T (˚C-1) Modulus (MPa)
Source: Modern Plastics Encyclopedia, Mid-October Issue, Vol. 66, No. 11, McGraw Hill, Inc., New York, New York, 1989.*Polymer Handbook, Second edition, J. Brandrup, E.H. Immergut, John Wiley and Sons, New York, New York, 1975.**TA Instruments Library (heating rate of 20˚C/min.).
1 TA287
Time-Temperature Superposition Using DMA Creep Data
Sujan E. Bin WadudTA Instruments, Inc., 109 Lukens Drive, New Castle, DE 19720
ABSTRACT
The principle of time-temperature superposition (TTS) extends the range offrequencies or times of viscoelastic properties beyond that measurable. It provides aunique way of estimating material viscoelastic properties over time. This principle issuccessfully used to determine the long-term properties of a magnetic tape/film heldunder a stress. Multiple creep experiments show excellent repeatability of 2.3 %.
INTRODUCTION
The concept of time-temperature superposition (TTS) comes from the observationthat the time-scales of the motions of constituent molecules of a polymer are affected bytemperature. More specifically, the motions or relaxations occur at shorter times at hightemperatures (1). Furthermore, by assuming that the whole relaxation spectrum of apolymer can be affected by increasing temperature, it is possible to look at the long-timeproperties of materials by simply changing the temperature.
From an experimental point of view, data from oscillation frequency sweeps, andcreep and stress-relaxation experiments performed at various isothermal temperatures canbe superposed to a reference temperature. These tests may be performed on solidpolymer samples using a DMA or melts using a rheometer.
A good application of TTS is the changing mechanical properties of films/fiberswound on a spool at high speeds and then stored. During production, tension ismaintained while winding the film/fiber. Under this tension, the materials stretch withstorage time. Creep is a perfect analogue of this process as a stress is applied to sampleand the deformation observed over time. It is shown that with creep TTS, the resultantinformation is extended to months, even years.
EXPERIMENTAL
The test sample is a film cut from a roll of magnetic tape, similar to that of audioor videotape. Such film is wound at high speeds onto the spool and stored, awaitingshipment. The width and thickness were 8.00 mm and 8 µm, respectively.
The tension-film clamp of the TA Instruments Q800 Dynamic MechanicalAnalyzer is used in all experiments. The loading of the sample requires some care toassure that there was no twists or folds. Improper loading becomes evident when thesample appears to be “breathing” when the MEASURE button is pressed and the
2 TA287
oscillations begin. When the sample is correctly loaded, the tensile oscillations do“pulse” when viewed from the side. The MEASURE step also determines the exactlength of the sample. The temperature range was 30 to 165 °C, in 5 °C steps. The 10MPa creep stress is applied for 10 min at each temperature. All these parameters areentered using the Creep TTS template available in the TA Instruments ThermalAdvantage software.
RESULTS AND DISCUSSION
All the log-log creep curves are overlaid in Figure 1 with compliance on the Y-axis and time on the X-axis. The increase in compliance with increasing temperature isclearly seen. This is expected since at higher temperatures, the relaxation occurs in ashorter time, enabling the sample to deform under the stress producing highercompliance.
3-1 0 1 2Log [time (s)]
-8
-10
-9
Log [compliance J(t) (m
^2/N)]
*30.0
35.040.045.050.055.060.0
65.070.075.080.085.0
90.095.0100.0105.0110.0115.0
120.0125.0130.0135.0140.1
145.0
30¡C
F i g u r e 1 - Cr e e p Cu r v e s f o r T T S i n t h e T h e r m a l Ad v a n t a g e T T S S o f t w a r e
If the selected reference temperature is taken at 30 °C and the shifting performedautomatically by the software, then the mastercurve shown in Figure 2 is obtained. Thedata spans a time range of approximately 0.1s to 1012 s (ca. 300 centuries).
Such an experiment shows that the sample is stretched with time. It is possible tocharacterize several such samples with known behavior and generate a data library. Themastercurve of a new product may then be compared with those in the library to estimatebehavior over time.
To test the repeatability of creep measurements, replicate experiments areperformed at 30 °C as shown in Figure 4. A comparison of compliance values at 8 min,produces a mean value of 364 µm2/N with a relative standard deviation of ± 2.3 %. SinceTTS is performed on log scales, the repeatability on this presentation is even better asshown in Figure 4.
3 TA287
13-2 -1 0 1 2 3 4 5 6 7 8 9 10 11 12Log [time (s)]
-8
-10
-9
Log [compliance J(t) (m
^2/N)]
30¡C
*30.035.0
40.045.0
50.055.0
60.065.0
70.075.0
80.0
85.090.0
95.0100.0
105.0110.0
115.0120.0
125.0130.0
135.0
140.1145.0
F i g u r e 2 - T T S Ma s t e r c u r v e at 30 ° C .
SUMMARY
TTS is a very useful tool to look at long-term mechanical properties of materials.It is shown that there is stretching of wound magnetic tapes with time due to the stressduring winding. The DMA is a superior analytical tool, with excellent repeatability, topredict the long-term mechanical properties of materials when used in conjunction withTTS principles. The TA Instruments Advantage software allows easy shifting of rawdata to generate a mastercurve (just 5 easy clicks of the mouse from starting a session to acomplete mastercurve!).
REFERENCES
1. John D. Ferry, Viscoelastic Properties of Polymers, 3rd Ed., John Wiley & Sons,1980, Chapter 11.
KEYWORDS
creep/stress relaxation, dynamic mechanical analysis, films/fibers, relaxations
4 TA287
362.5µm̂ 2/N
8.000min376.3µm̂ 2/N
353.9µm̂ 2/N
359.5µm̂ 2/N
367.3µm̂ 2/N
0
100
200
300
400
Cre
ep
C
om
pli
an
ce
(µ
m^
2/N
)
0 2 4 6 8 10 12 14 16
Decay Time (min)
Imation Magnetic Tape 1Imation Magnetic Tape 2Imation Magnetic Tape 3Imation Magnetic Tape 4Imation Magnetic Tape 5
Universal V3.1E TA Instruments
F i g u r e 3 - Cr e e p at 30 ° C
10
100
1000
Cre
ep
C
om
pli
an
ce
(µ
m^
2/N
)
0 2 4 6 8 10
Decay Time (min)
Imation Magnetic Tape 1Imation Magnetic Tape 2Imation Magnetic Tape 3Imation Magnetic Tape 4Imation Magnetic Tape 5
Universal V3.1E TA Instruments
F i g u r e 4 - Cr e e p Co m p l i a n c e Re p e a t a b i l i t y at 30 ° C .
1 TN 47
THERMAL APPLICATION NOTE
USING THE HEATER PID METHOD SEGMENT
Benjamin S. CroweTA Instruments, 109 Lukens Drive, New Castle DE 19720
The Heater PID method segment is used to change the performance of theinstrument furnace during the execution of a thermal method. PID stands forProportional, Integral, and Derivative, the three modes of traditional temperature control.The Heater PID segment specifies the control coefficients for each mode of temperaturecontrol. The instrument furnace is run by a control system that uses factory default PIDcoefficients. The default coefficients are automatically set and adjusted to give excellentfurnace performance under various operating conditions. However, sometimes it may beuseful to further optimize furnace performance for all or part of a specific method.
The Heater PID method segment provides the ability to change controlcoefficients while a thermal method is running. Every time the instrument is reset or amethod ends, the three PID coefficients are reset to their factory default settings. When aHeater PID segment is encountered in a running method, the current PID furnace controlcoefficients are immediately replaced with new coefficients from the Heater PID methodsegment. The new coefficients are used to control the furnace for the remainder of themethod, or until another Heater PID method segment is encountered. Determining what PID coefficients to use requires some trial and errorexperimentation on the part of the user. A general description of each control mode andadvice for determining useful parameters is provided below.
Proportional Control
Proportional control mode provides furnace power in direct proportion to thedifference (error) between the measured furnace temperature and the desired furnacetemperature. When the error is zero the applied power is zero. As the error increases theapplied power to the furnace is increased in proportion to the error until a maximumpermitted power is reached. Beyond this maximum power point, and at zero power, thefurnace is said to be “out of control”. The temperature error range between theapplication of zero power and maximum power is called the proportional band or “propband”.
The PID Proportional coefficient (W °C-1) determines the width of theproportional band. A coefficient of 1.0 delivers one watt of power for every °C oftemperature error. The maximum power available varies depending on the furnace typein use.
2 TN 47
Since some furnace power is required to maintain a furnace at an elevatedtemperature (unless there is no heat loss to the surroundings), there will always be a smalltemperature error that cannot be removed using only the proportional mode of control.This error is called “droop” or “offset”. The integral control mode is used to remove thistype of error.
Integral Control
Integral control mode provides extra furnace power to compensate for any long-term difference between measured furnace temperature and desired furnace temperature.The amount of temperature error is measured (integrated) over time to determine theaverage error. A power correction based on this average error is then applied to thefurnace. This type of correction is also called “reset”.
The PID Integral coefficient (W °C-1 s-1) determines how rapidly the offset erroris corrected. A coefficient of 1.0 delivers one watt of additional furnace power for every°C s of integrated temperature error.
Derivative Control
Derivative control mode is an anticipatory control function that measures the rateof change of the furnace temperature and reduces the furnace power to avoid temperatureovershoot. A negative power correction is applied to the furnace based on the rate ofchange (°C s-1) of the measured temperature. This type of correction is also called “rate”.
The PID Derivative coefficient (W °C-1 s-1) determines how much breaking actionto apply. A coefficient of 1.0 delivers minus one watt of power for every °C sec-1 ofmeasured heating rate.
Determining PID Coefficients
No one set of PID coefficients will produce optimal results under all conditions.A certain amount of experimentation is required to determine the best coefficients for aparticular set of conditions. Tradeoffs must be made between different aspects of furnaceperformance (e.g., rapid furnace response time versus larger temperature overshoot). The conventional PID coefficient tuning process involves making individual runsusing empty sample containers. Each run performs the method of interest, or just thecritical portion of the method of interest, such as a temperature ramp to isothermal hold,or an equilibration at elevated temperature. A Heater PID method segment is inserted asthe first step of the test method, or at the critical point in the test method, so thatexperimental PID coefficients can be tried and the effect on furnace performance noted.
The first step in the complete PID tuning process involves making a quickestimate of a set of stable PID coefficients. This is accomplished by adjusting eachcoefficient in turn and observing the result of the adjustment on temperature and heatingrate. Then further refinement of each coefficient is made to increase or decrease thecharacteristic effect of that coefficient on the furnace control.
Adjusting the Proportional Coefficient
The Proportional coefficient is adjusted first. The Integral and Derivativecoefficients are set to zero during this test. The Proportional coefficient is first set to anynominal value (one tenth of the maximum furnace power is suggested). The test method
3 TN 47
is run with the Heater PID method segment inserted. Sample temperature and heatingrate are plotted versus time.
If the result of the test is stable (no sustained oscillations in temperature) thenincrease the Proportional coefficient and repeat the test until a value of the Proportionalcoefficient is found that is just large enough to produce sustained oscillations intemperature around the temperature set point. Select one half of this value for theProportional coefficient.
Alternately, the Proportional coefficient can be determined byincreasing/decreasing the coefficient until the peak height of each temperature oscillationis approximately one quarter that of the peak height of the previous oscillation. Selectthis value for the Proportional coefficient.
Adjusting the Integral Coefficient
The Integral coefficient is adjusted next. The Proportional coefficient is set to thevalue determined by the previous testing. The Integral coefficient is set to any nominalvalue (twice the Proportional coefficient is suggested as a start). The Derivativecoefficient is set to zero. The same series of test runs are made as when adjusting theProportional coefficient. The temperature and heating rate are observed. Increase theIntegral coefficient until a sustained oscillation is achieved as in the proportional testing.Select one third of this value for the Integral coefficient.
Alternately, the Integral coefficient can be determined by increasing/decreasingthe Integral coefficient until the amount of observed temperature offset is acceptable.Select this value for the Integral coefficient.
Adjusting the Derivative Coefficient
The Derivative coefficient is adjusted last. The Proportional and Integralcoefficients are set to the values previously determined. The derivative coefficient is setto any nominal value (two percent of the Proportional coefficient is suggested as a start).The same series of test runs are made as when adjusting the Proportional and Integralcoefficients. The temperature and heating rate are observed. Increase the Derivativecoefficient until the temperature overshoot is acceptable without unduly compromisingthe maximum heating rate required. Select this value for the Derivative coefficient.
Final Coefficient Adjustment
If desired the PID coefficients can be further adjusted to improve furnace controlby adjusting one coefficient at a time and observing the effect on furnace control. Thefollowing guidelines can be used to help with this adjustment:
It is usually best to make final adjustments to the Derivative coefficient first, thenthe Proportional coefficient, and finally the Integral coefficient.
The Proportional coefficient controls the amount of power applied for each degreeof temperature error, and the Integral coefficient controls the amount of power applied tocorrect for temperature offset. Larger values for each of these coefficients will increasethe temperature overshoot and the amount of temperature oscillation, but will reduce thetime needed to reach a set point temperature and the amount of temperature offset.Smaller values will have the opposite effect.
4 TN 47
The Derivative coefficient controls the amount of temperature overshoot and themaximum heating rate obtainable when approaching a temperature set point. Largervalues of the coefficient will reduce the temperature overshoot and reduce the maximumheating rate. Smaller values will have the opposite effect.
KEYWORDS
differential scanning calorimetry, dynamic mechanical analysis, micro thermalanalysis, simultaneous thermogravimetry/differential scanning calorimetry,thermogravimetric analysis, thermomechanical analysis, theory
1 TA277
Characteristics of Tg Detection Using MicroThermomechanical Analysis
Carlton G. SloughTA Instruments, 109 Lukens Dr., New Castle, DE 19702
ABSTRACTThe detection of the glass transition (Tg) is a fundamental and important
measurement in the thermal analysis of polymers. Thermomechanical analysis(TMA) is a basic technique that easily measures the Tg in many polymers. InTMA, a probe is placed on a sample surface and detects Tg by either expansion orpenetration as the sample is heated. Recently, the advent of a new thermalanalysis technique, Micro Thermal Analysis (µTA ), has introduced athermomechanical technique based on detecting expansion or penetration with athermal Atomic Force Microscopy (AFM) probe. This technique, termedµTMA , can also detect Tg by penetration, but on cubic micrometer sizevolumes of material. As opposed to “macro” TMA, µTMA functions by heatingthe thermal probe. Characteristics of how this new technique detects Tg will bediscussed.
INTRODUCTIONThe glass transition temperature (Tg) is one of the most useful thermal
parameters in characterizing a polymer. Many important properties can becorrelated to Tg including molecular weight, crystallinity, degree of cure andhardness (1).
Thermomechanical analysis (TMA) is a useful technique for detecting Tg.In a TMA experiment a probe is lowered onto the surface of a sample and themovement of the probe is measured as the sample is heated. With a load appliedto the probe, a combination of modulus changes and expansion of the sample areobserved. Depending upon the probe / sample contact area and the load applied,the Tg can be detected by either an upward (expansion) or downward(penetration) movement of the probe. With large contact areas and low forcesexpansion is primarily observed, whereas, for small contact areas and high forcespenetration is primarily observed.
In Micro Thermal Analysis (µTA ) a tiny resistive thermal probe ismounted within an atomic force microscope (AFM) in place of the usual Si probe(2-4). The thermal probe can collect images related to sample topography andthermal conductivity. Using the images as guides, points can then be selected forfurther examination by local thermal analysis (LTA). In this technique, the probeis positioned at the selected points and the temperature is ramped from a start to a
2 TA277
final temperature at very high ramp rates (5-25° C/s). Typically a few cubicmicrometers are heated. By monitoring the vertical motion of the probe duringheating, a curve analogous to a thermomechanical curve is collected. Thetechnique is referred to as µTMA and is the focus of this paper. In addition, byplotting the power sent to the probe during a local thermal experiment a signalanalogous to a DTA signal is collected and termed µDTA . While neither signalis quantitative – only transition temperatures may be determined – the utility ofthe µTA technique lies in its ability to thermally characterize micrometer sizevolumes of material.
EXPERIMENTALTwo model systems were used to characterize how µTMA detects Tg:
polystyrene and 90-minute epoxy. The polystyrene (PS) was in pellet form anddistributed by the National Institute of Standards and Technology as a standardreference material (SRM 705a). Pellets were mounted on stainless steel metalstubs using double stick carbon black tape. These stubs were then mounted in the2990 µTA for analysis.
The 90-minute epoxy was a standard commercial two-component epoxyconsisting of a hardener and resin. The two components were mixed together ona small piece of aluminum foil and allowed to cure for one month prior to theexperiments. The aluminum foil plus epoxy was then mounted on a stainless steelmetal stub using double stick carbon black tape. The stub was then mounted inthe 2990 µTA for analysis.
RESULTS AND DISCUSSIONGenerally, the detection of Tg’s by TMA appears differently for thermoset
versus thermoplastic materials. For thermoplastic materials expansion is detectedprior to the Tg and penetration into the sample at the Tg, whereas for thermosetmaterials expansion is detected prior to and after the Tg, with penetration at theTg. These same types of curve characteristics are seen in µTMA also. Figures 1aand 1b illustrate these two types of characteristic Tg detection on polystyrene and90 minute epoxy respectively. The figures show plots of probe deflection versustemperature. A positively sloping curve indicates that expansion of theprobe/sample system is occurring while a negative slope indicates penetration dueto softening of the surface.
Figs. 1a and b. Tg detection on polystyrene and 90 minute epoxy respectively.
1.0
1.2
1.4
1.6
1.8
2.0
2.2
Sen
sor
(µm
)
20 40 60 80 100 120 140 160 180
Programmed Temperature (°C) Universal V3.
77ϒC
90 Minute Epoxy
-1.0
-0.5
0.0
0.5
1.0
1.5
Sen
sor
(µm
)
0 50 100 150 200 250
Programmed Temperature (°C) Universal V3.1
130ϒC
Polystyrene
Sens
or (
µm
)
3 TA277
One difference between macro TMA experiments and µTMA experimentsconcerns the expansion portion of the curves. Quartz probes are used with macroTMA and these have very low thermal expansion. Therefore the expansion that isdetected is mainly due to the sample. In µTMA experiments, however, the probeis made from platinum wire, and the expansion detected during a run includes theexpansion of this wire.
In conventional TMA, the higher the force used the stronger the deflectionat Tg. The same is true for µTMA. Figures 2 a and b show results for PS and 90minute epoxy using increasingly higher forces. The forces are only estimates andare calculated using a rough spring constant of 1N/m and an initial cantileverdeflection estimated by using a system-generated calibration constant. Table 1quantifies the increase in deflection generated by a 3x increase in force.
Figs. 2 a and b. Effect of increasing force on Tg detection.
Table 1Increase in
ForceIncrease inDeflection
Polystyrene 3x 2.5x
90 Minute Epoxy 3x 3x
Scan rate also has an effect on the detection of Tg with the Micro ThermalAnalyzer using µTMA. There are three heating rate effects. As the heating rate isreduced the sensor deflection at Tg is increased, the signal to noise ratio isdecreased and the transition temperature is shifted downward. Figures 3 a and billustrate this. Again, these are typical of macro TMA experiments also.
-2
-1
0
1
2
Sen
sor
(µm
)
20 70 120 170 220
Programmed Temperature (°C) Universal V3.
127ϒC - 3.6 µN
127ϒC - 2.8 µN
128ϒC - 2.0 µN
129ϒC - 1.2 µN
133ϒC - 0.4 µ N
Polystyrene
-1.5
-1.0
-0.5
0.0
0.5
Senso
r (µ
m)
20 40 60 80 100 120 140 160 180
Programmed Temperature (°C) Universal V3.
79°C - 5.0 µN
78°C - 3.8 µN
77°C - 2.7 µN
74°C - 1.6 µN
78°C - 0.5µN
90 Minute Epoxy
-2
-1
0
1
2
Sen
sor
(µm
)
0 50 100 150 200 250
Programmed Temperature (°C) Universal V3.
25ϒC/s
5ϒC/s
1ϒC/s
Polystyrene
0.8
1.0
1.2
1.4
1.6
Senso
r (µ
m)
20 40 60 80 100 120 140
Programmed Temperature (°C) Universal V3
25ϒC/s
1ϒC/s
5ϒC/s
90 Minute Epoxy
4 TA277
Figs. 3 a and b. Effect of ramp rate on Tg detection.
Table 2 below quantifies the effects seen with varying ramp rate for polystyrene.
Table 225°C/s 5°C/s 1°C/s
AverageTransition T (°C) 130 121 113
AveragePentration (µm) 1.63 2.58 2.98
Noise (nm) <1 ~3 ~20
A unique aspect of the Micro Thermal Analyzer, as applied to curingsystems, is its ability to collect both TMA and DTA data simultaneously. Boththe shift in Tg and the decrease in the exotherm associated with curing can bedetected and tracked – something macro TMA cannot do. Figure 4 shows anexample for 90-minute epoxy.
Figure 4a indicates that the Tg shifts from 48°C to a stable value of 72°Cin a span of about 245 hours. Figure 4b tracks the disappearance of the curingexotherm at 150°C over time. After 408 hours of curing the exotherm is nolonger detectable.
Figs. 4 a and b. a. Shift in Tg versus curing time. b. Elimination of curingexotherm with curing time.
Because µTMA is a local technique – it analyzes only a few cubicmicrometers of material – a distinct advantage over macro TMA is its ability totrack changes in Tg laterally over a surface. Figure 5 shows three µTMA plotstaken at three different positions on a polymer film (the derivative of the TMAsignal is plotted for better observation of the Tg). The original surface wasamorphous, but a conical dye was used to create a conical depression on thesurface. It is reasonable to believe that the polymer chains might orientthemselves at the point of highest force and therefore lose their amorphous nature.The data confirm this. Near the rim of the depression, the Tg is detectable. Asthe probe is moved towards the apex the Tg all but disappears. A distance of 1-2mm separates the rim from the apex
10
12
14
16
18
20
Senso
r (µ
m)
25 75 125 175
Programmed Temperature (°C) Universal V3
6 hrs.
72 hrs.
192 hrs.
245 hrs.
48ϒC
64ϒC
71ϒC
72ϒC
-0.003
-0.002
-0.001
0.000
0.001
0.002
0.003
Deriv.
Pow
er
(mW
/°C
)
25 75 125 175
Programmed Temperature (°C)Exo Up Universal V3.
6 hrs.
72 hrs.
192 hrs.
408 hrs.
5 TA277
Fig. 5. Lateral tracking of changes in Tg on a polymer film surface.
CONCLUSIONSDetection of Tg transitions by µTMA is not dramatically different than
detection by macro TMA. Data from µTA experiments on polystyrene and 90-minute epoxy indicate that signal strength at the Tg increases with increasingforce and with slower ramp rates. These observations also apply to macro TMAexperiments. The noise level of the µTMA signal also increases with decreasingramp rate, but not to a level that interferes with detection of the Tg.
However, detection of Tg by µTMA has some major advantages overconventional TMA for certain physical systems. Some of these advantagesinclude the ability to analyze very small samples that may be impossible toanalyze with macro TMA, and the ability to track changes in Tg over lateraldistances.
Furthermore, detection of Tg’s by µTA is unique in that with the addedµDTA signal, simultaneous tracking the Tg and the curing exotherm of thermosetsystems is possible. The µTMA signal will track changes in the Tg, while theµDTA signal will track changes in the curing exotherm.
REFERENCES1. James E. Mark et al., Physical Properties of Polymers, 1984, 55-97.2. A Hammiche et al., J. Vac. Sci. Technol. B, 1996, 14, 1486-1491.3. A Hammiche et al., Rev. Sci. Instrum., 1996, 67, 4268-4274.4. H M Pollock and A Hammiche, J. Phys. D: Appl. Phys., 2001, 34, R23-
R53.
84.88°C
Near Tip
Near Middle
Near Well Rim
-0.05
0.00
0.05
0.10
0.15
De
riv.
Se
nso
r (µ
m/°
C)
25 45 65 85 105 125 145 165
Programmed Temperature (°C) Universal V2
1 TA279
How Tzero Technology Improves DSC PerformancePart III: The Measurement of Specific Heat Capacity
R. Bruce CasselTA Instruments, 109 Lukens Drive, New Castle DE 19720
Abstract. Specific heat capacity (Cp) is a fundamental thermodynamic property. Itsmeasurement by DSC is a key indicator of changes in structure. Traditional DSC hasbeen used to measure Cp using ASTM standard E1269, which requires three scans: abaseline scan, a scan using a sapphire standard, and the sample scan (1). AdvancedTzeroTM technology, available with the Q1000 DSC, offers a significant advance in theease and reliability of measuring Cp.
Background. In order to raise the temperature of a material, heat must be supplied. Theamount of energy necessary to heat one gram of the material one degree Celsius is thespecific heat capacity. Cp is a characteristic thermodynamic property of a material. It isa measure of how the material stores additional energy at the molecular level as it isheated. For example, if the molecules in the material can only vibrate, as in a crystal,then Cp is low; if they can also rotate and translate, then the Cp is higher. When amaterial is heated through the glass transition region, the molecules gain mobility, thematerial softens, and Cp increases. So Cp indicates changes in structure.
Why is Cp Important to Measure? As measured by DSC, Cp is an absolute quantity. Itquantifies how much heat must be delivered to a substance to heat it over a temperaturerange, for example, to the moldingtemperature. Figure 1 shows Cp datafor polyethylene terephthalate (PET)showing that the amount of energyrequired to heat this material increaseswith temperature and goes through apeak during the crystalline melt. Thetotal energy required to heat a quantityof PET from one temperature (T) toanother is just the integral of this dataover that temperature range. And howmuch heat must be removed to cool itto a temperature where the dimensionsare stable (for example, where the end-product can be removed from themold) can be obtained from similar Cpdata taken in cooling. Hence, this Cpinformation, as a function oftemperature, is necessary engineering input for simulation software to predict processingconditions.
Figure 1. Specific Heat data of PET
-0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
0 50 100 150 200 250 300Temperature(°C)Exoup TAInstrument
2 TA279
The Cp of a material should always be positive. Apart from time-dependent processes,its value is independent of heating rate, and also sample size. So it is the natural way tocompare data run under different conditions. For example, in Figure 2 the heat flow datais shown for polymethylmethacrylate (PMMA) taken at four different scanning rates andthan normalized for Cp. The observed differences can be attributed to the timedependence of the Tg transition.
DSC Measurement of Cp. Inan ideal DSC there would be noheat flow signal unless a samplewith heat capacity were beingheated, or some other thermalprocess was taking place. In thisideal DSC, the empty panbaseline would be a straight lineat zero milliwatts. If a samplewere heated in this ideal DSCthen the displacement from thezero line would be given by:dQ/dt = Cp * β * W (eq. 1)where dQ/dt is heat flow, β isheating rate and W is the samplespecimen mass.
The problem is that most DSC’s exhibit a substantial heat flow offset even when there isno sample present, and this heat flow signal is strongly dependent on heating rate,temperature and other factors (2). So in order to obtain Cp from a traditional DSC it hasbeen necessary to subtract an empty pan baseline run under identical conditions, beforedetermining Cp from equation 1. A further limitation is that the calibration of theinstrument, both temperature scale and heat flow, is critical. Standard methodsrecommend a comparative technique whereby a specific heat capacity reference materialis measured under identical conditions and the sample Cp is obtained by comparing theirrespective heat flow data as their ratio(1). This lengthy procedure requiresthree analytical runs, each bracketedby equilibration steps as illustrated inFigure 3.
Because so much extra effort must beused to obtain Cp, most DSC methodscall for the less quantitative, heat flowsignal, which carries the arbitrarycomponent of the offset, slope andcurvature imposed by the instrumentbaseline. Were it not for the extradifficulty, all DSC data would bereported in Cp units.
The solution is Advanced TzeroTM
technology, available on the Q1000.In a recent advance from TA Instruments, a new DSC has been developed that providesan additional TzeroTM thermocouple sensor on the measurement cell (3, 4). This allowsthe use of a more complete heat flow equation that takes into account the asymmetries in
Figure 2. Raw DSC data for Cp using ASTMmethod
-100
0
100
200
300
400
Te
mp
era
ture
(°C
)
-30
-25
-20
-15
-10
-5
0
5
He
at
Flo
w (
mW
)
0 5 10 15 20 25 30 35
Time (min)
g
Exo up TA Instrumen t
Figure 2: PMMA Heat Flow Normalized for Cp
3 TA279
the cell. As a result, the DSC heat flow signal in the absence of a sample is very close tothe theoretical zero heat flow line (2), as illustrated in Figure 4. Using Advanced Tzerotechnology, the DSC and the pan response is incorporated into the initial calibration ofthe instrument. This means that whenever a sample is run, practically all of the thermaleffects of the cell and sample pan are analytically removed from the heat flow output.
So the only difference between theheat flow and Cp is a constantnormalization factor. The Q1000with Advanced TzeroTM
technology, therefore, provides adirect measure of Cp with a singlescan. An example of the direct Cpdata available with the Q1000 isshown in Figure 5.This has several importantramifications. First, there is noextra time required with the Q1000to obtain Cp data, which asdiscussed previously, is a moreaccurate form of DSC data.Second, every DSC scan on theQ1000 is a potential Cp analysis.Third, even when the data is left inheat flow units it has the same
absolute character as Cp; namely, the instrumental character has been removed, whichmakes analysis more accurate.
Cp from MDSC©. ModulatedDSC is an alternative approachto obtaining specific heat capacityinformation (5). MDSC is capableof generating Cp data with anaccuracy of up to +/- 2%. Whilefaster than the three experimentASTM approach, traditional MDSCwas somewhat time consuming as ituses underlying heating rates of<5ºC/min. This limitation is reducedby the 5°C/min MDSC experimentsprovided by TzeroTM technology,available on the Q100, and the10ºC/min MDSC experiments ofAdvanced TzeroTM technology,available on the Q1000. Hence, while a slower underlying rate and longer period stillensure optimum accuracy, accurate Cp data is available in a much shorter time by MDSCusing either the Q100 or Q1000. In addition, the Q100 or Q1000 provide Cp units on allthree modulated signals: total, reversing, and non-reversing. This provides additionalanalytical benefits.
Figure 6 shows the heat capacity of polystyrene obtained at 10ºC/min heating and coolingusing the Q1000 and MDSC©. One of the advantages provided by the presentation of
Figure 4. Baselines from Q 1000 DSCand 2920 DSC
-0.4
-0.2
0.0
0.2
0.4
0.6
Hea
t Flo
w (
mW
)
-100 0 100 200 300 400Temperature (°C)
Conventional BaselineT zero Baseline
Figure 5. Direct Cp of Sapphire on Q1000
Average Value of 8 Runs at 20¡C/min in a Hermetic Pan is 0.893 vs. a TheoreticalValue of 0.902 J/g¡C at 97¡C. Total Rangeof Results Varied Less Than +/- 2%. SampleWas Replaced At The End of Each Run.
97.00¡C0.9111J/g/¡C
97.00¡C0.8758J/g/¡C
-0.5
0.0
0.5
1.0
1.5
Hea
t Cap
acity
(J/g
/¡C)
0 50 100 150 200Temperature (¡C) Universal V3.1B TA Instruments
4 TA279
heat flow data in the form of heat capacity information is that all of the results may beeasily compared on the same axis.
Conclusion. Cp is a fundamental, thermodynamic property of material and is the bestway to compare samples. With past DSC technology, the only way to generate Cp waswith the time consuming ASTM method. Advanced TzeroTM technology available on theQ1000 provides maximum analytical flexibility. The Q1000 is the only instrument on themarket today that provides three ways to measure heat capacity: 1) directly, 2) 3-runASTM E1269 method, and 3) using MDSC.
References
1. ASTM E1269 “Specific Heat Capacity by Differential Scanning Calorimeter”,Annual Book of ASTM Standards, Vol. 14.02.
2. “How TzeroTM Technology Improves DSC Performance, Part I: Flat Baseline andGlass Transition Measurements”, TA Instruments Applications Note ____.
3. Louis Waguespack and Roger Blaine, “Design of a New DSC Cell with TzeroTechnology”, Proc. 29th Conf. N. Amer. Therm. Anal. Soc. (2001).
4. Robert L. Danley and Peter A. Caulfield, “DSC Baseline Improvements Obtainedby a New Heat Flow Measurement Technique”, Proc. 29th Conf. N. Amer. Therm.Anal. Soc., (2001).
5. “Modulated DSC Theory”, TA Instruments Applications Brief TA211
Figure 6. Polystyrene heating and coolingshowing all MDSC signals in Cp units
Total Cp on Heating
Total Cp on Cooling
Rev Cp on Cooling
Rev Cp on Heating
Non Rev Cp on Cooling
Non Rev Cp on Heating
Sample: Polystyrene-0.2
0.0
0.2
0.4
0.6
0.8
No
nre
v C
p (
J/g
/¡C
)
0.0
0.5
1.0
1.5
2.0
2.5
Rev
Cp
(J/
g/¡
C)
-1
0
1
2
3
Hea
t C
apac
ity
(J/g
/¡C
)
70 80 90 100 110 120 130Temperature (¡C)
Universal V3.1B TA Instrum
