REASERCH OF EPOXYSILOXANE POLYMERIC MATERIALS FORMATION FOR USE IN REINFORCED CONCRETE PRODUCT EQUIPMENT

ABSTRACT

This article presents the results of studies of the formation patterns of epoxysilane polymer materials for use in reinforced concrete product equipment. The studies have established that the working layers of epoxysiloxane polymers are predominantly siloxane polymer, in which fragments of epoxy polymer are found in the form of chemically cross-linked segments, and the layers on the substrate side, on the contrary, are epoxy polymer, in which siloxane polymer is found in the form of dispersed inclusions and chemically bonded fragments.

АННОТАЦИЯ

В данном статье приведены результаты исследований закономерности формирования эпоксисилановых полимерных материалов для применения в оснастках железобетонных изделий. Исследованиям установлено, что рабочие слои эпоксисилоксановых полимеров представляют собой преимущественно силоксано­вый полимер, в котором в виде химически сшитых сегментов находят­ся фрагменты эпоксидного полимера, а слои со стороны подложки, наоборот, эпоксидный полимер, в котором в виде дисперсных включе­ний и химически связанных фрагментов находится силоксановый по­лимер.

Keywords: siloxane polymer, formation patterns, reinforced concrete structures, equipment, aminophenol, piperidine.

Ключевые слова: силоксано­вый полимер, закономерности формирования, железобетонные конструкции, оснастка, аминофенол, пиперидин.

Introduction. Reinforced concrete products and structures are widely used in the construction industry worldwide. In this regard, the role of technological equipment, in which the main elements of modern construction are formed - reinforced concrete structures, as well as interior finishing elements - sheet and film polymer relief shells obtained by the method of thermal vacuum forming, increases. The production of fully factory-ready structures, and, consequently, the aesthetic level of construction, depends on the operability of the working elements of such equipment. In this regard, special attention is paid to the use of composite polymer materials in the equipment structures. They allow to improve the tribotechnical characteristics of the equipment, reduce the force of stripping, concrete adhesion, increase the factory readiness of building structures; increase the mechanical strength and durability of the equipment itself [1-4].

Objects of the study: epoxy resins ED-20 (State Standard 10587-84), EC-N (TU 6-05-1180-76), E-181 (TU 6-05-1747-76) were selected as polymer binders, and highly active amine hardener, which is a condensation product of formaldehyde and phenol with diethylenetriamine, UP-583-diethylenetriamino-methylphenol (TU-6-05-241-331-82), monocyanoethyldiethylenetriamine VII-06334 (TU-6-05-1663-78) and piperidine (TU-6-09-3673-74) - a secondary aromatic amine, were selected as hardeners. Dimethylsiloxane rubber (TU 38-105462-80) was chosen as a siloxane polymer; DMSA with a molecular weight of 18-21 thousand forms a high-strength vulcanizate; the hardener is a dimethylsiloxane rubber catalyst, methyl ester of orthotitanic acid (TU 602-805-78); the fillers were GS-2 graphite (State Standard 17022-76), strontium ferrite, iron powder grade PZhOMZ (State Standard 9848-74), solvents: acetone (State Standard 2603-79), toluene (State Standard 5789-78).

Research methods. In carrying out this work, IR spectroscopy was used to determine the tribological, physical and mechanical properties of composite polymer materials and coatings based on them, using generally accepted standard methods permitted in the CIS countries.

Results of the research and their analysis. The mixtures of epoxy oligomer ED-20 with amine hardeners and dimethylsiloxane rubber (DMSR) with methyl ester of orthotitanic acid (MEOTА), as well as mixtures of oligomer ED-20 with amine and siloxane hardeners were studied. The content of siloxane oligomers varied from 5 to 30 mass parts per 100 mass parts of epoxy oligomer ED-20. The time and temperature of thermostatting during mixing were 0.6-1.5 kS and 293-323 K, respectively. Amine hardeners of the epoxy oligomer were selected so that it was possible to identify the patterns of formation of the phase structure of epoxysiloxane polymers depending on the reactivity of amines. The nature of the kinetic process of gelation of the epoxy oligomer ED-20-piperidine system is close to the DMSR/ MEOTА system. In a mixture of these systems, the formation of globular structures of epoxy and siloxane polymers was observed, each on its own active polymerization center with their simultaneous gradient microphase separation. The gelation time of the ED-20/UP-583 system is significantly shorter than the DMSR/ MEOTА system. In a mixture of these systems, a faster formation of the gel fraction of the ED-20/UP-583 system occurs, which leads to the formation of an epoxy dimethyl siloxane polymer, in which the formation of a gradient structure is manifested to a lesser extent. A more uniform distribution of the siloxane phase in the epoxy matrix is ​​observed [5-9]. When using low-active monocyanoethyl diethylenetriamine (UP - 0633M), which is also a good diluent for the mixture, the initial phase structure formation of the DMSR/ MEOTА system occurs. In this case, a pronounced gradient separation of the mixture is observed with the transfer of the siloxane phase to the surface in contact with air. And only after this does the mixture gel. The working layer in contact with air has a high concentration of DMSR/ MEOTА, and the opposite layer in contact with the substrate has an insignificant concentration of this polymer. The transition to the working layer of the siloxane component depends on the amine hardener used and increases in the following series of hardeners: aminophenol, piperidine, monocyanoethyl diethylenetriamine. The process of mixture delamination ends with the formation of three interpenetrating layers: the upper surface layer enriched with dimethylsiloxane rubber; an intermediate layer consisting of epoxy and siloxane components; layer adjacent to the substrate, consisting mainly of an enokiid component with single inclusions of dimethylsiloxane rubber. For mixtures of epoxy oligomer ED-20 + KO-810; ED-20 + KO-812 with the same amine hardeners, a similar pattern of gradient microphase separation of components is observed, as for mixtures (ED-20 / amine) + (DMSR/ MEOTА). A significant difference between these mixtures is that when using DISK, the heat treatment process can be single-stage, whereas for mixtures with K0-8I0, KO-812 - this same process should be two-stage, since K0-8I0 and KO-812 begin to pass into a gel-like state at elevated temperatures.

Using optical microscopy and microhardness, it was established that the working layers of gradient epoxy siloxane polymers have a non-uniform "mosaic" structure. This is due to the fact that along with the siloxane phase, these surfaces contain particles of epoxy polymer. Table 1 presents data quantitatively characterizing the gradient microphase separation of oligomeric mixtures depending on their composition. As a consequence of this process, a change in the microhardness and contact angle of wetting with the "test" liquid is observed. The microhardness values ​​of the working layers were 130-160 MPa, with areas with a microhardness of 170-195 MPa, for which the epoxy phase is responsible; in the opposite layers of the samples. from the side of the substrate, the microhardness values ​​were 185-200 MPa. The "mosaic" structure of the polymer and, as a consequence, the heterogeneity of the microhardness of the working layers of the studied polymers is also due to the presence of roughness, the nature of which is determined by the regular alternation of the epoxy and siloxane phases in these layers.

The thickness of the working (siloxane component-enriched) layer of the sample was controlled by changing the oligomer ratio, time and temperature of thermostatting when mixing the components.

To assess the influence of the substrate on the nature and properties of the surface layers of epoxysiloxane polymers, the surfaces of samples obtained in steel molds were studied both "face" up (on the substrate) and "face" down (directly on the mold tray). It was found that the surfaces obtained "face" up always had layers enriched with the siloxane phase, and "face" down - with the epoxy phase.

The second section of this chapter presents the results of IR spectroscopic studies of epoxysiloxane polymers. In this case, the IR spectra of various layers of the samples were studied. It was revealed that during the formation of such polymers, conversion of epoxy groups (860 cm^-1) and interaction of hydroxyl groups with siloxane (3400 cm^-1) take place. The IR spectra of the working opposite layers are basically identical. However, they have characteristic differences. In the spectrum of the layer at the boundary with the substrate, there are bands at 3020, 3040 cm^-1 from the stretching vibrations of CH-bonds in the aromatic ring, and in the spectra of the upper layers, the intensity of these bands is much lower. The bands from the stretching vibrations of CH-bonds in alkyl groups in the region of 2800-2950 cm of the upper layer are close to the DMSR bands at 2925 cm^-1, and those of the lower layers are close to the cured ED-20. The bands at 1005 cm^-1 in the spectrum of the upper layer are close to the bands from deformation vibrations of the Si - (CH3)² bonds at 1010 and 1075 cm^-1, and in the spectra of the layer at the boundary with the substrate, the bands at 1025, 1100 cm^-1 are close to the bands from the C-O-C fragments at 1025, 1100 cm^-1. However, the incomplete coincidence of the bands of epoxy dimethyl siloxane polymers with the spectra of cured DMSR and ED-20 indicates a chemical interaction of these oligomers.

Conclusions. Thus, it can be concluded that the working layers of epoxysiloxane polymers are predominantly siloxane polymer, in which fragments of epoxy polymer are found in the form of chemically cross-linked segments, and the layers on the substrate side, on the contrary, are epoxy polymer, in which siloxane polymer is found in the form of dispersed inclusions and chemically bonded fragments.

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