RU2063079C1 - Method for producing multilayer electricity conducting material - Google Patents

Abstract

FIELD: manufacture of flexible electric heating elements for heating dwelling and industrial buildings. SUBSTANCE: stack is prepared from electricity conducting layer placed between insulating layers made of glass-reinforced fabric impregnated with epoxy resin of low curing temperature until its content in layer becomes 28-40%. Conducting layer is made of polycaproamide fabric containing carbon-black thread with initial surface resistance of 100-230 Ohm. Stack is formed at temperature of 120-140 C and static load of 0.3-4.5 kg/sq.cm. EFFECT: improved strength and mechanical endurance of composite conducting material. 1 dwg

Description

 The invention relates to the field of creating electrically conductive composite materials that can be used in the manufacture of flexible electric heating elements, widely used for heating domestic and industrial premises.

 A known method of producing a multilayer composite material, including the formation of a package of electrically conductive and insulating layers, where the electrically conductive layers are in the form of a thin layer of aluminum, and the electrically insulating layers are made of fiberglass, the layers are joined using varnish and the package is hot pressed. (French application N 2.617430, class B 32 V 25/20 - prototype).

 The disadvantage of this method is the relative fragility of the heating elements made of composite material, associated with the possibility of overheating due to the linear dependence of the current flowing in the material when the external voltage changes. In addition, the electrically insulating layer of fiberglass does not have sufficient strength and shape stability, and the manufacture of the material requires the use of press equipment, complicating the production process of electrically insulating material.

 The objective of the invention is to create a strong and durable electrically conductive composite material that provides self-regulation of the temperature when using it as a heating element in a given temperature range for a long time operation.

The problem is solved in that a package is formed of an electrically conductive layer enclosed between the electrically insulating layers of fiberglass, and the electrically conductive layer is made of polycaproamide fabric containing a black thread, with an initial specific surface resistance of 100-230 Ohms, the fiberglass is impregnated with epoxy resin with a curing temperature of not more than 140 ^o With up to its content 28 40% of the mass of the layer, and withstand the package at a static load of 0.3 to 4.5 kg / cm ² and a temperature of 120 140 ^o C.

The content of epoxy resin when impregnating fiberglass should not be lower than 28% by weight of the electrically insulating layer to ensure its complete and uniform impregnation, and should not exceed 40% since at the same time, the adhesion of the layers decreases and the monolithicity of the composite material is violated. Withstanding the composite material with a static load of 0.3 - 4.5 kg / cm ² allows you to achieve uniform impregnation and high strength of the connection layers without the use of press equipment. In this case, a decrease in the pressing temperature below 120 ^o C prevents the complete curing of the binder, and an increase above 140 ^o C causes its destruction and darkening of the heating surface. It should also be borne in mind that increasing the upper parameters increases the voltage inside the system, which violates the effect of thermal control.

The use as a conductive layer of a polycaproamide fabric containing a blackened thread with an initial specific surface resistance of 100 230 Ohms provides, together with the remaining parameters of the method, the effect of current stabilization (with an increase in voltage when current flows through such a composite material, it reduces the power to voltage ratio, which reduces heat transfer and eliminates overheating). Due to this property, in the manufacture of electric heating elements from this composite material, high durability (more than 600 thousand hours) in the operating temperature range (70 120 ^o С) is ensured.

 The method is implemented as follows.

An electrically insulating layer of fiberglass (GOST 19170 79) is prepared by impregnating it with a binder of epoxy resin. As an epoxy resin, any resin of this series with a curing temperature of not higher than 140 ^o C, for example, EDT 10P, which is an epoxy resin KDA or KDA 2 (TU 6-05-1380-76) (modified epoxy resin ED 20, can be used) aliphatic resin DEG 1) cured with TEAT (triethanolamine titanate (TU 6-05-1860-78)). From a mixture of KDA and TEAT (100 parts by weight and 10 parts by weight, respectively), a 50 to 60% solution of an alcohol-alcohol mixture is prepared (alcohol: acetone ratio 2 1). The binder is applied to the fabric on an impregnation machine to a content of 28 to 40 wt. and dried at a temperature not exceeding 100 ^o C. the Number of volatiles while 0.6-3 wt. (see drawing).

 As a conductive fabric, a fabric of the type NASTelektro (TU 6-06-I82-85) containing polycaproamide and conductive black-filled thread is used.

Several packages are laid on the prepared tool plate through the separation layer, formed from layers alternately stacked in the following order: resin-impregnated fiberglass conductive fabric with electrodes attached to it, resin-impregnated fiberglass. In the manufacture of heating elements, the layers of decorative material, for example, chintz or decorative film, are additionally laid as outer layers. Packages laid in this way are covered with a steel plate providing a static load of O, 3 4.5 kg / cm ² and heat treated at 120 140 ^o C 4 5 hours

To ensure the safety of the resulting electrically conductive composite material, the bags are vacuumized for 10-12 hours, at 120 - 150 ^o C and a vacuum of 650 mm Hg

 The drawing shows the dependence of the temperature on the surface of the formed electrically conductive material on the specific power of the material for various parameters of its receipt.

Curve 1 is a composite material obtained with a resin content in fiberglass of 28% and a pressing temperature of 120 ^o C;
Curve 2 resin content of 32% at a pressing temperature of 130 ^o C;
Curve 3 resin content of 40% at a pressing temperature of 140 ^o C;
In all cases, the surface resistivity of the tissue is 160 Ohms.

 Curve 4 prototype.

 The inflection on the graph is associated with stabilization of the current with increasing operating voltage and proves the high reliability of the material when used in heating elements in comparison with the known ones.

 Thus, the proposed method of manufacturing a multilayer composite material provides the creation of a durable and durable material that provides self-regulation of the temperature regime, which eliminates its overheating and increases the service life.

Claims (1)

A method of producing a multilayer composite electrically conductive material, comprising forming a packet of an electrically conductive layer enclosed between electrically insulating layers of fiberglass, bonding its layers with a polymer binder and keeping the packet under pressure at elevated temperature, characterized in that the electrically conductive layer is made of polycaproamide fabric containing a fused thread, with an initial specific surface resistance of 100-230 ohms, fiberglass is impregnated with epoxy resin EDT-10 P with temp rature curing to 140 ^o C until its content of 28-40% by weight of the layer, and the package was kept under static load 0.3-4.5 kg / cm² and a temperature of 120-140 ^o C until the volatile content of not more than 3%