METHOD FOR COATING AND PRODUCT PRODUCED IN ACCORDANCE WITH SAID METHOD

Abstract: The present invention relates to a method of coating at least one section of the surface (2) of a plastic or composite part with a layer (6) of an additive material. That section of the surface (2) of the part that is to be coated is pre-treated by degreasing, evening out, roughening, degreasing and drying in that order. A layer (4) of a thermosetting adhesive is then applied to the said section of the surface (2) of the part. Before coating is carried out, the adhesive layer (4) is heated to a temperature approaching its gel point. The surface is then coated by thermal spraying with a layer (6) of an additive material. After coating, the part (1) is heated to the setting temperature of the adhesive layer, causing this to set. The invention also relates to a product (1) of a plastic or composite material manufactured by the method in which at least one section of its surface (2) is coated with a layer (6) of an additive material.

Description: Method for coating and product produced in accordance The present invention relates to a method of coating at least one section of the surface of a plastic or composite part by means of thermal spraying with an additive material, as indicated in the pre-characterising clause of claim 1. The invention also relates to a product manufactured according to the above-mentioned method, of a plastic or composite material, in which at least a section of its surface is coated with a layer of an additive material, as indicated in the pre-characterising clause of claim 8. Coating metal parts by thermal spraying with an additive material in the form, for example, of a second metallic material or ceramics is already known. In this way modified surface characteristics can be achieved which allows the parts to be used in spheres of application that would otherwise be out of the question. The surface of the metal part to be coated in this way is usually pre-treated by blasting. The additive material is then sprayed on to the surface of the blasted part. The additive material, after spraying, is supposed to shrink as it is cooled by the surface and adheres in the small irregularities that are created by the blasting. The method described above does not function satisfactorily, however, when seeking to coat the above-mentioned plastic or composite parts with additive material by means of thermal spraying. The thermal conductivity of plastic or composite materials is generally too low for the coating material to shrink tight with sufficient speed. Plastic or composite materials furthermore tend to shrink somewhat on heating, which is also not conducive to good adhesion. If a composite surface is pre-treated by blasting, this can also lead to damage to the outermost layer of fibres in the composite, which adversely affects the surface strength. In one embodiment of a method according to the present invention, a coating is produced on at least one section of the surface of a plastic or composite part, as indicated by claim 1, which exhibits the advantages described below compared to coatings that are produced by known methods. With the method according to the present invention a product is produced, as indicated by claim 8, which exhibits the advantages described below compared to products that are produced by known methods. Preferred embodiments of the method and the products produced thereby also have any or some of the characteristics described in each of the subordinate claims. The method according to the invention and the products produced thereby have several advantages: By means of the method according to the invention, plastic or composite parts can be produced with coatings of various additive materials, such as ceramics, metal oxides, metals, metal alloys or plastics, the adhesion of which to the part is very good. Using the method according to the invention to treat a surface of a composite part avoids damage to the outermost layer of fibres and impairment of the surface strength resulting from this. The method according to the invention permits many new spheres of application for plastic and composite parts; for example composite parts can hereby be coated with titanium, for which there may be a number of medical applications. The invention will be explained in more detail below with the aid of an example of an embodiment of the method according to the invention and the product produced thereby and with reference to the drawings attached in which: Fig. 1. shows the pre-treatment of a section of the surface of a part that is to be coated. Fig 2. shows a layer of a thermosetting adhesive being applied to a section of the surface of the part that was pre-treated according to fig. 1. Fig 3. shows the thermosetting adhesive that was applied in fig. 2 being heated to a temperature approaching the gel point of the adhesive. Fig 4. shows the surface provided with the layer of thermosetting adhesive being coated by thermal spraying of an additive material. Fig 5. shows the part being placed in an oven, after coating according to fig. 4 and before heating to the setting temperature of the adhesive layer. Fig 6. shows the finished part after coating with an additive material and setting of the adhesive layer have been carried out. Figure 1 illustrates the pre-treatment of a section of the surface 2 of a part 1 made from a composite material. The part surface 2 in question is first degreased, for example with acetone. The surface 2 is then lightly sanded with a fine sandpaper or abrasive nylon 3 in order to remove irregularities and to roughen the surface slightly. Finally the surface is degreased and dried again. Figure 2 shows how a layer 4 of a thermosetting adhesive, here in the form of an adhesive film, is applied to the surface 2 pre-treated according to figure 1. In applying the adhesive film it is important to ensure that no contaminating substance is allowed to come into contact with the pre-treated surface 2 or the adhesive. Instead of applying the adhesive in the form of a film, as shown in figure 2, it may be applied, for example, by spraying or by applying it with a brush. Several different types of adhesive are conceivable, for example epoxy adhesive, acrylic adhesive, urethane adhesive or phenolic plastic-based adhesive. Figure 3 shows how the layer of thermosetting adhesive 4 is heated by means of a hot air gun 5 to a temperature approaching the gel point of the adhesive. This gives the adhesive layer 4 a very good adhesive capacity. The adhesive layer 4 can obviously be heated in other ways different from that illustrated in figure 3, for example in an oven or the like. Figure 4 shows how the pre-treated surface 2 provided with the adhesive layer 4 is coated with a layer 6 of an additive material by thermal spraying, for example by flame spraying. This additive material may be any of the following, for example: a ceramic; metal oxide; metal; metal alloy or plastic. The temperature of the sprayed material can be adjusted by the choice of spraying method. Conceivable methods of spraying in addition to flame spraying include, for example, electric arc spraying, plasma spraying or detonation spraying. The application temperature may be varied from approximately 50° C to several hundred degrees Celsius by the use of different spraying methods and additive materials. The application temperature and method of application are adapted to the adhesive used, its gelling and setting temperature, or vice versa. The adhesive is selected having regard to the additive material and the application temperature in order to achieve the best possible strength and surface layer quality for the coating 6. Figure 5 shows how the part 1 , after coating has been carried out, is placed in an oven 7 or the like for heating up to the setting temperature of the adhesive layer 4, so that this is made to set, which means that an excellent adhesive bond is obtained between the surface coating 6 and the composite material. Due to the fact that the adhesive layer 4, before coating, is heated to a temperature approaching its gel point, as in figure 3, the time taken for this stage of the method is minimised since only a certain further heating is required. Figure 6 shows the finished part 1 after it has been coated with a layer 6 of an additive material and the adhesive layer 4 has been set by the method according to the invention. The method according to the invention has given the part 1 a good surface coating 6, which for certain applications can be further improved by sealing it with phenolic resin- based paint when it has cooled to room temperature. This can prevent the adhesive from absorbing moisture, for example, which may adversely affect the adhesive bond. In addition the phenolic resin-based paint can give the surface a certain added protection, for example if the latter is to be exposed to high temperatures. It will be obvious to a person skilled in the art that the method according to the invention is not confined to the embodiment described above, but rather can lend itself to modifications within the framework of the idea of the invention defined in the following claims. After a first coating layer has been applied and set by the method according to the invention, for example, further layers of different materials can be applied on top of this by means of thermal spraying, without the need here to apply any adhesive film.

Claims: Claims 1. Method of coating at least one section of the surface (2) of a plastic or composite part by thermal spraying with a layer (6) of an additive material, characterised in that before coating with the additive material is carried out a layer (4) of a thermosetting adhesive is applied to the said section of the surface (2) of the part. 2. Method according to claim 1, characterised in that before coating is carried out the thermosetting adhesive layer (4) is heated to a temperature approaching its gel point. 3. Method according to claim 1 or 2, characterised in that the part (1), after coating, is heated to the setting temperature of the adhesive layer (4), thereby causing it to set. 4. Method according to any of the preceding claims, characterised in that the section of the surface (2) of the part that is to be coated is degreased, even out and roughened, degreased and dried in that order before application of the adhesive layer (4). 5. Method according to claim 1, characterised in that a ceramic, metal oxide, metal, metal alloy or plastic is used as additive material. 6. Method according to claim 1, characterised in that application of the thermosetting adhesive is carried out with adhesive in the form of a film. 7. Method according to claim 1, characterised in that the application of the thermosetting adhesive is done by spraying. 8. Product (1) of a plastic or composite material manufactured according to the method in any of the preceding claims, in which at least one section of its surface (2) is coated with a layer (6) of an additive material, characterised in that there is a layer (4) of a thermosetting adhesive between the said layer (6) and the surface of the product. 9. Product (1) of a plastic or composite material according to claim 8, characterised in that the layer (6) of additive material is composed of a ceramic, metal oxide, metal, metal alloy or plastic. 10. Product (1) of a plastic or composite material according to claim 8 or 9, characterised in that the thermosetting adhesive layer (4) is composed of an epoxy, acrylic, urethane or phenolic plastic-based adhesive.

Inventors: OBRELIUS PER, OBRELIUS, PER
Applicants: APPLIED COMPOSITES AB ACAB, OBRELIUS PER, OBRELIUS, PER
Application year: 1998
Main classification: B05D1
IPC codes: B05D1, B05D7