Research of adhesion strength of composite epoxy materials filled with mineral waste of various productions

ABSTRACT

The article presents the results of a study of the adhesion strength of composite epoxy materials filled with mineral waste from various industries, including waste from gold recovery plants.

АННОТАЦИЯ

В статье приведены результаты исследования адгезионной прочности композиционных эпоксидных материалов, наполненных минеральными отходами различных производств в том числе отходов золотоизвлекательных заводов.

Keywords: Phosphor gypsum, Gold Recovery Plant waste(GRPW), Epoxy resin (ER-20), phosphor slag, composite epoxy

Ключевые слова: Фосфорный гипс,  Отход золотоизвлекательной фабрики (ОЗИФ), эпоксидная смола (ЭД-20), фосфорный шлак, композитная эпоксидная смола.

Introduction.

To study the adhesive strength of epoxy composite materials and develop effective compositions of composite polymer materials, we selected the following secondary raw materials: phosphor slag, phosphor gypsum and GRPW, which are waste products of the Marzhanbulak gold recovery plant. We have studied the adhesive strength of composite epoxy materials filled with these mineral waste products.

Figure 1 shows the results of studies of changes in the adhesive properties of coatings based on filled epoxy compositions when exposed to aggressive media. It can be seen that in all cases, the fillers introduced into the composition increase the adhesive strength of the coatings.\

The idea of creating composite materials is not new. For example, our people have long used the adobe material in construction, in which clay serves as a binder (matrix), and straw acts as a reinforcing reinforcement. Also, in construction, asbestos cement has been used for a long time, consisting of a matrix cement and a fibrous natural material of asbestos as reinforcement. The properties of such composites are determined by the high strength of the reinforcing fibers, the rigidity of the matrix and the bond strength at the matrix-fiber interface. The ratio of these parameters characterizes the entire complex of mechanical properties of the material and the mechanism of its destruction.

Figure 1. Dependence of the adhesive properties of (aa-) compositions on the content of fillers (binder Epoxy resin ER-20): 1-phospho slag, 2-phospho gypsum, Z- GRPW

Basically, the adhesive interaction of the fiber and the matrix determines the level of properties of the composites and their operation during operation. Local stresses in the component reach their maximum values near or directly at the interface, where the destruction of the material usually begins. The interface must ensure efficient transfer of the load from the matrix to the fibers.

The adhesive bond at the interface should not be destroyed under the influence of thermal and shrinkage stresses due to differences in the temperature coefficient of linear expansion of the matrix and fiber, or as a result of chemical shrinkage of the binder during its hardening [2].

The adhesive strength depends on the binding energy, the contact completeness determined by the surface relief, the interfacial surface energy, wetting and other surface phenomena, as well as on the conditions of contact formation (pressure, temperature, etc.) [3].

To date, in Uzbekistan, the production of a new composite material for the local market-a plate made of gypsum-fiber mass has been mastered at some enterprises. In such a composite, the reinforcement is a recycled cellulose fiber evenly distributed in the gypsum mass[4].

At the same time, various technologies for the production of gypsum fiber boards are used, since the scarcity of secondary cellulose forces entrepreneurs to use plant-based raw materials, which greatly affects the production process, primarily on operations to ensure high adhesion of the fiber to the matrix (processing of fibrous raw materials, modification of the binder). In many cases, when looking for alternative raw materials for the production of gypsum fiber board, the choice falls on the straw of cereals, since this raw material can always be found at an affordable price and in large quantities. However, straw, like many organic cellulose fillers, along with its inherent valuable properties, has negative qualities that make it difficult to obtain high-strength composites[5].

The specific properties of such an organic cellulose aggregate include increased chemical aggressiveness, significant amounts of moisture deformation and the development of swelling pressure, pronounced anisotropy, high permeability, low adhesion to the matrix, and significant elasticity when compacting the mixture. This negatively affects the processes of matrix hardening, structure formation, as well as the strength and resistance of the composite material to moisture-changing influences.

This article discusses the materials of research on the establishment of the interaction of the adhesive with the substrate surface in a new composite material. Establishing the nature of the interaction is fundamental for understanding the mechanism of adhesion of fibers, in particular straw fibers to gypsum crystals, as well as for developing practical solutions to enhance the adhesion between them.

As can be seen from Fig. 1, with the introduction of up to 10 wt.h. phosphor gypsum into the epoxy composition, the adhesive strength does not decrease at all, and in the composition filled with phosphor slag and GRPW, the adhesive strength is mainly in a stable state. Further increase the content of fillers in the composition of the epoxy composition of phosphor slag, phosphor gypsum and Gold Recovery Plant waste(GRPW) adhesive strength) of the coatings increases (Fig.1) and passes through the maximum at a content of fillers equal to 30 wt. h. So, in the case of phosphor slag, the value a " reaches up to 11.37 MPa, in the case of phosphogypsum-10.93 MPa and in the case of GRPW -10.86 MPa. A further increase in the content of fillers leads to a decrease in coatings.

Such a change in the adhesive strength of the composition when filling with the absence of aggressive media is due to the fact that fine fillers, due to the presence of metal oxides in their composition, contribute to the interaction of the filler.

The optimal value of the adhesive strength of the compositions, with a content of fillers of 30 wt., h. is due to the fact that this concentration is critical. When the filler content is higher than the critical one, the uniformity of the structure of the studied compositions is sharply violated, and, accordingly, the adsorption interaction at the polymer - substrate interface is disrupted.

As can be seen from the curves of Fig. 1, that among the fillers phosphor slag, phosphor gypsum and GRPW significantly improve the adhesive properties of epoxy compositions based on resin ER-20 is observed in compositions filled with phosphor slag. This is due to the fact that the composition of these fillers contains metal oxides, especially in phosphor slag, which have a strengthening effect.

Thus, it was found that the fillers - industrial waste – phosphor slag, phosphor gypsum and GRPW - introduced into the epoxy composition based on the ER-20 oligomer significantly improve the adhesive strength, which is the main criterion for the durability of the resulting coating based on them.

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