Five methods for Thermal Properties Analysis of Materials (TG, TMA, DSC, DMA, DETA)

Introduction to thermal analysis

The essence of thermal analysis is temperature analysis. Thermal analysis technology is to measure the physical properties of substances with temperature changes under the control of program temperature (refers to constant temperature rise, constant temperature drop, constant temperature or step temperature rise, itp.), used to study the changes of physical parameters such as thermal, mechanical, acoustic, optical, electrical, magnetic, itp. occurring at a certain temperature, to jest, P = f(T). Design temperature changes according to certain laws, to jest, program control temperature: T = (T), so its property is both a function of temperature and a function of time: P =f (T, T).

Significance of material thermal analysis

It is widely used in the characterization of thermal properties, physical properties, mechanical properties and stability of materials, and has very important practical significance for the research and development of materials and quality control in production.

Commonly used thermal analysis method interpretation

According to the induction and classification of the International Thermal Analysis Association (ICTA), the current thermal analysis methods are divided into nine categories and seventeen, and the commonly used thermal analysis methods include thermogravimetry (TG), różnicowa kalorymetria skaningowa (DSC), static thermomechanical analysis (TMA), dynamic thermomechanical analysis (DMTA), dynamic dielectric analysis (DETA), itp. They are the function of measuring material weight, heat, rozmiar, modulus and compliance, dielectric constant and other parameters to temperature.

Five methods for Thermal Properties Analysis of Materials (TG, TMA, DSC, DMA, DETA)

Physical property	Analytical technique name	For short	Physical property	Analytical technique name	For short
1. Quality	1) Thermogravimetric method	TG	3. Enthalpy	9) Differential scanning calorimetry	DSC
	2) Measurement of isobaric mass change		4: Rozmiar	10) Thermal expansion method
	3) Escape gas detection	EGD	5. Mechanical properties	11) Thermomechanical analysis	TMA
	4) Escape gas analysis	EGA		12) Dynamic thermomechanical analysis	DMA
	5) Radiothermal analysis		6. Acoustic characteristics	13) Thermal sound method
	6) Thermal particle analysis			14) Thermoacoustic method
2.Temperatura	7) Heating curve measurement is not		7. Optical characteristics	15) Thermo-optical method
	8) Differential thermal analysis	DTA	8. Electrical characteristics	16) Thermoelectric method
			9. Magnetic properties	17) Thermomagnetism

(1) Thermogravimetric Analysis (TG)

Thermogravimetry (TG) is a technique for measuring the mass of a sample with temperature or time under programmed temperature control.

וScope of application:

(1) The main research material in inert gas, air, oxygen in the thermal stability, thermal decomposition and oxidative degradation and other chemical changes;

(2) study all physical processes involving mass changes, such as the determination of moisture, volatiles and residues, adsorption, absorption and desorption, gasification rate and gasification heat, sublimation rate and heating heat, the composition of polymers or blends with fillers, itp.

Detailed explanation of the principle:

Sample weight fraction w to temperature T or time t mapping thermogravimetric curve (TG curve): w= f (T or t), because most of the linear heating, T and t only a constant difference. The first derivative of a TG curve to temperature or time, dw/dT or dw/dt, is called a differential thermogravimetric curve (DTG curve).

Five methods for Thermal Properties Analysis of Materials (TG, TMA, DSC, DMA, DETA)

In Figure 2, the cumulative weight change at Ti at point B reaches the lower limit of thermobalance detection, which is called the reaction initial temperature. No change of weight can be detected at point C Tf, which is called the reaction end temperature; Ti or Tf can also be determined by extrapolation, which is divided into G-point H point; The temperature when the weight loss reaches a certain predetermined value (5%,10%, itp.) can also be used as Ti.Tp to represent the maximum weight loss rate temperature, corresponding to the peak temperature of the DTG curve. The area of the peak is directly proportional to the change of the weight of the sample.

Practical application:

Thermogravimetric method has become an important means to study the thermal change process of polymers because of its fast and simple. Na przykład, the TG curve of the blend of polytetrafluoroethylene and acetal copolymer in FIG. 3 can be used to analyze the composition of the blend. From FIG. 1, it can be found that when heated in N2, the acetal components decompose (o 80%) at 300~350℃, and the polytetrafluoroethylene begins to decompose (o 20%) at 550℃.

Five methods for Thermal Properties Analysis of Materials (TG, TMA, DSC, DMA, DETA)

Influencing factors:

(A) heating rate: the faster the heating rate, the larger the temperature lag, the higher the Ti and Tf, and the wider the reaction temperature range. It is recommended that polymer samples should be 10 K/min, inorganic and metal samples should be 10~20K/min;

(B) particle size and dosage of the sample: the particle size of the sample is not too large, and the tightness of the loading is moderate. The same batch of test samples, each sampleThe particle size and packing tightness should be consistent;

(C) atmosphere: the common atmosphere is air, O2, N2, He, H2, CO2, CI2 and water vapor. The reaction mechanism of different atmosphere is different. When the atmosphere reacts with the sample, the shape of TG curve is affected. (D) sample dish material and shape.

(2) Static thermomechanical Analysis (TMA)

Thermal mechanical analysis refers to a technology to measure the functional relationship between the deformation of a substance and the temperature and time under the program temperature and non-vibration load, mainly measuring the expansion coefficient of a substance and the phase transition temperature and other parameters.

Five methods for Thermal Properties Analysis of Materials (TG, TMA, DSC, DMA, DETA)

Szereg zastosowań:

Static thermomechanical analyzer is mainly used for the thermal expansion coefficient of inorganic materials, metal materials, composite materials and polymer materials (tworzywa sztuczne, guma, itp.); Glass transition temperature; Melting point; Softening point; Load heat deformation temperature; Creep and other tests.

Practical application:

(A) fiber, film research: can measure its elongation, shrinkage properties and modulus and the corresponding temperature, stress-strain analysis, freezing and heating stress analysis;

(B) the characterization of composite materials, in addition to the study of fiber with TMA, the reinforcement of composite materials, the glass transition temperature of resin Tg, gel time and fluidity, thermal expansion coefficient and other properties, as well as the dimensional stability of multi-layer composite materials, high temperature stability, itp., can be quickly measured and studied with TMA;

(C) Research on coatings: it can be understood whether the coating and the matrix match and the matching temperature range;

Five methods for Thermal Properties Analysis of Materials (TG, TMA, DSC, DMA, DETA)

(D) Research on rubber: it can be understood whether rubber is still elastic and stable in the harsh use environment

Influencing factors:

(A) heating rate: The temperature distribution of the sample is uneven if the heating rate is too fast

(B) Thermal history of the sample

(D) The pressure exerted by the probe: generally recommended 0.001~0.1N

(mi) Chemical changes in the sample

(F) external vibration

Five methods for Thermal Properties Analysis of Materials (TG, TMA, DSC, DMA, DETA)

(G) Kalibrowanie: probe, temperatura, ciśnienie, furnace constant, itp. Kalibrowanie

(H) atmosphere

(I) Sample shape, whether the upper and lower surfaces are applied in parallel

(3) Differential Scanning calorimetry (DSC)

How it Works:

Differential scanning calorimetry (DSC) is a technique for measuring the relationship between the power difference lost to a substance and a reference substance and the temperature at a programmed temperature. There are two kinds of differential scanning calorimetry (DSC) : compensation and thermal flow. The sample and the reference material container is equipped with two sets of compensation heating wire, when the sample in the heating process due to the thermal effect and the reference between the temperature difference △T, through the differential heat amplification circuit and the differential heat compensation amplifier, so that the current flowing into the compensation wire changes, when the sample heat absorption, the compensation amplifier makes the current of the sample side increase immediately; On the contrary, when the sample is heated, the current on one side of the reference increases until the heat balance on both sides and the temperature difference △T disappears.

Five methods for Thermal Properties Analysis of Materials (TG, TMA, DSC, DMA, DETA)

In differential scanning calorimetry, in order to keep the temperature difference between the sample and the reference object to be zero, the relationship between the heat and temperature necessary to apply in unit time is the DSC curve. The vertical axis of the curve is the heat added per unit time, and the horizontal axis is the temperature or time. The area of the curve is proportional to the change in enthalpy of heat. A typical DSC curve is shown in Figure 4.

Szereg zastosowań:

(1) Determination of curing reaction temperature and thermal effect of materials, such as reaction heat, reaction rate, itp.;

(2) measurement of thermodynamic and kinetic parameters of substances, such as specific heat capacity, heat of transition, itp.;

(3) measurement of crystallization, melting temperature and thermal effect of materials;

(4) the purity of the sample.

Influencing factors:

(A) heating rate, the actual test results show that the heating rate is too high will cause the internal temperature distribution of the sample is not uniform, the furnace body and the sample are alsoThere will be a thermal imbalance state, so the influence of heating rate is very complicated.

(B) Atmosphere: different gases have different thermal conductivity, which will affect the thermal resistance between the furnace wall and the sample, and affect the temperature and enthalpy of the peak.

(C) Przykładowe dawkowanie: not too much, so as not to make its internal heat transfer slow, large temperature gradient and peak shape expansion and resolution decline.

(D) sample size: When the powder size is different, due to the influence of heat transfer and diffusion, there will be differences in test results.

Five methods for Thermal Properties Analysis of Materials (TG, TMA, DSC, DMA, DETA)

(4) Dynamic Thermal Mechanical Analysis (DMA)

Dynamic thermomechanical analysis measures the mechanical properties of viscoelastic materials in relation to time, temperature or frequency. The sample deforms under the action and control of periodic (sinusoidal) varying mechanical stresses.

Szereg zastosowań:

Dynamic thermomechanical analyzer is mainly used to test the glass transition temperature, load thermal deformation temperature, creep, energy storage modulus (rigidity), loss modulus (damping performance), stress relaxation and so on of inorganic materials, metal materials, composite materials and polymer materials (tworzywa sztuczne, guma, itp.).

Basic principles of DMA:

DMA is to characterize the characteristics of materials through the state of molecular motion, molecular motion and physical state determine the dynamic modulus (stiffness) and damping (energy loss of the sample in vibration), when a variable amplitude of sinusoidal alternating stress is applied to the sample, a pre-selected amplitude of sinusoidal strain will be generated, the strain of viscoelastic sample will lag a certain phase Angle 8. As shown in Figure 5.

Five methods for Thermal Properties Analysis of Materials (TG, TMA, DSC, DMA, DETA)

DMA technology divides material viscoelasticity into two modules:

A storage modulus E’, mi’ is directly proportional to the maximum elasticity of the sample stored in the weekly period, reflecting the elastic component of the material’s viscoelasticity and characterizing the stiffness of the material; And the loss modulus E”, mi” is directly proportional to the energy consumed by the sample in the form of heat in the weekly interim, reflecting the viscous part of the material’s viscoelasticity, indicating the damping of the material. The damping of the material has also become internal consumption, expressed by tan8, the ratio of the energy loss and the maximum elastic storage energy of the material in the weekly midterm is equal to the loss modulus E” and the energy storage modulus E. DMA using temperature scanning, from the auxiliary ambient temperature to the melting temperature, tan delta shows a series of peaks, each peak will correspond to a specific relaxation process. By DMA can be measured phase Angle tan8, loss modulus E” and energy storage modulus E with temperature, frequency or time change curve, not only gives a wide range of temperature, frequency range of mechanical properties, but also can detect the material glass transition, low temperature transition and secondary relaxation process. Na przykład, the loss peak can represent the transformation of a certain unit movement. Figure 6 shows the curve of polystyrene tg with temperature change. It can be inferred from the figure that the peak may be the movement of phenyl groups around the main chain; The peak may be caused by the existence of the head structure; The peak is the movement of benzene around the bond connected to the main chain.

Influencing factors:

Heating rate, grubość próbki, metal coating or not, fixture type, itp