RU2434033C2 - Polyamide composite material modified with fullerene filling materials (versions) - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: composite material consists of a 12-unit polyamide matrix and a modifying carbonaceous additive - fullerene C₆₀ or a mixture of fullerenes C₆₀ and C₇₀. Components are in the following ratio, wt %: fullerene C₆₀ or mixture of fullerenes C₆₀ and C₇₀ 0.001-1.0, 12-unit polyamide - the rest up to 100. In the second version, the modifying carbonaceous additive is fullerene soot with fullerene content of 3-16 wt %. The fullerene soot is added in amount of 0.01-1.0 wt %.

EFFECT: invention enables to increase the strength of the composition with increase in elasticity, raises softening, melting and destruction temperature in air, while density and water-absorption remain virtually unchanged.

2 cl, 3 dwg, 1 tbl, 11 ex

Description

The invention relates to polymeric materials of the polyamide class of 12-block structural purposes and can be widely used in various industries for the manufacture of parts and structures with increased requirements for strength and elasticity while maintaining the initial density and moisture absorption.

There is experience of a significant change in a number of properties of block polyamides by their filling - combination with substances of various nature, soluble or not in the polymer matrix. Distributed in the polymer matrix, these fillers substantially modify the properties of the polymer base. Inorganic powders, polymers, and organic and inorganic fibers, including glass and carbon fiber, are used as fillers. Modifiers are based on a number of factors. In the case of ultrafine fillers used in concentrations of less than 0.5 wt.%, The modifiers act as artificial nucleation centers, changing the structure and crystallinity of polyamides. Particles with a pronounced shape anisotropy, primarily fibers, change the properties of the polymer matrix, not only affecting its structure, but also changing the mechanism of destruction of the polymer sample by redistributing stresses inside it. The most common and widespread method of modifying polyamides in Russia (6-block polyamide, caprolon) aimed at increasing its hardness, increasing electric strength and improving a number of other properties, is the modification of caprolon with finely ground graphite (TU 6-06-38-89 “Graphite-filled polyamide composition 6-block "). This material is processed by milling, turning, drilling and grinding. The material has a low coefficient of friction and can work without lubrication in friction units. This material is produced in the process of low-temperature polymerization of lactam aminocaproic acid in the presence of alkaline catalysts and various activators. The graphite-filled composition of 6-block polyamide with a graphite content of 2 wt.% Provides longer work of parts from it in friction and sliding units. The disadvantage of graphite-filled caprolon is the low level of impact strength, tensile strength and a drop in general mechanical properties, including a decrease in Young's modulus. Such a change in mechanical properties excludes the use of graphite-filled compositions in products and parts that carry significant mechanical loads.

Attempts to use a similar modification were made with respect to the 12-block polyamide. So in the application US No. 20080171824, publ. July 17, 2008, “Polymers filled highly expanded graphite” describes the introduction of a 12-block polyamide into a matrix at a concentration of up to 5 wt.% Graphite and carbon black in the process of fiber spinning and pressing. The effect of such a modification is in many ways similar to the modification of these caprolon additives, i.e. increased rigidity, linear expansion coefficient, temperature resistance, for some compositions with a high graphite content, an increase in electrical conductivity is observed. However, such a modification negatively affects the mechanical properties, causing a decrease in the strength and elasticity of the Young's modulus.

Improving the mechanical characteristics of the 12-block polyamide is achieved by introducing fiberglass into this matrix. Known application US No. 20080167415, publ. 07/10/2008, “Polyamide molding materials reinforced with flat glass fibers and injection molded part made this”. 40-80 wt.% Fiberglass of a special form is introduced into the polyamide matrix, which provides a 2-3-fold increase in the strength and Young's modulus of the composition. Thus, a high increase in mechanical strength is ensured. At the same time, the increase in mechanical characteristics is accompanied by an almost 2-fold increase in the specific gravity of the composition, which affects the weight characteristics of the final products. The problem of creating such compositions is the achievement of a uniform distribution of the modifier in the polymer matrix. Given the lack of affinity between the polymer matrix and fiberglass, the latter tends to form agglomerates during the pressing process, which leads to a decrease in the mechanical characteristics of the composite material.

Closest to the claimed invention by its technical nature (prototype) is a polyamide composite material (options) (RF Patent No. 2316571; publ. 02/10/2008), which is a composition based on polyamide 6-block structural and antifriction purpose with a carbon additive modifying it . Either C ₆₀ or C ₇₀ fullerenes, or a mixture thereof with a carbon additive content of 0.0001 ÷ 1.5 wt.%, Or fullerene soot, the content of which is 0.01 ÷ 3.0 wt.%, Are used as a carbon additive. The composition based on 6-block polyamide is intended to replace conventional 6-block polyamide in its fields of application.

The main disadvantages of compositions based on polyamide 6-block modified with carbon additives with fullerene filling are:

- insufficient improvement of mechanical characteristics, including compressive and tensile strength, Young's modulus, tensile elongation, elasticity;

- the selected method for the synthesis of composite material (anionic polymerization in the presence of sodium and toluidinediisocyanate) does not ensure the stability of fullerenes under polymerization conditions and, as a result, fullerenes chemically change during the synthesis. As a result, a set of valuable physicochemical characteristics of fullerenes cannot be stored in the final product.

The objective of the proposed technical solution is to increase the mechanical characteristics of the material, expanding the temperature working range for products from the claimed composition.

The problem is solved in two versions, providing the same result and interconnected by a single inventive concept.

According to the first embodiment, in a polyamide composite material consisting of a matrix of polyamide and a carbon additive modifying it; fullerene C ₆₀ , or a mixture of fullerenes C ₆₀ , C ₇₀ , is used as a carbon additive, and a 12-block polyamide matrix is used as a polyamide matrix in the following ratio of components, wt.%:

fullerene C ₆₀ , or a mixture of fullerenes C ₆₀ , C ₇₀ 0.001-1.0, 12-block polyamide the rest is up to 100.

In a second embodiment, in a polyamide composite material consisting of a matrix of polyamide and a carbon additive modifying it; fullerene soot with a fullerene content of 3 to 16 wt.% is used as a carbon additive, and a 12-block polyamide matrix is used as a polyamide matrix in the following ratio of components, wt.%:

Fullerene soot 0.01-1.0, 12-block polyamide the rest is up to 100.

Moreover, the improvement of mechanical characteristics is achieved using the first type of carbon additive (about 10 times), while the second type of carbon additive provides a greater increase in the ductility of the composition. To improve the temperature characteristics, the use of both modifying additives is equivalent.

The invention consists in the following. Fullerene C _{60 is} soluble in a 12-block polyamide matrix. At the same time, fullerene soot and C ₇₀ fullerene are insoluble in this matrix. The following regularity is known for the action of combined fillers in filling crystallizable polymers. In the case when the polymer is enhanced by a combined filler, the maximum effect is observed for the case when one component is weakly dispersed in the polymer matrix, forms significant aggregates, and the degree of dispersion of the other is large. In this highly dispersed filler promotes the crystallization of polymers with the formation of small spherulites and increases the degree of crystallinity of the polymers. In addition, the finely dispersed filler is concentrated in the interfacial regions and thus affects the structure and morphology of the crystalline polymer at various levels of its organization, and leads to changes in the size, shape, and type of distribution of supramolecular structures. Particulate filler particles are concentrated in amorphous regions. Since the filler tends to accumulate in less orderly regions, the effect of the filler on the properties of the crystallizing polymer, due to its effect on the amorphous part, can be achieved at much lower concentrations of the filler than if it is introduced into an amorphous polymer. This may be one of the reasons for the increase in the strength characteristics of filled crystalline polymers at low concentrations of filler. This case is observed for a mixture of C ₆₀ , C ₇₀ fullerenes, since C ₆₀ fullerene is dissolved in the polymer matrix, but C ₇₀ fullerene is not. The same effect is associated with an increase in the mechanical characteristics of polymer composites reinforced with fullerene soot, since the C ₆₀ fullerene in its composition dissolves in the polymer matrix, while the remaining components do not.

The invention is illustrated by graphs, which shows the change in the Young's modulus of the composition depending on the proportion of the carbon additive.

Figure 1. The dependence of Young's modulus, a specific compression method, on the amount of fullerenes block 12 entered in the polyamide C ₆₀ (1), fullerene mixture _of C _60, C ₇₀ (2).

Figure 2. Dependence of the Young's modulus determined by the compression method on the amount of 12-block fullerene soot introduced into the polyamide.

Figure 3. The temperature regime for the synthesis of polymer compositions based on a modified 12-block polyamide.

Description of the technology for the synthesis of compositions based on 12-block polyamide modified with fullerene fillers.

Three types of fullerene fillers were investigated:

- individual fullerene C ₆₀ (purity 99.9%),

- a mixture of fullerenes C ₆₀ , C ₇₀ (68% of fullerene C ₆₀ , 30% of fullerene C ₇₀ by weight, the sum of higher fullerenes is about 2%),

- fullerene soot.

Fullerene soot is the main raw material for producing fullerenes and is ultrafine carbon - the product of electric arc burning of graphite electrodes in an inert gas atmosphere with an average particle size of 0.5-1.0 microns. Fullerene soot is a product of extraction of fullerenes C ₆₀ and C ₇₀ (with a small, up to 2 wt.% Admixture of higher fullerenes - C ₇₆ , C ₇₈ , C ₈₄ , C ₉₀ ...).

The starting material for the composition, laurylactam, is provided in the form of large flat granules with a diameter of up to 15 mm and a thickness of up to 3 mm. During grinding, laurolactam is simultaneously mixed with stearic acid in a ratio of 69.4 / 1, which corresponds to a predetermined ratio of the starting reagents 98.5% to 1.42%. Grinding is carried out to a powder with a particle size of less than 0.2 mm. Both modifiers are provided as powders. First, weighed portions of a mixture of laurolactam and stearic acid (8 weigheds of 30 g each). The estimated amount of additives for the preparation of materials with specified concentrations of 0.006 g, 0.012 g, 0.018 g and 0.024 g, respectively. Weighing of fullerenes is carried out on an analytical balance with an accuracy of up to 0.00005 g. Samples of the modifier are placed in plastic glasses with the reaction mixture and mixed thoroughly. The polymerization process is carried out with different heating rates of the heating cabinet and lasting from 2 to 12 hours.

As a result, compact samples of polymer compositions weighing 30-50 g, modified:

- individual fullerene C ₆₀ (purity 99.9%) with a content in the samples from 0.001 to 1.0 wt.%,

- a mixture of C ₆₀ , C ₇₀ fullerenes (68% C ₆₀ fullerene, 30% C ₇₀ fullerene by weight, the sum of higher fullerenes about 2%) with a content in the samples from 0.001 to 1.0 wt.%,

- fullerene soot with its content in the samples from 0.01 to 5 wt.%.

As a result, visually homogeneous samples were obtained either of orange color (modified by individual C ₆₀ fullerene), brown (modified by C ₆₀ / C ₇₀ fullerene mixture), or black (modified by fullerene soot).

Tests of samples of modified polymer compositions were carried out in accordance with GOSTs adopted for polymeric materials of the polyamide class, which include unmodified 12-block polyamide.

Table 1 shows the results of testing the compressive strength, Young's modulus, elasticity for unmodified 12-block polyamide and modified compositions with different compositions.

Table 1 Modifier The content of the modifier, wt.% E, MPa (determined by compression method) E, GPa (obtained on an ultrasonic installation) σ _p , MPa ε _p ,% - 846 ± 70 2.42 ± 0.19 67 ± 5 16 ± 1 S ₆₀ 0.02 1007 ± 43 2.61 ± 0.06 72 ± 5 20 ± 2 0.04 978 ± 92 2.96 ± 0.08 69 ± 5 17 ± 1 0.06 998 ± 71 2.84 ± 0.12 71 ± 6 22 ± 2 0.08 1035 ± 79 2.48 ± 0.06 68 ± 4 28 ± 2 C ₆₀ - C ₇₀ 0.02 1087 ± 19 3.44 ± 0.13 84 ± 5 32 ± 2 0.04 1012 ± 45 3.30 ± 0.18 75 ± 5 19 ± 1 0.06 820 ± 38 3.51 ± 0.14 110 ± 5 30 ± 2 0.08 1081 ± 65 3.41 ± 0.16 96 23 ± 3 Fullerene soot 0.1 725 ± 78 2.98 ± 0.07 85 ± 15 42 ± 2 0.2 899 ± 92 3.07 ± 0.13 110 33 ± 2 0.5 1007 ± 26 2.65 ± 0.21 66 ± 2 20 ± 1

The graphs show the change in the Young's modulus of the compositions depending on their composition.

From the table and graphs it is seen that the addition of fullerene fillers, carried out in accordance with the claimed invention, leads to:

- to increase strength and elasticity by 30-50%. This effect is similar to the introduction of fiberglass, however, in contrast to the introduction of fiberglass, the content of fullerene modifier is 10-1000 times less. In addition, the introduction of a fullerene modifier does not affect the density of the sample,

- to increase the temperature of softening, melting and the beginning of thermal degradation by 10-15 ° C.

At the same time, such characteristics as density and moisture absorption remain almost unchanged.

Claims (2)

1. Polyamide composite material modified with fullerene fillers, consisting of a matrix of polyamide and a carbon additive modifying it, wherein the carbon additive is C ₆₀ fullerene or a mixture of C ₆₀ , C ₇₀ fullerenes, characterized in that the polyamide matrix 12 is used -block in the following ratio of components, wt.%:
fullerene C ₆₀ or a mixture of fullerenes C ₆₀ , C ₇₀ 0.001-1.0 12-block polyamide the rest is up to 100 2. Polyamide composite material modified with fullerene fillers, consisting of a matrix of polyamide and a carbon additive modifying it, wherein fullerene carbon black with a content of fullerenes from 3 to 16 wt.%, Characterized in that the polyamide is used as a carbon additive, is used a 12-block polyamide matrix in the following ratio of components, wt.%:
fullerene soot 0.01-1.0 12-block polyamide the rest is up to 100

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