Modulated Differential Scanning Calorimetry ® (MDSC®) MDSC® Training Course Topics • What is actually measured by MDSC • • • • • • – MDSC does not measure the reversibility of transitions Understanding heat flow from DSC and MDSC experiments Calculation of MDSC signals Heat capacity calculation Optimization of MDSC experimental conditions Characterization of transitions involving a change in heat capacity (glass transition etc.) Measurement of polymer melting and crystallinity – When not to use MDSC What Does MDSC® Measure? • As will be shown, MDSC separates the Total heat flow of • • • DSC into two parts based on the heat flow that does and does not respond to a changing heating rate MDSC applies a changing heating rate on top of a linear heating rate in order measure the heat flow that responds to the changing heating rate In general, only heat capacity and melting respond to the changing heating rate. The Reversing and Nonreversing signals of MDSC should never be interpreted as the measurement of reversible and nonreversible properties MDSC® Separates the Total Heat Flow Signal of DSC into Two Parts dH DSC heat flow signal dt Cp Sample Heat Capacity SampleSpecific Heat xSample Weight dH dT Cp f (T, t) dt dt dT Heating Rate dt f (T ,t) Heat flow thatis functionof time at an absolute temperatu re (kinetic) Understanding Heat Capacity and the Benefits of Being Able to Measure It Understanding Heat Capacity • Heat Capacity or Specific Heat is the amount of heat required to change the temperature of a specific mass of material (no transition in structure): Heat Capacity = Specific Cp (J/g°C) x Sample Weight (g) • Heat capacity is a measure of molecular motion. Heat capacity increases as molecular motion increases. Vibration – occurs below and above Tg Rotation – polymer backbone and sidechains (in and above Tg) Translation – entire polymer molecule (above Tg) • Transitions in the structure of a material are important because they result in changes in heat capacity (molecular mobility) and other important physical, and sometimes chemical, properties • Thermodynamic property of material (vs. heat flow). Heat flow is relative; whereas, the heat capacity is absolute Changes in Heat Capacity Indicate Significant Changes in Physical Properties Sample: Polystyrene Size: 14.0200 mg Method: Anneal80 Comment: MDSC.3/40@2; After Anneal @ 80øC various times DSC File: C:\TA\Data\Len\FictiveTg\PSanneal80.002 -0.3 Translation 2.0 -0.4 Rotation Vibration 1.5 Glass Transition is Detectable by DSC Because of a Step-Change in Heat Capacity Heat Capacity Heat Flow -0.7 Temperature Below Tg - lower Cp - lower Volume - lower CTE - higher stiffness - higher viscosity - more brittle - lower enthalpy 1.0 -0.6 [ ––––– · ] Heat Flow (mW) Heat Capacity (J/g/°C) -0.5 -0.8 -0.9 0.5 -1.0 70 Exo Up 90 110 Temperature (°C) Universal V3.8A TA Instruments Understanding Heat Capacity and the Benefits of Being Able to Measure It (cont.) Understanding the Benefits • Knowledge of the baseline due to heat capacity is important for almost all DSC and MDSC measurements because all transitions must be analyzed between two points on the heat capacity baseline for accurate temperatures and heats of transition. – It is often impossible to identify the heat capacity baseline in DSC data – The MDSC Reversing signals (Cp and Heat Flow) provide the heat capacity baseline – Although melting is primarily seen in the Reversing signal, it is a latent heat (no change in sample temperature) and is not a heat capacity component Without Knowledge of the Baseline Due to Capacity, File:Heat C:\TA\Data\Len\Epoxy\MDSCiso100.001 DSC Analysis of This Epoxy is Not Possible Sample: Epoxy Size: 10.8500 mg Method: MDSCiso.5/40@100 Comment: MDSC iso@100 0.2 0.4 Heating Experiment at at 3°C/min Heating Experiment 3 C/min after 160min Isothermal Cure @ 100°C After 160 min Isothermal Cure at 100 C Note Inability to Measure Tg or Integrate Note Inability to Peak Due to Cure Measure Tg Nonreversing -0.6 Total -1.0 Reversing 110.75°C 117.14°C 31.08J/g 0.0 0.0 -0.4 -0.4 -0.8 All Signals at Same Sensitivity 119.12°C(H) 0.2810J/g/°C -1.4 -1.2 52 Exo Up 0.4 [ ––––– · ] Rev Heat Flow (mW) Sample: Epoxy Size: 10.85 mg [ –– –– – ] Nonrev Heat Flow (mW) Heat Flow (mW) -0.2 Note Onset of Decomposition Note Onset of Decomosition Before before Complete Cure Complete Cure 102 152 Temperature (°C) 202 252 Universal V3.8A TA Instruments Understanding the Heat Flow Signal from DSC and MDSC® Experiments • For a given sample, the rate of heat flow (mW = J/sec) due to heat capacity is linearly proportional to heating rate. • At a heating rate of zero, the heat flow due to heat capacity is also zero. dH dT Cp f (T, t) dt dt • Any heat flow detected at a zero heating rate must be due to kinetic processes ƒ(T,t) in the sample. • The purpose of MDSC is to separate the total heat flow into the part that responds to heating rate and the part that responds to absolute temperature. Heat flow due to heat capacity responds linearly to heating rate Comparison of DSC and MDSC Heat Flow and Heat Capacity Signals dH dT Cp f (T, t) dt dt DSC MDSC® COMMENTS Total Heat Flow Modulated Heat Flow Signals contain all thermal events occurring in the sample Total Heat Flow Quantitatively the same in both techniques at the same average heating rate Reversing Heat Flow Heat capacity component of total heat flow Nonreversing Heat Flow Kinetic component of total heat flow Heat Capacity All calculated heat flow signals are also available in heat capacity units Selecting MDSC® Mode and Type of Experiment Storing MDSC® Signals Signal Selection Button Selecting MDSC® Signals for Plotting in Universal Analysis Average & Modulated Temperature 62 62 Modulate +/- 0.42 °C every 40 seconds (Heat-Iso) Ramp 4.00 °C/min to 290.00 °C Temperature (°C) Temperature (°C) 56.5 Amplitude 60 56.5 56.0 56.0 55.5 55.5 55.0 55.0 Modulated Temperature (°C) 60 Modulated Temperature 57.0 58 58 54.5 13.70 13.75 13.80 13.85 13.90 13.95 14.00 54.5 14.05 Time (min) 56 56 Average Temperature 54 54 Note that temperature is not decreasing during Modulation i.e. no cooling 52 13.0 13.5 14.0 Time (min) 14.5 52 15.0 Modulated Temperature (°C) 57.0 Average & Modulated Heating Rate; MDSC® Does Not Require Cooling During Modulation 10 10 Period Note That Heating Rate is Never Negative (no cooling) 8 6 6 Average Heating Rate 4 4 2 2 Modulated Heating Rate 0 13.0 13.5 14.0 Time (min) 14.5 0 15.0 Deriv. Modulated Temperature (°C/min) Deriv. Temperature (°C/min) 8 Signal Calculations (cont.) Reversing Heat Flow • Calculated from Reversing Heat Capacity signal Heat Flow Amp Rev Cp x KCp Rev HeatingRate Amp Rev Heat Flow Rev Cp x Avg Heat Rate Calculation of MDSC® Reversing Heat Flow and Heat Capacity Signals Signal Calculations (cont.) Nonreversing Heat Flow • Calculated by subtracting the Reversing Heat Flow signal from the Total Heat Flow signal dH dT Cp f (T, t) dt dt Total = Reversing + Nonreversing Nonreversing = Total – Reversing Calculated MDSC® Heat Flow Signals Separation of Transitions into Modulated DSC® Signals MDSC® Data Signals dH dt dT Cp dt Total = Reversing + Transitions: f (T, t) Nonreversing Heat Capacity Enthalpic Recovery Glass Transition Evaporation Most Melting Crystallization Thermoset Cure Protein Denaturation Starch Gelatinization Decomposition Some Melting Calibration • Cp Calibration is independent of heating rate • • – 0-5°C/min Cp Calibration is independent of amplitude – 0-1°C Cp Calibration is dependent on period and purge gas – Calibrate with period that you intend to use for subsequent runs – Use purge gas that you plan to use for subsequent runs Set Mode & Test as shown above 1.2 1.2 1.1 1.1 1.0 1.0 0.9 0.9 Plot Heat Capacity and Rev Cp vs. temperature 0.8 0.7 0 50 100 150 Temperature (°C) 200 250 0.8 0.7 300 [ ––––– · ] Rev Cp (J/g/°C) Heat Capacity (J/g/°C) Sapphire Cp data Sapphire Cp data 1.2 1.2 Total 1.1 276.85°C 1.076J/g/°C Theoretical Values 1.1 176.85°C 0.9975J/g/°C 1.0 1.0 126.85°C 0.9423J/g/°C Reversing 76.85°C 0.8713J/g/°C 0.9 0.9 26.85°C 0.7788J/g/°C Theoretical values of Sapphire indicated 0.8 0.7 0 50 100 150 Temperature (°C) 200 250 0.8 0.7 300 [ ––––– · ] Rev Cp (J/g/°C) Heat Capacity (J/g/°C) 226.85°C 1.041J/g/°C View spreadsheet of data Cp Data Table Temperature Heat Capacity °C J/g/°C 26.85 0.7675 36.85 0.7887 46.85 0.8086 56.85 0.8275 66.85 0.8454 76.85 0.8614 86.85 0.8765 96.85 0.8914 106.85 0.9069 116.85 0.9217 126.85 0.9339 136.85 0.9467 146.85 0.9573 156.85 0.9674 Rev Cp J/g/°C 0.7816 0.8026 0.8223 0.8405 0.8578 0.873 0.8869 0.9008 0.9133 0.9256 0.9378 0.9479 0.9582 0.9676 Temperature Heat Capacity 166.85 0.9778 176.85 0.9874 186.85 0.9974 196.85 1.005 206.85 1.012 216.85 1.021 226.85 1.03 236.85 1.037 246.85 1.048 256.85 1.056 266.85 1.066 276.85 1.074 286.85 1.082 Rev Cp 0.9761 0.9826 0.9903 0.9978 1.004 1.01 1.016 1.022 1.027 1.032 1.036 1.041 1.044 Determining K Temperature Heat Capacity °C J/g/°C 26.85 0.7675 36.85 0.7887 46.85 0.8086 56.85 0.8275 66.85 0.8454 76.85 0.8614 86.85 0.8765 96.85 0.8914 106.85 0.9069 116.85 0.9217 126.85 0.9339 136.85 0.9467 146.85 0.9573 156.85 0.9674 166.85 0.9778 176.85 0.9874 186.85 0.9974 196.85 1.005 206.85 1.012 216.85 1.021 226.85 1.03 236.85 1.037 246.85 1.048 256.85 1.056 266.85 1.066 276.85 1.074 286.85 1.082 Rev Cp J/g/°C 0.7816 0.8026 0.8223 0.8405 0.8578 0.873 0.8869 0.9008 0.9133 0.9256 0.9378 0.9479 0.9582 0.9676 0.9761 0.9826 0.9903 0.9978 1.004 1.01 1.016 1.022 1.027 1.032 1.036 1.041 1.044 Theo. Cp K Meas. Cp The heat capacity calibration constant, K, is calculated as the ratio of the theoretical heat capacity of a standard material, to the measured heat capacity of the material. Sapphire Cp Values Aluminum Oxide Specific Heat Capacity* °C J/g°C °C J/g°C °C J/g°C -143.15 -133.15 -123.15 -113.15 -103.15 -93.15 -83.15 -73.15 -63.15 -53.15 -43.15 -33.15 -23.15 -13.15 -3.15 6.85 16.85 26.85 36.85 46.85 56.85 0.2349 0.2739 0.3133 0.3525 0.3912 0.4290 0.4659 0.5014 0.5356 0.5684 0.5996 0.6294 0.6577 0.6846 0.7102 0.7344 0.7574 0.7792 0.7999 0.8194 0.8380 66.85 76.85 86.85 96.85 106.85 116.85 126.85 136.85 146.85 156.85 166.85 176.85 186.85 196.85 206.85 216.85 226.85 236.85 246.85 256.85 276.85 0.8556 0.8721 0.8878 0.9027 0.9168 0.9302 0.9429 0.9550 0.9666 0.9775 0.9879 0.9975 1.0074 1.0164 1.0250 1.0332 1.0411 1.0486 1.0559 1.0628 1.0758 286.85 296.85 306.85 316.85 326.85 336.85 346.85 356.85 366.85 376.85 386.85 396.85 406.85 416.85 426.85 446.85 466.85 486.85 506.85 526.85 546.85 1.0819 1.0877 1.0934 1.0988 1.1040 1.1090 1.1138 1.1184 1.1228 1.1272 1.1313 1.1353 1.1393 1.1431 1.1467 1.1538 1.1605 1.1667 1.1727 1.1784 1.1839 *Taken from ASTM E1269, Standard Test Method for Determining Specific Heat Capacity by Differential Scanning Calorimetry, which references Archer, D.G.,J. Phys. Chem. Ref. Data, Vol.22, No. 6, pp. 1441-1453. Determining K @ 1 temperature Temperature Heat Capacity °C J/g/°C 26.85 0.7675 36.85 0.7887 46.85 0.8086 56.85 0.8275 66.85 0.8454 76.85 0.8614 86.85 0.8765 96.85 0.8914 106.85 0.9069 116.85 0.9217 126.85 0.9339 136.85 0.9467 146.85 0.9573 156.85 0.9674 166.85 0.9778 176.85 0.9874 186.85 0.9974 196.85 1.005 206.85 1.012 216.85 1.021 226.85 1.03 236.85 1.037 246.85 1.048 256.85 1.056 266.85 1.066 276.85 1.074 286.85 1.082 Rev Cp Lit value J/g/°C 0.7816 0.8026 0.8223 0.8405 0.8578 0.873 0.8869 0.9008 0.9133 0.9168 0.9256 0.9378 0.9479 0.9582 0.9676 0.9761 0.9826 0.9903 0.9978 1.004 1.01 1.016 1.022 1.027 1.032 1.036 1.041 1.044 KCp K RevCp 1.0109 1.0038 Theo. Cp K Meas. Cp Determining K(multiple temperatures) Temperature Heat Capacity °C J/g/°C 26.85 0.7675 36.85 0.7887 46.85 0.8086 56.85 0.8275 66.85 0.8454 76.85 0.8614 86.85 0.8765 96.85 0.8914 106.85 0.9069 116.85 0.9217 126.85 0.9339 136.85 0.9467 146.85 0.9573 156.85 0.9674 166.85 0.9778 176.85 0.9874 186.85 0.9974 196.85 1.005 206.85 1.012 216.85 1.021 226.85 1.03 236.85 1.037 246.85 1.048 256.85 1.056 266.85 1.066 276.85 1.074 286.85 1.082 Rev Cp Lit value J/g/°C 0.7816 0.8026 0.8223 0.8405 0.8380 0.8578 0.873 0.8869 0.9008 0.9133 0.9168 0.9256 0.9378 0.9479 0.9582 0.9676 0.9775 0.9761 0.9826 0.9903 0.9978 1.004 1.0250 1.01 1.016 1.022 1.027 1.032 1.0628 1.036 1.041 1.044 Theo. Cp K Meas. Cp Determining K(multiple temperatures) Temperature Heat Capacity °C J/g/°C 26.85 0.7675 36.85 0.7887 46.85 0.8086 56.85 0.8275 66.85 0.8454 76.85 0.8614 86.85 0.8765 96.85 0.8914 106.85 0.9069 116.85 0.9217 126.85 0.9339 136.85 0.9467 146.85 0.9573 156.85 0.9674 166.85 0.9778 176.85 0.9874 186.85 0.9974 196.85 1.005 206.85 1.012 216.85 1.021 226.85 1.03 236.85 1.037 246.85 1.048 256.85 1.056 266.85 1.066 276.85 1.074 286.85 1.082 Rev Cp Lit value J/g/°C 0.7816 0.8026 0.8223 0.8405 0.8380 0.8578 0.873 0.8869 0.9008 0.9133 0.9168 0.9256 0.9378 0.9479 0.9582 0.9676 0.9775 0.9761 0.9826 0.9903 0.9978 1.004 1.0250 1.01 1.016 1.022 1.027 1.032 1.0628 1.036 1.041 1.044 Avg KCp K RevCp 1.0127 0.9970 1.0109 1.0038 1.0104 1.0102 1.0128 1.0209 1.0064 1.0298 1.0107 1.0124 Theo. Cp K Meas. Cp Type K values into Cell Calibration table Optimization of MDSC® Experimental Conditions MDSC® controls the Heating Rate(s) applied to the sample through three experimental parameters: 1. Average Heating Rate (°C/min) – Typically less than 5°C/minute in order to get a minimum of 4-5 temperature modulations during a transition 2. Temperature Modulation Amplitude (± °C) – Typically ± 0.1 to 2°C 3. Temperature Modulation Period (Seconds) – Typically 40 – 100 seconds Optimization (cont.) Proper selection of the three experimental parameters is important in order to maximize the quality of the results. • Specific recommendations for different types of transitions will be provided in later sections. • In general, temperature is controlled to either provide or not provide cooling during the temperature modulation. • The combination of temperature modulation amplitude and period control the range in heating rate while its average is defined by the specified heating rate. MDSC® Heat-Iso Amplitudes (no cooling/measure crystallinity) Period (sec) H e a t i n g 40 50 60 70 80 90 100 0.1 0.011 0.013 0.016 0.019 0.021 0.024 0.027 0.2 0.021 0.027 0.032 0.037 0.042 0.048 0.053 0.5 0.053 0.066 0.080 0.093 0.106 0.119 0.133 1.0 0.106 0.133 0.159 0.186 0.212 0.239 0.265 R 2.0 0.212 0.265 0.318 0.371 0.424 0.477 0.531 a t 5.0 0.531 0.663 0.796 0.928 1.061 1.194 1.326 e This table is additive, i.e. the heat only amplitude for a period of 40 sec & a heating rate of 2.5°C/min is the sum of the values for 2.0°C/min & 0.5°C/min Amplitude (40s,2.5°C/min)=0.212+0.053=0.265°C MDSC® Heat-Iso Temperature Modulation No Cooling Heating Rate never goes below 0°C/min MDSC® Heat-Cool Temperature Modulation Heating & Cooling Heating Rate goes below 0°C/min Optimization of MDSC® Conditions for Glass Transitions w/ a Q Series MDSC (heat-cool) MDSC® Analysis of the Glass Transition The following measurements will be illustrated • Measurement of Tg in Complex Samples • Quantitative Measurement of Amorphous Structure in Materials • Quantitative Measurement of Enthalpic Recovery (Relaxation) in Aged Samples – Glass transition is frequency dependent – MDSC applies a frequency (Period) during the measurement and this affects the measured temperature of the Reversing signal – It is necessary to do a “Frequency Correction” in order to measure absolute values of enthalpic recovery Measuring Tg in Complex Samples with MDSC® • Complex samples are ones that have overlapping • • transitions which make it difficult to detect or measure Tg MDSC experimental conditions which provide some cooling during temperature modulation are recommended Use an underlying heating rate that is slow enough to provide 4 or more modulation cycles over the transition of interest in order to improve separation of overlapping events (resolution) Figure 25 - MDSC® of Frozen Sucrose Solution Sample: Epoxy Size: 10.8500 mg Method: MDSCiso.5/40@100 Comment: MDSC iso@100 File: C:\TA\Data\Len\Epoxy\MDSCiso100.001 Advantage of MDSC® for Post Cure Scan DSC 0.2 0.4 Heating Experiment 3 C/min Heating Experiment atat 3°C/min 160min Isothermal Cure @ 100°C Afterafter 160 min Isothermal Cure at 100 C Nonreversing -0.6 Note Inability to Measure Tg Total -1.0 Reversing 110.75°C 117.14°C 31.08J/g 0.0 0.0 -0.4 -0.4 -0.8 All Signals at Same Sensitivity 119.12°C(H) 0.2810J/g/°C -1.4 -1.2 52 Exo Up 0.4 [ ––––– · ] Rev Heat Flow (mW) Sample: Epoxy Size: 10.85 mg [ –– –– – ] Nonrev Heat Flow (mW) Heat Flow (mW) -0.2 Note Onset of Decomosition before Complete Cure 102 152 Temperature (°C) 202 252 Universal V3.8A TA Instruments DSC of Complex Polymer Blend MDSC® of Complex Polymer Blend Optimization of MDSC® Experimental Conditions for Analysis of Melting and Crystallinity • Sample Size; 10-15mg • Period – 40 sec. Q Series for crimped pans – 60 sec. Q Series for hermetic pans • Heating Rate – Slow enough to get a minimum of 4-5 cycles at halfheight of the melting peaks • Amplitude – Use “Heat-Iso” amplitude which provides no cooling during temperature modulation (see Table) – Crystallization will not be caused by a lowering of the temperature Optimization of MDSC® Conditions for Melting (cont.) Issues with Use of MDSC in Melting Region Before discussing how MDSC® can be used to analyze melting and crystallinity, it is necessary to discuss some technical issues with the measurement. • Issue 1: MDSC® cannot provide a meaningful measurement on samples that have a narrow melting range (pure metals and chemicals). The reason is that the temperature of the sample cannot be modulated during melting (Figures 43-44). • Issue 2: Because there are two simultaneous endothermic processes occurring during melting (heat capacity and latent heat of fusion), and because those processes respond differently to temperature modulation, the separation of the Total signal into the Reversing and Nonreversing components changes when experimental conditions are changed (Fig 4553). MDSC® Should Not Be Used on Sharp Melting Transitions MDSC® of Water Melting/Boiling MDSC® Raw Data Signals on Polymer Blend MDSC® of 57/43 % PET/PC Blend Sample: Quenched PET and PC Size: 13.6000 mg DSC Method: MDSC .318/40@3 Comment: MDSC 0.318/40@3; PET13.60/PC 10.40/Al film 0.96mg File: C:\TA\Data\Len\Crystallinity\qPET-PC.002 3 57% PET; 43% PC MDSC Signals 2 Heat Flow (mW) 270.00°C -1 -3 155.00°C 270.00°C 1 0 -1 -2 [ ––––– · ] Rev Heat Flow (mW) 95.13J/g 110.00°C [ –– –– – ] Nonrev Heat Flow (mW) 1 -3 93.60J/g -5 -4 Initial Crystallinity = 93.6 + (-95.1) = -1.5 J/g -5 50 Exo Up 100 150 Temperature (°C) 200 250 300 Universal V3.8A TA Instruments DSC Analysis of Cycoloy C2950: Standard DSC Ramp Sample: Cycoloy C2950 Size: 5.5740 mg 0.0 Method Log: 1: Equilibrate at 0.00°C 2: Ramp 5.00°C/min to 300.00°C 3: End of method Using standard DSC a single glass transition is observed. Heat Flow (W/g) -0.1 107.05°C 113.87°C(I) 119.62°C -0.2 -0.3 0 Exo Up 50 100 150 Temperature (°C) 200 250 300 Universal V4.3A TA Instruments DSC Analysis of Cycoloy C2950: MDSC Heat Cool Heat Method/ First Heat Sample: Cycoloy Size: 6.3900 mg 0.00 First Heat Cycle -0.02 -0.04 106.65°C 110.99°C(I) 159.55°C 115.08°C Rev Heat Flow (W/g) Using MDSC two glass transitions are observed in the MDSC Reversing heat flow signal. 165.47°C(I) -0.06 168.89°C 0 Exo Up 50 100 150 Temperature (°C) 200 -0.08 250 Universal V4.3A TA Instruments Using the TMA Q400 to Observe the Glass Transitions in Cycoloy C2950 Sample: Cycoloy C2950 Size: 1.8208 mm 500 Glass Transition 108.90°C 0 113.39°C(I) 185.1µm Dimension Change (µm) 115.28°C -500 Glass Transition 136.34°C 144.27°C(I) 1742µm -1000 Method Log: 1: Force 0.200 N 2: Ramp 5.00°C/min to 200.00°C 3: End of method -1500 152.25°C -2000 20 40 60 80 100 120 Temperature (°C) 140 160 180 200 Universal V4.3A TA Instruments Summary • MDSC® is a slow technique. Always start the analysis of a new material with standard DSC and only use MDSC if you need. – – – – Improved sensitivity Better resolution Separation of overlapping transitions Most accurate measurement of polymer crystallinity • Don’t forget that MDSC can be used while • • cooling Optimum results require the selection of optimum experimental conditions When in doubt, ask TA Instruments for help? What if I need help? • On-site training & e-Training courses - see Website • Call the TA Instruments Hotline • • – 302-427-4070 M-F 8-4:30 Eastern Time – thermalsupport@tainstruments.com Call the TA Instruments Service Hotline – 302-427-4050 M-F 8-4:30 Eastern Time Check out our Website – www.tainstruments.com