Gas pyrolysis resin as a plasticizer for composite elastomer materials

. The aim of the study is to study the effect of gas pyrolysis resin on the properties of elastomeric composite materials. It has been established that in the presence of it in the thiuram vulcanizing system, the relative rate of vulcanization of styrene-butadiene rubber increases, the time to reach the optimum vulcanization decreases, but the degree of vulcanization decreases, proportional to the maximum torque, and when using a sulfur vulcanizing system, it activates the vulcanization process, which is facilitated by the presence in its composition of active functional groups (-OH, -COOH, etc.). It is shown that the tensile strength and relative elongation of the vulcanizates increase, while the elasticity remains at an average level.


Introduction
Obtaining composite elastomeric materials with a certain set of properties is associated not only with the development of elastomers of various chemical structures, but also with the creation of appropriate structures. One of the main methods of structural modification of elastomeric materials is plasticization. Plasticization of elastomers leads to an improvement in the elasticity of materials, gives them frost resistance, and also facilitates their processing [1][2][3].
Currently, dibutyl phthalate (DBP) and dibutylcebatsionate (DBS) are widely used as plasticizers in the production of composite elastomeric materials. However, due to the lack of their production, much attention is paid to finding new opportunities for obtaining plasticizers with new structures and properties.
The purpose of this work is to study the effect of secondary raw materials, the production of polypropylene, on the properties of composite elastomeric materials based on styrene-butadiene rubbers.
The objects of the study are the gas-pyrolysis resin of secondary raw materials, the production of polypropylene, as a standard rubber mixture based on styrene-butadiene rubber. The properties of the gas-pyrolysis resin were studied by physico-chemical methods, IR spectroscopy, and viscometry. The production of rubber compounds was carried out on laboratory mixing rollers RC-WW 150/330 (Rubicon, Germany). The determination of the Mooney viscosity of rubber compounds was carried out on a Mooney viscometer MV 2000 (Alpha Technologies, England). The stress relaxation test is carried out on the same specimens as the Mooney viscosity immediately after completion of the viscosity measurement by stopping the rotor very quickly and measuring the drop in the final Mooney viscosity over time. The vulcanization kinetics of rubber compounds was determined on an ODR 2000 rheometer (Alpha Technologies, UK). Technical indicators were determined according to the relevant state standards.

Results and discussion
The creation of ingredients for polymeric materials based on raw materials of nonpetroleum origin is an important task of modern chemistry of macromolecular compounds. In this regard, of undoubted interest are secondary raw materials for the production of polypropylene gas pyrolysis resin.
Studies show that gas pyrolysis resin is a black, odorless, hard substance (Table 1). It consists mainly of arenes and olefins with 6-12 carbons. The amount of olefins is 23.7%, and arenes are 67.18%. Also, it contains alane, diene, cycloalkanes. Qualitative-quantitative analysis showed the correspondence of the components with the spectra, their number is 90-97%. The gas pyrolysis resin was thermally treated at 270°C for one hour, the weight loss was 50% of the total sample weight. Its number average molecular weight according to gel chromatography is ≈700. The resulting mass (Plasticizer P 125) was investigated by the IR method, the results of which are shown in Fig.1. IR spectroscopic studies show that the structure of P 125 is close to 80-85% of the structures of plasticizers used in the production of composite elastomeric materials. Comparative physical and chemical properties of industrial plasticizers P 125 are given in Table 2. The main research methods for determining the plasticizing properties of plasticizers are the determination of the glass transition temperature of polymers and fluidity. Below are data on the effect of P 125 on the glass transition temperature of styrene-butadiene rubber, based on measurements of deformation and elastic modulus (Table 3). From all the above data, it should be noted that as the content of P 125 increases, the glass transition temperature of styrene-butadiene rubber naturally decreases. This means that in the presence of P 125, styrene-butadiene rubber retains its highly elastic properties at lower temperatures than unplasticized rubber. In this case, a frequency dependence of the deformation and the value of the glass transition temperature is observed. The higher the frequency, i.e. the shorter the exposure time, the higher the glass transition temperature of the plasticized system. The data in the table show that with an increase in the content of P 125, the glass transition temperature of styrene-butadiene rubber can be greatly reduced. In this regard, too much P 125 should not be added to rubber, as this can cause a sharp decrease in the pour point and narrow the temperature range of high elasticity. It is known [4][5][6] that plasticizers slow down the formation of vulcanization structures (networks) with various types of cross-links. The effect of P 125 on the kinetics of vulcanization of rubber compounds based on styrene-butadiene rubber was studied (Table  4).  Studies show that the introduction of P 125 into the elastomer composition significantly affects the structuring kinetics. The increase in the rate of structuring may be due to the participation of P 125 in the process of structuring due to functional groups [7][8][9], which is also evidenced by an increase in the number of cross-links and an increase in the elasticstrength properties of the composites (Fig. 2). Simultaneously with an increase in the strength of composites (by 13-17%), there is a decrease in elasticity, residual elongation, and an increase in rigidity. This circumstance can be explained by an increase in the degree of crosslinking and the introduction of P 125 into the composition, which lead to a deterioration in the flexibility of elastomer macromolecules [10,11]. The equilibrium swelling of vulcanizates with respect to machine oil, gasoline, kerosene, etc. has been studied. and clarified the relative oil and petrol resistance of the compositions.

Сonclusion
Thus, the study of the behavior of P 125 in rubber compounds and vulcanizates showed that, being a product of a multifunctional action, they exhibit the properties of a plasticizer, at the same time the stickiness of rubber compounds increases, and the strength characteristics of rubbers improve.