SU855740A1 - Electroconducting composition - Google Patents

Description

(54) ELECTRICAL CONDUCTING COMPOSITION

one

The invention relates to polymeric compositions that can be used in electrical engineering, electronics and other industries to produce electrically conductive products or coatings and, in particular, in cable technology for leveling the electric field in epoxy couplings.

Electroconductive compositions containing epoxy resin, hardener and conductive filler — graphite 1 are known.

However, such compositions have low mechanical strength, unstable electrical properties, are processed only by pressing and cannot be used for applying thin coatings.

Compositions containing diane epoxy resin, a hardener of hot curing, a solvent — acetone, and a conductive filler — acetylene carbon black C2 or aliphatic epoxy resin, a hardener of cold hardening polyethylene polyamine (PEPA) and acetylene soot f3 are also iesvestic.

The disadvantage of such compositions is an increase in the specific volume electrical resistance at elevated temperatures 4 and 5 and poor compatibility of soot with epoxy resin, due to the formation of large soot aggregates. This is an obstacle to the occurrence of conductive chain structures and leads to instability and anisotropy of the electrical conductivity of the Gb3 compositions.

The purpose of the invention is to reduce the specific volume electrical resistance of the electrically conductive composition 15 at elevated temperatures.

The goal is achieved in that the composition contains epoxy, PEPA. acetylene soot and, in addition, 20 graphite and solvent - a mixture of ethyl cellosolve and chlorobenzene, and as an epoxy resin - a diane epoxy resin with an epoxy content of 8-11 in the following ratio of components, mac.: Dianova epoxy resin with an epoxy content of 8- 11,100 Polyethylenepolyamine 10-13 30 Acetylene black 15-45

Graphite

Ethyl cellosolve Chlorobenzene

Most characteristic

the proposed composition

Table 1,

Tab

100

100

100 100 100

10 13 10 13 10 15 35

15 22 35 45

10 52 15 30

about 100

140 175 150 175

ol 100 140 175 150 175 It was established that when the content of PEPA is less than 10 mash. the composition does not cure due to a lack of hardener, and with a hardener content above 13 mph. its excess is a plasticizer, which also prevents the composition from curing. With the introduction of acetylene black, less than 15 wt. Hours, the composition does not have the necessary conductivity, and an increase in the content of the core is more than 45 mas. Hours leading to: fragility of the coatings. Reducing the content of graphite to less than 10 mas. Hours. results in the same effect as the reduction of soot content when more than 52 wt.h is introduced into the composition. graphite sharply decreases its adhesion to brass. When the solvent content is more than the proposed coating, the coating is uneven due to possible draining, while a decrease in the solvent content below the proposed one increases the viscosity of the composition and makes it difficult to process. Samples of the composition are prepared as follows. . Epoxy resin Dianova containing epokigrupp 8-11 (for example, brand ED-8) is dissolved in a mixture of chlorobenzene and ethyl cellosolve. To the resulting solution, pre-prepared fillers are added during repainting, and then PEPA hardener. After mixing, the resulting composition is cast into disks with a thickness of 0.7-0.1 mm and a diameter of 8-1 cm for subsequent tests. The specific volume resistance of the samples is determined after curing at room temperature for 24 hours using the following procedure:

The ends of the sample, cut out in the form of a strip, are attached. The current electrodes, which are connected to an E6-10 ohmmeter, determine the resistance value of the sample section and calculate the specific volume resistance p by the formula

,

Tch t,

where R is the resistance of the sample between the collector electrodes, ohm;

S is the sample cross section, If is the distance between the electrode-.

mi, see

The value of the specific volume resistance of each recipe is taken as the arithmetic average of five measurements. Measurements are taken at room temperature.

The measurement results are shown in table 2.

Table 2 The conductive screens in the couplings are located between the metal (brass, aluminum) electrodes and epoxy insulation. Therefore, specific requirements are imposed on the electrically conductive material: the composition must have high adhesion both to the metal electrodes and to the insulating epoxy compound from which the coupling parts are cast. Adhesion is evaluated according to the tiball system 7 at room temperature before and after three times cyclic heating: 2000 s for one hour — room temperature according to the following procedure: a grid with a square side of 5 mm is cut into the surface of the applied conductive coating (total number of squares is 100 ). When peeling more than 75 squares out of 100, the adhesion value is 2 points, when peeling 50-60 squares - 3 points, 20-30 squares - 4 points, and when peeling less than 20 squares, 5 points.

As follows from Table 2, the proposed composition possesses high adhesion to brass and aluminum, and a low value of specific volume electrical resistance (10 8 Ю ohm.cm). Adhesion to the insulating epoxy cured compound for all formulations is 5 points. The thermal cycling effect practically did not change the adhesive properties of the coating.

In order to determine the influence of the outside temperature on the specific volume resistance of the proposed composition, the samples are placed in a thermos bottle, maintained for 10 minutes at a certain temperature, after which, without removing it from the thermostat, the specific volume resistance is determined by the described method.

The drawing shows the dependence of the specific volume resistance of the proposed composition (formulations 2, 3, 5). From the drawing, it follows that Py of the proposed composition at temperatures of 20 -80 ° practically does not change, and in the temperature range of 80-19Ю® C its value decreases by 20 -70% compared to baseline.

Thus, the proposed composition fully satisfies the requirements for materials for producing thin electrically conductive coatings that work satisfactorily over a wide temperature range.

Claims (7)

1. Margupov M.A. Features of obtaining electrically conductive polymeric materials. Avtoref.dis. Tashkent, 1974, p. 23. 2. Gul V.E. Investigation of the structure of conductive compositions based on hardened resins. - High-medical compounds, 1962, T.4, № 15, p. 649. 3. Gul In .E. et al. The influence of the spatial structure of electrically conducting polymeric materials on their 0 electrical conductivity. - Plastics, No. 5, 1965, p. 49. 4. Gul V.E. et al. Study of temperature dependence and current-voltage characteristics of polymers 5 spatial structures. - Plastics, (9, 1965, p. 38. 5. Gul V.E. Conductive polymeric materials. M., Knowledge, 1969, p. 23. 6. The same with. 20. 0 7. Yakubovich S.V. Test paints and coatings. M., Goskhimizdat, 1952.