Method of determining glass-transition point of tetrazole-based polymer composite materials

FIELD: chemistry.

SUBSTANCE: disclosed is a method of determining the glass-transition point of tetrazole-based polymer composite materials based, according to which the glass-transition point is determined from the change of slope of a curve of temperature versus the inverse of dielectric constant 1/ε'=f(T).

EFFECT: high accuracy and reliability of determining the glass-transition point of tetrazole-based polymer composite materials.

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The invention relates to the field of innovative technologies and can be applied to improve the efficiency of determining functional parameters of polymer composites, which is the element base for future technical systems and devices.

Composites - volume monolithic artificial combination of diverse shape and properties of two or more components, with clear boundary, using the advantages of each of them and showing new properties, due to boundary processes. For composite materials characterized by the following signs: form and composition of the components determined in advance; the components are present in amounts providing the desired properties of the material; the material is homogeneous in the macro-scale and heterogeneous at the microscale; material there is a clear border between the components and gradientnoi patterns. One of the components of the material is continuous throughout the volume of the matrix component, a discontinuous volume, separated by a matrix, is reinforcing or reinforcing.

The composite differs from the alloy to the fact that in the finished composite individual components retain their properties. Components must interact at the interface of the composite, showing only positive new properties. This result mo is only be obtained in the case if composite materials are successfully combined the properties of the components, i.e. during operation of the composite should be shown only the required properties of the components, and their shortcomings, completely or partially neutralized.

Perfectly justified and purposeful creation of composites with desired properties is only possible with the knowledge of the physico-chemical structure of components, the physical chemistry of the processes at the interface, mechanics of deformation and fracture of heterogeneous and anisotropic phone

If the polymer composite materials (PCM) cooling to a very low temperature at which molecular mobility is missing, and then perform electrical measurements, gradually increasing the temperature, the PCM will then "unfreeze" the different types of molecular motion.

Almost every kind of "unfrozen" thus the molecular movements will leave its imprint on the curves tgδ=f(T), ε'=f(T), ε"=f(T) and so on Each type of molecular motion is usually associated with a certain relaxation process, the cause of which is this type of molecular motion. At very low temperature relaxation times almost all relaxation processes are very high, and for them the condition ωτ>>1. So the AK in the first approximation exp ~(U/RT), with increasing temperature all relaxation times are reduced (sometimes mnogokratko), and when for any relaxation process the condition ωτ=1, the temperature dependence of diabeticheskih losses (for example, tgδ) appears high. Under these same conditions will increase the dielectric constant.

If measurements at a fixed frequency over a very wide temperature range, it is possible to identify all specific to the polymer relaxation processes due to different types of molecular motion, which can be realized in the polymer. The manifestation of each type of molecular motion, which leads to significant changes of the temperature dependence of electrical properties, usually interpreted as the temperature transition. In amorphous polymers the temperature transitions are relaxing in nature. In crystalline polymers to thermal transitions are and thermodynamic phase transitions [1].

Major thermal transitions in amorphous polymers is shown in Fig.1. Usually the temperature transitions, starting with the most intensive high-temperature transition, denoted by Greek letters α, β, γ, δ. Accordingly relaxation processes occurring during the temperature decrease, usually denoted α, β, γ, δ.

On the main relaxation process, which is the main relaxation area (α - relaxation), associated with the transition from the glassy state in highly elastic (or Vice versa). This temperature change is "unfreezing" segmental mobility microprocessor type and leads to major change in the electrical parameters and the appearance of the most intense peak losses. Molecular mobility in this case is due to large kinetic elements of the main polymer chain. The temperature transition, the corresponding α-relaxation, can be single or multi-blade block.

The physical properties of a polymer in the glassy state is very significantly different from similar properties in the highly elastic state. Conventional boundary between these States is the glass transition temperature Tg- the most important characteristic of amorphous polymers, introduced by Aberration. Below the glass transition temperature see temperature at which the viscosity of the polymer is not less than 1012PA·C. It is also interpreted as the temperature below which the "frozen" motion segments of the polymer molecules [2].

There are many methods of experimental determination of glass transition temperature. There is a method of determining the glass transition temperature by acoustic emission method, which bases the n measuring pulse rate (activity) of pulses, occur in the material [3]. In the course of the experiment is the simultaneous measurement of temperature and activity of acoustic emission (AE) during cooling of the material, the glass transition temperature is determined by a sharp increase in AE activity. The disadvantage of this method is the need for simultaneous measurement values of the two parameters.

There is a method of determining the glass transition temperature of the polymer, including photoresistive films by building a "thermo-optical curve taken in a wide range of temperatures (100-180°C) [4]. As a temperature-dependent parameter selects the refractive index of the film, which is controlled at a wavelength of 546.1 nm. The disadvantages of this method are the need to conduct a series of experiments on the same system and the narrow temperature interval.

The use of dielectric method sometimes due to the difficulties in measuring the temperature and frequency dependencies of the dielectric loss at low frequencies. So urgent is the issue of empowerment of the method of dielectric spectroscopy to determine the Tg.

The purpose of the invention is the creation of a new method for determination of glass transition temperature, using as a criterion to estimate the values of Tgtemperature dependence of the reciprocal dielectric permeable the minute 1/ε'.

According to the relaxation model Drude dielectric response of the dielectric permittivity as a function of temperature and frequency is determined by the expression:

where, ω=2πf is the angular frequency, τ(T) is the relaxation time depending on the temperature, ε- dielectric constant when f→∞, εs- dielectric constant when f→0. Decomposition of complex dielectric permittivity of its real and imaginary parts we obtain:

To describe the features of the relaxation processes in the transition region of the glass transition, in the work of the authors [5] introduced an empirical model of the temperature dependence of the time of vitrification:

Approximation of the experimental curves of the temperature dependence of the reciprocal dielectric constant, under views (1)-(3) leads to at least two straight portions, which correspond to stay polymer systems in glassy and highly elastic state (Fig.2). In the transition region, called the glass transition temperature, there is a sharp change in the dielectric constant and the presence of the maximum tangent of the dielectric loss. Therefore, the temperature dependency 1/ε' can be used for op is adelene interval vitrification.

List of figures

Fig.1 is a Diagram of temperature transitions in amorphous polymer.

Fig.2 - Temperature dependence of the reciprocal dielectric constant at a frequency of 2.10-2Hz. The solid line is theoretical calculation according to the model.

Fig.3 - Temperature dependence of the reciprocal dielectric constant for a sample of system No. 1.

Fig.4 - Temperature dependence of the reciprocal dielectric constant for a sample of system No. 2.

Here is an example implementation of the method.

The study of the temperature dependence of the dielectric parameters (components of the complex dielectric permittivity ε' and ε").

Samples for the study were right-on the basis of poly-N-methylallyl-5-vinyltetrazole (MPWT AND, with the use of plasticizers dimethylformamide (DMF) (system No. 1) and dimethylphthalate (DMF) (system No. 2). Modifier for samples No. 2 was KNO3(55%). The curing of the samples was carried out by low-temperature curing agent di-N-oxide-1,3-dinitrile-2,4,6-treatinent (TONE-2).

Measurement of dielectric spectra were carried out on the installation "Concept 41" company NOVOCONTROL Technologies GmbH & Co, which consists of a frequency analyzer impedance measuring cell systems, temperature control systems, automatic data collection the Dewar vessel with the evaporation system and supply of gaseous nitrogen according to the method described in the work, in a wide interval of frequencies (f=10-1-106Hz) and temperatures (T=273-423 K).

The study on the temperature dependence of the reciprocal dielectric constant 1/ε' (1 Hz frequency) detected the existence of two regions - from 273 K to 325 K and 325 K to 393 K for a system of sample No. 1 (Fig.3), from 273 K to 310 K and 310 K to 393 K for a system of sample No. 2 (Fig.4).

The first area is marked by a sharp decrease in 1/ε', for such a significant change of the temperature dependence of the dielectric parameters associated with the main transition temperature of the glassy state in highly elastic (or Vice versa).

The second area corresponds to the area of highly elastic to plastic state. Analysis of the temperature dependence shows that this area is characterized by a gradual decrease in 1/ε' and output it on a stable plateau.

The temperature at which there is a change of character of the temperature dependence of the reciprocal dielectric constant for all investigated systems the same as their glass transition temperature (table.1)

Table 1
The polymer-plasticizer-[modificar]-hardener
PolymerTgfrom the literature
(MPWT-A) (DMF) (TONE-2)324 K325 Kthe 6 is
(MPWT-A) (DMF) (MeO-TONE)329 K330 Kthe 6 is
(MPWT-A) (DMF) [KNO3(55%)] (TONE-2)310 K310 Kthe 7 is
(MPWT-A) (DMF) [KCl(70%)] (TONE-2)326 K326 Kthe 8 is
(MPWT-A) (DMF) (Dur-TONE)327 K-

Thus, the detected pilot feature can be used as an alternative method of determining 7g new tetrazole-containing polymer systems.

Sources of information

1. Bartenev, M., Zelenev Yu Century Physics and mechanics of polymers. - M.: Higher school. - 1984. - S. 391;

2. Kozlov N. A. Mitrofanov, A. D. C. Polymer physics: Textbook. manual / Vladim. state University; Vladimir, 2001. 345 S.;

3. Patent - 94029964.

4. Patent - 2193186.

5. Vendik, I. B.; Vendik, O. G.; Afanasjev, V. P.; Sokolova, I. M.; Chigirev, D. A.; Castro, R. A.; Jansen, K. M. B. Correlation between Electrical and Mechanical Properties of Polymer Composite / Proceedings of the Electronic Components and Technology Conference (ECTC), 2011 IEEE 61st. Lake Buena Vista, Florida USA. May 31 - June 3, 201. P. 1697-1702. DOI: 10.1109/ECTC.2011.5898740.;

6. Petrakov P. C. study of the relaxation properties of new tetrazole-containing polymer and model compounds based on it // Diss. for obtaining the academic Art. K. so-called Biysk. 2012.;

7. Kalinin, M. A., Petrakov P. C., Lushin E. P., Tereshchenko, I. A., Sapozhnikov So Century. // Theses and reports the IV-th all-Russian scientific-practical conference of students, postgraduates and young scientists. / Alt. state technology. University, BTI. Biysk: Izd-vo Alt. state technology. University, 2010. S. 59.;

8. Nasonov, A. D. Effect of chemical structure of modifiers on the viscoelastic properties of new tetrazole-containing polymer / A. D. Nasonov, E. A. Paznikov, P. C. of Petrakov, M. A. Kalinin, P. D. Dove // Electronic journal. Scientific notes. - S. 11-14. http://www.scientific-notes.ru/index.php?page=6&new=15.

The method of determining the glass transition temperature of polymer composite materials on the basis of tetrazole, characterized in that the glass transition temperature is determined by the change in the slope of the graph of the temperature dependence of the reciprocal of the real part of the complex dielectric constant 1/ε'=f(T).



 

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