GB2433466A

GB2433466A - Moulding materials

Info

Publication number: GB2433466A
Application number: GB0525912A
Authority: GB
Inventors: Arshad Choudry
Original assignee: Advanced Composites Group Ltd
Current assignee: Cytec Industrial Materials Derby Ltd
Priority date: 2005-12-21
Filing date: 2005-12-21
Publication date: 2007-06-27
Also published as: GB0525912D0

Abstract

A moulding material, which may be used for producing moulded articles with high quality surface finishes, comprises a fibrous material 112 and a resinous material 114 carried by the fibrous material, the weight of the resinous material being between 5 and 150 grams per square metre (gsm). The resinous material may form a continuous film over the fibrous material, or be present in the form of stripes or in a regular or irregular pattern. A second resinous layer 16 may be carried on the opposite side of the fibrous layer. The moulding material may be cured using vacuum bag techniques against a mould surface of mould tool 20.

Description

1 2433466 Moulding Materials The present invention relates to moulding

materials, and particularly, but not exclusively to moulding materials for producing moulded articles with high quality surface finishes.

It has long been a desire to produce fibre-reinforced composite articles with very high quality surface finishes using the conventional vacuum bag cure process. Surface finishes that are substantially free of surface pitting and free of visible impurities are the aim. Increasingly, the production of moulded composite articles with high quality surface finishes is being demanded in industries such as the aerospace, motor sport, automotive and marine industries where the aesthetic appearance of particular surfaces of moulded articles is important, as well as the physical and chemical properties of the fibre reinforced composite.

Attempts to achieve such surface finishes have involved the use of a prepreg, as the surface ply, which comprises a fibre layer to one side of which is attached a heavy resin layer. When laying the prepreg against a mould surface, the dry resin surface is placed against the mould, and as the prepreg is cured, the resin moves through the fibre layer to the mould surface, to fully impregnate the fibre layer. This arrangement can produce a reasonably good surface finish on the moulded article, so long as the resin is of the appropriate viscosity.

However, this method has disadvantages. Firstly, there is no tack on the dry fibre surface and therefore it can be very difficult to securely locate the prepreg against non-horizontal mould surfaces. Moreover, it is found that dry fibres often remain on the surface of the cured article where the resin has not been able to fully impregnate or "wet out" the fibrous layer.

An alternative approach is to attach the prepreg described above with the resin surface against the mould. However this can still suffer from the disadvantage of poor tack, because for such a configuration the resin generally needs to be of a high viscosity, which means that the resin has low inherent tack.

With this approach it is also found that the resin can adopt a milky appearance when cured, thus providing the surface with an undesirable appearance. Further, the surface of the cured article can tend to be pitted as a consequence of air remaining entrapped between the mould surface and the resin surface.

A third approach to producing high quality surface finishes in moulded composite articles is to provide a fine surface veil such as a glass cloth between the resin layer of the prepreg and the mould surface. However, again there are problems of lack of tack. Also the surfacing veil naturally becomes incorporated into the finished surface, thus affecting the aesthetic appearance of the moulded surface (particularly where the weave of the fibrous layer is visible in the moulded article). The surfacing veil can also cause air entrapment and also disruption of the surface finish if the surface requires to be lightly sanded, for example prior to the application of a protective coating.

According to the present invention there is provided a moulding material comprising a fibrous material and a resinous material carried by said fibrous material, the weight of the resinous material being between 5 and 150 grams per square metre (gsm).

The weight of resinous, and fibrous, materials is conventionally measured in the composites industry as the weight comprised over a square metre of the material. Typically the weight is measured in grams and thus referred to as grams per square metre (gsm).

Preferably the weight of the resinous material is between 10 and 100 gsm.

Most preferably the weight of the resinous material is between 20 and 70 gsm.

Preferably the resinous material is located on or towards one side of the fibrous material. Preferably the resinous material comprises a resinous layer.

Preferably the resinous layer comprises a relatively thin film. Preferably the resinous material forms a continuous film over the fibrous material. Alternatively or in addition the resinous material may be present in regions of relatively high and relatively low resin content, and may be in the form of stripes, or other regular or irregular patterns.

Preferably the fibrous material comprises a fibrous layer.

The resinous layer may have a weight of approximately 5ograms per square metre, with the fibrous layer having a weight preferably in the order of 25ograms per square metre.

Preferably the resinous layer is generally uniformly distributed over the fibrous layer such that the relative weights of the resinous material and fibrous layer are between 5 and 40%, and desirably between 10 and 30% per unit of surface area of the fibrous layer carrying the resinous layer.

Preferably the resinous layer is at least partially unimpregnated on the fibrous layer to provide the moulding material with tack on one surface.

Preferably the resinous material has a viscosity of between 500 and 50,000 Pas at approximately 25C. Preferably the resinous material has a viscosity of between 1000 and 10,000 Pas at approximately 25C.

The resinous material may comprise a material including, but not limited to, any one or more of epoxy phenol novolacs, epoxy novolacs, epoxy cresol novolacs, bis phenol A epoxy resins, bisphenol F epoxy resins, multifunctional resins, multifunctional epoxy resins, phenolics, cyanate esters, BMI's, polyesters, thermoplastic materials, other thermosetting materials. The resinous material can contain up to 70% by weight, but ideally less than 40% by weight additives not covered by the above. These additives may fall into a number of categories, such as thermoplastics, flame retardants, fillers and curing agents, including combinations and blends of the above and others well known to those skilled in the art.

Alternatively, or in addition, the resinous material may comprise a thermoplastic material.

The fibrous layer may comprise a single layer of material or alternatively may comprise a plurality of layers of material. The fibrous material may be generally continuous within the layer, such as woven material. Alternatively, or in addition, the fibrous material may be generally discontinuous within the layer, such as chopped strand mat. The layers may comprise the same or alternatively different types of fibrous material. The fibrous material may comprise, but is not limited to, one or more of glass fibre, carbon fibre, aramid, PE, PBO, boron natural fibres, stitched UD, UD tape, non woven material such as glass or polyester thermoplastic fibres or blends thereof.

The moulding material may comprise a second layer carried on the other, opposite side of the fibrous layer. Preferably the second layer is a resinous layer and may be of greater weight than the said resinous layer. Preferably the second resinous layer comprises the bulk, and preferably the balance, of resin used to impregnate the fibrous layer during curing of the moulding material.

The second layer may comprise a layer of resin or a prepreg. The second resinous layer may have a weight of between 20% and 150% of the weight of the fibrous material. Preferably the second resinous layer is generally uniformly distributed over the fibrous layer such that the relative weights of the resinous material in the second layer and the fibrous layer are between 50% and 150%, and desirably between 80% and 120% per unit of surface area of the fibrous layer carrying the second resinous layer. The second resinous layer may have a weight of approximately 250 grams per square metre.

The second resinous layer preferably comprises a thermoset resin or a blend of resins including, but not limited to any one or more of epoxy phenol novolacs, epoxy novolacs, epoxy cresol novolacs, bis phenol A epoxy resins, bisphenol F epoxy resins, multifunctional resins, multifunctional epoxy resins, phenolics, cyanate esters, BMI's, polyesters, thermoplastic materials, other thermosetting materials. The resinous material can contain up to 70% by weight, but ideally less than 40% by weight additives not covered by the above. These additives may fall into a number of categories, such as thermoplastics, flame retardants, fillers and curing agents, including combinations and blends of the above and others well known to those skilled in the art.

Preferably the moulding material comprises a prepreg or preform.

Further according to the present invention there is provided a method of manufacturing a moulding material comprising applying a resinous layer to one side of a layer of fibrous material, the weight of the resinous layer being between and 150 gsm.

Preferably the resinous layer is applied to be carried by the fibrous layer generally as a relatively thin layer or film on a surface thereof, which may be at least partially impregnated into the fibrous layer. A second resinous layer may be applied on the other, opposite surface of the fibrous layer.

Preferably the resinous layer(s) and fibrous layer are as described in any of paragraphs seven to seventeen above in any of the preceding thirteen paragraphs.

Still further according to the present invention there is provided a method of forming a fibre-reinforced composite body with a high quality surface finish, the method comprising locating a moulding material as described above, with the resinous material located against a mould surface, and subjecting the material to appropriate cure conditions to cure the material to form a moulded article.

The method preferably involves curing the moulding material using vacuum bag cure techniques.

Preferred embodiments of the present invention will now be described by way of example only, with reference to the accompanying drawings, in which:-Fig. 1 is a diagrammatic cross-section of a moulding material according to a first embodiment of the invention; Fig. 2 is a diagrammatic cross-section of a moulding material according to a second embodiment of the present invention; and Fig. 3 is a diagrammatic cross-section of the moulding material of Fig. 2 in location on a mould for vacuum bag cure.

The present invention provides a moulding material 10, 110 comprising a fibrous material 12, 112 and a resinous material 14, 114 the weight of the resinous material 14, 114 being between 5 and 150 gsm. The moulding material 10, 110 is in the form of a prepreg and the relative weights of the fibrous material 12, 112 and resinous material 14, 114 are determined with reference to the weight of the other, in the prepreg.

The moulding material of the present invention is primarily intended for use in the production of fibre-reinforced composite articles, which find many applications in many industries, such as the aerospace, motor sport, automotive and marine industries.

For certain applications, the production of moulded articles with high quality surface finishes is necessary or desired. For such surfaces, the aim is to provide a surface that is essentially free of surface pitting and other visible imperfections. Increasingly, for example, there is a desire for the outermost fibrous layer to be visible through the surface of the moulded article. Woven carbon fibre is considered to provide an aesthetic finish to a moulded article, if it can be clearly viewed through the outer surface of the moulded article.

The moulding material 10 as shown in Fig. 1 is suitable for providing such high quality surfaces on articles moulded therefrom.

The fibrous material 12 comprises a layer of any suitable fibrous material, such as carbon, glass, aramid or any other suitable material or combination of materials. The fibrous material is in the form of a flexible, planar sheet or layer and may be woven or unwoven according to the desired properties of the article and visual characteristics sought.

The resinous material 14, is also in the form of a generally planar layer or film carried on one side of the fibrous layer 12.

The resinous layer may have little or no impregnation into the fibrous layer 12, but it is preferred that there is some impregnation to at least adhere the resin layer 14 to the fibrous layer 12.

It is also within the scope of the present invention that the resinous layer 14 is fully impregnated into one surface of the fibrous layer, but it is desirable that there remains tack on the surface of the material 10, to facilitate location of the moulding material 10 in a mould.

The weight of the resinous layer 14 is considerably less than the weight of the fibrous layer 12, and this is an important feature of the moulding material.

The resinous layer 14 is generally uniformly distributed to form a continuous layer over the fibrous layer 12 such that the resinous layer 14 has a weight of between 5 and 150 gsm in the moulding material.

In further embodiments the weight of the resinous material is between 10 and 100 gsm, and in particularly preferred embodiments the weight of the resinous material is between 20 and 70 gsm.

The optimum weights of the resin layer 14 and the fibrous layer 12 can be determined according to the nature of the respective layers, the desired properties of the moulded article and its surface etc. However, the above ranges have been shown to provide excellent quality surface finishes for a wide range of resin and fibre combinations, using conventional vacuum bag techniques, as will be described.

Within the above range, a most preferred range for many commonly used resins, such as thermoset epoxies, polyesters, phenolics, BMls and cyanate esters or blends thereof, is with a resinous material between 5 and 150 gsm in weight.

It has been found that using resinous materials with viscosities between 500 and 50,000 Pas at approximately 25C, and more desirably between 1000 and 10,000 Pas at approximately 25C, produces moulded articles with excellent surface qualities.

In one particular example, the resinous layer 14 comprises a thermoset resin, such as ACG MTM 56-1 with a weight of approximately 50 grams per square metre. This resin is supplied by Advanced Composites Group Limited, of Heanor, Derbyshire, U.K. It is a modified epoxy resin system. The fibrous layer 12 comprises a woven carbon fibre material with a weight of approximately 250 grams per square metre. The resinous layer 14 is lightly impregnated into one surface of the fibre material. Conventional laminating techniques may be employed to form the moulding material 10, which is generally in the form of a prep reg.

The invention also provides a method of manufacturing a moulding material 10 by applying to one side of the fibrous layer 12 the resinous layer 14, such that the weight of the resinous layer is between 5 and 150 gsm..

The resinous layer can be applied by conventional laminating techniques essentially bring the two layers together under appropriate conditions of temperature and/or pressure to result in lamination of the two layers together and as described above partial and/or full impregnation, if desired.

Fig. 2 shows a moulding material 110 according to a second embodiment of the present invention. The moulding material 110 comprises a layer of fibrous material 112 and a layer of resinous material 114. These layers 112, 114 are as described above in relation to moulding material 10.

However, in moulding material 110, a second layer 16 is provided on the other side or surface of the fibrous layer 112 to form a moulding material or prepreg with a resin-fibre-resin sandwich construction. The second layer 16 is a resinous layer in this embodiment and comprises the bulk of the resin that will impregnate the fibrous material 112 during curing of the moulding material 110.

The second resinous layer 16 comprises the balance of resin needed to wet out and provide full impregnation of the fibrous layer 112 during cure, as will be described.

The second resinous layer may comprise a layer of resin, or it may comprise a conventional form of prepreg having sufficient resin load to provide for the balance of resin for wetting out the fibrous layer 112 during the moulding process.

The second resinous layer has a weight of between 20% and 150% by the weight of the fibrous material. The second resinous layer is generally uniformly distributed over the fibrous layer such that the relative weights of the resinous material in the second layer and fibrous layer are between 50% and 150% and preferably between 80% and 120% per unit of surface area of the fibrous layer carrying the second resinous layer. The second resinous layer has a weight of approximately 250 grams per square metre.

The second resinous layer comprises a thermoset resin or a blend of resins including, but not limited to any one or more of epoxy phenol novolacs, epoxy novolacs, epoxy cresol novolacs, bis phenol A epoxy resins, bisphenol F epoxy resins, multifunctjonal resins, multifunctional epoxy resins, phenolics, cyanate esters, BMI's, polyesters, thermoplastic materials, other thermosetting materials. The resinous material can contain up to 70% by weight, but ideally less than 40% by weight additives not covered by the above. These additives may fall into a number of categories, such as thermoplastics, flame retardants, fillers and curing agents, including combinations and blends of the above and others well known to those skilled in the art.

The second resinous layer 16 may be attached to the surface of the fibrous material 112 with little or no impregnation, or it may be partially impregnated into the fibrous layer 112.

It is important that the fibrous layer 12, 112 comprises pathways for the removal of air from therewithin, during curing, to eliminate the formation of voids.

In this regard it is desirable that the fibrous layer 12, 112 is at most, partially impregnated by the combined resin layers 14, 114 and 16, whereby to comprise areas of dry fibre, unimpregnated with resin to provide the said pathways.

The invention further provides a method of forming a fibre-reinforced composite body with a high quality surface finish.

Fig. 3 is a diagrammatic cross-section of the moulding material 110 of Fig. 2 located against a mould surface 18 of a mould tool 20.

The material 110 is located beneath a vacuum bag arrangement 21 according to known vacuum bag moulding techniques.

The material 110 is moulded under appropriate cure conditions according to the resinous materials 114, 16 and the desired characteristics and properties of the moulded article. Generally non-ambient temperature and/or pressure conditions are involved.

When forming moulded articles using the moulding material 10, the resin layer 14, 114 is located against the mould surface 18.

The inherent tack of the resinous material 14, 114 on the fibrous layer 12, 112, provides for the secure location of the moulding material against mould surfaces, especially non-horizontal mould surfaces thus facilitating lay-up in the mould.

Under cure conditions, the resinous materials in the layers 14, 114 become less viscous and move to impregnate the fibrous layer 12, 112. Air from within the fibrous layer is drawn out along the pathways provided and from within the vacuum bag 21 through the outlet "0".

The relatively light weight of the surface resin layer 14, 114 produces zero or virtually zero pitting in the surface of the moulded article. It is further found that there is zero or virtually zero fibre penetration through the surface of the moulded article and where clear resins are used there is excellent clarity of the surface providing excellent visibility of the fibrous material 12, 112 through the surface of the moulded article.

These results are due to the light weight surface layer 14, 114 impregnating the fibrous layer during curing, its relatively thin film characteristic acting to prevent the entrapment of air between it and the mould surface 18, thus facilitating the production of a pit free surface. This is also found to facilitate the production of a clear resin surface without any clouding or milking effect experienced with known arrangements. The direction of impregnation of the surface layer 14, 114 into the fibrous layer 12, 112, i.e. from the mould surface 18, also acts to prevent fibres from the fibrous layer breaking the surface. This arrangement also obviates the need to use a surface veil.

The bulk of resin required to impregnate and wet out the fibrous layer 112 during cure is provided by the second resinous layer 16, which as described, may be provided as a part of the moulding material 110, or may be provided during lay-up in the mould. This layer 16 provides the balance of resin needed to wet out the fibrous layer 12, 112, taking into account the resin impregnating the layer 12, 112 from the resinous layer 14, 114.

Various modifications may be made without departing from the spirit or scope of the present invention. Although use of vacuum bag techniques is advantageous, other cure techniques can be used. The resinous material may be applied in a form other than a continuous film or layer, for example stripes, blocks or other patterns and formations. The second layer may include fibrous material, and may comprise a fully or partially impregnated prepreg material.

Whilst endeavouring in the foregoing specification to draw attention to those features of the invention believed to be of particular importance it should be understood that the Applicant claims protection in respect of any patentable feature or combination of features hereinbefore referred to and/or shown In the drawings whether or not particular emphasis has been placed thereon.

Claims

Claims: 1. A moulding material comprising a fibrous material and a

resinous material carried by said fibrous material, the weight of the resinous material being between 5 and 150 grams per square metre (gsm).

2. A moulding material according to claim 1, in which the weight of the resinous material is between 10 and 100 gsm.

3. A moulding material according to claim 1 or claim 2, in which the weight of the resinous material is between 20 and 70 gsm.

4. A moulding material according to any preceding claim, in which the resinous material is located on or towards one side of the fibrous material.

5. A moulding material according to any preceding claim, in which the resinous material comprises a resinous layer.

6. A moulding material according to claim 5, in which the resinous layer comprises a relatively thin film.

7. A moulding material according to any preceding claim, in which the resinous material forms a continuous film over the fibrous material.

8. A moulding material according to any preceding claim, in which the resinous material is present in regions of relatively high and relatively low resin content.

9. A moulding material according to claim 8, in which the resinous material is present in the form of stripes.

10. A moulding material according to claim 8 or claim 9, in which the resinous material is present in a regular pattern.

11. A moulding material according to claim 8 or claim 9, in which the resinous material is present in an irregular pattern.

12. A moulding material according to any preceding claim, in which the fibrous material comprises a fibrous layer.

13. A moulding material according to claim 12, in which the resinous layer has a weight of approximately 50 grams per square metre, and the fibrous layer has a weight in the order of 250 grams per square metre.

14. A moulding material according to claim 12 or claim 13, in which the resinous layer is generally uniformly distributed over the fibrous layer such that the relative weights of the resinous material and fibrous layer are between 5 and 40%, per unit of surface area of the fibrous layer carrying the resinous layer.

15. A moulding material according to claim 14, in which the relative weight of the resinous material and fibrous layer are between 10% and 30%.

16. A moulding material according to any of claims 12 to 15, in which the resinous layer is at least partially unimpregnated on the fibrous layer to provide the moulding material with tack on one surface.

17. A moulding material according to any preceding claim, in which the resinous material has a viscosity of between 500 and 50,000 Pas at approximately 25C.

18. A moulding material according to any preceding claim, in which the resinous material has a viscosity of between 1000 and 10,000 Pas at approximately 25C.

19. A moulding material according to any preceding claim, in which the resinous material comprises a material including, but not limited to, any one or more of epoxy phenol novolacs, epoxy novolacs, epoxy cresol novolacs, bis phenol A epoxy resins, bisphenol F epoxy resins, multifunctional resins, multifunctional epoxy resins, phenolics, cyanate esters, BMI's, polyesters, thermoplastic materials, other thermosetting materials.

20. A moulding material according to any preceding claim, in which the resinous material contains up to 70% by weight of additives.

21. A moulding material according to claim 20, in which the resinous material contains less than 40% by weight of additives.

22. A moulding material according to claim 20 or claim 21, in which the additives fall into a number of categories, such as thermoplastics, flame retardants, fillers and curing agents, including combinations and blends thereof.

23. A moulding material according to any preceding claim, in which the resinous material comprises a thermoplastic material.

24. A moulding material according to any of claims 12 to 23, in which the fibrous layer comprises a single layer of material.

25. A moulding material according to any of claims 12 to 24, in which the fibrous layer comprises a plurality of layers of material.

26. A moulding material according to any of claims 12 to 25, in which the fibrous material is generally continuous within the layer.

27. A moulding material according to any of claims 12 to 25, in which the fibrous material is generally discontinuous within the layer.

28. A moulding material according to any of claims 25 to 27, in which the layers comprise the same type of fibrous material.

29. A moulding material according to any of claims 25 to 27, in which the layers comprise different fibrous material.

30. A moulding material according to any previous claim, in which the fibrous material comprises one or more of glass fibre, carbon fibre, aramid, PE, PBO, boron natural fibres, stitched UD, UD tape, glass, polyester thermoplastic fibres or blends thereof.

31. A moulding material according to any of claims 12 to 30, in which the moulding material comprises a second layer carried on the other, opposite side of the fibrous layer.

32. A moulding material according to claim 31, in which the second layer is a resinous layer.

33. A moulding material according to claim 31 or claim 32, in which the second layer is of greater weight than the said resinous layer.

34. A moulding material according to claim 32 or claim 33, in which the second resinous layer comprises the bulk of resin used to impregnate the fibrous layer during curing of the moulding material.

35. A moulding material according to claim 34, in which the second resinous layer comprises the balance of resin to impregnate the fibrous later during cure.

36. A moulding material according to any of claims 31 to 35, in which the second layer comprises a layer of resin.

37. A moulding material according to any of claims 31 to 35, in which the second layer comprises a prepreg.

38. A moulding material according to any of claims 31 to 37, in which the second resinous layer has a weight of between 20% and 150% of the weight of the fibrous material.

39. A moulding material according to any of claims 32 to 38, in which the second resinous layer is generally uniformly distributed over the fibrous layer such that the relative weights of the resinous material in the second layer and the fibrous layer are between 50% and 150%, per unit of surface area of the fibrous layer carrying the second resinous layer.

40. A moulding material according to claim 39, in which the relative weights of the resinous material in the second layer and the fibrous layer are between 80% and 120%.

41. A moulding material according to any of claims 32 to 40, in which the second resinous layer has a weight of approximately 250 grams per square metre.

42. A moulding material according to any of claims 32 to 41, in which the second resinous layer comprises a thermoset resin or a blend of resins including one or more of epoxy phenol novolacs, epoxy novolacs, epoxy cresol novolacs, bis phenol A epoxy resins, bisphenol F epoxy resins, multifunctional resins, multifunctional epoxy resins, phenolics, cyanate esters, BMI's, polyesters, thermoplastic materials, other thermosetting materials.

43. A moulding material according to any of claims 32 to 42, in which the resinous material contains up to 70% by weight, additives.

44. A moulding material according to claim 43, in which the resinous material contains less than 40% additives, by weight.

45. A moulding material according to claim 43 or claim 44, in which the additives comprise one or more of thermoplastics, flame retardants, fillers and curing agents, including combinations and blends thereof.

46. A moulding material according to any preceding claim, in which the moulding material comprises a prepreg or preform.

47. A method of manufacturing a moulding material comprising applying a resinous layer to one side of a layer of fibrous material, the weight of the resinous layer being between 5 and 150 gsm.

48. A method according to claim 47, in which the resinous layer is applied to be carried by the fibrous layer generally as a relatively thin layer or film on a surface thereof.

49. A method according to claim 47 or claim 48, in which the resinous layer is at least partially impregnated into the fibrous layer.

50. A method according to any of claims 47 to 49, in which a second resinous layer is applied on the other, opposite surface of the fibrous layer.

51. A method according to any of claims 47 to 50, in which the resinous layer(s) and fibrous layer are as claimed in any of claims 1 to 46.

52. A method of forming a fibre-reinforced composite body with a high quality surface finish, the method comprising locating a moulding material as claimed in any of claims 1 to 46, with the resinous material located against a mould surface, and subjecting the material to appropriate cure conditions to cure the material to form a moulded article.

53. A method according to claim 52, in which the moulding material is cured using vacuum bag cure techniques.

54. A moulding material substantially as hereinbefore described with reference to the accompanying drawings.

55. A method of manufacturing a moulding material substantially as hereinbefore described with reference to the accompanying drawings.

56. A method of forming a fibre-reinforced composite body substantially as hereinbefore described with reference to the accompanying drawings.

57. Any novel subject matter or combination including novel subject matter disclosed herein, whether or not within the scope of or relating to the same invention as any of the preceding claims.