DE102011052000B3 - Use of gel-coat comprising multicomponent laminating, infusion or wrapping epoxy-based resin system and nanoscale hydrophilic metal oxide particles, e.g. as friction- and wear protective layer in fiber reinforced plastic composite cylinders - Google Patents

Abstract

Use of a gel-coat comprising a multicomponent laminating-, infusion- or wrapping epoxy-based resin system and nanoscale hydrophilic metal oxide particles made of silicon dioxide, aluminum oxide, titanium dioxide, or a combination of hydrophilic silicon dioxide, aluminum oxide or titanium dioxide and hydrophobic silicon dioxide, as friction- and wear protective layer in fiber reinforced plastic composite cylinders (1) for providing a low-friction, wear-resistant and ductile cylinder surface, is claimed. An independent claim is also included for the fiber reinforced plastic composite cylinder comprising the low-friction, wear-resistant and ductile cylinder surface exhibiting the above gel-coat.

Description

The invention relates to the use of a functional layer based on organic-ceramic polymer nanocomposites as an inner cylinder surface and diffusion barrier for tribologically and mechanically loaded fiber-plastic composite cylinders. The lightweight design cylinder is characterized in that a sealed piston moves axially along the cylinder surface and at least the cylindrical portion of a fiber plastic composite (FKV) consists, on the inner surface of the functional layer is applied as a gel coat. The functional layer is used as a low-friction, wear-resistant, ductile and diffusion-tight cylinder surface, for example in hydraulic and pneumatic cylinders, piston accumulators, gas pressure and shock absorbers, gas springs and piston pumps in FKV construction or FKV-metal mixed construction.

Due to the high achievable specific rigidities and strengths, continuous fiber-reinforced FRP structures are virtually predestined for lightweight construction applications. However, unlike metal cylinders, those made of fiber-reinforced plastics have lower hardness, wear and diffusion resistance. Therefore, in addition to the load-bearing FKV cylinder structure, these require an additional hard, tight, wear-resistant component as the inner cylinder surface. According to the state of the art, thinly rolled steel inner liners are used for this purpose. These are not only costly, but also severely limit the geometric shape, promote leaks at the transitions from cylinder surface to other functional surfaces and have very high stresses due to the different stress-strain behavior of FRP structure and steel inner liner. In order to avoid delamination or failure of the inner liner, additional stiffening of the FRP structure is required in such cases, which leads to higher material and process costs as well as to increased component mass.

To counteract these disadvantages, wear-resistant, ductile, media-tight as well as economically applicable functional layers on the inner FKV surface of the cylinder are required. Great potential is offered by organic-ceramic surface layers based on polymer nanocomposites. By incorporating hard inorganic particles into polymeric matrices, the hardness and stiffness and thus the wear resistance of the duromeric polymer can be significantly increased. Due to the small particle size in the nanometer range, the ductility of the polymer depending on particle material, concentration and quality of the dispersion process can be obtained or u. U. additionally be increased. Therefore, the gel-coat used according to the invention in comparison to the conventional steel inner liner for internal pressure loaded cylinder represents a mechanically adapted alternative. The invention aims at introducing finely dispersed nanoscale metal oxide particles into a thermosetting resin system with good affinity to the polymer matrix of the FKV cylinder structure. This allows the setting of the required hardness, wear resistance and intrinsic viscosity of the resin system for use as a wear-resistant, but also ductile gel coat as tribologically and mechanically loaded cylinder surface in FKV cylinder structures.

To provide fiber-reinforced plastic composite structures with organic-ceramic nanocomposite gel coats in order to adjust specific properties on the surface of the FRP structure is known from the prior art.

So is out of the EP 1 866 363 B1 a swimming pool gel-coating, in which inorganic pigments, in particular spinel with an unsaturated polyester resin and a filler consisting of kaolinite, corundum, alumina trihydrate and / or boehmite are used. By means of such a coating, bleaching under the action of chlorine water can be prevented and a haptically appealing surface quality can be achieved. The provision of extraordinary wear resistance and good sliding friction properties are not the focus of this coating for fiber-reinforced plastics composites.

According to WO 2009/109193 For example, an organic ceramic polymer coating is applied to composite materials to achieve the lotus blossom effect, which consists of a particle-enriched gel coat. The reinforcing material used are particulate oxide ceramics, preferably silicon dioxide (SiO ₂ ), aluminum oxide (Al ₂ O ₃ ), titanium dioxide (TiO ₂ ) and zirconium oxide (ZrO ₂ ). Subsequent sanding of the gel-coat surface produces nanoscale elevations on the surface due to the particles contained, which cause the desired lotus flower effect. However, such coatings on fiber composite materials are not aimed at improving the tribological properties.

Further wear protection layers are known, of which the following are briefly presented.

In the publication DE 10 2009 043 435 A1 a lubricating varnish for coating a metal component is proposed, wherein a base varnish as a matrix at least one lubricant and a wear protection material are added.

In the DE 198 57 316 A1 Powder-coated substrates are presented, which can be applied to a surface coated with a powder coating, where they form a scratch- and abrasion-resistant cover layer.

The document DE 198 11 790 A1 introduces transparent lacquer binders that contain nanoparticles and allow improved scratch resistance. In addition, a use in clearcoat applications is proposed.

Another means of producing wear-resistant surfaces on non-wear-resistant, uncured materials is disclosed in U.S. Pat DE 195 14 432 A1 demonstrated.

The object of the present invention is an alternative use for gel coats of a multi-component lamination, infusion or winding resin system based on epoxy and nanoscale hydrophilic metal oxide particles of SiO ₂ , Al ₂ O ₃ , TiO ₂ or a combination of hydrophilic SiO ₂ , Al ₂ O ₃ or TiO ₂ and hydrophobic SiO _{2 to} propose.

According to the invention the object is achieved by the use of a coating having the features according to claim 1. Advantageous embodiments are the subject of dependent claims.

The polymeric component of the gel coats for cylinder liners of fiber-plastic composite cylinders is preferably a highly cross-linking and chemically stable thermosetting resin system having good chemical affinity for the matrix resin system of the FKV cylinder structure to be coated. Particularly preferably, the same resin system is used both for the gel coat and for the matrix of the FKV structure. This ensures the best possible chemical adhesion of the gel coat to the fiber composite structure with maximum adhesive strength. As the matrix resin, an epoxy resin system is particularly preferably used. In particular lamination, infusion and winding resin systems consisting of the individual components resin, hardener and u. U. accelerator.

As particulate reinforcing agents of the thermosetting resin system, the matrix component of the gel coats, pyrogenic metal oxides are preferably used in the form of hydrophilic aluminum oxide (Al ₂ O ₃ ), silicon oxide (SiO ₂ ) and titanium dioxide (TiO ₂ ). Particular preference is given to using hydrophilic Al ₂ O ₃ particles. The hydrophilic particles can be introduced alone or in combination with hydrophobic SiO ₂ particles, wherein the particles of hydrophilic SiO ₂ , Al ₂ O ₃ or TiO ₂ separated in the dispersing process take on the task of increasing the wear resistance. The particles of hydrophobic SiO ₂ serve to adjust the processing-relevant intrinsic viscosity of the gel coats.

The individual particles, or primary particles, preferably have a size of 10 nm to 100 nm, preferably 12 nm to 80 nm and particularly preferably from 15 nm to 50 nm. Their specific surface area (BET) is preferably in a range from 40 m ² / g to 200 m ² / g and. more preferably between 50 m ² / g and 160 m ² / g. These nanoparticles are used alone or in combination at concentrations of preferably from 0.25% by volume to 12% by volume and more preferably from 0.5% by volume to 8% by volume, based on the total volume of the suspension in the resin or hardener component of the gel coat. Resin system introduced. In a direct subsequent application of the gel coat, the particles can also be incorporated into the finished resin-hardener mixture. Advantageously, gel coats with such a composition have proven to be particularly resistant to wear and at the same time bring about an improvement in the mechanical properties while maintaining the rheological characteristics required for the processing process.

The dispersion of the metal oxides present in nanopowder form with the liquid resin component preferably takes place with the aid of a two-stage process consisting of predispersion with dissolver and subsequent real comminution in a stirred ball mill or optionally with the aid of the ultrasonic dispersion technique. The aim is to introduce the particles as finely dispersed as possible in the liquid resin and / or hardener component, so that they are best isolated as primary particles.

In the particularly preferred dispersion by means of dissolvent technology, the liquid resin and / or hardener component (dispersant) and the particulate metal oxides (dispersant) in the o. Concentrated concentration in the mixing vessel and then predispersed under degassing by means of a rotating toothed disc. The real comminution of the particle agglomerates in the thermoset polymer is then carried out preferably with the aid of a stirred ball mill, with the addition of grinding beads shear and compressive stress conditions for comminution of the particle structures are created. By means of this dispersion method, the particle agglomerates can be largely converted into primary particles and the particulate reinforcing materials present on the nanometer size scale (<100 nm) exploit their full performance potential.

Thus, after the comminution and mixing process, the nanoparticles are finely dispersed and largely isolated as primary particles in the liquid phase consisting of resin and / or Hardener component, but usually in the low-viscosity hardener component of the gel-coat resin system, before.

After completion of the dispersion process, the grinding beads are separated from the finely dispersed resin system nanoparticle batch and the suspension is stored until dry, dark and air-tight. If necessary, the suspension is mixed with the remaining resin components and can then be applied to the winding core for the production of the FKV cylinder structure.

The production of such organic-ceramic tread within FKV cylinders thus takes place in two essential process steps. In a first step, the dispersion of the resin system nanoparticle mixture and then in a second application of the gel coats for the preparation of the tread is performed.

The application of the gel coat can be done by means of a brush, but particularly preferably by using a paint spray gun with the much thinner and more homogeneous layers can be applied. Further preferred is a doctor blade for the application of the gel coat used.

It is possible to subsequently apply the gel coat layer on the component, but preferably the gel coat before the actual laminate buildup on the mold, z. B. the winding core applied. Advantageously, thereby better surface properties can be achieved.

In addition to the excellent abrasion resistance and the protection of the tread from aggressive media, a high-quality surface is produced which, as is usual with gel coats, is decisively determined by the shaping tool surface.

On the inner surface of the predominantly wound FKV cylinder tube, the nanoparticle-modified gel coat offers a good adhering, smooth cylinder surface with excellent friction and wear characteristics in hydraulic piston strokes and a diffusion barrier against hydraulic fluids.

• a) Bereitstellung des Harzsystems mit Harz- und Härterkomponente, sowie der oxidkeramischen Nanopartikel,
• b) Einmischen des partikulären Verstärkungsstoffes in das Dispersionsmittel bestehend aus Harz und/oder Härter,
• c) Aufbrechen unerwünschter Partikelstrukturen (Agglomerate und Aggregate) mittels Dispergiertechnik mit dem Ziel der weitestgehenden Vereinzelung und Überführung in Primärpartikel,
• d) Mischen der Harz- und Härterkomponenten nach dem vom Hersteller angegebenen stöchiometrischen Verhältnis und
• e) Gel-Coat Applikation auf der formgebenden Wickelkemoberfläche zur Herstellung der FKV-Zylinderstruktur.

The use of the gel coats to produce a low-friction and wear-resistant cylinder surface of FRP cylinders can be subdivided into the following steps:

• a) provision of the resin system with resin and hardener component, as well as the oxide ceramic nanoparticles,
• b) mixing the particulate reinforcing agent into the dispersing agent consisting of resin and / or hardener,
• c) breaking up of unwanted particle structures (agglomerates and aggregates) by means of dispersion technology with the aim of the greatest possible separation and conversion into primary particles,
• d) mixing the resin and hardener components according to the manufacturer's stoichiometric ratio and
• e) Gel-coat application on the forming winding core surface for the production of the FKV cylinder structure.

The steps b) and d) can be partially or completely combined.

The application of the gel coats used according to the invention as friction-resistant and wear-resistant cylinder running surface for tribologically and mechanically loaded FKV cylinders will be explained in more detail below with reference to figures. Showing:

1 a FKV cylinder structure with the gel coat used according to the invention,

2 a schematic representation of the application of the gel coat on the cylindrical core by means of spraying, and

3 schematic representation of the application of the gel coat by doctor blade technique.

1 schematically shows the gel coat used according to the invention as a cylinder surface 2 in a fiber-plastic composite cylinder 1 , The FKV cylinder 1 consists of a sliver, a so-called roving, which in turn consists of a plurality of reinforcing single fibers 3 consists. These are in the matrix of the fiber-reinforced plastic composite 4 embedded.

By using chemically equivalent matrices for both the FKV and the gel coat, an excellent cohesive bond between the two components can be achieved. The surface quality of the gel coats is decisively determined by the shaping tool surface and, with appropriate surface treatment of the winding core, achieves the required roughness values for piston stroke-loaded cylinders.

The production of the endless fiber reinforced cylindrical component of the FKV cylinder 1 is preferably carried out in the filament wet winding process or in the dry-winding process with subsequent resin impregnation in the RTM process.

The winding takes place on a shaping winding core 6 which is typically designed as a polished steel core. The application of the gel coats used in accordance with the invention is preferably a process directly preceding the winding process and is carried out optionally by brushing or spraying. Due to the better layer thickness homogeneity, reproducibility and automatability, compressed air spraying or compressed airless spraying ( 2 ).

The mixing of the resin 11 and hardener component 10 , which contains the finely dispersed nanoparticles in this embodiment, via the supply lines 13 in the mixing head 9 the multi-component spray gun 8th , The mixing of the components can optionally also manually or mechanically before filling the spray gun 8th respectively.

Another particularly suitable method of applying the gel coat to the winding core is the application of the nanoparticle-modified resin system by means of doctor blade technology ( 3 ). This is a squeegee 12 parallel to the cylinder axis of the winding core 6 positioned at a defined distance to the core surface. The squeegee plate is wedge-shaped, so that here is a reservoir of the nanoparticle-modified resin mixture 5 forms and on the rotating core, a thin resin film is applied. By controlling the distance of the doctor blade to the core, the wet film thickness of the film and thus of the subsequent gel coat can be controlled.

In the gel-coat application, the particle-modified resin system is in the direction of rotation in both the spray and the squeegee technique 7 moving and provided with release agent winding core 6 applied. By a subsequent incipient networking is the fishing of the located on the uniform rotating core winding gel coats. Depending on the resin system used, the crosslinking can be started already at room temperature or at elevated temperatures or initiated, for example, by UV light.

To achieve an optimal cohesive connection between gel coat 2 and to ensure laminate, takes place immediately after the winding process on which on the winding core 6 partially crosslinked nanoparticle-modified gel coat 2 ,

After curing of the FKV structure and the gel coat 2 becomes the winding core 6 from the FKV cylinder 1 removed from the mold. The gel coat 2 is now stuck to the inner surface of the FKV cylinder 1 connected and as a tribologically and mechanically heavy-duty cylinder surface 2 of the FKV cylinder 1 ready for use.

LIST OF REFERENCE NUMBERS

1

Fiber-reinforced plastic cylinder

2

Gel coat as cylinder surface

3

Single reinforcing fiber

4

Matrix of the fiber-reinforced plastic composite

5

Nanoparticle-modified resin mixture

6

winding core

7

direction of rotation

8th

Spray gun

9

Mixing head with nozzle

10

Container with hardener and nanoparticles

11

Container with resin

12

squeegee sheet

13

supply lines

Claims (12)

Use of a gel coat of a multi-component lamination, infusion or winding resin system based on epoxy and nanoscale hydrophilic metal oxide particles of SiO ₂ , Al ₂ O ₃ , TiO ₂ or a combination of hydrophilic SiO ₂ , Al ₂ O ₃ or TiO ₂ and hydrophobic SiO ₂ as a friction and wear protection layer in fiber-reinforced plastic composite cylinders (FKV cylinder) to provide a friction-minimized, wear-resistant and ductile cylinder surface. Use of a gel coat according to claim 1 as a running surface in piston stroke loaded cylinders, such as in hydraulic and pneumatic cylinders, piston accumulators, gas pressure and shock absorbers, gas springs and piston pumps and as a friction and wear protection layer in plain and roller bearings. Use of a gel coat according to claim 1, characterized in that the particles are finely dispersed and largely isolated in the resin and / or hardener component, but usually introduced into the low-viscosity hardener component of the resin system. Use of a gel coat according to any one of the preceding claims, characterized in that the mixing and breaking of the particle agglomerates preferably by means of ultrasonic technology and more preferably in a two-stage process, which consists of predispersion in a dissolver and real comminution in a ball mill, takes place. Use of a gel coat according to one of the preceding claims, characterized in that the resin system for producing the gel coat is identical to the matrix resin system of the FKV structure to be coated. Use of a gel coat according to any one of the preceding claims, characterized in that the introduced nanoparticles have a size of 10 nm to 100 nm, preferably from 12 nm to 80 nm and particularly preferably a size of 15 nm to 50 nm. Use of a gel coat according to one of the preceding claims, characterized in that the nanoparticles contained preferably have a specific surface area (BET) of 40 m ² / g to 200 m ² / g and particularly preferably from 50 m ² / g to 160 m ² / g have. Use of a gel coat according to one of the preceding claims, characterized in that the nanoparticles contained a proportion of preferably 0.25 vol% to 12 vol% and particularly preferably from 0.5 vol% to 8 vol% based on the total volume of the coating exhibit. Use of a gel coat according to one of the preceding claims, characterized in that the gel coat is preferably applied by spraying or by means of a doctor. Use of a gel coat according to one of the preceding claims, characterized in that the gel coat is applied to the mold of the FKV structure. Use of a gel coat according to one of the preceding claims, characterized in that the cylindrical component of the FKV structure is produced in the filament wet winding process or in the combined dry winding process with subsequent resin injection in the RTM process. A fiber-plastic composite cylinder with a friction-minimized, wear-resistant and ductile cylinder surface comprising a gel coat according to one of the preceding claims.

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