RU2755343C1 - Method for obtaining polymer-composite material and composite reinforcement - Google Patents

Abstract

FIELD: building materials.

SUBSTANCE: invention relates to the field of building materials and is intended for the reinforcement of building structures. The method of obtaining a polymer-composite material is a multi-stage production of a colloidal solution based on epoxy resin with the addition of carbon nanotubes using heating and ultrasonic action. On the basis of a colloidal solution, a polymer composite material is manufactured, consisting of an epoxy resin, a hardener, an accelerator, a plasticizer and multilayer carbon nanotubes. With the use of a polymer composite material made according to the described method, a stressed reinforced composite reinforcement is produced. It consists of strained reinforcing fibers of straight glass roving made of alkali-resistant E-glass with a tension increase of 50-1500 kg, polymer and a twisted strand of straight glass roving made of alkali-resistant E-glass.

EFFECT: invention allows obtaining a reinforced stressed composite reinforcement with improved physical and mechanical characteristics, increased resistance to aggressive environments.

2 cl, 1 dwg

Description

The invention relates to the field of building materials and is intended for the reinforcement of building structures.

A nano-modified epoxy binder for composite materials is known from the prior art (RU 2584013, publ. 05/20/2016, bull. No. 14). The nanomodified epoxy binder for composites includes dian epoxy resin and amine hardener. As a hardener, it contains a polyamine brand "Aramine-T", which is a modified aromatic polyamine. The composite material contains silicate-type nanoparticles, which are organophilic clay of the "Monamet 1E1" brand, and carbon-type nanoparticles, which are carboxylated carbon nanotubes of the "Taunit-M" brand. If necessary, it contains a plasticizer-flotation agent oxal T-92, which is a mixture of dioxane alcohols and their high-boiling ethers. The composite material contains an active diluent, which is a condensation product of aniline and epichlorohydrin (EA brand epoxyaniline resin). These components are contained in the composite material in the following ratio (wt%): epoxy resin (4.12-72.44), silicate-type nanoparticles (0.51-1.81), carbon-type nanoparticles (0.02-0 , 45), plasticizer (0.0-0.56), active diluent (3.78-65.52), aromatic amine hardener (22.69-28.1). The main disadvantage of this invention is its cold curing type. An amine hardener is used as a hardener. The curing process is very long and is not suitable for the production of composite rebar using hot cure and anhydrite hardener. Also, the disadvantages can be attributed to the stage of dispersion (mixing) of nanomaterials that are too short in time. Carbon nanotubes (CNTs), like other nanoparticles, form rather strong agglomerates and aggregates that cannot be broken up and evenly mixed with epoxy resin in 20-30 minutes.

The closest technical solution is an epoxy composition for high-strength, alkali-resistant structures (patent for invention RU 2536141 C2, publ. 20.12.2014, bull. No. 35). The hot curing epoxy composition as a binder for the manufacture of fiberglass materials includes an epoxy dian oligomer of the ED-20 brand, a hardener - iso-methyltetrahydrophthalic anhydride (iso-MTHFA) and a polymerization reaction catalyst, according to the invention, it additionally contains carbon-type nanomaterials as a modifying additive , which are carbon nanotubes (CNT), or carbon nanofibers (CNF), or a mixture of carbon nanomaterials: fullerene, nanotubes, nanofibers (CUNM), or carbon black (soot), with the following content of components, parts by weight: epoxy oligomer - 100, iso-MTHFA - 80, the above catalyst - 1.5, carbon nanomaterials - 0.05-1.5. The disadvantage of this invention is the mixing of carbon nanomaterial with the components of the polymer matrix using an ultrasonic generator with an insufficiently effective frequency of 22 kHz. In combination with a short time of heat and mechanical treatment, this invention does not allow achieving a high degree of uniformity of distribution of CNTs and, accordingly, high mechanical and chemical resistance of a polymer composite material (PCM).

The main drawback of all known products is the weak tension (stress) of the reinforcing threads (fibers) of the bearing rod (trunk) of the composite reinforcement. It is in the strong preliminary stress (tension) of the reinforcing fibers of the trunk that the main potential for enhancing the strength characteristics of composite reinforcement is concentrated. The reinforced nanomodified polymer matrix also helps to enhance these characteristics, but its contribution to this enhancement is much more modest. Only by reinforcing the polymer in the composite matrix and introducing various fillers into it can only a slight enhancement of the physicomechanical characteristics of the composite reinforcement be achieved.

The technical problem to be solved by the claimed invention is to create a PCM with enhanced resistance to mechanical and chemical stress.

The technical result provided by the given set of features is to increase the mechanical and chemical resistance of the polymer matrix.

The claimed technical solution is aimed at developing a method for producing a polymer-composite material for reinforced composite reinforcement.

Reinforced stressed composite reinforcement is used for reinforcement:

- conventional building structures and products;

- prestressed building structures and products;

- monolithic concrete and prefabricated buildings;

- thermal insulation wall panels;

- marine and port facilities;

- soil foundations of buildings and structures;

- foundations of highways and roads;

- fastening of various soils;

- for anchoring retaining walls and structures in the ground.

At its core, composite reinforcement is a bundle of reinforcing fibers securely enclosed in a strong polymer matrix. The tensile strength and modulus of elasticity of the composite reinforcement is determined by the filaments of glass, basalt, carbon or aramid reinforcing fibers, of which its supporting rod (the reinforcement barrel) consists. The uniform high tension (stress) of these threads makes them work simultaneously as a whole and can significantly increase the tensile strength and modulus of elasticity of the composite reinforcement. A polymer matrix is used to fasten these threads into a solid, strong bearing rod, as well as to protect against the unwanted effects of aggressive media.

The main disadvantage of all manufacturers of composite reinforcement is the weak tension of the reinforcing fibers. After solidification of the polymer matrix, the fibers inside are in a relaxed (sagging) state. In such an unstressed composite reinforcement, when a longitudinal tensile load occurs, it is absorbed by the polymer matrix. Polymer is not the strongest component in composite reinforcement, it deforms and breaks down before the reinforcing fibers begin to work. Only then do the reinforcing fibers stretch and begin to resist the breaking load. And since they were not evenly tensioned initially, they will not stretch and resist the load evenly. As a result, the declared theoretical tensile strength, elastic modulus, bending strength and most other physical and mechanical characteristics of such composite reinforcement in practice do not coincide with reality, but much less.

In the claimed reinforced stressed composite reinforcement, all the fibers of the power rod before polymerization are strongly and evenly stretched (strained) by a powerful pulling device, tensile force: 50-1500 kg. Together with the reinforced nano-modified polymer matrix, the claimed reinforced stressed composite reinforcement is a single stressed monolith with uniform physical and mechanical characteristics in any section.

The introduction of modifiers (fillers) into the polymer matrix in a certain ratio, the orientation of the fillers make it possible to create a polymer strengthened to mechanical stress with increased resistance to aggressive media (acid resistance and alkali resistance).

The most effective is a nano-modified polymer matrix, in which the usual epoxy resin is replaced by a modified epoxy resin, which, before curing, is a colloidal solution, in which the dispersion medium is an ordinary epoxy resin, and the dispersed phase is carbon nanomaterials: multilayer carbon nanotubes, the concentration of the dispersed phase (carbon nanomaterial) in the dispersion medium is in the range of 0.001 - 5% of the mass of the dispersion medium. The optimum concentration of carbon nanomaterial is 0.1% of the mass of the dispersion medium.

Particles of carbon nanomaterials tend to form agglomerates and aggregates. It is necessary to destroy them and distribute nanoparticles evenly throughout the volume of the polymer and achieve its homogeneity.

To prevent the formation of agglomerates and aggregates, as well as to uniformly distribute CNTs over the entire volume of the polymer, it is proposed to use the sequential creation of colloidal compositions: from a 10% concentrated colloidal solution to a solution with a working concentration (up to a concentration of 0.1%) with a step of decreasing the concentration of 10: 1. With a step of more than 100: 1, CNTs are not distributed evenly enough; a step less than 10: 1 is not economically viable. To prevent the formation of agglomerates and aggregates, a heated vacuum dissolver and an ultrasonic mixer are used.

The colloidal system is obtained in three stages.

The first stage is the preparation of a concentrated 10% colloidal solution with a CNT concentration of 10%, which is the basis for the subsequent creation of a solution of the required concentration in the following sequence:

1. A concentrated colloidal solution is created from epoxy resin and CNTs with a mass ratio of epoxy resin to CNTs of 10: 1.

2. The colloidal solution is stirred for 20-30 hours in a vacuum dissolver at a temperature of 55-80 ° C.

3. The colloidal solution is stirred for 20-30 hours in an ultrasonic mixer with a frequency of 25-60 kHz.

If the uniformity of the distribution of CNTs over the entire volume of the solution is insufficient (agglomerates and aggregates of carbon nanotubes are clearly visible under a microscope with 1000x magnification), steps 2 and 3 are successively repeated until the colloidal solution is homogeneous.

The second stage - from the 10% colloidal solution obtained at the first stage, a 1% colloidal solution with a CNT concentration of 1% is prepared:

1. A concentrated 10% colloidal system is introduced into the epoxy resin, obtained at the first stage in the ratio by weight of epoxy resin to the colloidal system as 10: 1.

2. The colloidal solution is stirred for 2-5 hours in a vacuum dissolver at a temperature of 55-80 ° C.

3. The colloidal solution is stirred for 2-5 hours in an ultrasonic mixer with a frequency of 25-60 kHz.

If the uniformity of the distribution of CNTs over the entire volume of the solution is insufficient (agglomerates and aggregates of CNTs are clearly visible under a microscope with 1000x magnification), steps 2 and 3 are successively repeated until the colloidal solution is homogeneous.

The third stage - from the 1% colloidal solution obtained in the second stage, a colloidal solution with a CNT concentration of 0.1% is prepared:

1. A concentrated colloidal system is introduced into the epoxy resin, obtained in the second stage in a ratio by weight of epoxy resin to the colloidal system as 10: 1.

2. The colloidal solution is stirred for 2-5 hours in a vacuum dissolver at a temperature of 55-80 ° C.

3. The colloidal solution is stirred for 2-5 hours in an ultrasonic mixer with a frequency of 25-60 kHz.

If it was not possible to evenly distribute the nanoparticles throughout the entire volume of the solution and achieve its homogeneity, then steps 2 and 3 are repeated until the colloidal solution is homogeneous.

Thus, the process of preparing a polymer matrix consists in replacing the main component - epoxy resin - with a working colloidal solution with a CNT concentration of 0.1% of the mass of the dispersion medium. The creation of a colloidal solution with a CNT concentration of more than 5% does not make sense, because the price of the matrix more than doubles.

Further, a hardener, an accelerator and a plasticizer are added to the resulting colloidal solution with the following ratio of components (in fractions):

- colloidal solution - 1;

- hardener - 0.8;

- accelerator - 0.04-0.06;

- plasticizer - 0.04-0.1.

Examples of the ratio of components:

Example 1.

- epoxy resin - 1 kg;

- hardener - 0.8 kg;

- accelerator - 0.05 kg;

- plasticizer - 0.05 kg;

- multilayer carbon nanotubes - 0.001 kg.

Example 2.

- epoxy resin - 1 kg;

- hardener - 0.8 kg;

- accelerator - 0.06 kg;

- plasticizer - 0.1 kg;

- multilayer carbon nanotubes - 0.05 kg.

Example 3.

- epoxy resin - 1 kg;

- hardener - 0.8 kg;

- accelerator - 0.04 kg;

- plasticizer - 0.04 kg;

- multilayer carbon nanotubes - 0.00001 kg.

The epoxy resin used is ED-20 epoxy resin, or DER-331 epoxy resin, Epikot epoxy resin, or KER-828 epoxy resin.

Iso-MTHFA (Iso Methyltetrahydrophthalic anhydride) is used as a hardener.

DMP-30 (Alkofen) is used as an accelerator.

DEG-1 is used as a plasticizer.

The strength of the composite reinforcement is determined by the strength of the reinforcing fibers of its bearing bar (trunk). The more threads in the support bar, the greater the strength of the composite reinforcement. But the content of polymer in it also decreases, i.e. its protection from aggressive environmental factors decreases, as well as the ability to form a single strong stressed monolith from reinforcing fibers.

Thus, the optimal range of the ratio of the reinforcing fibers to the composite-polymer material by weight is from 75% to 90% of the reinforcing fibers in the composite.

The minimum content of reinforcing fibers in composite reinforcement is uniquely determined by GOST 31938 - 2012: 75% by weight. With a decrease in the content of reinforcing fibers less than 75%, the tensile strength, elastic modulus and other physical and mechanical characteristics of the composite reinforcement sharply decrease. With an increase in the content of reinforcing fibers over 90%, the technical ability to reliably enclose this fiber in a polymer material sharply decreases, and it becomes small. Composite reinforcement becomes dry to the touch, prickly, crunches and breaks at any bend. All physical and mechanical characteristics also drop sharply. Composite reinforcement shows the best performance when the content of uniformly stretched reinforcing fibers is 80-85%.

Glass roving made of alkali-resistant E-glass with an increase in tension of 50-1500 kg is used as reinforcing fibers.

The required amount of reinforcing fibers is filled with polymer, after which the curing process takes place.

When using an anhydride hardener, which is iso-MTHFA, temperature is a prerequisite for curing the epoxy resin. When the temperature rises to 60 (the curing process begins, and when the temperature rises after 80 (the polymerization rate increases exponentially)). However, high temperatures have a negative effect on the finished cured polymer. At temperatures above 150 (destruction (destruction) of polymer molecules begins).

For curing, the company's production line with an eleven-meter polymer oven with eight heating zones is used.

At the beginning of the process, the high temperature does not have a destructive effect on the polymer molecules. Epoxy is still liquid, and so far consists exclusively of a mixture of monomer and hardener molecules. Composite fittings enter the furnace cold (<30 °). It is necessary to warm up the reinforcement as quickly as possible, but so that the reinforcement itself (its polymer) does not heat up above 150 °. Thus, in the first two temperature zones of the furnace, the temperature rises to 300-350 °. In this case, the optimal production speed is 10-20 m / min. With such ratios of temperature and production rate, the composite reinforcement quickly heats up, an avalanche-like polymerization process starts, the polymer temperature of the composite reinforcement does not exceed 120-130 ° C.

The temperature in the middle of the furnace (3-5 temperature zones) is 200-250 °, and at the end of the furnace (6-8 temperature zones) 150-200 °. It is important to keep the temperature of the composite reinforcement at the outlet from the furnace not higher than 150 °. The optimum production speed is 20 m / min.

The essence of the invention is illustrated by drawings, which show:

figure 1 is a sectional view of a reinforced stressed composite reinforcement,

where

1 -polymer composite material;

2 - twisted straight glass roving thread;

3 - stressed reinforcing fibers.

The advantages of the product obtained by the declared method are:

1. CNTs are evenly distributed in the epoxy resin before polymerization. The electron clouds of carbon atoms in CNTs combine with the electron clouds of epoxy monomer atoms to form a strong bond.

2. During polymerization, the molecules of the epoxy resin monomers line up in a three-dimensional spatial lattice, forming a strong epoxy polymer structure.

3. Carbon nanotubes additionally strengthen the three-dimensional spatial structure of the polymer matrix, reinforcing it and thereby increasing the physical and mechanical characteristics of the polymer composite material in which it is used.

4. The impregnation and protection of the reinforcing fibers of the polymer composite material (composite reinforcement) from the environment by the polymer matrix is improved.

5. A strong, stressed monolith with reinforcing fibers is formed.

6. The resistance of the polymer matrix to aggressive environments is increased. This is especially true for polymer composite material (composite reinforcement), because its main application is the reinforcement of the alkaline environment of concrete.

Claims (2)

1. A method of producing a polymer composite material, including mixing an epoxy resin, a hardener, an accelerator, a plasticizer and carbon nanotubes, characterized in that first a colloidal solution is prepared by sequential creation of colloidal solutions in such a way that the first stage includes the creation of a concentrated colloidal solution from epoxy resin and carbon nanotubes with a mass ratio of 10: 1, stirring the solution for 20-30 hours in a vacuum dissolver at a temperature of 55-80 ° C, stirring the solution for 20-30 hours in an ultrasonic mixer with a frequency of 25-60 kHz, after which the second stage is carried out , including mixing the epoxy resin and the colloidal solution obtained in the first stage with a mass ratio of 10: 1, stirring the solution for 2-5 hours in a vacuum dissolver at a temperature of 55-80 ° C, stirring in an ultrasonic mixer for 2-5 hours at a frequency 25-60 kHz, after which the third stage is carried out, including mixing the epoxy resin and the colloidal solution obtained in the second stage with a mass ratio of 10: 1, stirring the solution for 2-5 hours in a vacuum dissolver at a temperature of 55-80 ° C, stirring in an ultrasonic mixer for 2-5 hours at a frequency of 25 -60 kHz, then a hardener, an accelerator and a plasticizer are added to it and mixed, while the epoxy resin, hardener, accelerator, plasticizer and multilayer carbon nanotubes included in the resulting polymer composite material are in a ratio of 1: 0.8: (0.04 ÷ 0.06) :( 0.04 ÷ 0.1) :( 0.00001 ÷ 0.05). 2. Reinforced strained composite reinforcement containing strained reinforcing fibers of straight glass roving from alkali-resistant E-glass with a tensile force of 50-1500 kg, polymer composite material and twisted glass roving thread from alkali-resistant E-glass, characterized in that the polymer composite material is made by the method according to claim 1.

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