DSC
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2005 Training School DSC DSC: Terminology Amorphous Phase - The portion of material whose molecules are randomly oriented in space. Liquids and glassy or rubbery solids. Thermosets and some thermoplastics. zCrystalline Phase - The portion of material whose molecules are regularly arranged into well defined structures consisting of repeat units. Very few polymers are 100% crystalline. zSemi-crystalline Polymers - Polymers whose solid phases are partially amorphous and partially crystalline. Most common thermoplastics are semi-crystalline. zMelting - The endothermic transition upon heating from a crystalline solid to the liquid state. This process is also called fusion. The melt is another term for the polymer liquid phase. zCrystallization - The exothermic transition upon cooling from liquid to crystalline solid. Crystallization is a function of time and temperature. zCold Crystallization - The exothermic transition upon heating from the amorphous rubbery state to the crystalline state. This only occurs in semi-crystalline polymers that have been quenched (very rapidly cooled from the melt) into a highly amorphous state. zEnthalpy of Melting/Crystallization - The heat energy required for melting or released upon crystallization. This is calculated by integrating the area of the DSC peak on a time basis. z TA Instruments DSC’s DSC 2010 DSC 2910 DSC 2920 Q系列™ DSC Q1000 是顶级的带有多种可选配置的研究级DSC Q100 是具有扩展功能的研究级DSC Q10 是基本型 DSC DSC Q10P & DSC Q1000 with Pressure Cell DSC 光量热附件 SDT Q600 •SDT Q600 同步 DSC-TGA: 同时测量热流 和重量变化信号 DSC: 典型 DSC 转变 热流 -> 放热 氧化 或分解 熔化 玻璃化转 变 交联 结晶 温度 (固化) Understanding DSC Signals Heat Flow • Relative Heat Flow: measured by all DSCs except TA Q1000. The absolute value of the signal is not relevant, only absolute changes are used. • Absolute Heat Flow: used by Q1000. Dividing the signal by the measured heating rate converts the heat flow signal into a heat capacity signal From desktop, double-click on Q Series Explorer Icon Q Series Explorer shows all the instruments attached to your system Signal Display Method Segments Real-Time Plot Summary, Procedures, & Notes Runs in the Sequence Calibration • Q100 & Q1000 ¾Tzero™ Calibration ¾Cell Constant and Temperature Calibration • Q10 ¾Baseline Calibration ¾Cell Constant and Temperature Calibration Calibration • Q100 & Q1000 ¾Tzero™ Calibration ¾Cell Constant and Temperature Calibration • Q10 ¾Baseline Calibration ¾Cell Constant and Temperature Calibration To begin calibration start DSC Calibration Wizard Select Heat flow signal & type of cooler Q1000 = T4P Q100 = T4 Q10 = T1 Select which calibration to perform Tzero Calibration Enter parameters for first run (empty cell) Start experiment Enter weight of sapphire samples When run is completed, capacitance & resistance are plotted and saved Always run Indium for Cell Constant Enter parameters for Indium sample Enter temperatures for Indium run Start experiment Data is analyzed automatically Calibration • Q100 & Q1000 ¾Tzero™ Calibration ¾Cell Constant and Temperature Calibration • Q10 ¾Baseline Calibration ¾Cell Constant and Temperature Calibration To begin calibration start DSC Calibration Wizard Select type of calibration to run Enter parameters Review summary Enter sample information Finish entering sample information Review checklist Baseline calibration running Start calibration analysis File is opened automatically Select limits then click on Limits Ok button Click on Accept to save calibration Once the file is analyzed and the results are saved, a checkmark appears next to the filename To begin calibration start DSC Calibration Wizard Select type of calibration to run Enter parameters Review summary Enter sample information Finish entering sample information Review checklist Start calibration analysis File is opened and analyzed automatically. Click analyze to change limits, or accept Tzero™ Heat Flow Equation Heat Flow Sensor Model qr qs Cs Cr Tr Ts Besides the three temperatures (Ts, Tr, T0); what other values do we need to calculate Heat Flow? Rr Rs How do we calculate these? T0 ⎛ 1 dTs d∆ T ∆T 1 ⎞ q=− + ∆T0 ⎜⎜ − ⎟⎟ + (Cr − Cs ) − Cr Rr dτ dτ ⎝ Rs Rr ⎠ Measuring the C’s & R’s • Tzero™ Calibration calculates the C’s & R’s • Calibration is a misnomer, THIS IS NOT A • CALIBRATION, but rather a measurement of the Capacitance (C) and Resistance (R) of each DSC cell After determination of these values, they can be used in the Four Term Heat Flow Equation showed previously Measuring the C’s & R’s • Preformed using Tzero™ Calibration Wizard 1. Run Empty Cell 2. Run Sapphire on both Sample & Reference side A few words about the Cs and Rs • The curves should be smooth and continuous, • • • without evidence of noise or artifacts Capacitance values should increase with temperature (with a decreasing slope) Resistance values should decrease with temperature (also with a decreasing slope) It is not unusual for there to be a difference between the two sides, although often they are very close to identical Good Tzero™ Calibration Run Enable and Select Diagnostic Signals Check this box! Enable and Select Diagnostic Signals Select 1-8 for an RCS or all of them for an LNCS More on Diagnostic Signals later Advanced Tzero™ Technology • During transitions and MDSC® experiments, the heating • • • rates of the sample pan, sample calorimeter, reference pan and reference calorimeter may be very different. Sample pans have thermal resistance and heat capacity and sample and reference pans rarely have the same mass. Advanced Tzero includes the heat capacity of the pans and the heating rate differences between the sample and reference calorimeters and pans. Peaks are taller and sharper, hence both resolution and sensitivity are dramatically improved. Advanced Tzero™ Model Advanced Tzero is a further refinement of the Tzero model and takes the measurement up to the sample pan, one step closer to the actual sample q sam Advanced Tzero model includes the Pans Q1000 m pr c pan m ps c pan T pr T ps Rp qs Q100 Tzero models the Calorimeters Cpan Rp Rs Rp Ts qr Tr Cr Cs Rs Rr T0 Advanced Tzero™ • The pan type MUST match the pan that you are using • Be sure and enter pan weights Coolers • Refrigerated Cooling Accessory (RCS) • Liquid Nitrogen Cooling Accessory (LNCS) • Finned Air Cooling Accessory (FACS) • Quench Cooling Accessory (QCA) Coolers • Cooling device sits on flange • Nickel cooling rods transfer cooling to furnace/cell Used to select type of cooler, and to specify status between runs RCS • Temperature Range ¾-90°C to 550°C RCS • Temperature Range • • ¾-90°C to 550°C Cell purge and base purge required when RCS is running Secondary purge is optional, but recommended when using in highly humid environments ¾Dry N2 to cooling gas port on back of DSC RCS • Temperature Range • • • ¾-90°C to 550°C Cell purge and base purge required when RCS is running Secondary purge is optional, but recommended when using in highly humid environments ¾Dry N2 to cooling gas port on back of DSC Ensure that cell remains above ambient using unload range and standby temperature Unload range is the temperature that the cell will go to at the end of a run If unload temperature range is not active, cell can be controlled by using standby temperature LNCS • Temperature Range ¾-180°C to 550°C LNCS • Temperature Range • • • ¾-180°C to 550°C Cell purge and base purge required when LNCS is running Secondary purge is optional, but recommended when using in highly humid environments ¾Dry N2 to cooling gas port on back of DSC Ensure that cell remains above ambient using unload range and standby temperature FACS • Temperature Range ¾Ambient to 725°C FACS • Temperature Range ¾Ambient to 725°C • Dry air to cooling gas port • Quench cooler available to cool down quicker between runs (not for sub-ambient use) QCA • Temperature Range • ¾-180°C to 550°C Cell purge and base purge required when using a QCA Topic • • • • Keeping your DSC cell clean Calibration Sample Preparation Thermal Method Keeping the DSC Cell Clean • One of the first steps to ensuring good data is • to keep the DSC cell clean How do DSC cells get dirty? ¾Decomposing samples during DSC runs ¾Samples spilling out of the pan ¾Transfer from bottom of pan to sensor How do we keep DSC cells clean? • DO NOT DECOMPOSE SAMPLES IN THE DSC CELL!!! • Run TGA to determine the decomposition • • • temperature ¾Stay below that temperature! Make sure bottom of pans stay clean Use lids Use hermetic pans if necessary TGA Gives Decomposition Temperature Cleaning Cell • If the cell gets dirty ¾Clean w/ brush Brush gently both sensors and cell if necessary Be careful with the Tzero™ thermocouple Blow out any remaining particles Brushing the Sample Sensor Heat Flow Calibration (Cell Constant) • Heat Flow Calibration of Differential Scanning • • • Calorimeters – ASTM E-968 Enthalpy Calibration Performed using Calibration Wizard One Run ¾Indium metal Sample Weight 1-5mg Pre-melt sample the first time you run it Heating rate of 10°C/min Dependent upon purge gas Cell Constant • The cell constant is calculated as the ratio of the theoretical heat of fusion of a standard material, to the measured heat of fusion Cell Constant = Hf (Theoretical) / Hf (Measured) • Cell Constant should be 0.95-1.20 in N2 Temperature Calibration • Temperature Calibration of Differential • • • Scanning Calorimeters – ASTM E-967 Performed using Calibration Wizard Indium Cell constant run also performs temperature calibration Can do up to 5 standards ¾Pure metals typically used - In, Sn, Zn, Pb ¾We’ve found that on the Q series DSC’s one temperature calibration point is all that is usually needed Sample Pans • Type of pan depends on¾Sample form ¾Volatilization ¾Temperature range • Use lightest, flattest pan possible • Always use reference pan of the same type as sample pan Standard DSC Pans (Crimped) • Pan & lid weighs ~23mg, bottom of pan is flat • Used for solid non-volatile samples • Always use lid (see exceptions) • ¾Lid improves thermal contact ¾Keeps sample from moving Exceptions to using a lid ¾Running oxidative experiment ¾Running PCA experiment Standard DSC Pans (Crimped) • Crimped pans are available in: • ¾Aluminum - up to 600°C ¾Copper - up to 725°C (in N2) ¾Gold - up to 725°C Standard Pans without lids ¾Graphite - up to 725°C (in N2) ¾Platinum - up to 725°C Hermetic Pans (Sealed) • Pan & Lid weigh ~55mg, bottom of pan is not • • • as flat as std pans Used for liquid samples and samples with volatiles Always use lid (same exceptions as before) After sealing pans, should form dome Hermetic Pans (Sealed) • Hermetic Pans are available in: ¾Aluminum – <600°C; <3 atm (300 kPa gage) ¾Alodined Aluminum - <600°C; <3 atm (300 kPa gage) • (For aqueous samples) ¾Gold – <725°C, <6 atm (600 kPa gage) Specialized Sealed Pans ¾High Volume - 100µL; <250°C; 600 psig(4.1 MPa) ¾High Pressure - 35µL; <300°C; 1450 psig(10 MPa) • Note: 3 atm is approximately 44 psig It Does Matter What Pan you use Monohydrate Pharmaceutical sample Sample Shape • Keep sample thin • Cover as much as the bottom of pan as possible Sample Shape • Cut sample to make thin, don’t crush • If pellet, cut cross section Sample Shape • Cut sample to make thin, don’t crush • If pellet, cut cross section • If powder, spread evenly over the bottom of the pan Using Sample Press • When using crimped pans, don’t over crimp • Bottom of pan should remain flat after crimping Crimped Pans Hermetic Pans Good Not Sealed Sealed Bad • When using Hermetic pans, a little more • pressure is needed Hermetic pans are sealed by forming a cold wield on the Aluminum pans Sample Size • Larger samples will increase sensitivity • but……………. Larger samples will decrease resolution • Goal is to have heat flow of 0.1-10mW going through a transition Sample Size • Sample size depends on what you are measuring ¾If running an extremely reactive sample (like an explosive) run very small samples (<1mg) ¾Pure organic materials, pharmaceuticals (1-5mg) ¾Polymers - ~10mg ¾Composites – 15-20mg Purge Gas • Purge gas should always be used during DSC • experiments ¾Provides dry,inert atmosphere ¾Ensures even heating ¾Helps sweep away any off gases that might be released Nitrogen ¾Most common ¾Increases Sensitivity ¾Typical flow rate of 50ml/min Purge Gas • Helium • ¾Must be used with LNCS ¾High Thermo-conductivity ¾Increases Resolution ¾Upper temp limited to 350°C ¾Typical flow rate of 25ml/min Air or Oxygen ¾Used to view oxidative effects ¾Typical flow rate of 50ml/min Sample Temperature Range • Rule of Thumb ¾Have 2-3 minutes of baseline before and after transitions of interest - if possible DO NOT DECOMPOSE SAMPLES IN DSC CELL ¾Temperature range can affect choice of pans ¾Just because the instrument has a temperature range of –90°C to 550°C (with RCS) doesn’t mean you need to heat every sample to 550°! Effect of Heating Rate PMMA 10.04mg Thermal History • The thermal history of a sample can and will • affect the results The cooling rate that the sample undergoes can affect : ¾ Crystallinity of semi-crystalline materials ¾ Enthalpic recovery at the glass transition • Run Heat-Cool Heat experiments to see effect of & eliminate thermal history ¾ Heat at 10°C/min ¾ Cool at 10°C/min ¾ Heat at 10°C/min Heat-Cool-Heat of PET 1.5 1.0 Cool Heat Flow (W/g) 0.5 Second Heat 0.0 First Heat -0.5 -1.0 -1.5 20 60 100 140 180 Temperature (°C) 220 260 Help • Instrument Error messages • Instrument Log • On-line Help • Getting Started Guide To see help for error, click on error description, then click on error help HELP!!
