《Modern Research Methods in Polymer Science》 Drs. Wei Tian & Yanhui Chen Sep-Dec. 2014 Let’s start….

Thermal Analysis Modern Research Methods in Polymer Science Differential Scanning Calorimetry (DSC) Thermogravimetric Analyzer (TGA) Today’s topic is thermal analysis, it includes three techniques, Dynamic Mechanical Analyzer (DMA)

Power compensation DSC Differential Scanning Calorimetry (DSC) DTA inaccurate enthalpy uneven baseline degradation temperature RT-1200 ºC Features Heat flux DSC accurate enthalpy flat baseline overshoot -30-300 ºC Features Power compensation DSC accurate enthalpy intermediate baseline isothermal study -30-600 ºC； Features Let’s talk about DSC first. Its equipment looks like this. About the heating chamber, it could be like DTA, differential thermal analysis. In this technique it is the heat flow to the sample and reference that remains the same rather than the temperature. When the sample and reference are heated identically, phase changes and other thermal processes cause a difference in temperature between the sample and reference. It means DTA measures the difference in temperature between the sample and the reference when they are both put under the same heat. It has some features, like inaccurate enthalpy, uneven baseline. It can be used to measure the degradation temperature. Its temperature range is from RT-1200 ºC. It could be heat flux DSC. The heat is transferred through the plate, Like DTA, it still is used to measure the difference in temperature between the sample and the reference. Its features are accurate enthalpy, flat baseline, the temperature is easily overshoot, and its range is from -30-300 ºC. In fact, the most popular one is power compensation DSC, it keeps the temperature constant rather than the heat, so that it has accurate enthalpy , intermediate baseline. The most important thing is it can be used in isothermal study, the temperature ranges from -30-600 ºC； The principle for DSC technique is to use voltage to keep ΔT = TS‐TR= 0 vs. T 在相同的条件下进行等温加热或冷却，当样品发生相变时，在样品和参比物之间就产生一个温度差。放置于下面的热电偶会产生温差电势UΔT，经差热放大器放大后送入功率补偿放大器，功率补偿放大器自动调节补偿加热丝的电流，目的是使样品和参比物之间温差趋于零，即两者温度始终维持相同。此补偿热量即为样品的热效应，以电功率形式显示于记录仪上。 Differential Scanning Calorimeters (DSC) measures temperatures and heat flows associated with thermal transitions in a material. Common usage includes investigation, selection, comparison and end-use performance evaluation of materials in research, quality control and production applications. Properties measured by TA Instruments’ DSC techniques include glass transitions, "cold" crystallization, phase changes, melting, crystallization, product stability, cure / cure kinetics, and oxidative stability.  Principle: Voltage to keep ΔT = TS‐TR= 0 vs. Time

Main influencing factors Differential Scanning Calorimetry (DSC) 01 Sample mass a: big amount b: small amount 3-15mg 02 Heating rate 5-10 ºC/min a: 5; b: 20; c: 60; d: 120 03 N2, He Atmosphere Anti-oxidation Anti-corrosion 04 Eliminate the influence of previous thermal history, like temperature, time. Thermal history 10 ºC/min Tm+30 ºC 5~10 min many factors can influence the DSC results, which we should pay attention to. At first, In order to get accurate results, the sample mass should be in the range of 3-15mg， because different amount can give rise different results as you can see from the picture. We need to set an standard here for comparison. Secondly, the heating rate should be in the range of 5-10 C/min. But if you are studying the influence of heating rate on the melting behavior of samples, you can change the heating rate of course. That is another story. Thirdly, about atmosphere, we normally put the samples under the N2 or He, in order to avoid the oxidation or corrosion. Final one is thermal history, usually, we put the samples at the temperature of Tm+30 C for 5-10 min, in order to eliminate the influence of previous thermal history like temperature, time and thermo mechanical history. Main influencing factors

Specific heat capacity Differential Scanning Calorimetry (DSC) Tm Tg Tc Application Specific heat capacity ΔH There are some typical application of DSC, like Tg, glass transition temperature, Tm, melting temperature, Tc crystallization temperature, ΔH delta H, the endothermic enthalpy or exothermic enthalpy. You can calculate the crystallinity, record the kinetics and reaction. Or calculate the specific heat capacity. 玻璃化转变温度；结晶熔融温度；相容性; 结晶与熔融热焓、结晶度；氧化诱导期；比热容；固化热焓与固化度；结晶与固化动力学；（稳态）等温结晶与固化。 Reaction Crystallinity Kinetics

Crystallization & Melting Differential Scanning Calorimetry (DSC) Example Crystallization & Melting Tm Tc ΔHm △ W △T 𝑋𝑐= ∆ 𝐻 𝑚 ∆ 𝐻 𝑚 0 ×100% Here is an example. There are some parameters you should know about. Let’s look at the above red curve. Tim means the initial melting temperature, showing the deviation of the heating curve from the baseline. Teim means the extrapolate initial temperature, is the cross point between the baseline and the tangent line. Then goes to the Tpm, the peak melting temperature, this is the usually we called Tm. Tefm you can easily understand, that is, extrapolate final temperature. Tfm, the final melting temperature. △W is half width of the peak, Do you know what it is corresponding to? The regularity. △Hm is calculated based on this closed area, using this you can calculate the crystallininty. Let’s look at the below purple curve. According what I just said, you should know what Tic means. How about Tpc? Acctually, it is Tc.

Modulated DSC Differential Scanning Calorimetry (DSC) permit separation of the total heat flow signal into its thermodynamic (heat capacity) and kinetic components.  offer simultaneous improvements in sensitivity and resolution. separate overlapping events that are difficult or impossible to do by standard DSC. Moreover, there is a newly developed DSC technique, it is called modulated DSC. As you can see from this picture, besides the normal linear heating curve, a sine heating wave is added. In this way, modulated DSC will permit separation of the total heat flow signal into its thermodynamic (heat capacity) and kinetic components, offer simultaneous improvements in sensitivity and resolution, separate overlapping events that are difficult or impossible to do by standard DSC. As you can see, the total curve can be divided into two parts, the reversing and nonreversing. Normally, the reversing part is relevant to heat capacity, while the nonreversing to the kinetics. Do you know what kind of procedure corresponds to the reversing part? Tg, How about the nowreversing one? Like chemical reaction, relaxation and cold crystallization. Modulated DSCTM measures both heat flow and heat capacity in a single experiment by superimposing a modulated heating rate (changing heating rate) on top of a linear heating rate.由调制式DSC 得到的结果不仅提供了传统DSC 可以提供的“总”热流, 同时它把“总”热流分为与热容相关的（可逆的）和动力学相关的（不可逆的）分量。玻璃化转变温度为可逆的，不可逆的曲线反映了如化学反应（氧化、固化、分解等）和非平衡相转变（冷结晶、松弛等）的存在。

Pérez, R. A.; López, J. V., et al. Macromolecules 2014, 47, 3553. Differential Scanning Calorimetry (DSC) Description About the description of DSC, it is usually very simple. You need to put the DSC type, the sample mass, calibration materials, and the thermal procedure. I want to invite one person to read this aloud for us. Who want to be the volunteer? If not, I will choose one randomly. Pérez, R. A.; López, J. V., et al. Macromolecules 2014, 47, 3553.

Zero position detector Thermogravimetric Analyzer (TGA) Zero position detector Mass change Reversible force Zero position Scale Mass change Beam inclines Deflection Scale OK. Let’s move on to the TGA. Its equipment looks like thisThermogravimetric analysis (TGA relies on a high degree of precision in three measurements: mass change, temperature, and temperature change. Therefore, the basic instrumental requirements for TGA are a precision balance with a pan loaded with the sample, and a programmable furnace. The furnace can be programmed either for a constant heating rate, or for heating to acquire a constant mass loss with time.

Main influencing factors Thermogravimetric Analyzer (TGA) 01 Sample mass Pan material 1: powder 2: particle 2-5mg 02 Heating rate 5-15 ºC/min 03 40mL/min Air flow rate Chemical Reaction 04 Avoid: Vibration Flotage Condensation instrumental factors There are some influencing factors we should pay attention to. First, the sample mass should be in the range of 2-5mg. The use of pan materials depends on your sample. Heating rate should be in the range of 5-15 C/min. 40 mL/min Air flow rate is the best for chemical reaction. When we are using TGA, we need to avoid Vibration, Flotage, and Condensation Main influencing factors

Copolymer and blend analysis Thermogravimetric Analyzer (TGA) Thermostability Composition analysis Application Reaction Solidification Its application includes: 玻璃化转变温度；结晶熔融温度；相容性; 结晶与熔融热焓、结晶度；氧化诱导期；比热容；固化热焓与固化度；结晶与固化动力学；（稳态）等温结晶与固化。 Degradation kinetics Copolymer and blend analysis

Example Thermogravimetric Analyzer (TGA) Weight loss Tei Ti T1% T5% W1 Ti : initial degradation temperature Tei : Degradation temperature T1% , T5% ,T10% ,Ta% : temperatures correspond to the weight loss of 1%, 5%, 10% and a%, respectively Tf : final degradation temperature Tei Ti Weight loss T1% T5% W1 T10% Ta% Here is an example. This is a sample degradation procedure upon heating. There also are some parameters, like Ti : initial degradation temperature, Tei : Degradation temperature, T1% , T5% ,T10% ,Ta% : temperatures correspond to the weight loss of 1%, 5%, 10% and a%, respectively. Tf : final degradation temperature. It shows the degradation of two components. Plateau Plateau Component 1 Component 2 Tf Weight loss region

Description Thermogravimetric Analyzer (TGA) Ok. About this description, who want to be the volunteer? Rafique, F. Z.; Vasanthan, N. The Journal of Physical Chemistry B 2014, 118, 9486.

Dynamic Mechanical Analyzer (DMA) Modulus Dual cantilever Single cantilever Tension Three-point bending Simple shear Compression Let’s talk about the final one technique, DMA, is a technique where a small deformation is applied to a sample in a cyclic manner. This allows the materials response to stress, temperature, frequency and other values to be studied. The deformation can be applied in different modes. Like Dual cantilever, single cantilever, three-point bending tension, simple shear and compression. Normally, for an elastic material, if a deformation is applied, the response is immediate. However, for a complete viscous material, there will be 90 degree delay. For polymers, it is a viscoelastic material, its response to the deformation should in the middle, which introduces three parameters, E’：E apostrophe，the storage modulus, E’’: E double apostrophes, the loss modulus, tan delta” loss factor. E’’/E’

Main influencing factors Dynamic Mechanical Analyzer (DMA) 01 Sample preparation Uniform Precisely measure 02 Frequency Low frequency is benefit for studying small structure 03 Amplitude Stiff sample: low amplitude Soft sample: high amplitude 04 Heating rate Consistency 1-2 ºC/min There are some influencing factors we should pay attention to. First, the sample preparation procedure, the sample should be uniform and precisely measured. Low frequency is benefit for studying small structure, For Stiff sample, we should use the low amplitude, for the soft sample, high amplitude is applicable. In order to keep consistency, the heating temperature should be in the range of 1-2 C/min. Main influencing factors

Application Dynamic Mechanical Analyzer (DMA) Glass transition Multiple transition behavior Application DMA can be used to study Glass transition, Multiple transition behavior, Crystallization and orientation, and Crosslinking and solidification. 玻璃化转变温度；结晶熔融温度；相容性; 结晶与熔融热焓、结晶度；氧化诱导期；比热容；固化热焓与固化度；结晶与固化动力学；（稳态）等温结晶与固化。 Crosslinking and solidification Crystallization and orientation

Examples Dynamic Mechanical Analyzer (DMA) Temperature Ramps on Polycarbonate Here are two examples. This is a temperature scanning, it shows the temperature transition, specifically, glass transition temperature upon heating. its shows different Tg based on storage modulus, loss modulus and tandelta. So in the paper, you should indication your basis. Normally, we are using the peak of Tandelta as the Tg. This one is doing a frequency scanning Frequency scanning

Description Dynamic Mechanical Analyzer (DMA) Ok. Let’s move to the final part. Luo, F.; Xu, C., et al. Polymer 2012, 53, 1783.

References 田 威，孔 杰，胡思海. 高聚物的现代研究方法[M]，西北 工业大学出版社，2014. Andrey Tarasov. Thermal Analysis: methods, principles, application[R], Lecture series heterogeneous catalysis, 2012. http://www.tainstruments.com http://www.perkinelmer.com