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D. JAGAN MOHAN New Technology Research Centre University of West Bohemia Plzen, Czech Republic.

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Presentation on theme: "D. JAGAN MOHAN New Technology Research Centre University of West Bohemia Plzen, Czech Republic."— Presentation transcript:

1 D. JAGAN MOHAN New Technology Research Centre University of West Bohemia Plzen, Czech Republic

2 refers to the use of external techniques to probe into the internal structure and properties of a material.


4 Mikhail Tswett, Russian, 1872-1919 Botanist In 1906 Tswett used to chromatography to separate plant pigments He called the new technique chromatography because the result of the analysis was 'written in color' along the length of the adsorbent column Chroma means “ color ” and graphin means to “ write ”

5 …is a technique used to separate and identify the components of a mixture. Works by allowing the molecules present in the mixture to distribute themselves between a stationary and a mobile medium. Mobile phase Mobile phase is a liquid as water or dilute alcohol Separation mechanism Based on difference between the solutes molecular weights. Molecules will distribute themselves outside & inside the pores according to their size.

6 This type is also known as:

7 GPC can determine several important parameters. These include number average molecular weight, weight average molecular weight, and the most fundamental characteristic of a polymer its molecular weight distribution. These values are important, since they affect many of the characteristic physical properties of a polymer. Tensile strength Elastomer relaxation time Brittleness Toughness Softening temperature Cure time Elastic modulus Hardness Adhesive strength Impact strength

8 Separation based on Size Large molecules Polymer solution medium molecules small molecules Column "Size Exclusion" chromatography Molecular weight distribution Number average Molecular weight Weight average Molecular weight

9 Small particles can enter gel and have more volume to traverse. They elute later Large particles cannot enter gel and are excluded. They have less volume to traverse and elute chromatogram flow time

10 Inside the gel permeation chromatograph, the dissolved sample is injected into a continually flowing stream of solvent (mobile phase). The mobile phase flows through millions of highly porous, rigid particles (stationary phase) tightly packed together in a column. GPC separates molecules in solution by their "effective size in solution." To prepare a sample for GPC analysis the polymer sample is first dissolved in an appropriate solvent. The pore sizes of these particles are controlled and available in a range of sizes. SEC was first developed in 1955 by Lathe and Ruthven

11 Solvent delivery system injector Column(s) detector(s) Data system Solvent supply Mobile phase sample Schematic of a basic Gel permeation chromatograph

12 Large molecules are excluded Small molecules penetrate pores of particles Polymer – Dissolving in solvent Membranes – Passed through std. sol. MWCO ( Molecular weight Cut-Off )

13 High temperature GPC


15 Modern instrumentation used for thermal analysis usually consists of the following parts: sample holder/compartment for the sample sensors to detect/measure a property of the sample and the temperature an enclosure within which the experimental parameters (temperature, speed, environment) may be controlled a computer to control data collection and processing sample PC Temperature Control (Furnace) Sensors Basic Principles of Thermal Analysis

16 Differential two calorimeters (for sample and reference) with the same heat transfer behavior (for compensation purpose) Scanning the common operation mode is to run temperature or time scans Calorimeter instrument to measure heat or heat flow

17 The portion of material whose molecules are randomly oriented in space. Liquids and glassy or rubbery solids. Thermosets and some thermoplastics. The portion of material whose molecules are regularly arranged into well defined structures consisting of repeat units. Very few polymers are 100% crystalline. Polymers whose solid phases are partially amorphous and partially crystalline. Most common thermoplastics are semi-crystalline. 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. Amorphous Phase Crystalline Phase Semi-crystalline Polymers Melting

18 Semi-Crystalline (or Amorphous) Crystalline Phase melting temperature T m (endothermic peak) Amorphous Phase glass transition temperature (T g ) T g < T m Crystallisable polymer can crystallize on cooling from the melt at T c (T g < T c < T m )

19 Gas control Furnace Detectors Sample Reference Temperature controller Data acquisition Microvolt amplifier differential detector signal amplifier furnace temperature controller gas control device data acquisition device

20 Sample Pan Pan sealed DSC measures the temperatures and heat flows associated with transitions in materials as a function of time and temperature in a controlled atmosphere. These measurements provide quantitative and qualitative information about physical and chemical changes that involve endothermic or exothermic processes, or changes in heat capacity.

21 Temperature Heat Flow - > exothermic Glass Transition Crystallization Melting Cross-Linking (Cure) Oxidation Typical DSC Curve of a Thermosetting Polymer

22 Exothermic upwards Endothermic downwards Y-axis – heat flow X-axis – temperature (and time) Desolvation Glass Transition (T g ) Crystallization (T c ) Melting (T m ) Decomposition H2OH2O Temperature ( o C) Typical Features of a DSC Trace

23 -1.5 -0.5 0.0 0.5 1.0 1.5 Heat Flow (W/g) 04080120160200240 Temperature (°C) cooling first heating second heating DSC Curve : Heat/Cool/Heat

24 Onset = Melting point (mp) Heat of fusion (melting) = integration of peak Temperature ( o C)

25 Temperature (°C) 150152154156 0 -2 -4 -6 DSC Heat Flow (W/g) 10mg 4.0mg 15mg 1.7mg 1.0mg 0.6mg Indium at 10°C/minute Normalized Data 158160162164166 Onset not influenced by mass

26 A technique measuring the variation in mass of a sample undergoing temperature scanning in a controlled atmosphere Thermobalance allows for monitoring sample weight as a function of temperature The sample hangs from the balance inside the furnace and the balance is thermally isolated from the furnace

27 Gas IN


29 Temperature Poly(PMDA-ODA-TMAc) Poly(PMDA-ODA-TPC) Poly(PMDA-ODA-IPC) % 0 20 40 60 80 °C100200300400500600700800 Nitrogen IDT Poly(PMDA-ODA-TMAc) Poly(PMDA-ODA-TPC) Poly(PMDA-ODA-IPC Temperature % 0 20 40 60 80 100 °C100200300400500600700800 Oxygen IDT - Initial decomposition Temp CD - Complete decomposition CD Data : Weight Vs Time Weight Vs Temperature Weight Loss

30 Weight Loss (%) Temperature ( o C) Step-I Step-II Step-III

31 UVX-raysIR  -rays RadioMicrowave 300-30 ~10 -4 > 300~10 -6 Visible ~10 15 ~10 13 ~10 10 ~10 5 ~10 17 ~10 19 10 nm1000 nm 0.01 cm 100 m~0.01 nm~.0001 nm nuclear excitation (PET) core electron excitation (X-ray cryst.) electronic excitation (p to p*) molecular vibration molecular rotation Nuclear Magnetic Resonance NMR The entire electromagnetic spectrum is used by chemists:

32 A molecule such as H 2 O will absorb infrared light when the vibration (stretch or bend) results in a molecular dipole moment change

33 A molecule can be characterized (identified) by its molecular vibrations, based on the absorption and intensity of specific infrared wavelengths. O-H Bend O-H Stretching Water

34 The Infrared region is divided into: near, mid and far-infrared. – Near-infrared refers to the part of the infrared spectrum that is closest to visible light and far- infrared refers to the part that is closer to the microwave region. – Mid-infrared is the region between these two

35 O  H single bond N  H single bond C  H single bond C ≡ C C ≡ N C=O C=N C=C C  C C  N C  O Fingerprint Region Bonds to H Triple bonds Double bonds Single Bonds 4000 cm -1 2700 cm -1 2000 cm -1 1600 cm -1 400 cm -1 The four primary regions of the IR spectrum

36 Porous materials have highly developed internal surface area that can be used to perform specific function. Almost all solids are porous except for ceramics fired at extremely high temperatures Non-porous solid Low specific surface area Low specific pore volume Porous solid High specific surface area High specific pore volume

37 Dead end (open) closed Inter-connected (open) Passing (open) Open pores are accessible whereas closed pores are inaccessible pores. Open pores can be inter- connected, passing or dead end.

38 2 nm50 nm Micropores Mesopores Macropores Zeolite, Activated carbon, Metal organic framework Mesoporous silica, Activated carbon Sintered metals and ceramics Porous material are classified according to the size of pores: material with pores less than 2 nm are called micropores, materials with pores between 2 and 50 nm are called mesopores, and material with pores greater than 50 nm are macrospores Size of Pores (IUPAC Standard)

39 Gas adsorption Gas adsorption Small angle Neutron scattering Small angle X-ray scattering SEM TEM Mercury Porosimetry Techniques

40 Typical Pore Structure

41 Gel permeation chromatography (GPC) is a type of size exclusion chromatography (SEC), that separates analytes on the basis of size. DSC is a thermoanalytical technique in which the difference in the amount of heat required to increase the temperature of a sample and reference is measured as a function of temperature TGA is a type of testing performed on samples that determines changes in weight in relation to a temperature program in a controlled atmosphere. IR spectroscopy used to identify and study chemical structure of material in the Infra red region Porous material : micropores, mesopores and macropores


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