RU2546675C2 - Method of determining crystallinity of diphenylamine-based compositions - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to a method of determining crystallinity of binary phlegmatising compositions based on diphenylamine (DPA), which do not contain other imine and amine compounds. The method can be used, for example, to study the nature of distribution of components in a composition, porosity in a diffusion zone and other physical and chemical properties of propellant powder. The method is based on using an infrared spectroscopy method and includes the following: preparing samples in molten form; taking photometric measurements in the 3300-3400 cm^-1 range and calculating crystallinity (X) using the formula: $$Х=\frac{{С}_{Х}}{{С}_{\text{DPA}}}\cdot 100\%,$$

where C_DPA is the ratio of absorption band intensities of a doublet of valence vibrations of NH groups of the initial DPA at υ₁=3380 cm^-1 to υ₂=3350 cm^-1 $${С}_{\text{DPA}}=\frac{J_{NH3380}}{J_{NH3350}}$$

C_X is the ratio of absorption band intensities of a doublet of valence vibrations of NH groups in the investigated mixture at υ₁=3380 cm^-1 to υ₂=3350 cm^-1. It is preferable to use only high-melting compounds (boiling point higher than 100°C) to determine DPA.

EFFECT: method improves accuracy of determining crystallinity and enables to select an optimum composition for phlegmatisation of energy compositions.

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Description

The invention relates to physicochemical analysis and can be used to determine the degree of crystallinity of binary phlegmatizing compositions based on diphenylamine.

The invention is intended to determine the degree of crystallinity of binary mixtures based on diphenylamine (DPA) by IR spectroscopy.

Several methods are known for determining the degree of crystallinity of polymers and compositions based on them:

1. X-ray diffraction [1], based on the concept of the structure of cellulose as a polymer consisting of two phases: crystalline with varying degrees of imperfection and amorphous, which is considered on the basis of ideas about an ideal melt. The degree of crystallinity found from X-ray diffraction studies characterizes the fraction of regularly packed molecules, the combination of which determines the appearance of Bragg reflections in the diffraction pattern, taken in relation to randomly oriented molecules scattering radiation diffusely.

To calculate the degree of crystallinity, the Ruland method is implemented in combination with the method for extracting scattering of the amorphous component. The contours of the peaks were approximated by the Gauss function. The degree of crystallinity was calculated both from the X-ray diffraction patterns obtained for reflection and from the resolution of the diffraction patterns recorded in the transmission geometry.

2. X-ray structural [2], developed for modified celluloses and based on extremely complete analysis of the peak shape of X-ray diffraction patterns (002). All information is extracted from the slopes of the peak (002) obtained during measurements in a small range of angles (2-3 °). Based on the data obtained, a model of cellulose with a more complex structural organization, including deformed (curved) macromolecular chains, is proposed. The proposed method is designed to determine the degree of crystallinity of cellulose.

3. Non-destructive [3], which includes heating the sample to the formation of the crystalline phase, and measure the rate of thermal expansion of the sample at the maximum temperature and at its minimum value in the temperature range corresponding to the formation of the crystalline phase, and the degree of crystallinity is determined from the ratio of the indicated thermal sample expansion. This method was proposed to study the physical and structural properties of composite materials based on polymers and alloys.

4. Ultrasonic [4], which consists in the fact that the pulses of ultrasonic vibrations are emitted by the emitter, the pulses transmitted by the sample are received by the receiver, the speed of their propagation and the attenuation coefficient of the ultrasonic vibrations are measured, and the crystallinity of the elastomer is calculated based on the measured parameters of the ultrasonic vibrations.

5. The method [5], taking into account the piezoelectric and pyroelectric properties of cellulose in wood. The approach allows us to assess the degree of crystallinity of many fiber-forming polymers.

6. Differential scanning calorimetry (DSC) [6], which allows the degree of crystallinity of various components, including binary Polyethylene-Polypropylene (PE-PP) mixtures in an isotropic and oriented state, to be determined with high accuracy by changing the degree of absorption and determining the melting temperature [7] ] and mixtures of copolymers of ethylene with vipilacetate (SEVA), because depending on the content of vinyl acetate (VA) unusual properties of the compositions are realized. So, for the mixture SEVA-14 + SEVA-22 (the number is the VA content in%), the concentration dependence of the degree of crystallinity (k), estimated by the DSC method, has a positive deviation from additive values [8].

The disadvantages of all the methods considered are the difficulty in identifying complex mixtures of components, the use of expensive equipment and the high complexity of the process.

The closest technical solution is a method for determining the degree of crystallinity of cellulose by IR spectroscopy [9], according to which the ratio of the intensity of the absorption band at 1372 cm ^-1 (deformation vibrations of CH groups) to the intensity of the absorption band at 2900 is proposed as a criterion for the degree of crystallinity of cellulose cm ^-1 (stretching vibrations of CH groups).

The disadvantage of this method is the limited nature of the studied objects, i.e. the ability to assess the degree of crystallinity of only various types of cellulose.

Therefore, the aim of the invention is to develop a criterion for assessing the degree of crystallinity of binary compositions based on DFA. The basis of the proposed method for assessing the degree of crystallinity is the measurement of the ratio of the absorption maximum of stretching vibrations of NH groups at υ ₁ = 3380 cm ^-1 to υ ₂ = 3350 cm ^-1 .

When developing this method for assessing the crystallinity of binary compositions based on DFA, it was found that for the initial crystalline DFA (with a crystallinity of 100%), this absorption band represents a doublet with two maxima at υ ₁ = 3380 cm ^-1 and and υ ₂ = 3350 cm ^-1 . In the case of complete amorphization of the composition based on DPA, its state of aggregation changes, i.e. it becomes liquid and its crystallinity is 0%. The basis of the proposed method for assessing the degree of crystallinity is based on measuring the ratio of the absorption maximum of stretching vibrations of NH groups at υ ₁ = 3380 cm ^-1 to the maximum at and υ ₂ = 3350 cm ^-1 .

In preparing mixtures for testing, the powdered components of the powders were thoroughly mixed with DFA in an agate mortar, then heated to full melt and the film was cast on KBr substrates. Samples obtained in this way are photometric in the region of 3300-3400 cm ^-1 and the ratio of the absorption bands of the doublet of the stretching vibration band of NH groups is calculated according to the formula (1)

where X is the degree of crystallinity of the composition,%;

C _X is the ratio of the intensities of the absorption bands of the doublet of stretching vibrations of NH-groups in the test mixture;

With _DFA - the ratio of the intensities of the absorption bands of the doublet of stretching vibrations of NH-groups of the original DFA.

As the second component of the mixture, for example, camphor, dinitrotoluene (DNT), centralit II (C II) and other compounds that do not have NH and NH ₂ groups in the structure can be used.

For example, in binary mixtures of DPA: camphor, splitting of the band of stretching vibrations of NH groups is not observed, i.e. the degree of crystallinity of these mixtures is 0. In contrast to them, in the IR spectra of binary DFA mixtures: C II (C I), the doublet of the stretching vibration band of NH groups is split and the degree of crystallinity of these binary mixtures is 70-98%. The test results of mixtures of various compositions are given in table 1.

In the analysis of binary mixtures based on DPA, the fact that the NH groups are present only in the structure of the DPA molecule, and the remaining components do not contain NH groups (secondary aromatic amine groups), was primarily taken into account. Below are the structural formulas of the compounds used (table 2):

All of the above compounds except for DFA do not contain secondary aromatic amine groups.

The change in the shape of the absorption band of stretching vibrations of NH groups and the ratio of the intensities of absorption bands are caused by the processes of formation of intermolecular bonds with the participation of protons of NH groups of compounds. The energy of the resulting intermolecular bonds correlates with the degree of crystallinity of the tested mixtures: the higher the energy of the formed complexes, the lower the degree of crystallinity.

Our proposed method allows with high expressivity, accuracy and information content to assess the degree of crystallinity of various binary compositions based on DFA and, in particular, to choose the optimal composition for phlegmatization of energy compositions.

Information sources

1. The degree of crystallinity of cellulosic materials and the determination of sizes of coherent scattering regions / L.A. Aleshina, L.A. Lugovskaya, A.D. Fofanov II All-Russian Conference "Chemistry and Technology of Plant Substances" // Kazan.- 2002.

2. Quantitative x-ray structural analysis of modified celluloses / N.A.Sekushin, L.S. Kocheva, V.A. Demin // Chemistry of plant raw materials. 1999. No. 1.P. 59-64.

3. Patent No. 2064678 of the Russian Federation, IPC ⁷ G01N 33/44, G01N 25/02. The method of determining the degree of crystallinity of materials / Lobachev K.I .; Batalov BC; Applicant and patent holder Special Design and Technology Bureau of Lighting and Light-Signaling Instruments of Electroluch Joint-Stock Company - No. 4808391/25; declared 03/30/1990; publ. 07/27/1996.

4. Patent No. 2291420 of the Russian Federation, IPC ⁷ G01N 29/07, G01N 29/11. A method for determining the degree of crystallinity of elastomers by the ultrasonic method / Bityukov V.K., Khvostov A.A., Sotnikov P.A .; applicant and patent holder State educational institution of higher professional education Voronezh State Technological Academy - decl. 07/11/2005; publ. 01/10/2007

5. A new approach to determining the degree of crystallinity of cellulose in wood / N.Yu. Evsikova, N. S. Kamalova, N. N. Matveev, V. V. Postnikov // IZVESTAN RAS. The series is physical. 2010, vol. 74, No. 9, p. 1373-1374.

6. Differential scanning calorimetry / Emelin, A. L. // Textbook, M: Moscow State University. - 2009.

7. The relationship of the structure and properties of PE-PP mixtures / Pryadilova OV, Petronyuk Yu.S., Chertyshnaya Yu.V., Ledneva OA, Popov AA // Butlerov messages. 2002. No. 11. T.Z.

8. Structural features of binary mixtures of ethylene vinyl acetate copolymers / Stoyanov O.V., Gerasimov V.K., Chalykh A.E., Khuzakhanov PM, Akhmadiev PP, Aliev A.D., Vocal M.V. // Structure and the dynamics of molecular systems. Yalchik 2006, p.265-268.

9. Cellulose and its derivatives / Bikels N., Segal L. // M .: "World", 1974. S.231-233.

Claims (1)

A method for determining the degree of crystallinity of diphenylamine-based compositions that do not contain other imino and amino compounds, characterized in that the samples are prepared in the form of a melt, photometer in the region of 3300-3400 cm ^-1 , and the degree of crystallinity (X) is calculated by the formula

where С _DFA is the ratio of the intensities of the absorption bands of the doublet of stretching vibrations of NH groups of the initial DFA at υ ₁ = 3380 cm ^-1 to υ ₂ = 3350 cm ^-1

C _X - the ratio of the intensities of the absorption bands of the doublet of stretching vibrations of NH-groups in the test mixture at υ ₁ = 3380 cm ^-1 to and
υ ₂ = 3350 cm ^-1 .