RU2313622C2 - Method for applying electroplated nickel coating onto articles of glass filled polyamide - Google Patents

Abstract

FIELD: processes for strengthening glass filled polyamide while keeping its tensile strength value.

SUBSTANCE: method comprises steps of successively working article for increasing its impact viscosity, heat resistance and adhesion in solution of salt of metal selected from group containing iron, copper and zinc; then treating article in solution of sodium sulfide; applying nickel coating with thickness more than 50 micrometers.

EFFECT: improved strength of glass filled polyamide with such nickel coating.

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Description

The invention relates to electrolytic coating, in particular to methods for applying metal coatings to plastics, for example thermoplastics.

Known galvanic metallization of plastics according to the classical scheme:

etching, activation in a solution containing palladium salts, the chemical deposition of a layer of copper or nickel followed by galvanic metallization (see, for example, US patent No. 4444836, CL B23B 5/16, 1984).

The disadvantage of this process is the low adhesion of the coating, as well as the use of precious metals.

A known method of metallization of polymers on the sublayer of sulfides of various metals from US patent No. 3658661, CL. C25D 5/56, 1972

For the prototype, a method was selected for preparing the surface of polymeric materials for chemical metallization (see, for example, ed. St. USSR No. 1724741, Ml. C25D 5/54), in which sulfides of transition metals (Fe, Cu, Zn) are introduced into the polymeric material for increasing the strength of the material, resistance to temperature differences and adhesion of the metal coating deposited by chemical deposition from a nickel plating solution.

This method of metallization of plastics is difficult to implement.

It is known that the filling of a thermoplastic matrix with fiberglass helps to increase the tensile strength of such a composite material, but at the same time its resistance to shock loads decreases (A.A. Berlin. S.A. Wolfson and others. "Principles of creating composite materials", M., Chemistry, 1990, p.16-17).

In practice, products made from such materials cannot withstand the effects of combined loads (tensile and impact).

The invention is aimed at solving the problem of hardening glass-filled polyamide - increase toughness and heat resistance while maintaining its tensile strength and increase the adhesion of the metal coating to the polymer.

To solve this problem, the method of applying a galvanic nickel coating on a glass-filled polyamide product includes processing the product to increase its impact strength, heat resistance and adhesion in a solution of a metal salt selected from iron, copper and zinc, then processing the product in a sodium sulfide solution and subsequent application of nickel coatings with a thickness of more than 50 microns.

In the proposed method, a glass-filled polyamide is used as a polymeric material, having greater strength, but having low deformability, i.e. lower toughness. During the galvanic metallization of glass-filled polyamide over a sublayer of a metal sulfide selected from iron, copper and zinc, we obtain increased impact strength, heat resistance, and adhesion.

Details were made according to the classical technology with copper and nickel coatings, according to which the surface is first sensitized by treating with a solution of tin salts, then it is activated with a solution of a catalytically active metal, for example, palladium, and according to the technology using transition metal sulfides with the subsequent deposition of a layer of galvanic nickel. The deposition of a metal coating on parts of glass-filled polyamide on a sulfide sublayer includes the following operations:

1. Sandblasting.

2. Washing in an ultrasonic bath in an aqueous solution of a technical detergent.

3. Flushing in running water.

4. Degreasing in an alkaline solution.

5. Rinsing in running water.

6. Application of a sulfide sublayer by sequential treatment in solutions of the following composition, g / l:

solution No. 1:

- copper sulfate 5-water from 100 to 200;

- aqueous ammonia from 100 to 150;

- hydroquinone from 1 to 5;

solution No. 2:

- sodium sulfide from 1 to 10.

7. Electroplating nickel plating.

Application of a sulfide sublayer is also possible from solutions of copper chlorides or sulfates or iron or zinc chlorides.

Measurements of adhesive strength (GOST 9.313-89) showed that the adhesive strength of a metal layer by a sulfide sublayer is 3 times higher than by classical technology.

Parts were tested for combined tensile and impact loads. At the same time, parts manufactured by classical technology were destroyed, and parts with a sulfide sublayer passed the test.

The tensile strength was controlled on samples according to GOST 11262-80, impact strength - according to GOST 4647-80, heat resistance according to Martens - according to GOST 21341-75.

The dependence of impact strength, tensile strength and heat resistance on the thickness of the Nickel coating deposited on a sulfide sublayer on a glass-filled polyamide is presented in the table.

Coating thickness, microns 0 twenty 35 fifty 60 80 Impact strength KJ / m ² 22 thirty 33 37 38 40 Tensile strength, MPa 101 101 101 101 101 101 Martens heat resistance, ° С 120 160 179 190 198 200

It should be noted that polyamides are hydrophilic polymers, their water absorption reaches several percent (in some cases up to 8%) and significantly affects (reduces) strength and toughness [see Technical properties of polymeric materials: Uch. - reference, pos. / V.K. Kryzhanovsky, V.V. Burlov, A.D. Panimatchenko, Yu.V. Kryzhanovskaya - St. Petersburg, Publishing House "Profession", 2003, p. 43). In addition, it is well known that the strength properties of thermoplastics (polyamide, etc.) are significantly affected by the modes of processing them into products [see Encyclopedia of Polymers. M., "Soviet Encyclopedia", 1977, v.2. p.80]. Glass-filled polyamide, consisting of polyamide reinforced with filler - long segments of glass filaments (not more than 35%), retains hydrophilicity and is processed similarly to thermoplastics. Moreover, the above factors do not affect the essence of the proposed method of increasing the impact strength and heat resistance of glass-filled polyamide. Thus, it seems to us advisable to consider the relative change in toughness and heat resistance obtained after plating.

Coating thickness, microns 0 twenty 35 fifty 60 80 Change in toughness after metallization 1.0 * 1.36 1,50 1.68 1.73 1.82 Martens heat resistance change after metallization 1.0 * 1.33 1.49 1,58 1.65 1,67 * Note: impact strength and heat resistance of uncoated glass-filled polyamide are taken as a unit.

As follows from the above example, the result of the implementation of the claimed method of applying metal coatings to plastics is to increase the impact strength and heat resistance of glass-filled polyamide while maintaining its tensile strength.

Parts made of metallized glass-filled polyamide can be used in serial production in such areas as engineering, instrumentation, etc., since they have high strength characteristics and heat resistance at their low cost.

Claims (1)

A method for applying a nickel plating to a glass-filled polyamide product, including sequential processing of the product to increase its impact strength, heat resistance and adhesion in a solution of a metal salt selected from iron, copper and zinc, then processing the product in a sodium sulfide solution and subsequent coating of a nickel coating with a thickness more than 50 microns.