1 9 9 9 V O L U M E 1

• NEW Evolved Gas Collector 2

• MDSC patent update 2

• Simultaneous DSC-TGA 3

• NEW DMA submersible clamps 4

• Torsional analysis of solids 4

• Pharmaceutical Applicationsof Micro-Thermal Analysis 5

• New Applications Literature 5

• 3D TREF for Polyolefin Research 6-7

• Post NATAS seminars announced 8

In this issue: Page

THE TA HOTLINE

TA Instruments proudly announces theintroduction of the AR 500 Rheometer. Thisnew instrument has been designed to meetthe growing demand for a rheometer thatcan provide high performance, ease-of-use,and an economical price. The AR 500 iscapable of performing both controlled stressand controlled rate measurements. It isapplicable to a wide range of materialsincluding liquids, pastes, gels, and softsolids such as foods, pharmaceuticals,polymers, inks, and consumer products.

The AR 500 offers a broad torque range,multiple measurement modes, precise andrapid control of temperature (5 availabletemperature control systems), direct quanti-fication of normal force, inertia correction,automatic gap set, and a wide variety ofsample geometries. Teamed with new, easy-to-use Rheology Advantage software, theAR 500 enables even inexperiencedrheologists to characterize their samplessuccessfully.

NEW!AR 500RHEOMETER

that is customizable to match individualneeds and preferences.

Take advantage of wizards, templates,autoqueuing, and Navigator scripts toautomate all aspects of sample testingfrom experiment design and sampleidentification to data analysis andhardcopy generation. This software’spowerful new features will revolutionizethe way you work in your lab.

INTRODUCING

AdvantageSoftware

New Advantage software for thermalanalysis and rheology is designed to makeit easier than ever to expand the capabili-ties of your lab by integrating both of thesepowerful materials characterizationtechniques.

Advantage software provides unmatchedcapabilities and ease-of-use with extensiveon-line & context sensitive help, versatilereal-time plot, save session, automatedanalysis, automated time-temperaturesuperposition, the latest theoretical modelsand an easy-to-learn intuitive layout

See page 4 for news abouttorsional analysis of solids for the

AR1000 & 500 Rheometer!

22

At this year’s PittCon conferenceTA Instruments introduced our newEvolved Gas Collector (EGC) system, whichpermits the collection of volatiles anddecomposition products from thermo-gravimetric analysis (TGA) and Micro-TAexperiments.

Later the collected gases can bethermally desorbed onto a Gas Chrom-atography – Mass Spectrometer (GC-MS)system for separation and identification.The GC-MS system can be located inanother lab, building or country. Thestainless steel collection tubes are specifi-cally designed and optimized for thecollection of gases from TGA and Micro-TAexperiments.

For TGA users, the system is comple-mentary to the direct connection of anMass Spectrometer (MS) or FTIR to theTGA furnace. For Micro-TA users, thesystem adds another dimension tomaterials characterization. Collection tubesare available for use with the TGA 2050and TGA 2950, fitted with the Evolved GasAnalysis (EGA) furnace, and for the Micro-TA 2990.

For additional information, contactyour TA Instruments representative or askfor brochure TA-255.

Evolved GasCollector (EGC)

Since its introduction at the 1998PittCon, this new technique has figuredprominently in assorted articles andreceived several awards. At introduction,the µTA 2990 received the PittCon Goldaward for best new product in 1998.

In the fall of 1998 the µTA 2990 wonthe R&D100 award for technical achieve-ment. The R&D 100 Awards recognize the100 most technologically significant newproducts annually. Selected productsdemonstrate improvements which areattributed to significant breakthroughsin technology. This means the productsshould exhibit multiple levels of improve-ment over existing technology.

Most recently the µTA 2990 receiveda Millennium Award from the British

Micro-Thermal Analysis Award

Gray Slough and John Furry of theMicro-Thermal Analysis development team

Government. Dr. Trevor Lever accepted theaward during the Confederation of BritishIndustry Conference (CBI) in Birmingham,England in November.

TA Instruments is committed to develop-ment of versatile solutions to solve toughmaterials characterization problems.

TA Instruments Wins Its Decision in

MDSC® Patent Infringement Action

Against the Perkin-Elmer Corporation

We continue to receive a lot of questions about the status of the legal

and patent actions taken by TA Instruments, Inc. to defend it’s patented

temperature-modulated DSC (MDSC®) technology. Although the legal

processes could continue for a year or two, the current status is quite

clear:

1. On December 7, 1998, the US District Court for the District of

Delaware ruled that, as a matter of law, the Perkin-Elmer Corpo-

ration was liable for infringing seven claims asserted at trial by

TA Instruments, Inc. with respect to its US patent numbers

5,224,775; 5,346,306 and 5,439,291.

2. On March 5, 1999, the US District Court for the District of Delaware

issued an Order enjoining the Perkin-Elmer Corporation from making,

using, offering for sale, selling or distributing its Dynamic Differential

Scanning Calorimetry (DDSC) accessory or any calorimeters that

incorporate a DDSC accessory.

3. Outside the United States, patents relating to TA Instruments, Inc.

modulated-temperature technology have been issued in Canada and

Europe and are pending in Japan.

TA Instruments intends to continue its strategy of market leadership in

the development of new products and innovative technologies. Consistent

with that goal is our resolve to protect those investments by vigorous

defense of patented and proprietary technology.

31999 Volume 1

Figure 1Sodium ChlorideSimultaneous DSC-TGA withoutDynamic Normalization

Temperature (°C)

2

0

-2

-4

-6

-8

-10

-12

700 860820780740

Wt C

orre

cted

Hea

t Flo

w (W

/g)

Without Dynamic NormalizationMeasured Heat of Fusion declineswith each subsequent heat

797.8°C

803°C

Heat #1

Heat #2

Heat #3

393.8J/g

362.8J/g

334.9J/g

Figure 2Sodium ChlorideSimultaneous DSC-TGAwith Dynamic Normalization

Temperature (°C)

2

0

-2

-4

-6

-8

-10

-12

-14 65

700 860820780740

Wt C

orre

cted

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/g)

Wei

ght

480.1 J/g

485.7 J/g

485.8 J/g

803°C

85

80

75

70

Improved results withDynamic Normalization

DSC data is routinely “normalized” bydividing the heat flow signal by the sampleweight. This normalization provides theability to quantify heats of fusion, reaction,etc. in units of energy per unit mass so thatsamples of different sizes can be easilycompared. The sample weight used in thiscalculation is typically the initial weight ofthe sample. However, many samples exhibitweight loss prior to the transition of interest,so use of the initial weight could inducesubstantial error.

Using its unique Dynamic Normalization™

algorithm, the SDT enables the user tospecify how the DSC signals are to benormalized. Figure 1 shows DSC data from3 sequential heats of Sodium Chlorideusing standard normalization. It would seemthat the magnitude of the melting endothermdecreases with each heat. However, the TGAdata shown in figure 2 shows that there is aweight loss associated with the volatilizationof NaCl that occurs upon melting. Theresult is that in each sequential heat, thereis less sample weight.

The DSC data shown in figure 2 illustratesthe benefit of Dynamic Normalization. Herethe sample weight for transition normalizationwas taken as the weight at the beginning ofeach transition, and indeed all three heatsshow reproducible heats of fusion.

The TA InstrumentsSDT 2960 combinestwo thermal analysis

measurements in a singleinstrument, thus providingeasier interpretation ofresults and improvedproductivity at an attractiveprice. The STD 2960’sexceptional TGA & DSCsensitivity and stablebaseline, over a widetemperature range result inunmatched performance.

A unique feature of theTA Instruments SDT 2960 is the ability tocalculate normalized DSC data based onthe “actual” weight of the sample. Mostinstruments simply use the initial sampleweight for this calculation. This practicecan yield misleading results since theweight of the sample can (and often does)change during the experiment. The SDT

2960 provides the user with the ability tospecify how the DSC signals are to benormalized, providing more accurate,meaningful, and repeatable results.

Further improvements over competitiveinstruments include mechanical andelectronic automation features that willappeal to novices as well as experiencedthermal analysts. Convenient and easysample handling minimizes the possibilityof damaging the balance mechanism orthermocouples. The furnace assemblyoperates via a motor-driven screw for precisealignment and automatic opening andclosing. The balance is based on a provenhorizontal design, which assures excellentsample/atmosphere interaction whileminimizing chimney and sample weight

New SDT 2960

Simultaneous DSC-TGA

effects. In addition, low volume inside thebalance and sample areas permits rapidatmosphere changeover. Furthermore, theoverall atmospheric flow dynamics makethe SDT 2960 ideal for coupling to a massspectrometer or FTIR for evolved gasanalysis.

TA Instruments proprietary electronicsand furnace design assure precise tempera-ture control for stable baselines and optimumDSC performance. Proprietary softwarecorrects for beam growth effects at elevatedtemperatures, even under changing weightconditions. Five-point temperature calibrationcapability optimizes the accuracy oftemperature measurements.

The SDT 2960 is one of TA Instruments’many thermal analysis and rheologytechniques that complement each other.These modules, along with TA Instrumentscontrollers and software, constitute themost complete, versatile, and cost effectivesystems available for characterizingmaterials.

SDT 2960 is based on adual beam horizontal design

to assure easy, reliable andtrouble-free operation.

3

4

Don’t turn your Lab Upside Downto run Samples in Solution!Don’t turn your Lab Upside Downto run Samples in Solution!

TA Instruments new Submersion Clampsfor the DMA 2980 provide the ability to testviscoelastic properties of materials in solu-tion. The clamps are available as optionalaccessories for the DMA 2980 DynamicMechanical Analyzer and can be added toexisting instruments.

Many materials including bio-engineeredpolymers, automotive polymers, and foodsare used “in solution.” Testing thesematerials in conditions that simulate the realworld provides more meaningful results thatbetter correlate with end use performance.The clamps are easily and convenientlymounted to the instrument, providingin-solution testing without cumbersomeinstrument manipulations.

DSC evaluation of foods and biologicalmaterials usually requires larger samplesbecause those materials are dilute solutionsand the transitions of interest are nothighly energetic. Hence, new large volumestainless steel pans were developed tomeet this need.

These consist of a pan, a lid, and ano-ring seal. The pans are sealed using adie set which fits the standard DSC samplepress. The pan specifications include:internal volume 100mL; temperature range-100 to 250°C; internal pressure <25 atm.

Pans are available as an accessory kit,PN 900825.901, which includes the die set,pans, lids, o-rings and other necessaryitems.

Large VolumeDSC pans

4

DMA 2980

SubmersibleClamps

Torsional analysis of SolidsTA Instruments recently introduced the

capability to analyze solids in torsion. Thenew Environmental Test Chamber (ETC) isdesigned for use with AR 1000 and AR 500rheometers to accommodate standard samplesizes and test methods including ASTM D4065.The ETC provides the ability to analyze solidsamples in torsion with excellent temperaturecontrol over a wide temperature range (-150to 400°C). Additionally, parallel plate andcone & plate geometries can be used tocharacterize liquids, gels, pastes, andsoft solids over the same temperaturerange. This allows the rheologist tomeasure samples as diverse assteel and water, and thepolymer chemist to charac-terize his materials overtheir complete viscoelasticspectrum.

Principle of OperationThe ETC is a clam

shell design whichcombinesresistiveelementsfor radiantheating, andsmall jetsof liquidnitrogen forcooling andsubambienttemperature operation.The advanced chamberdesign provides rapidcooling while minimizingnitrogen usage and frosting around themeasuring system shaft, even during longexperiments at low temperatures.

Solids in TorsionTraditionally, controlled strain rheom-

eters have been used for measuring solidsin torsion. However, controlled straininstruments suffer from transducercompliance with high stiffness measure-ments (e.g., thermoplastics below Tg in atemperature ramp or at high frequencies),which results in the actual strain being lessthan requested. Also, because of the limitedtorque range of the transducer, controlledstrain rheometers often must increase theapplied strain with low stiffness measure-

ments (e.g., as the material softens in atemperature ramp, or at low frequencies)to stay within the operating range of theinstrument. In effect, there is only a verylimited range where the strain is actuallyconstant.

The AR1000, with its superior torquerange (10 -4 to 10 2 mNm) and high strainresolution, together with the ETC andTorsion Clamps, does not suffer from theselimitations and allows both controlled stressand controlled strain operation for optimum

sample measurement. To preventsample buckling, and to ensureaccurate results, torsion measure-ments on solids must be madewith the sample in tension. Thetorsion clamps for the AR1000accommodate both rectangularand cylindrical samples in a widerange of thicknesses (diameters),

without the need formounting shims.The clamps areself-aligning withthe lower clampassembly heldstationary, whi le

the upperclamp isattachedto the free-floating, air-bearing driveshaft. Oncemounted, theoperator can

set an initial tensioning force, as well as atension adjustment range and maximumallowable length change, to automaticallyaccommodate material stiffness variationswith temperature.

Available as an upgradeto existing AR1000 users

The Environmental chamber can beadded to existing AR1000/500 rheometerswith normal force capability, running undernew Rheology Advantage Software. Contactyour local TA Instruments representative foradditional information on this exciting newcapability.

51999 Volume 1

NEW APPLICATIONSLITERATURE

Summarized below are titles for recent additions to ourapplications literature list. Contact your local TA InstrumentsRepresentative to obtain a free copy of these items or purchasethe entire library on CD-Rom (version 2.5 is now available).

Thermal AnalysisMicro-Thermal Analysis: a new form of analytical microscopy [Ref. No. TA-247]

Recent developments in the application of thermal analysis to polyolefins [Ref. No. TA-248]

Using Micro-Thermal Analysis to characterize the nanoworld [Ref. No. TA-249]

Determining volatile organic carbon by DSC [Ref. No. TA-250]

Obtaining kinetic parameters by modulated TGA [Ref. No. TA-251]

Recent progress in Micro-Thermal Analysis [Ref. No. TA-252]

Overlapping coal decomposition reaction [Ref. No. TA-253]

Characterization of PET by DSC and MDSC® [Ref. No. TS-35]

Characterization of polymer film by TMA penetration [Ref. No. TS-36]

Determination of curie point temperature by TGA [Ref. No. TS-37]

Characterization of polyurethane by MDSC [Ref. No. TS-38]

Characterization of polyurethane by TGA and Hi-Res TGA [Ref. No. TS-39]

Characterization of polyvinyl chloride (PVC) by DMA [Ref. No. TS-40]

Characterization of polyvinyl chloride (PVC) by MDSC [Ref. No. TS-41]

Subambient characterization of soft foam materials by DMA [Ref. No. TS-42]

Characterization of the glass transition temperature of lactose by MDSC [Ref. No. TS-43]

Characterization of semi-crystalline pharmaceutical compounds by MDSC [Ref. No. TS-44]

Characterization of the effect of water as a plasticizer on lactose by MDSC [Ref. No. TS-45]

Characterization of printed circuit board materials by DMA [Ref. No. TS-46]

Characterization of packaging films performance by DMA creep compliance [Ref. No. TS-47]

Characterization of packaging films performance by DMA storage modulus [Ref. No. TS-48]

Characterization of packaging films performance by DMA creep recovery [Ref. No. TS-49]

Characterization of a styrene pigment with MDSC® [Ref. No. TS-50]

Thermal imaging with Micro-Thermal Analysis [Ref. No. TS-51]

Local Thermal Analysis of Polymer film using µTA [Ref. No. TS-52]

Analysis of polymer melt using Micro-Thermal Analysis [Ref. No. TS-53]

The degree of cure of thermosetting resins using DSC [Ref. No. TS-54]

Using online signal display for optimizing conditions with DMA [Ref. No. TS-55]

Crystallinity variation of a polymer coated metal foil detected by µTA [Ref. No. TS-56]

Pharmaceutical application of Micro-Thermal Analysis [Ref. No. TS-57]

Polymer blend study by Micro-Thermal Analysis [Ref. No. TS-58]

Detection of high energy particles by Micro-Thermal Analysis [Ref. No. TS-59]

Characterization protein denaturation by DSC using high volume sample pans [Ref. No. TS-60]

Determination of linear viscoelastic region of a polymer using strain sweepon the DMA 2980 [Ref. No. TS-61]

Effect of frequency on the modulus and glass transition temperature of PET [Ref. No. TS-62]

Determining the optimum sample size for testing film in the DMA 2980 [Ref. No. TS-63]

Measurement of the glass transition using DMA [Ref. No. TS-64]

Characterization of EPDM rubber by DSC and DMA [Ref. No. TS-65]

Characterization of epoxy reinforced glass by DSC and DMA [Ref. No. TS-66]

Characterization of an acrylic/melamine copolymer blend by DSC and DMA [Ref. No. TS-67]

Determination of Crystallinity of a common automotive thermoplastic [Ref. No. TS-68]

Characterization of a polyester resin/catalyst system by TGA, DSC and DMA [Ref. No. TS-69]

PTFE/PEEK carbon fiber blend analysis by DSC [Ref. No. TS-70]

Characterization of a PTFE/PEEK carbon fiber blend by TGA and Hi-Res™ TGA [Ref. No. TS-71]

Characterization of a polyurethane hot melt adhesives by DSC and DMA [Ref. No. TS-72]

RheologyControlled stress rheometry as a tool to measure grease structure and yield at

various temperature [Ref. No. RH-066]

Yield stress studies on greases [Ref. No. RH-067]

Environmental Test Chamber (ETC) product bulletin [Ref. No. RH-068]

Concentric cylinders product bulletin [Ref. No. RH-069]

Extended Temperature Module product bulletin [Ref. No. RH-070]

AR 500 product bulletin [Ref. No. RH-071]

Micro thermal analysis (µTA) uses athermal probe within an atomic force micro-scope (AFM) to collect images related tosample topography and thermal conductivity.Points can then be selected for examinationby local thermal analysis (LTA). The probeis positioned at the selected points and thetemperature is ramped at very high ramprates (5-25°C/s). Signals analogous to TMAand DTA are collected simultaneously. A modu-lated temperature signal can be superimposedupon the base ramp to increase sensitivity.

A pharmaceutical tablet is easily mountedin the µTA 2990 straight from the packagewith no special preparation. This tablet containstwo chemical compounds: paracetamol anda neutral excipient. The above images wereobtained simultaneously and display thetopography and relative thermal conductivityof a 100µm2 area. While the topographydoes not indicate the presence of multiplecomponents, the thermal image does show

contrast due to an area of relatively highthermal conductivity on the left hand side.

With the tip positioned on the region ofhigh thermal conductivity, no transition isobserved up to 300°C. Data collected withthe probe positioned in the surrounding darkregion, however, clearly shows a transition inboth the DTA (melting event) and TMA (asoftening event) signals at ~173°C. Valuesfor paracetamol by standard DSC list a meltingtemperature of ~170°C, thus identifyingthe dark region in the thermal image asparacetamol and the bright area as theexcipient.

PharmaceuticalApplications ofµTA 2990

Topography

0µm

50µm

100µm

0µm 50µm 100µm0µm 50µm 100µm

Thermal Conductivity

40 90 140 190 240 290

-6

-10

2

6

-20

-.08

.08

.04

-.04

Programmed Temperature (°C)

Sen

sor

(µm

)

Der

iv. P

ower

(mW

/°C)

Dark Area

Micro TMA Data

Bright Area

Derivative Micro DTA Data

170.13°C

NOWAvailable for

download from the

TA Instruments Website

www.tainst.com

6

Strip-ChartRecorder

Triple DetectorsIR Cone (C)DP viscosity (IV*C)Dual-Angle LS (VI*C)

TemperatureEquilibrationCoil

TemperatureControllers

PulseDampener

Pump

Column

Oven

Molecular weight and chain branchingare the two most important molecularparameters of interest in the polyolefinresearch. Though all polyolefins are derivedfrom simple carbon-carbon bonds, the endproducts cover a wide spectra of end-useproperties ranging from coatings, lubricants,rubbers, films, bottles, cables, fibers, pipes,and so on. This wide functional diversity ismade possible by controlling polymermolecular weight and branching.

High density polyethylene (HDPE) resinsconsist of linear polymer molecules withlittle or no branching. Low density polyeth-ylene (LDPE) resins consist of polymermolecules containing long chain branching(LCB). Polymer LCB is an important factorfor melt flow properties and product fabri-cation processing conditions. Polymershort chain branching (SCB) in linear lowdensity polyethylene (LLDPE) is achievedthrough incorporation of a-olefincomonomer into the polyethylenebackbone. SCB affects resin density andthe sample’s DSC curves. Differences inpolymer SCB distribution have strongeffects on polymer crystallinity, morphology,optics and tensile properties. Polymersmade from metallocene catalyst (m-LLD)have narrower SCB distributions thanthose made from the Ziegler Natta process(ZN-LLD). Often, the terms SCB distribution,and copolymer (or chemical) compositiondistribution (CCD) are used interchangeably.

Being all carbons and hydrogens in makeup,polyolefins are a difficult polymer forchemical analysis. This makes GPC, gelpermeation or size exclusion chromatog-raphy SEC1, an important analyticaltechnique for polyolefins. GPC separatespolymers by size and, therefore, providesan indirect measure of the polymermolecular weight distribution (MWD).Since LCB adds to molecular weight morethan to molecular size, adding a lightscattering (LS) and a viscosity detector toGPC in the form of 3D-GPC or TriSEC2

becomes a valuable tool to detect polymerLCB and the true MW of LDPE resins.

A Triple-DetectorTREF Instrumentfor Polyolefin ResearchThis article is an abbreviated version of a paper by Wallace W. Yau andDavid Gillespie of the Chevron Chemical Company, LLC. For additional information,or a copy of the complete article, contact the author at: WWYA@chevron.com

It should be noted however, GPC is nota sensitive tool to detect SCB. At the lowcomonomer levels commonly used incommercial LLDPE products, there are notenough molecular weight or size changesto make significant changes in GPC elutioncurves. A more sensitive technique for thedetection of SCB, based on polymer solutioncrystallization process, has been made possiblein the form of the Tref technique, 3 i.e.,temperature rising elution fractionation. Trefrelies on the crystallization and re-dissolutionprocess to separate polymers having differentdegrees of branching. With the MW-sensitivedetectors installed in a 3D-Tref instrument,one can determine both LCB and SCBdistribution in one experiment.

The Automated3D-TREF InstrumentOur triple-detector Tref instrument hasbeen assembled using parts retrofitted intoa Waters’ 150C GPC system (see Figure 1).The Tref oven heater is externally controlledto provide the programmed cooling (from145°C to 25°C) and heating (from 25°C to145°C) cycles during a Tref experiment. Ina Tref experiment, a sample solution isinjected and held inside the Tref columnduring the cooling cycle to allow polymermolecules to crystallize and form a coatingon the surface of the Tref packing particles.This is followed by the heating and elutioncycle, during which the polymer moleculesare re-melted and re-dissolved into thesolvent flow stream. The solute moleculesare detected by the IR-LS-Viscosity tripledetectors as they emerge from the Trefcolumn at different elution temperatures.Polymer molecules with higher SCBcontent elute from the column first at lowerelution temperature.

Typical HDPE ResultsTriSEC can more easily detect sampledifferences for broad MWD HDPE samples,as compared to the Tref technique (seeFigure 3). However, the Tref analyses haveproven useful in many cases where there isintentional copolymerization added for the

Figure 2Triple-Detector GPC and

3D-Tref of Two HDPE Resins

Figure 1Automated TREF Instrument

with Triple IR-LS-Viscosity Detectors (3D-TREF)

6

GPC Elution Volume (ml)

3D-GPC of HDPE2200

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Sample F (HDPE-2, NIST-1475, d=0.978, MI=2.07)

15 Degree LS Signal = M*C

DP Viscosity Signal = IV*C

IR Conc. Signal = C

Tref Elution Temperature (C)

3D-Tref of HDPE2200

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Sample F (HDPE-2, NIST-1475, d=0.978, MI=2.07)

15 Degree LS Signal = M*C

DP Viscosity Signal = IV*C

IR Conc. Signal = C

71999 Volume 1

purpose of toughening HD film products.This is the case illustrated here for sample 1,which is a HDPE with a density value of 0.939,which is not a true homopolymer per se. Thefact that the high melting “homopolymerfraction” takes the form of a split doublepeak is quite intriguing. Viewing the relativepeak height of the LS and viscosity signals,one would have to conclude that the peakelution at the highest temperature has MWvalues at least a factor 2 or 3 higher thanthe peak occurring at the next highestelution temperature. One could speculatethat these twin peaks might arise from thedifferent catalyst sites with distinct MWpreferences. If this is the case, it could giveeven more power to the 3D-Tref technique.It would mean that characteristics ofindividual sites in a heterogeneous systemcould be tracked and studied in detail asone varies reaction and catalyst conditions.However, a lot of work needs be done to makesure that this peak splitting is not an artifactcaused by any yet unexplained events in theTref process!

Typical LDPE ResultsLDPE resins are perhaps the most interestingresins that can be seen in TriSEC and 3D-Trefcurves (see Figure 3). Unlike the HD and LLDcases, the heights of the LS and the viscositysignals can actually follow an opposite trendunder the LCB conditions. Higher degrees ofLCB give larger LS peaks but relativelysmaller viscosity peaks. This is true because,with LCB, there is more mass packed into asmaller volume. We note these detectorbehaviors for LDPE resins in both theTriSEC and the 3D-Tref curves. For theseLD resins, the MW and polydispersity valuesfrom conventional broad HDPE calibrationare very different from the “true” valuesdetermined from the LS results. From the3D-Tref scan, there is one more observationthat we can make. Note that the LD peaks inTref are fairly narrow and they are highlydownshifted in their Tref elution tempera-tures. These features are interesting evidenceto the fact that these LDPE polymer moleculescontaining LCB actually have a high level ofSCB incorporated within them. The SCB’sare distributed fairly uniformly across thesample MWD.

ComplementarySynergism with DSCFigure 4 shows the Tref and DSC scans fora polymer blend sample made up with a 1:1mixture of a LDPE resin and a HDPEstandard (NIST 1484). One notices that the

Tref elution temperature of the twopeaks is similar to that seen in the DSCscan, except that the Tref temperatures aremuch lower. This downshift of the Trefelution temperature from DSC can bereasonably understood by examining theequation shown at the top of Figure 4. Theadditional requirement of the entropy ofdissolution in the Tref case could be themajor factor causing the temperaturedownshift of the Tref peaks.

It is interesting to compare the Tref andDSC peak height of the LD componentwith that of the HD component in Figure 4.We see that all these detector responses areshowing us complementary informationabout this LDPE peak. The Tref-IR signaltells us the weight content of this compo-nent in the sample. The Tref-LS signal showsus that it is a very high molecular weightcomponent, revealing the LCB nature ofthis component. The LCB character of thiscomponent is also reflected in the low heatof fusion feature of this peak seen in theDSC scan.

In many ways, the two techniques of Trefand DSC are somewhat related. But, in someways, they can be used to our advantage togive us complementary information inunderstanding polymer structures. The3D-Tref approach has the advantage ofbeing able to give more quantitative assess-ment of the weight fraction distributionof polymer SCB and LCB. The advantageof DSC is its ability to study the samplethermal properties and the polymer memoryeffects of thermal and stress history infabricated polymer products. Since DSCdeals with the polymer solid and melt, itcan be used to study polymer entanglementeffects. Tref is a solution technique thatcharacterizes the structural features of theindividual isolated molecules.

References1 Yau, W. W.; Kirkland, J. J.; and Bly, D. D.,

Modern Size Exclusion Liquid Chromatography;Wiley: New York, 1979.

2 Haney, M. A.; Gillespie, D; and Yau, W. W.,Today's Chemist, 3 (11), 39 (1994).

3 Wild, L., Adv. Polym. Sci., 98, 1-47 (1990).

Figure 3Triple-Detector GPC and 3D-Tref of Two LDPE Resins

Figure 4Synergism of TREF-LS and DSCA Blend of LDPE-1 and HDPE (NIST 1484)

7

GPC Elution Volume (ml)

3D-GPC of LDPE2200

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12 2824201614 30262218

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tect

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mv)

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Sample G (LDPE-1, d=0.917, MI=12)

Sample H (LDPE-2, NIST-1476, d=0.931, MI=1.19)

15 Degree LS Signal = M*C

DP Viscosity Signal = IV*C

IR Conc. Signal = C

3D-Tref of LDPE2200

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0

De

tect

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Sample H (LDPE-2, NIST-1476, d=0.931, MI=1.19)

15 Degree LS Signal = M*C

DP Viscosity Signal = IV*C

IR Conc. Signal = C

Tref Elution Temperature (C)25 10585654535 115957555

Elution Temperature before offset correction

3

1

0

20 806040

Hea

t Flo

w (

mv)2

120 140100

LS (M*C)

Delta H >melting[Delta S]

Delta-H*C

IR (C)

86.8°C

116.6°C

DSC scan

NBS1484+LDPE Blend

30

0

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ecto

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The TA HotlineAttn.: Jim SchilthuisTA Instruments, Inc.109 Lukens DriveNew Castle, DE 19720-2795Telephone: (302) 427-4000Fax: (302) 427-4001e-mail: info@tainst.com

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Internet: http://www.tainst.com

Pharmaceutical customers, as part ofthe requirements for FDA or GLP certifica-tion, are interested in validation that theirinstruments are properly installed andoperate correctly. IQ (installation qualifica-tion) and OQ (operational qualification)are targeted to meet that need. IQ/OQconsist primarily of detailed documentationof our installation/calibration processeswhich the service engineers provide at thetime of original installation. This includes:

• Calibration using traceablereference materials

• Meets FDA, ISO andASTM requirements

• Independent qualificationincreases productivity

IQ/OQ is an option available forinstallations of the DSC 2010, DSC 2910,and DSC 2920 (includes LNCA, RCS, orautosampler, if part of system); TGA 2050and TGA 2950 (includes autosampler);and TMA 2940.

IQ/OQ is part of our ever-growingoffering of customer support services.Contact your representative foradditional details.

IQ/OQCertificationOne of the things that differentiates

TA Instruments from our competitorsis the after-sale service and support

we provide to our customers, and to thetechnical community in general.

Seminars and workshops are routinelyheld in cities around the world in a effortto make technology conveniently availableto all. Recent examples include a seriesof two-day workshops, which were heldin 16 cities around the US. One day wasdevoted to DSC and TGA training withintroductions to Modulated DSC® andMicro -Thermal Analysis, with the 2ndday focusing on Rheology and DMA, withintroductions to the new solids in torsioncapability (for the AR 1000 & AR 500)and Compressional Rheology. Thefourteenth annual rheology symposiumwas held at Lake Tahoe this spring. This3-day course, designed for those whowant to get beyond the basics, featuredlectures by distinguished speakers fromboth industry and academia.

This September, for the third consecutiveyear, we will hold a two-day Post NATAS

Post NATAS Seminarsseminar following the NATAS conference.NATAS is the North American ThermalAnalysis Society. The annual conferencedraws thermal analysts from aroundthe world. The 1999 NATAS conferenceis scheduled for September 20 -22 inSavannah, Georgia (visit www.natas.orgfor more information on NATAS).

By scheduling this seminar tofollow the conference, we intend tomake access as convenient as possibleby allowing participants to simplyextend their stay. Indeed, the seminarsin 97 & 98 were well attended, andreceived positive reviews.

This year’s seminar (Sept. 23 & 24)will focus on Modulated DSC®. Day onewill feature invited speakers on the topicof new applications for MDSC. Day twowill be designed to provide practicaltraining for MDSC users, includingtheory, calibration, experiment designand set up, data interpretation, andapplications.

Watch the TA Instruments web site, www.tainst.com foradditional information and registration.

Use the enclosed postage paid reply card for early registration!

Visit the TA Instruments websiteand click on ANSWERMAN

to receive help in solving yourmaterials characterization problems.

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