STUDY OF TEMPERATURE DEPENDENCE OF THE DEFORMATION PROPERTIES OF THERMOREACTIVE POLYURETHANE USING THERMOMECHANICAL METHOD

АННОТАЦИЯ

В этой статье образец полиуретана, был получен поликонденсацией 4,4-метилендифенилдиизоцианата и полиэфирполиола. Температурная зависимость деформационных свойств приготовленного образца полиуретана изучалась термомеханическим методом.

ABSTRACT

In this article, a polyurethane sample was obtained by polycondensation of 4,4-methylene diphenyl diisocyanate and a polyester polyol. The temperature dependence of the deformation properties of the prepared polyurethane sample was studied by the thermomechanical method.

Ключевые слова: поликонденсация, деформация, температура стеклования, температура размягчения, аморфное состояние, температура перехода на высокоэластического состояния, статическое напряжение.

Keywords: polycondensation, deformation, glass transition temperature, softening temperature, amorphous state, transition temperature to a highly elastic state, static stress.

Introduction. Today, polymeric materials are widely used in all areas of the country's real economy . One of these main areas is the mining and metallurgical industry, which uses various pumps operating in aggressive environments. Polyurethane materials are used to increase the wear resistance of continuously operating pump parts [1]. These coating parts wear out after a certain period of time due to wear and are replaced with new polyurethane coatings. At the Navoi Mining and Metallurgical Combine (NMMC), 80-100 tons of polyurethane material is accumulated as waste annually. The processing of these resulting wastes, as well as the study of the physical and mechanical properties of the processed polyurethane material, are relevant [2]. In the production of parts with high properties, it is desirable to use thermosetting polymers. The main factor in the production of a polymeric material of complex composition is a plasticizer, which forms the basis of the polymer. At present, plasticizers are used to produce polymers and polymer composites with high physicochemical properties. These include, for example, polyolpolyisocyanates, polycarbonate polymers, epoxyurethane-based polymers, and other thermosetting polymers [3,4]. These 4,4-methylenediphenyl-diisocyanate-containing thermosetting polyurethanes also have a three-component network macromolecular structure, high temperature, chemical attack, deformation resistance and resistance to aggressive environments compared to thermoplastic polymer materials. In addition, it is convenient to obtain various components from liquid thermosetting polyurethanes [5, 6].

Research object. Based on the collected data from the literature review, the stated goal of this study is to study the thermomechanical properties of polyurethane based on 4,4-methylenediphenyl diisocyanate and polyester polyol.

Table 1 lists the production parameters for the thermoset polyurethane material. Polyurethane with this composition is used for lining internal walls of pumps pumping acid solutions, for a panel of sieves, as well as vibration damping bricks [7].

Table 1.

Synthesis of polyurethane material

Based on the values given in Table 1, a polyurethane sample was prepared and the thermomechanical properties of this sample were studied [ 8 , 9 ].

Methods and materials

Amorphous polymers, in addition to the state of glass transition and fluidity, also have a state of high elasticity, not found in other polymers. The state of high elasticity, fluidity, and the glassy state of the polymers were determined according to GOST 270-75 and GOST 32618.2-2014 on an RMI-60 testing machine [10] .

Results and discussion . The transition interval of a polyurethane sample from one state to another under the influence of various temperatures was determined by the thermomechanical method. The studies were carried out with the help of experiments, special devices, tools, as a result of which a graph of the temperature dependence of the deformation was built.

Where: T _S - softening temperature; T _G is the glass transition temperature; T _IHE - transition to a highly elastic state; T _SIS is the beginning of strain inversion; T _ERW - end of reverse warp
Figure 1. Thermomechanical curve of a polyurethane sample

From Fig. 1, the thermomechanical curve shows that at a temperature of 73 °C , the deformation of the urethane-forming aliphatic groups occurs at a low temperature, and the glass transition begins at a temperature of 116°C. An increase in temperature leads to the transition of the polymer sample to a state of increased elasticity, which occurred at a temperature of 135°C. Between T _IHE and T _SIS there is an increase in temperature from 135°C to 160°C, and it is found that with an increase in temperature there is a permanent deformation of the sample. This means that the diisocyanate polyurethane is in a highly elastic state in the temperature range of 135-160°C. Distance between T _IHE and T _SIS thermomechanical curve is called the upper elastic limit. The next section of the thermomechanical curve is the interval between the points T _SIS and T _ERW , in which the curve deviates from the upper elastic limit, i.e., an inversion of the sample deformation is observed. The inversion value of the strain is 25 µm. The strain inversion of the sample occurred in the temperature range 135–160°C. Based on the above data, the following table 2 was created.

Table 2.

Thermomechanical parameters of the polyurethane sample

Based on the thermomechanical analysis data, the graph curve showed that the polymer goes into a softened state, starting from 72 °C. The presence of a high elastic plateau on the thermomechanical curve indicates that the new polymer has a densely reticulated supramolecular structure, i.e., the polymer has a thermosetting character.

Conclusion

As a result of the research, it was found that at temperatures below the melting temperature of a thermosetting polyurethane sample, polyurethane is solid, its deformation is small, and at higher temperatures, the deformation increases sharply. It has been found that the viscosity of the polymer in the liquefied state decreases with increasing temperature.

References:

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