SYNTHESIS AND PROPERTIES OF ORGANIC SILICON (OLIGO) POLYMERS

ABSTRACT

In the article, the process of production of urethane-group organosilicon compounds and the factors affecting it have been studied, and optimal conditions have been found. In the study, an oligomer was synthesized based on local raw materials: glycerol, methanal and urea. The viscosity of the obtained oligomer in the presence of tetraethoxysilane at different temperatures was determined on a viscometer (Viscotester 2 Plus). It was determined that the physicochemical properties of the obtained oligomer depend on the amount of tetraethoxysilane. As a result of studying the thermal properties of the synthesized polymer, it was recommended as a matrix for thermostable dyes.

АННОТАЦИЯ

В статье изучен процесс получения кремнийорганических соединений уретановой группы, факторы, влияющие на него, и найдены оптимальные условия. В ходе исследования был синтезирован олигомер на основе местного сырья: глицерина, метаналя и мочевины. Вязкость полученного олигомера в присутствии тетраэтоксисилана при различных температурах определяли на вискозиметре (Viscotester 2 Plus). Установлено, что физико-химические свойства полученного олигомера зависят от количества тетраэтоксисилана. В результате изучения термических свойств синтезированного полимера он был рекомендован в качестве матрицы для термостабильных красок.

Keywords: urea, glycerin, tetraethoxysilane, corrosion, thermal stability, properties, polymer.

Ключевые слова: мочевина, глицерин, тетраэтоксисилан, коррозия, термостабильность, свойства, полимер.

Introduction

Synthetic and natural polymers are an important part of life today and are now used in almost every industry. Today, traditional synthetic polymer materials and natural polymer materials are used. However, the disadvantage of such polymer materials is high flammability compared to other materials. Therefore, most of the final products containing polymer (for example, cables, carpets, furniture cabinets, various fabrics, etc.) create a need to create and use a new composition of heat-insulating polymers with a high degree of fire resistance to protect public safety from fire. Obtaining high-dispersion refractory and heat-insulating coatings based on organosilicon compounds, studying their properties, and developing and applying technologies for obtaining organosilicon materials are of both practical and theoretical importance [1].

Silica materials have been produced commercially since the 1940s. Over the past 80 years, the production of organosilicon materials has increased several times and is used in many fields, including engineering, construction, electrical, transportation, aviation, defense, textile and cosmetic industries. Taking into account the above, it is possible to obtain a new type of polymer compounds based on tetraethoxysilane to increase the range of currently used organic silicon compounds [2]. 

The purpose of this article is to obtain temperature-resistant oligomers based on local reactants. The following were selected as tasks of the research: selection of research objects; obtaining oligomers based on tetraethoxysilane with them; to study the physico-chemical properties of obtained oligomers. Glycerin, methanal, urea and tetraethoxysilane were used as research objects in this article. We know that oligomers and polymers containing silicon are resistant to temperature. Therefore, tetraethoxysilane was chosen as the object of research.

Methods and results

Synthesis of organosilicon polymers with urethane group. Organic compounds were used to obtain high-dispersion fire-resistant and heat-insulating fillers based on the transfer of urethane oligomer to a mesh state with tetraethoxysilane, to obtain paints and to increase the fire resistance of wood and building materials with the help of them, as well as to protect them from the effects of fire in multiple stages.

The reaction of di-, triurethane production in the presence of glycerol, urea, and formaldehyde was studied. Kinetic parameters (temperature, type of catalyst, presence of organic solvent) ensure that the amount of functional groups varies.

The experiment was carried out as follows: 50 grams of urea were placed in a flask equipped with a stirrer, a reflux condenser and a thermometer and heated to 95 - 100 °C. When stirring, the temperature of the reaction mass rises to 120 °C after adding glycerol in an equimolar ratio at a rate not lower than 100 °C. At this temperature, the reaction is carried out for 30 minutes. Then, the temperature was raised from 120 °C to 135-140 °C for 15 minutes and maintained for 2 hours, and tetraethoxysilane was added taking into account the degree of burning. At the temperature range of 125-130 °C, ammonia separation began, and when ammonia separation ended, the temperature was slowly lowered. Oligomer formation was carried out on the basis of the following chemical reaction:

The properties of the dark brown mass were studied. It is insoluble in water and non-polar solvents, soluble in polar solvents [3-6].

DISCUSSION

The dependence of the degree of adhesion on the viscosity of the reaction mixture was studied by controlling the amount of tetraethoxysilane added (Table 1).

Table 1.

The effect of the ratio of substances on the degree of adhesion of the obtained polymer

An increase in temperature leads to an increase in the speed of the process and an increase in the yield of polymer stitching. The effect of the ratio of reacting components on the obtained product was studied. As can be seen from Table 1, viscosity increases with increasing amount of stitches in the obtained polymer. The ratio of components exceeding 10:1 leads to the transformation of the polymer into a solid mass (through a rubbery mass).

Based on the above, research was continued taking the optimal ratio as 10:1 (50:5). Also, the polymerization kinetics at different temperatures were studied. (Table-2)

Table 2.

Properties of the resulting polymer in the 50:5 ratio

In heterogeneous reactions, reactants differ in that they are in different phases. Let's pay attention to the laws of interfacial reactions associated with the interaction of solids with gases, liquids and solids, which is especially important for choosing the optimal conditions for the formation of new materials. Reactions involving solids have two distinct characteristics. First, chemical changes occur in a limited zone of a solid and are described at the local level.

Second, when several reagents are involved in the reaction, solid products can form a layer that makes it difficult for the reaction to proceed.

The progress of this process is a measure of the rate of the reaction, as it leads to the reduction of the initial amount of the reactant involved in the reaction and the formation of the product. When interpreting the kinetics of heterophase reactions between solid and liquid or gas, the following kinetic principles should be used - the rate of heterogeneous reaction is proportional to the total effective area of the reagent-product interface. This principle applies only when there is no dissolution of the reagent. In an isotropic reaction, the advance rate of the interface is constant under isothermal conditions. This principle applies as long as the final product does not interfere with contact with reagents or removal of volatile products. When one or more product phases form a layer that prevents direct contact between the reagents, the overall reaction rate can be controlled by the diffusion of the reagents through this layer. The kinetic state of the overall process is determined by geometric factors and the influence of the product layer of the reaction. The rate at which a solid reacts with a gas or liquid can depend on its concentration.

Interactions in multicomponent systems are a set of parallel and sequential reactions, and it is not always possible to isolate a kinetically significant reaction or reaction step.

In order to study the thermal properties of the synthesized polymer, a composition was prepared based on it.

1 - kaolin 30%, urethane organosilicon polymer, liquid glass concentrate 67%;

2 - kaolin 30%, urethane organic silicon polymer, liquid glass concentrate 77%;

3 - kaolin 20%, urethane organosilicon polymer, liquid glass concentrate 75%.

Thermal mass reduction of the prepared composition was studied (Table 3).

Table 3.

Test results for evaluating the fire protection performance of liquid glass-based coatings

The results of Table 3 show that according to the requirements of SST 16363-98, all coatings with compositions No. 1, No. 2 and No. 3 belong to the II group of fire retardancy. Thus, the obtained results indicate the effectiveness of fire protection of the obtained compositions. This is especially noticeable in compositions No. 1 and No. 2, coatings containing newly modified kaolin, which lose the least weight, so there are high indicators of fire protection efficiency for wood materials. In addition, in order to test the flame retardant properties on wooden samples with dimensions of 90x55x25 mm, the following fire retardant paint formulas were prepared: "fire resistant heat insulator" + "binding component" + "polymer component" with coating content from 8% to 95%. Kaolin powder with a grain size of 40-80 microns was used as a fire-resistant heat-insulating coating as a fire-retardant component.

According to the requirements of the normative documents of the field of fire safety, the critical temperature for metal structures, that is, the temperature at which the metal structure loses its strength, is 500 °C. For wood samples, the temperature is 250-300 °C. Taking this property into account, test experiments were conducted. Experiments were conducted to evaluate the effectiveness of thermal protection of wood of the newly developed composition (fibrous material that improves adhesion, mechanical properties, and additives that increase resistance to cold temperature and atmospheric effects).

According to the measurement results presented in Table 4, it was found that the highest exhaust gas temperature was observed during the test of the control sample (without refractory coating). A control sample introduced into the fire began to burn actively and lost 16% of its mass after 120 seconds; an increase in the temperature of the surface of the sample occurs.

As can be seen from Table 4, the values of the control sample were the lowest and the values of sample 2 were found to be the most fire resistant. At 5-6 minutes, the temperature of the exhaust gases was 145-155 °C, which showed low indicators of the efficiency of burning the sample.

Table 4.

Fire test results of 100x50x50 wooden bars

A typical untreated wood sample first ignited in the range of 180-220 °C and then started to smolder. During the thermal analysis of the obtained heat-insulating polymer-based wood materials, the mass change in it started at 260 °C, and the mass change at 522 °C is 27.4%, but during the thermal treatment, the heat-insulating polymer-based wood samples produced smoke. , but no ignition was observed. Part of the mass reduction in the wood sample may be due to the loss of moisture in the wood.

In the researches, with increasing temperature, the mass of a common wood sample is observed to decrease rapidly due to charring and sticking of wood in the range of 215-320 °C. During the thermal analysis of wood samples treated on the basis of heat-insulating polymer, mass reduction at 260 °C was 5.2%. In this case, the decrease in mass is mainly due to the decrease in moisture in the wood sample.

Conclusion

The physical state, structure and chemical composition of the synthesized (oligo)polymers, the external field (ultrasound, heat) and chemical reagents were applied to the synthesis process to achieve the specified thermal and physical parameters of refractory compositions. Development of fire protection mechanisms of wooden and inorganic building structures using the created compositions; effective fire-resistant coatings based on urethane were created, with the help of which methods of increasing the fire resistance of wooden and inorganic building structures and multi-level fire protection were developed.

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