Thermal method of analysis.

THERMAL METHOD OF ANALYSIS, , DTA , DSC , PRINCIPLE, INSTRUMENTATON, APPLICATIONS

1. THERMAL METHOD OF ANALYSIS DTA AND DSC Presented by: Shubham Sharma Pharmaceutical Chemistry Roll no. : 20029 Presented to : Dr. Renu C hadha Professor ,UIPS, Panjab University SEMINAR ON Email : [email protected] 5/29/2021

2. CONTEN T S INTRODUCTION TYPES OF DIFFERENT THERMAL ANALYSIS DTA PRINCIPLE INSTRUMENTATION APPLICATION DSC PRINCIPLE INSTRUMENTATION APPLICATION FACTOR AFFECTING TO THERMAL ANALYSIS REFERENCES 5/29/2021 UIPS, PANJAB UNIVERSITY

3. I NTRODUCTION THERMAL ANALYSIS Techniques in which a physical (thermal) property of a substance is measured as a function of temperature while the substance is subjected to a controlled temperature variation. THERMAL ANALYSIS means the analysis of a change in a property of a sample, which is related to an imposed temperature alteration . 5/29/2021 UIPS, PANJAB UNIVERSITY 3

4. There is difference between “ thermo analytical techniques ” and “thermoanalytical methods”. The techniques are characterized by the suffix “-metry”, while the more comprehensive methods , which include the evaluation and interpretation of the measured property values, are indicated by adding “analysis”. Measurements are usually continuous and the heating rate is often, but not necessarily, linear with time. The results of such measurements are thermal analysis curves and the features of these curves (peaks, discontinuities, changes of slope, etc.) are related to thermal events in the sample. When matter is heated, it undergoes Physical Changes :- Phase change such as melting Vaporization, crystallization, transition between crystal structures, change in microstructures in metal alloy & polymers, Chemical Changes :- Include reaction to form new products, oxidation, decomposition, corrosion. Continued…. 5/29/2021 UIPS, PANJAB UNIVERSITY 4

5. T YPES OF D IFFERENT T HERMAL A NALYSIS Properties Techniques Methods Abbreviations Mass Thermogravimetry The r mogravimetric Analysis TGA Pressure Thermomanometry The r momanometric Analysis TMA Electric Properties Thermoelectrometry Thermoelectric Analysis TEA Optical Properties Thermooptometry The r mooptometric Analysis TOA Dimensions or Mechanical Properties Thermomechanometry The r momechan i cal Analysis TMA Temperature Thermometry Heating & Cooling Curve Analysis -- Temperature Difference Differential Thermometry Differential Thermal Analysis DTA Heat flow Di f ference Differential Scanning Calorimetry -- DSC 5/29/2021 UIPS, PANJAB UNIVERSITY 5

6. DIFFERENTIAL THERMAL ANALYSIS Principle:- Differential thermal analysis (DTA) is a technique in which the difference in temperature between a substance and a reference material is measured as a function of temperature while the substance and reference material are subjected to a controlled temperature program. The differential temperature is plotted against temperature or time is called DTA curve . Both sample & reference material heated in controlled condition . If any reaction (physical or Chemical changes ) takes place temperature difference (∆T) will occur between sample & reference material. 5/29/2021 UIPS, PANJAB UNIVERSITY 6

7. REFERENCE MATERIAL The reference material should have the following characteristics: It should undergo no thermal events over the operating temperature range. It should not react with the sample holder or thermocouple . Both the thermal conductivity and the heat capacity of the reference should be similar to those of the sample. For inorganic samples- Alumina, and carborundum, SiC, For organic compounds- octyl phthalate and silicone oil. 5/29/2021 UIPS, PANJAB UNIVERSITY 7

8. INST R UME N TA TI O N Furnace Sample Holder Temperature meas u rement C o mp u ter - D a ta acquisition , processing & control system 5/29/2021 UIPS, PANJAB UNIVERSITY 8

9. F URNACE Both sample & reference material match thermally & arranged systematically with the furnace, so that both are heated or cooled in identical manner. The metal block surrounding the well act as heat sink. Temperature of the heat sink slowly increases by using internal heater. Its temperature range from ambient temperature to l600°C SAMPLE HOLDERS Sample holder called crucible are made up of metallic (Aluminum , Platinum) & ceramic (silica). Sample are usually 1- 10 mg for analysis. The dimension of two crucibles & cell well are as nearly identical as possible. 5/29/2021 UIPS, PANJAB UNIVERSITY 9

10. T EMPERATURE MEASUREMENT Pair of thermocouples used in DTA. 5/29/2021 UIPS, PANJAB UNIVERSITY 10

11. DTA CURVE The initial decrease in T is due to the glass transition. The glass transition temperature Tg is the characteristic temperature at which glassy amorphous polymers become flexible or rubber like. The two maxima are the result of exothermic processes in which heat is evolved from the sample, thus causing its temperature to rise. When heated to a characteristic temperature, many amorphous polymers begin to crystallize as microcrystals, giving off heat in the process. Crystal formation is responsible for the first exothermic peak . The minimum labeled "melting" is the result ofan endothermic process in which heat is absorbed by the analyte . The second peak in the figure is endothermic and involves melting of the microcrystals formed in thc initial exothermic process. The third peak is exothermic and is encountered only if the heating is performed in the presence of air or oxygen. The final negative change in ∆T results from the endothermic decomposition of the polymer to produce a variety of products. 5/29/2021 UIPS, PANJAB UNIVERSITY 11

12. APPLICATIONS DTA is a widely used tool for studying and characterizing polymers. The types of physical and chemical changes in polymeric materials that can be studied by DTA. DTA is also used in the ceramics and metals industry. DTA is used to study decomposition temperatures, phase transitions, melting and crystallization points, and thermal stability. An important use of DTA is for the generation of phase diagrams and the study of phase transitions. The DTA method also provides a simple and accurate way of determining the melting, boiling, and decomposition points of organic compounds. 5/29/2021 UIPS, PANJAB UNIVERSITY 12

13. D IFFERENTIAL S CANNING C ALORIMETRY Principle:- Differential Scanning Calorimetry (DSC) is a Thermal Analysis technique in which the heat flow rate (power) to the sample is monitored against time or temperature while the temperature of the sample, in a specified atmosphere, is programmed. It is measure heat into or out of sample. Di f fer e n c es in heat fl o w o c c u r with the o c c u rrence of two major events- The heat ca p ac i ty of the sample which in c r ea ses with t emperature . Transitions occur 5/29/2021 UIPS, PANJAB UNIVERSITY 13

14. I NSTRUMENTATION Furnace Sample Holder Temperature meas u rement C o mp u ter - D a ta acquisition , processing & control system 5/29/2021 UIPS, PANJAB UNIVERSITY 14

15. INSTRUMENTATION Types of DSC Power-compensated DSC Heat-flux DSC Modulated DSC 5/29/2021 UIPS, PANJAB UNIVERSITY 15

16. POWER-COMPENSATED DSC In power-compensated DSC, the temperatures of the sample and reference are kept equal to each other while both temperatures are increased or decreased linearly. The power needed to maintain the sample temperature equal to the reference temperature is measured. 5/29/2021 UIPS, PANJAB UNIVERSITY 16

17. 2. HEAT-FLUX DSC In heat-flux DSC, the difference in heat flow into the sample and reference is measured while the sample temperature is changed at a constant rate. Both sample and reference are heated by a single heating unit. 5/29/2021 UIPS, PANJAB UNIVERSITY 17

18. 3. MODULATED DSC Modulated DSC (MDSC) uses the same heating and cell arrangement as the heat-flux DSC method. In MDSC, a sinusoidal function is superimposed on the overall temperature program to produce a micro heating and cooling cycle as the overall temperature is steadily increased or decreased. Differential Scanning Calorimetry – Principle of Operation A sample is placed inside a crucible which is then placed inside the furnace of the DSC system along with a reference pan which is normally empty (inert gas may be used). By applying a controlled temperature program (isothermal, heating or cooling at constant rates), phase changes can be characterized and/or the specific heat of a material can be determined. Heat flow quantities are calculated based on calibrated heat flow characteristics of the cell. 5/29/2021 UIPS, PANJAB UNIVERSITY 18

19. According to the thermal transformation, an endothermic or exothermic effect is recorded. In the case of an endothermic effect, it is needed to provide heat to the system for its transformation(sample absorbs energy). This will result in a decrease of the temperature in the system during the transformation(sample releases energy ). In the case of an exothermic effect, the system provides heat during its transformation. This results in an increase of the temperature in the system. ENDOTHERMIC AND EXOTHERMIC EFFECTS - common endothermic effects: melting, sublimation first order and second order phase transitions evaporation, dehydration denaturation (protein) gelatinization (starch with water) common exothermic effects Crystallization, Gelation (gel formation) Oxidation, combustion, Decomposition, ignition, explosion Fermentation, Most of the chemical reactions, Polymerization, reticulation 5/29/2021 UIPS, PANJAB UNIVERSITY 19

20. DSC CURVE Analysis of a polymer shows several features due to physical and chemical changes, including: DSC of polymer 5/29/2021 UIPS, PANJAB UNIVERSITY 20

21. APPLICATIONS Glass Transition Temperatures :- Determination of the glass transition temperature T, is one of the most important applications of DSC. The physical properties of a polymer undergo dramatic changes at Tg, where the material goes from a glassy to a rubbery state. At the glass transition, the polymer undergoes changes in volume and expansion, heat flow and heat capacity. The change in heat capacity is readily measured by DSC . Crystallinity and Crystallization Rate:- In most cases DSC is one of the easiest methods for determining levels of crystallinity . Reaction Kinetics:- Many chemical reactions, such as polymer formation reactions, are exothermic and readily monitored by DSC methods . Melting points – crystalline materials. Desolvation :- adsorbed and bound solvents Purity determination :- contamination 5/29/2021 UIPS, PANJAB UNIVERSITY 21

22. F ACTOR AFFECTING TO T HERMAL ANALYSIS Instrumental Furnace Heating rate-↑es heating rate , ↑es decomposition Furnace atmosphere- pure intert gas like N 2 Sample characteristics Sample particle size Weight of sample Polymorphic transitions :- P olymorphs and pseudo polymorphs Processing conditions :- environmental factors Compatibility :- interactions between components Decomposition kinetics :- chemical and thermal stability 5/29/2021 UIPS, PANJAB UNIVERSITY 22

23. REF E R E N C ES Douglas A. Skoog, Principles of Instrumental Analysis, 6 th Edition , 894-904 . Michael E. Brown ,Introduction to Thermal Analysis Techniques and Applications , 2 nd Edition. Gurdeep Chatwal , Instrumental methods of chemical analysis : Analytical Chemistry. 5/29/2021 UIPS, PANJAB UNIVERSITY 23