Influence of a magnetic field on the structure and electrical strength of polystyrene

. The mechanism of action of the H field will be different depending on whether the polymer is in a molten form, or in the form of a solution under highly elastic conditions. The H-effect of spin-dependent reactions that, it can take place in a polymer as the main mechanism of the action of a magnetic field should be clearly felt. Our results confirm this. It is proved (by experiments) that the effect of a magnetic field on composites obtained by crystallization from a solution or a molten substance directly in a constant magnetic field can lead to the expected results.


Introduction
Recently, a wide space is given to the study of the effect of magnetic field (fixed or inflexive fields) high energy particles ℽ-irradiation on different types of polymers and polymer composites.Thus researches are focused on obtaining new type of magnetic composite materials, nanocomposites with properties resistant to elastic and antistatic, electroactive, physical-mechanical, electret and radiation effects and expanding their application possibilities [1][2][3].Another group of studies focuses on changes in the physical and mechanical properties of polymers and composite materials based on them during operation in a magnetic field and predicting these changes [4].When nano-sized particles with high chemical activity are added to the polymer, the physico-chemical, electrical, optical and other properties of the polymer change sharply depending on the size, shape, agglomeration and volume of the addition [5,6].
The mechanism of the effect of the magnetic field on polymers is not so clear at first glance.Thus, the mechanism of the effect of the magnetic field on polyethylene, polypropylene and other materials with weak polarity, which do not have a magnetic moment, has not yet been fully studied.Therefore, scientific research in this direction continues [9].

Literature review and problem statement
According to the studies performed, a magnetic field can change the rate of deformation and flow of diamagnetic, as well as the mobility of various structural units of solid polymers.In the work [1][2][3][4][5], the author first studied the effect of a permanent magnetic field at a magnetic field H=5kE on a mixture of vulcanized rubber SKN-40 with oligoetheracrylate at a temperature of 433 K.By electron microscopy, it has been determined that supramolecular structures are oriented in the direction of the magnetic field during vulcanization.
The impact of a magnetic field also increases the resistance of vulcanizers to destruction by 20-30%.Other studies provide data on the change in the diamagnetic sensitivity along with the relaxation and mechanical properties of polymers under the effect of magnetic fields (MF).It has been shown that at a magnetic field H=20 kE, the rate of abrupt deformation during the flowing process of epoxy and polyester resins decreases [6][7][8][9].Depending on the dispersion of metal fillers in porous polymer matrices, new composites with complex properties, para-, dia-, and ferromagnetic parameters have been obtained under various crystallization conditions [10][11][12].
It should be noted that the impact of a permanent magnetic field on the properties of polymers can be explained by the anisotropy of the diamagnetic sensitivity and the directed action of the field on molecules due to an increase in the degree of ordering of the molecule [13,14].From the point of view of the electro physics of polymer dielectrics, the influence of a magnetic field on electric charges is carried out under the influence of the Lawrence force, which leads to a decrease in the mobility of charges due to a change in the trajectory of movement and, consequently, dielectric losses (tg).One of the factors directly affecting the orientation of polymer chains is the magnetic field.

Solution of the problem
It is known that a magnetic field affects the electret and dielectric properties, micro strength, and structural changes in thermoplastics and thermosets, including epoxy resins.These experimental results have not yet found a worthy explanation.However, it should be noted that the behavior of polymers in a magnetic field will be determined by structural changes and features of various relaxation processes.To understand all the physical phenomena that occur during the treatment of polymers with a magnetic field, it is important to carefully study this issue using spectroscopic methods.
In this study, samples of polystyrene film were obtained from its solution in benzene under the influence of a magnetic field.In this case, the solution for obtaining a film is placed between the poles of a permanent magnet so that its lines of force are parallel to the longitudinal axis of the resulting film [8].The polymer solution is kept at room temperature (293 K) under the effect of a magnetic field until the solvent is completely evaporated.The magnetic field strength can be changed within 1.8÷4.0kE by adjusting the distance between the poles of the permanent magnet (Figure 1).It is better to place the samples in the same place and change the intensity of the magnetic field by shunting [9].In the study of the structural properties of polymer composite materials, the IR spectroscopy method was used.The IR spectra of the obtained PS films were taken in the initial state (without the action of a magnetic field) and after the action of a magnetic field.By increasing the electrical voltage at a constant rate before and after effect of the magnetic field, the breakdown voltage (Ubr) of the PS films is recorded in expression (1).The electrical hardness Ebr is defined as where h -is the film thickness, Ubr -is the breakdown voltage.On Figure 2 shows the dependence of the short-term electrical strength (Ebr) of PS films on the magnetic field strength (H).For each value of the magnetic field, Ebr was determined at 10-15 different points of the samples, and their average numerical value was taken as the final value.As it can be seen from the figure, the electrical strength of PS increases at low field values due to the influence of a constant magnetic field during film deposition, and saturation is observed at high values of H.An increase in electrical strength occurs due to the ordering of the structure, due to the orientation of polymer chains, as well as changes in the supramolecular structure (SMS) [10,11,15].The saturation observed at high values of H≥1.5 kE may be due to the maximum orientation of the polymer chains.Directional orientation can be achieved by the action of a magnetic field in the case of high viscosity polymer fluidity.If hardening occurs directly in a magnetic field, at H,  ⊥  then the degree of orientation of the material can be increased as a result of regular sequential and selective fixation of the structure.
A change in the properties of the PS film as a result of the action of a constant magnetic field on the corresponding solution also leads to a change in the molecular structure and, accordingly, the mobility of various functional groups.This can be seen from the change in the intensity of the absorption bands in the IR spectra of these groups.Changes in the IR spectra of samples tested for short-term breakdown strength are shown in Table .1 [12].As can be seen from Table .1, a constant magnetic field does not affect the IR absorption of the 3450÷3600 cm-1 band belonging to OH groups.At the same time, the intensity of absorption increases in the bands at 1280, 1350 and 1735 cm-1 belonging to ethers, nitrogenous compounds and C=O groups, respectively.An increase in the intensity of the absorption band at 1280 cm-1 indicates the process of building an ether bond (C-O-C), as well as the process of oxidation in the bands 1350 and 1735 cm-1.This indicates a change in the regularity of the internal structure due to the construction through C-O-C bonds.A slight increase in the intensity of the absorption band of the C=O group (1735 cm-1) at strong polarity is most likely due to the corresponding orientation in a constant magnetic field [13].
Thus, we can say that a constant magnetic field causes a slight increase in the electrical strength (Ebr) of PS films, which correlates with a change in the structure of PS films deposited from solutions of benzene and toluene in a magnetic field.As can be seen, the crystallization of PS films in a magnetic field leads to a more uniform distribution of SMS elements, resulting in a rotational action of the Lawrence force on electric charges, which leads to an elongation of their trajectory, a decrease in their mobility, and an increase in the Ebr value.Let us note some data related to the action of a permanent magnetic field on polymers, comparing them with our results.According to some experimental data, the temperature dependence of the dielectric loss angle tgδ of polymethylmethacrylate in a permanent magnetic field H shows a shift towards higher temperatures.Interestingly, the displacement effect becomes more pronounced when the direction of the vector  ⃗ ⃗ is directed along the polymer surface.
The micro strength of polymethylmethacrylate decreased at a pulsed magnetic field of 30 T (B = µµ0H) [14].We tried to explain the reason for such experimental results by the enhancement of relaxation excitation, i.e. interaction of certain radicals.In addition, we emphasize that the effect of a magnetic field on a polymer is not associated with a reorientation of macromolecular parts.Our results and the effect of the magnetic field on solid polymers depend on the physical state of the polymer.

Conclusions
That is, the mechanism of action of the H field will be different depending on whether the polymer is in a molten form, or in the form of a solution under highly elastic conditions.According to prof.E. L. Frankevich, the H-effect of spin-dependent reactions that, it can take place in a polymer as the main mechanism of the action of a magnetic field should be clearly felt.Our results confirm this.It is proved (by experiments) that the effect of a magnetic field on composites obtained by crystallization from a solution or a molten substance directly in a constant magnetic field can lead to the expected results.

Fig. 1 .
Fig. 1.Magnetic devices for exposing thin polymer layers (films) to a magnetic field: 1-polymer composite alloy; 2-electromagnetic poles; 3-copper thermostatic layer; 4-measuring unit and winding for adjusting the voltage of the magnetic field H; 5-temperature measuring and regulating unit.

Fig. 2 .
Fig.2.Dependence of the electric strength of PS films on the intensity of the magnetic field (Н): 1film crystallized from a solution in a magnetic field; 2 -ordinary film in a magnetic field.

Table 1 .
Values of some IR absorption bands for polystyrene films dependence on intensity of magnetic fields.