MOULDING MATERIALS WITH IMPROVED SURFACE FINISH

Abstract

An improved surface finish on articles moulded from prepregs is obtained by providing a surface finishing film on the surface of the prepreg and a surface venting layer on the surface of the surface finishing film in which the finishing film comprises a flowable tacky resin and the venting layer contains perforations which allow passage of the resin through the venting layer to provide removable adhesion between the surface of the mould and the moulding composition during moulding.

Claims

1. A moulding material comprising a layer of a fibrous material in a curable resin matrix provided on at least one surface with a surface finishing film comprising tacky resin wherein a veil is provided on the surface of the finishing film remote from the moulding material and perforations are formed in the veil to allow passage of the tacky resin of the surface finishing film through the veil during a moulding operation.

2. A moulding material according to claim 1 in which the surface finish film comprises a particulate filler.

3. A moulding material according to claim 1 wherein the fibrous material in a curable resin is a prepreg and is provided with a support structure on at least one surface thereof and the surface finishing film is provided on the surface of the support structure remote or spaced from the prepreg and the veil provides a surface venting structure on the surface of the finishing film remote or spaced from the support structure.

4. A moulding material according to claim 3 in which the layer of a fibrous material in a curable resin matrix is coupled with a syntactic film on the side of the prepreg remote or spaced from the support structure.

5. A moulding material according to claim 4 in which a further prepreg layer is provided against the back of the syntactic film.

6. A moulding material according to claim 3 in which the support structure is a fibrous material that is not impregnated with resin.

7. A moulding material according to claim 3 in which the support structure is a fibrous material that is partially impregnated with resin.

8. A moulding material according to claim 1 in which the surface finishing film is fibre reinforced.

9. A moulding material according to claim 1 in which the perforations in the veil are of average diameter from 1 mm to 10 mm, with a spacing of from 1 mm to 50 mm.

10. A moulding material according to claim 3 in which the thickness ratio of the surface finishing film in relation to the syntactic film is less than 1:2 and greater than 1:6.

11. A stack of the moulding materials according to claim 1.

12. A cured moulding comprising a multilayer material composite comprising a layer of fibrous material in a cured resin matrix attached on one surface to the first surface of a support structure which in turn is attached at its second surface to the first surface of a finishing film which is attached at its second surface to a surface of a perforated veil.

13. The cured moulding according to claim 12 comprising a plurality of layers of the cured multilayer material.

14. A cured moulding according to claim 12 comprising an automobile component, an aerospace component or a wind turbine component, such as a part of a blade of a wind turbine.

15. A cured moulding according to claim 12 in which the perforations in the veil are of average diameter from 1 mm to 10 mm, with a spacing of from 1 mm to 50 mm.

16. (canceled)

17. (canceled)

18. A moulding process comprising placing a moulding material according to claim 1 in a mould wherein pressure is exerted within the mould whereby the resin from the surface finishing film passes through the veil into contact with the mould surface, and remains in contact with the mould surface during the moulding process.

19. A process according to claim 18 in which the resin is curable by heat and the mould is heated to cure the resin.

Description

[0087] The invention is illustrated by reference to the accompanying drawing of FIG. 1 and the following Examples.

[0088] FIG. 1 presents a diagrammatic view of a multilayer material. This material was prepared in which layer (1) is a first prepreg layer, layer (2) is a syntactic film comprising a resin containing micro balloons, layer (3) is a second prepreg layer, layer (4) is a support structure comprising a TFP 20 gsm carbon fibre veil (Comparative Examples 1 and 2) or a S5030 glass fibre veil (Comparative Examples 3 to 5 and Example 6), layer (5) is a surface finishing film and layer (6) is a surface venting structure comprising a Trinitex veil. Layer 7 represents a mould surface.

[0089] The surface finishing film, the syntactic film and both prepregs all contain epoxy resin matrices, and the surface finishing film also contains 21% solid glass microspheres by weight, the syntactic film also contains 21% glass balloons based on the weight of the film, and the prepreg matrices also contain 70% by weight of carbon fibre based on the overall weight of the prepreg.

[0090] The thickness of the layers was as follows:

[0091] Surface finishing film@500 gsm=370 microns

[0092] Syntactic film @500 gsm=600 microns

[0093] The surface venting structure is a veil (Trinitex K914 from Ahlstrom) with and without perforations provided therein.

[0094] FThe epoxy resin matrices used in these various layers were as follows.

TABLE-US-00001 TABLE 1 Wt % in Wt % in Wt % in relation relation relation to to to Surface matrix Syntactic matrix Prepreg matrix film matrix % film matrix % matrix % Bis-A Epoxy 33 Bis-A Epoxy 36 Bis-A Epoxy 44.00 Epikote 154 26 Epikote 154 28 Epikote 154 36 PD3614 11 PD3614 11 PD3614 14 Spheriglass 21 S38 XHS 21 3000 CP03 Aerosil R202 5 DICY 2 Dyhard 100E 2 Dyhard 100E 3 URONE 2 U52M 2 U52M 3 Total 100.00 Total 100.00 Total 100.00

[0095] The materials are as follows:

TABLE-US-00002 Bis-A Epoxy weight of 330. Difunctional liquid bisphenol A resin of epoxy equivalent Epikote 154 (Momentive) Polyfunctional epoxy phenol novolac resin PD3614 (Struktol) Nitrile rubber modified epoxy prepolymer (adduct) based on Bisphenol-A-diglycidyl ether (DGEBA) DICY (Alzchem) Dicyandiamide micronized hardener/ curing agent URONE (Emerald) Cure accelerator 4,4 Methylene bis (phenyl dimethyl urea)

[0096] The Additives used in the matrices were as follows:

TABLE-US-00003 Aerosil R202 (Momentive) Fumed silica after treated with a polydimethylsiloxane Spheriglass CP03 (Potter) Solid glass microspheres, improved mechanical properties S38 XHS (3M) Glass bubbles, for low cost, low density filler

[0097] The layers were laid up as shown in FIG. 1 and the composite placed in a mould where it was heated to 130 C. for 30 minutes under a pressure of 1 bar. The mould was allowed to cool and when the cured moulding was removed from the mould the surface at the surface venting structure was inspected.

COMPARATIVE EXAMPLE 1

[0098] Materials corresponding generally to the multilayer material of FIG. 1 were produced, either without the presence of the surface venting veil, or with an unimpregnated or fully impregnated non-perforated veil. The support structure was a TFP 20 gsm carbon fibre veil. The surface finish without a surface veil was poor. If the surface veil was fully impregnated or not impregnated at all the surface finish was also poor.

COMPARATIVE EXAMPLE 2

[0099] Comparative Example 1 was repeated except that the veil was impregnated with various patterns of resin. The surface quality was poor with many pin holes.

COMPARATIVE EXAMPLE 3

[0100] Comparative Example 1 was repeated, except that the support structure was changed to a S5030 glass fibre veil and an uncatalysed resin was applied as dots to the surface of the veil and compared with a veil without dots. In both instances the surface finish was poor.

COMPARATIVE EXAMPLE 4

[0101] Comparative Example 3 was repeated except that a resin dissolved in methyl ketone was sprayed into the surface of the veil. The surface finish was very poor.

COMPARATIVE EXAMPLE 5

[0102] Comparative Example 3 was repeated except that a spray mount was applied to the surface of the mould or the veil. The surface finish was very poor in both cases.

EXAMPLE 6

[0103] A moulding material corresponding generally to the multilayer material of FIG. 1 was produced, except that holes were punched in the surface venting structure (Trinitex K914 veil) before it was applied to the surface finish film.

[0104] The following hole patterns were used. [0105] i) 3 mm diameter holes space 20 mm apart [0106] ii) 3 mm diameter holes spaced 35 mm apart [0107] iii) 2 mm diameter holes spaced 20 mm apart [0108] iv) 2 mm diameter holes spaced 35 mm apart [0109] v) 4.5 mm diameter holes space 35 mm apart [0110] vi) 6 mm diameter holes spaced 35 mm apart.

[0111] Good surface finish was obtained with all these patterns. The larger diameter holes were found to provide somewhat better removable adhesion to the mould surface.