WO2008075011A1

WO2008075011A1 - Composite material

Info

Publication number: WO2008075011A1
Application number: PCT/GB2007/004828
Authority: WO
Inventors: Adam Chaplin; Brian Wilson; Alan Wood
Original assignee: Victrex Manufacturing Ltd
Current assignee: Victrex Manufacturing Ltd
Priority date: 2006-12-21
Filing date: 2007-12-17
Publication date: 2008-06-26
Anticipated expiration: 2009-06-21
Also published as: TW200844149A; GB0625486D0

Abstract

A method of preparing a composite material as described, the method comprising contacting a polymeric material and nanoparticles in a selected solvent so the solvent dissolves the polymeric material; mixing the polymeric material and nanoparticles in the solvent; and removing the solvent to produce the composite material. The polymeric material may be amorphous and may be selected from polyarletherketones, polyarlethersulphones, polyetherimides and PBI.

Description

COMPOSITE MATERIAL

This invention relates to a composite material and particularly, although not exclusively, relates to a process for preparing a composite material which incorporates nanoparticles, for example fullerenes, in the form of, for example, nanotubes.

Fullerenes are molecular carbon species having at least 60 carbon atoms. Example of fullerenes include carbon nanotubes (SWNTs) and multi-walled carbon nanotubes

(MWNTs) . SWNTs include hollow molecules of pure carbon linked together in a hexagonally bonded network to form a hollow cylinder. The tubes are seamless with open or capped ends. The diameter of SWNTs is usually in the range 0.7 to 2nm and typically approximately lnm.

Composite materials which comprise thermoplastic polymers and carbon nanotubes have been proposed. For example, WO98/39250 describes in claim 122 a composite material which comprises a thermoplastic polymer in which a carbon nanotube material is embedded. Polyetheretherketone is referenced in a list of 12 polymer types. However, no details are included on how a composite of, for example, polyetheretherketone and carbon nanotubes may be prepared.

SWNTs and MWNTs (and other nanoparticles) have a high aspect ratio and tend to stick to one another, which makes it difficult to disperse them in polyetheretherketone and/or difficult to provide composite materials with a high loading of such materials. It is an object of the present invention to address the above described problems.

According to a first aspect of the invention, there is provided a method of preparing a composite material which comprises nanoparticles and a polymeric material, the method comprising:

(a) contacting both the polymeric material and nanoparticles in a selected solvent so that said polymeric material dissolves in said solvent;

(b) mixing the polymeric material and nanoparticles in said solvent; and

(c) removing said solvent to produce said composite material.

Nanoparticles may suitably be in accordance with the definition in PAS71 (issued by BSI, UK) which describes a nanoparticle as a particle having one or more dimensions of the order of lOOnm or less. Thus, nanoparticles described herein suitably have dimensions of less than lOOnm. In some embodiments, the nanoparticles may have dimensions of less than 50nm or even less than IOnm.

Said nanoparticles may be any type of such particles. They may be organic, inorganic or metals. Examples of nanoparticles include VGCF (Vapour Grown Carbon Fibre) , Zinc Silicate nanoparticles, Nano diamonds, Nano silicon, Nano metals (e.g. gold, iron oxide), Carbon nanotubes (single and multi walled), Fullerite, Fullerenes, Carbon Buckyballs/Buckypaper, Carbon nanotorus, Nano ceramic particles, Titanium dioxide nanoparticles, Endohedral fullerenes, Alumina nanoparticles, Magnetic materials such as Barium ferrite nanoparticles, Polymeric nanoparticles, Hydroxyaptite nanoparticles.

Said composite material may comprise a said polymeric material which defines a matrix and additional material distributed within the matrix wherein a major amount of said additional material is comprised of said nanoparticles .

When said nanoparticles comprise fullerence moieties, said fullerene moieties suitably include a major amount of carbon nanotubes. Said carbon nanotubes may be SWNTs or MWNTs. Said fullerene moieties preferably comprise or, more preferably, consist essentially of SWNTs.

Unless otherwise specified herein, where reference is made to a material including a "major amount" of a component, the specified component may be present at level of at least 60wt%, suitably at least 70wt%, preferably at least 80wt%, more preferably at least 90wt%, especially at least 95wt% of the total weight of the material and, preferably, the material consists essentially of the specified component .

When said nanoparticles comprise fullerene moieties, said fullerene moieties suitably include a major amount of carbon nanotubes. Said carbon nanotubes may be SWNTs or MWNTs. Said fullerene moieties preferably comprise or, more preferably, consist essentially of SWNTs.

The ratio of the weight of nanoparticles (e.g. fullerene moieties) to polymeric material contacted in step (a) may be at least 0.001, preferably at least 0.005, more preferably at least 0.009, especially at least 0.01. The ratio may be less than 0.3, preferably less than 0.2, especially less than 0.01.

The ratio of the weight of solvent present in step (a) (suitably total solvent if more than one type of solvent is used) to the weight of polymeric material (suitably total polymeric material if more than one type of polymeric material is used) is preferably at least 10, more preferably at least 15, especially 19 or greater. The ratio may be less than 40, preferably less than 30.

Step (a) preferably includes raising the temperature to facilitate dissolution of said polymeric material. For example, the temperature may be raised to between 40 to 100⁰C, preferably 50⁰C to 80⁰C.

In a preferred embodiment, the method includes a step (a^*) prior to step (a) of contacting the nanoparticles in said solvent and preferably dispersing said nanoparticles therein. The step (a^*) preferably includes directing an oscillating energy source into the fluid. The step preferably uses ultrasound to sonicate the nanoparticles in said fluid and disperse them therein. Energy is preferably applied in step (i) for at least 30 minutes, preferably at least 1 hour, preferably at least 1.5 hours.

Dispersion in step (a^*) may be carried out at a temperature greater than ambient temperature, for example at 30-70⁰C. Then, preferably, in step (a) said polymeric material is contacted with said dispersion. Said polymeric material is suitably in a particulate, for example granular or powder form. The polymeric material is then dissolved and dispersed in said solvent, in step (b) . This preferably involves use of an oscillating energy source as aforesaid.

Solvent may be removed in step (c) by any suitable means.

It may be removed by evaporation. In one preferred embodiment, said polymeric material may be caused to precipitate in step (c) and, suitably thereafter the solvent is removed for example by filtration (or the like) .

Step (c) preferably includes contacting the mixture of step (b) with another solvent, suitably a non-solvent for the selected solvent of step (a) , thereby to cause precipitation of polymeric material with nanoparticles dispersed therein. Suitably, the solvent used in step (c) is aqueous and preferably comprises a major amount of water.

Said polymeric material may be a polymer material which is compatible, preferably miscible with polymeric materials which include moieties I, II and/or III as hereinafter described. Said polymeric material is preferably miscible with polyaryletherketones, for example polyetherketone, polyetheretherketone and polyetherketoneetherketoneketone. Said polymeric material may be amorphous or crystalline. A wide range of solvents may be available for dissolving an amorphous polymeric material. Examples of polymeric materials include polyaryletherketones, polyarylether sulphones, polyetherimides and PBI. Said polymeric material is preferably melt processible. Except where otherwise stated throughout this specification, any alkyl, akenyl or alkynyl moiety suitably has up to 8, preferably up to 6, more preferably up to 4, especially up to 2, carbon atoms and may be of straight chain or, where possible, of branched chain structure. Generally, methyl and ethyl are preferred alkyl groups and C₂ alkenyl and alkynyl groups are preferred.

Except where otherwise stated in this specification, optional substituents of an alkyl group may include halogen atoms, for example fluorine, chlorine, bromine and iodine atoms, and nitro, cyano, alkoxy, hydroxy, amino, alkylamino, sulphinyl, alkylsulphinyl, sulphonyl, alkylsulphonyl, amido, alkylamido, alkoxycarbonyl, haloalkoxycarbonyl and haloalkyl groups. Preferably, optionally substituted alkyl groups are unsubstituted.

Said polymeric material may be of a type which includes:

(i) phenyl moieties;

(ii) ketone and/or sulphone moieties; and

(iii) ether and/or thioether moieties.

Preferably, said polymeric material has a moiety of formula

and/or a moiety of formula

and/or a moiety of formula

wherein the phenyl moieties in units I, II, and III are independently optionally substituted and optionally cross- linked; and wherein m,r,s,t,v,w and z independently represent zero or a positive integer, E and E' independently represent an oxygen or a sulphur atom or a direct link, G represents an oxygen or sulphur atom, a direct link or a -O-Ph-0- moiety where Ph represents a phenyl group and Ar is selected from one of the following moieties (i)*, (i)**, (i) to (x) which is bonded via one or more of its phenyl moieties to adjacent moieties

Unless otherwise stated in this specification, a phenyl moiety may have 1,4- or 1,3-, especially 1,4-, linkages to moieties to which it is bonded.

In (i)*, the middle phenyl may be 1,4- or 1, 3-substituted.

Said polymeric material may include more than one different type of repeat unit of formula I; more than one different type of repeat unit of formula II; and more than one different type of repeat unit of formula III. Preferably, however, only one type of repeat unit of formula I, II and/or III is provided.

Said moieties I, II and III are suitably repeat units. In the polymeric material, units I, II and/or III are suitably bonded to one another - that is, with no other atoms or groups being bonded between units I, II, and III.

Where the phenyl moieties in units I, II or III are optionally substituted, they may be optionally substituted by one or more halogen, especially fluorine and chlorine, atoms or alkyl, cycloalkyl or phenyl groups. Preferred alkyl groups are Ci-io, especially Ci_4, alkyl groups.

Preferred cycloalkyl groups include cyclohexyl and multicyclic groups, for example adamantyl.

Another group of optional substituents of the phenyl moieties in units I, II or III include alkyls, halogens, C_yF_2y+i where y is an integer greater than zero, 0-R^q (where R^q is selected from the group consisting of alkyls, perfluoralkyls and aryls) , CF=CF₂, CN, NO₂ and OH. Trifluormethylated phenyl moieties may be preferred in some circumstances .

Preferably, said phenyl moieties are not optionally- substituted as described.

Where said polymeric material is cross-linked, it is suitably cross-linked so as to improve its properties. Any suitable means may be used to effect cross-linking. For example, where E represents a sulphur atom, cross-linking between polymer chains may be effected via sulphur atoms on respective chains. Preferably, said polymeric material is not optionally cross-linked as described.

Where w and/or z is/are greater than zero, the respective phenylene moieties may independently have 1,4- or 1,3- linkages to the other moieties in the repeat units of formulae II and/or III. Preferably, said phenylene moieties have 1,4- linkages.

Preferably, the polymeric chain of the polymeric material does not include a -S- moiety. Preferably, G represents a direct link.

Suitably, "a" represents the mole % of units of formula I in said polymeric material, suitably wherein each unit I is the same; "b" represents the mole % of units of formula II in said polymeric material, suitably wherein each unit II is the same; and "c" represents the mole % of units of formula III in said polymeric material, suitably wherein each unit III is the same. Preferably, a is in the range 45-100, more preferably in the range 45-55, especially in the range 48-52. Preferably, the sum of b and c is in the range 0-55, more preferably in the range 45-55, especially in the range 48-52. Preferably, the ratio of a to the sum of b and c is in the range 0.9 to 1.1 and, more preferably, is about 1. Suitably, the sum of a, b and c is at least 90, preferably at least 95, more preferably at least 99, especially about 100. Preferably, said polymeric material consists essentially of moieties I, II and/or III.

Said polymeric material may be a homopolymer having a repeat unit of general formula

or a homopolymer having a repeat unit of general formula

or a random or block copolymer of at least two different units of IV and/or V

wherein A, B, C and D independently represent 0 or 1 and E, E¹ , G, Ar, m, r, s, t, v, w and z are as described in any statement herein.

As an alternative to a polymeric material comprising units IV and/or V discussed above, said polymeric material may be a homopolymer having a repeat unit of general formula

Of-co4fo4f-G ^■ O-tfco-fO- •H>HfoH-E- ι\

or a homopolymer having a repeat unit of general formula -OfSO₂-IfO- O4fso₂4O- VM4 b" v*

or a random or block copolymer of at least two different units of IV* and/or V*, wherein A, B, C, and D independently represent 0 or 1 and E, E', G, Ar, m, r, s, t, v, w and z are as described in any statement herein.

Preferably, m is in the range 0-3, more preferably 0-2, especially 0-1. Preferably, r is in the range 0-3, more preferably 0-2, especially 0-1. Preferably t is in the range 0-3, more preferably 0-2, especially 0-1. Preferably, s is 0 or 1. Preferably v is 0 or 1. Preferably, w is 0 or 1. Preferably z is 0 or 1.

Preferably, said polymeric material is a homopolymer having a repeat unit of general formula IV.

Preferably Ar is selected from the following moieties (xi)*, (xi)**, (xi) to (xxi) :

(xi)**

In ⁽xi⁾*, the middle phenyl may be 1,4- or 1,3- substituted. Preferably, (xv) is selected from a 1,2-, 1,3-, or a 1,5- moiety; (xvi) is selected from a 1,6-, 2,3-, 2,6- or a 2,7- moiety; and (xvii) is selected from a 1,2-, 1,4-, 1,5-, 1,8- or a 2,6- moiety.

One preferred class of polymeric material does not include any moieties of formula III, but suitably only includes moieties of formulae I and/or II. Where said polymeric material is a homopolymer or random or block copolymer as described, said homopolymer or copolymer suitably includes a repeat unit of general formula IV. Such a polymeric material may, in some embodiments, not include any repeat unit of general formula V.

Suitable moieties Ar are moieties (i)*, (i) , (ii) , (iii) and (iv) and, of these, moieties (i)*, (i) and (iv) are preferred. Other preferred moieties Ar are moieties (xi)*, (xii) , (xi) , (xiii) and (xiv) and, of these, moieties (xi)*, (xi) and (xiv) are especially preferred.

An especially preferred class of polymeric material are polymers (or copolymers) which consist essentially of phenyl moieties in conjunction with ketone and/or sulphone moieties and in conjunction with ether moieties. That is, in the preferred class, the polymeric material does not include repeat units which include -S- or aromatic groups other than phenyl. Preferred polymeric materials include:

(a) a polymer consisting essentially of units of formula IV wherein Ar represents moiety (iv), E and E' represent oxygen atoms, m represents 0, w represents 1, G represents a direct link, s represents 0, and A and B represent 1 (i.e. polyetheretherketone) .

(b) a polymer consisting essentially of units of formula IV wherein E represents an oxygen atom, E¹ represents a direct link, Ar represents a moiety of structure (i) , m represents 0, A represents 1,

B represents 0 (i.e. polyetherketone) ;

(c) a polymer consisting essentially of units of formula IV wherein E represents an oxygen atom, Ar represents moiety (i) *, m represents 0, E' represents a direct link, A represents 1, B represents 0, (i.e. polyetherketoneketone) .

(d) a polymer consisting essentially of units of formula IV wherein Ar represents moiety (i) , E and E' represent oxygen atoms, G represents a direct link, m represents 0, w represents 1, r represents 0, s represents 1 and A and B represent 1. (i.e. polyetherketoneetherketoneketone) .

(e) a polymer consisting essentially of units of formula IV, wherein Ar represents moiety (iv) , E and E' represents oxygen atoms, G represents a direct link, m represents 0, w represents 0, s, r, A and B represent 1 (i.e. polyetheretherketoneketone) .

(f) a polymer consisting essentially of units of formula IV, wherein E represents an oxygen atom, E' represents a direct link, Ar represents a moiety of structure (ii) , m represents 0, A represents 1, B represents 0 (i.e. polyethersulphone) .

(g) a polymer consisting essentially of units of formula V, wherein E and E' represent oxygen atoms, Ar represents moiety (xi)**, m represents 0, z represents 1, G represents a direct link, v represents 0, C and D represent 1 (i.e. polysulphone) .

Said solvent selected in step (a) is preferably of a type and/or the conditions of steps (a) and (b) are such that said solvent does not substantially functionalise the polymeric material.

In general terms, phenyl moieties for example included in polymeric materials which include moieties I, II and/or III are more susceptible to electrophilic attack when they are bonded to electron-donating groups (e.g. ether or thioether moieties) and are less susceptible when bonded to electron withdrawing moieties (e.g. carbonyl and/or sulphone moieties) . Thus a moiety -carbonyl-phenyl- carbonyl has a very low susceptibility to electrophilic attack whereas a moiety -ether-phenyl-ether has a higher susceptibility. Also, multi-phenylene groups (i.e. (phenyl) _n where n is an integer of 2 or greater) and fused ring aromatic moieties tend to be more susceptible to electrophilic attack (compared to single phenylene) due to the greater electron density of such groups.

Preferably, said polymeric material does not include multi-phenylene or fused ring aromatic groups. Preferably, said polymeric material consists essentially of moieties described in (i) , (ii) and (iii) above, for example I, II and III. Preferably, said polymeric material does not include thioether moieties. Preferably, said polymeric material includes at least some ether moieties.

Said polymeric material may be a homopolymer or copolymer which includes a repeat unit selected from:

- ether-phenyl-ether-phenyl-ketone-phenyl ether-phenyl-ketone-phenyl- ether-phenyl-ketone-phenyl-ketone-pheny1- ether-phenyl-ketone-phenyl-ether-phenyl-ketone pheny1-ketone-phenyl- - ether-phenyl-ether-phenyl-ketone-phenyl-ketone -phenyl- ether-phenyl-sulphone-pheny1- ether-phenyl-C (CH₃) ₂-phenyl-ether-phenyl-sulphone- phenyl.

Of the aforesaid, ether-phenyl-ether-phenyl-ketone-phenyl, ether-phenyl-ketone-phenyl and ether-phenyl-sulphone- phenyl units are preferred.

Preferably, said polymeric material is a homopolymer which preferably consists essentially of the repeat units described in the preceding two paragraphs. It is preferably selected from polyetheretherketone, polyetherketone and polyethersulphone, with polyetheretherketone and polyetherketone being especially preferred. Said polymeric material is preferably semi-crystalline. The level and extent of crystallinity in a polymer is preferably measured by wide angle X-ray diffraction (also referred to as Wide Angle X-ray Scattering or WAXS) , for example as described by Blundell and Osborn (Polymer 24, 953, 1983) . Alternatively, crystallinity may be assessed by Differential Scanning Calorimetry (DSC) .

The level of crystallinity in said polymeric material may be at least 1%, suitably at least 3%, preferably at least 5% and more preferably at least 10%. In especially preferred embodiments, the crystallinity may be greater than 30%, more preferably 40%, especially 45%.

The glass transition temperature (T_g) of said polymeric material may be at least 140⁰C.

Said polymeric material may have an inherent viscosity (IV) of at least 0.1, suitably at least 0.3, preferably at least 0.4, more preferably at least 0.6, especially at least 0.7

(which corresponds to a reduced viscosity (RV) of least

0.8) wherein RV is measured at 25⁰C on a solution of the polymer in concentrated sulphuric acid of density 1.84gcm^"3, said solution containing Ig of polymer per 100cm^"3 of solution. IV is measured at 25°C on a solution of polymer in concentrated sulphuric acid of density 1.84gcm³, said solution containing O.lg of polymer per 100cm³ of solution.

The measurements of both RV and IV both suitably employ a viscometer having a solvent flow time of approximately 2 minutes . The main peak of the melting endotherm (Tm) for said polymeric material (if crystalline) may be at least 300⁰C.

Said solvent may be selected according to the nature of the polymeric material having regard to the considerations discussed above. Said solvent is preferably a strong acid. It may include a -SO₃H moiety. It may be selected from sulphuric acid and a sulphonic acid. A sulphonic acid may be an optionally-substituted alkyl or aryl sulphonic acid and, of these, an optionally-substituted alkyl sulphonic acid is preferred. An especially preferred alkyl sulphonic acid is methane sulphonic acid.

Preferred solvents for step (a) are sulphuric acid and methane sulphonic acid. Sulphuric acid may be between 98% and 98.5% acid (preferably it is about 98%). Such a concentration will dissolve, for example, polyetherketone and polyethersulphone but it is not a sufficiently strong sulphonating agent to substantially sulphonate the phenyl groups thereof. Higher concentrations, for example greater than 99% could disadvantageously sulphonate such polymers. Methane sulphonic acid may be used to dissolve polymers which are more susceptible to electrophilic substitution reactions compared to polyetherketone and polyethersulphone, such as polymers which include phenyl groups bonded to both an oxygen atom and a carbonyl group. Methane sulphonic acid can dissolve, for example polyetheretherketone, whilst leaving it substantially unsulphonated.

According to a second aspect of the invention, there is provided a mixture formed in step (b) of the method of the first aspect per se. The mixture suitably includes a polymeric material and nanoparticles, for example fullerene moieties dispersed in a said selected solvent. The mixture of the second aspect may have any feature of the mixture of the first aspect. In a preferred embodiment, said mixture comprises nanoparticles, for example fullerene moieties, at least one polymeric material selected from polyetheretherketone, polyetherketone and polyethersulphone and a solvent which includes a -SO₃H moiety.

The composite material prepared in a method according to the first aspect may include residual solvent. Accordingly, in a second aspect, the invention provides a composite material which includes a polymeric material and nanoparticles, for example fullerene moieties, and residual solvent, of a type as described in any statement herein. The solvent may be one which includes a -SO₃H moiety. The amount of residual solvent is preferably less than 1 wt% of the total weight of composite material.

Said composite material may include at least 0.1 wt%, preferably at least 0.2wt%, more preferably at least 0.3wt% of nanoparticles, for example fullerene moieties, especially SWNTs. Advantageously, the process of the first aspect may be used to make composite materials having up to 20 wt% of said nanoparticles, for example 1 to 20 wt%, preferably 2 to 5wt% of nanoparticles.

In one embodiment, said composite material described herein may comprise a major amount of a single polymeric material all of which is suitably dissolved in said solvent in step (i) of the method of the first aspect. In another embodiment, a composite material may be prepared which comprises polymeric material in step (c) and other polymeric material introduced into the composite material in another step. Thus, the process of the first aspect may include the optional step of contacting, in a step subsequent to step (c) , a further polymeric material with said composite material in order to form a further composite material. In the optional step, the further polymeric material may be the same or different to the polymeric material precipitated in step (c) . Preferably, the majority of polymeric material (s) in the composite material comprises a said polymeric material present in step (c) .

The invention extends, in a third aspect, to a method of making a second composite material which comprises:

(i) selecting a composite material (herein referred to as "said first composite material") prepared according to said first aspect; and

(ii) contacting said first composite material with further polymeric material in order to prepare said second composite material.

The method may be used to reduce the wt% of nanoparticles in said first composite material and/or to incorporate into said first composite material different types of polymers.

Said polymeric material (hereinafter "said first polymeric material") in said first composite material may be any of the polymeric materials described according to the first aspect. Said polymeric material is preferably melt processible. Its degradation temperature is suitably- higher than its melting point (suitably by at least 10⁰C, preferably by at least 20⁰C) so that it can be extruded without significant degradation. Said first polymeric material is preferably a polyaryletherketone (especially selected from polyetheretherketone, polyetherketone and polyetherketoneketone) , a polyarylethersulphone (especially polyethersulphone) and polysulphone . In the most preferred embodiment said first polymeric material is polyetheretherketone or polyetherketone.

Said further polymeric material may be any of the polymeric materials described according to the first aspect. Said further polymeric material is preferably melt processible. Its degradation temperature is suitably higher than its melting point (suitably by at least 1O⁰C, preferably by at least 20⁰C) so that it can be extruded without significant degradation. Said further polymeric material may be selected from polyaryletherketones, polyarylether sulphones, polyetherimides and PBI provided the selected material is melt processible. In one embodiment, said first polymeric material in said first composite material and said further polymeric material may be the same. For example, both may be polyetheretherketone or polyetherketone. In this case, the material may be used to adjust the level of nanoparticles in the first composite material to a desired level. In another embodiment, said polymeric material in said first composite material and said further polymeric materials may be different. For example, said first polymeric material in said first composite material could be a polyaryletherketone, especially polyetheretherketone or polyetherketone and said further polymeric material could be a polyetherimide. In one embodiment, said first polymeric material in said first composite material may be one which is generally more soluble in solvents than said further polymeric material. For example, said first polymeric material may be amorphous. It may for example comprise a polyetherimide or polyethersulphone. Said further polymeric material may have some cystallinity and may be any such polymers described herein. In preferred embodiments it may comprise moieties I, II and/or III as described. In this case, it may be easier to produce a solution of the first polymeric material and disperse nanoparticles therein and thereby prepare a composite material which may subsequently be blended, for example melt blended, with said further polymeric material to produce a said second composite material.

Said second composite material may be prepared by melt processing said first composite material and said further polymeric materials together at a temperature in the range 300 to 400⁰C, preferably in the range 340 to 400⁰C, more preferably in the range 340 to 380⁰C.

In the process of making said second composite material, the ratio of the weight of said first composite material to that of said further polymeric material contacted in step (ii) is suitably less than 1, is preferably less than 0.75 and more preferably is less than 0.5. The ratio may be at least 0.05, preferably at least 0.1.

In step (ii) said first composite material and further polymeric material are preferably contacted at an elevated temperature, suitably of greater than 5O⁰C, preferably greater than 100⁰C, more preferably greater than 200⁰C, especially at greater than 300⁰C. The temperature preferably does not exceed 500⁰C, more preferably does not exceed 450⁰C during step (ii) .

Preferably, step (ii) includes the use of an extruder, for example a twin-screw extruder. Thus, step (ii) preferably involves subjecting said first composite material and said further polymeric material to an elevated temperature and high shear.

The process of the first or third aspects may involve blending one or more fillers with the polymeric materials. Examples of fillers include fibrous fillers, such as inorganic fibrous materials such as glass fiber, asbestos fiber, silica fiber, alumina fiber, zirconia fiber, boron nitride fiber, silicon nitride fiber, boron fiber and potassium titanate fiber and high-melting organic fibrous materials such as polyamide, fluorocarbon resins, polyester resins and acrylic resins. Other fillers may be non-fibrous fillers such as mica, silica, talc, alumina, kaolin, calcium sulfate, calcium carbonate, titanium oxide, ferrite, clay, glass powder, zinc oxide, nickel carbonate, iron oxide, quartz powder, magnesium carbonate and barium sulfate. The non-fibrous fillers are generally in the form of powder or flaky particles.

The invention extends, in a fourth aspect, to a composite material prepared in a process described herein.

The invention extends, in a fifth aspect, to a composite material comprising a first polymeric material which is amorphous and/or is a polyetherimide or polyethersulphone and a further polymeric material which may have some crystallinity and may be a polymer which comprises moieties I, II and/or III as described herein.

The invention extends to a composite material comprising polyetheretherketone and at least 0.1 wt% of nanoparticles, for example fullerene moieties.

Said composite material may include at least 0.5 wt%, preferably at least 1 wt%, more preferably 1 to 20 wt%, especially 1 to 5 wt% of nanoparticles.

The invention extends to a composite material comprising a first polymeric material (suitably as described above, preferably polyetheretherketone) , a further polymeric material (suitably as described above, preferably polyetherimide) and nanoparticles, for example fullerene moieties .

The composite materials described herein may be used for producing materials with improved thermal, electrical and wear characteristics. They may be used to produce materials with improved mechanical properties, surface finish, lower diffusion rates and improved recyclability .

Some composite materials described herein (e.g. which include fullerene moieties) may be used in electrostatic discharge (ESD) or as anti-static applications. The invention extends to the use of a composite material described for electrostatic discharge or in an anti-static application. The invention extends to an ESD tube or ESD film for example for a photocopier or printer; a wafer carrier, for example a silicon wafer carrier; a chip carrier tray, for example a silicon chip carrier tray; or a test socket for example for testing silicon chips, incorporating a composite material as described herein.

Any feature of any aspect of any invention or embodiment described herein may be combined with any feature of any aspect of any other invention or embodiment described herein mutatis mutandis.

Specific embodiments of the invention will now be described by way of example.

SWNTs - refers to "single-walled nanotubes" obtained from Carbon Nanotechnologies, Inc of Houston, USA. MWNTs - refers to "multi-walled nanotubes" obtained from Hyperion Catalysis of Cambridge, USA.

Example 1 - Preparation of composite of polyetherketone and SWNTs

A 250ml round-bottomed flask was charged with SWNTs (O.lg) and 98% sulphuric acid (200g/108ml) . The flask was immersed in an ultrasonic bath, heated to 50⁰C and was sonicated at this temperature for 1 hour. Polyetherketone granules (1Og) , obtained from Victrex PIc of UK, were then added with stirring. The mixture was sonicated at 60⁰C for a further 2 hours to produce a polyetherketone/acid solution with dispersed SWNTs. The polyetherketone/SWNT composite was isolated by re-precipitation by dripping it into demineralised water (IL) through a PTFE colander, to yield black beads. These beads were then washed with further IL portions of water until the conductivity of the washings was below lOμS. The wet beads were dried in a circulating air oven. Example 2 - Reprocessing of polyetherketone/SWNT composite with further polyetheretherketone

The procedure of Example 1 was repeated to produce 20Og of the polyetherketone compound containing 5 wt% SWNTs. The polyetherketone/SWNT compound (20Og) was blended with polyetherketone (PEEK HT™ 22P, Victrex pic) (180Og) using a ZSK 25 WLE Twin Screw Extruder to produce a compound containing 0.5wt% SWNTs.

Example 3- Reprocessing of polyetherketone/SWNT composite with polyetheretherketone

The procedure of Example 1 was repeated to produce lOOg of the polyetherketone compound containing 5 wt% SWNTs. The polyetherketone/SWNT compound (10Og) was blended with polyetheretherketone (PEEK™ 450P, Victrex pic) (190Og) using a ZSK 25 WLE Twin Screw Extruder to produce a compound containing 0.25wt% SWNTs.

Example 4 - Preparaton of composite of polyetherketone and MWNTs and reprocessing

The procedure of Example 1 was repeated except the SWNTs were replaced with MWNTs to produce 20Og of polyetherketone compound containing 5 wt% MWNTs. The polyetherketone/SWNT compound (20Og) was blended with polyetherketone (PEEK HT™ 22P, Victrex pic) (1800g) using a ZSK 25 WLE Twin Screw Extruder to produce a compound containing 0.5wt% SWNTs. Example 5 - Preparation o_f composite of polyetheretherketone and SWNTs

The procedure of Example 1 was repeated except the 98% sulphuric acid (200g/108ml) was replaced with methane sulphonic acid (20Og) and the PEEK HT granules were replaced with polyetheretherketone (PEEK™ 450P, Victrex pic) to produce a PEEK/SWNT compound containing 1 wt% SWNTs.

Example 6 - Preparation of polyethersulpone/SWNT composite followed by reprocessing

The procedure of Example 1 was repeated except the PEEK HT was replaced with polyethersulphone (BASF, Ultrason 3010) on a scale to produce lOOg of PES/SWNT compound containing

5wt% of SWNTs. The PES/SWNT compound (10Og) was blended with polyethersulphonee (BASF, Ultrason 3010) (190Og) using a ZSK 25 WLE Twin Screw Extruder to produce a compound containing 0.25wt% SWNTs.

Example 7 - Preparation of composite of polyetheretherketone/polyetherimide and SWNTs

A 1000ml round-bottomed flask was charged with SWNTs (5g) and N-methylpyrollidinone (NMP) (900ml) . The flask was immersed in an ultrasonic bath, heated to 50⁰C and was sonicated at this temperature for 1 hour. Polyetherimide granules (95g) (Ultem 1000, from General Electric_. Company), were then added with stirring. The mixture was sonicated at 6O⁰C for a further 2 hours to produce a polyetherimide/NMP solution with dispersed SWNTs. The polyetherimide/SWNT composite was isolated by re- precipitation by dripping it into demineralised water (5L), to yield black beads. These beads were then washed with further IL portions of water to remove the residual NMP. The wet beads were dried in a circulating air oven. The polyetherimide/SWNT compound (10Og) was blended with polyethereetherketone (PEEK 450P, Victrex pic) (90Og) using a ZSK 25 WLE Twin Screw Extruder to produce a compound containing 0.5wt% SWNTs.

By processes analogous to the processes in the aforementioned examples, composite materials may be prepared comprising other types of nanoparticles.

The invention is not restricted to the details of the foregoing embodiment (s) . The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings) , or to any novel one, or any novel combination, of the steps of any method or process so disclosed.

Claims

1. A method of preparing a composite material which comprises nanoparticles and a polymeric material, the method comprising:

(a) contacting both the polymeric material and nanoparticles in a selected solvent so that said polymeric material dissolves in said solvent; (b) mixing the polymeric material and nanoparticles in said solvent; and

(c) removing said solvent to produce said composite material .

2. A method according to claim 1, wherein said composite material comprises a said polymeric material which defines a matrix and additional material distributed within the matrix wherein a major amount of said additional material is comprised of said nanoparticles.

3. A method according to claim 1 or claim 2, wherein the ratio of the weight of nanoparticles to polymeric material contacted in step (a) is at least 0.001 and is less than 0.3.

4. A method according to any preceding claim, wherein the method includes a step (a)* prior to step (a) of contacting the nanoparticles in said solvent and dispersing said nanoparticles therein.

5. A method according to claim 4, wherein the step (a)* includes directing an oscillating energy source into the solvent .

6. A method according to any preceding claim, wherein said polymeric material is miscible with polyaryletherketones .

7. A method according to any preceding claim, wherein said polymeric material is selected from polyaryletherketones, polyarylethersulphones, polyetherimides and PBI .

8. A method according to any preceding claim, wherein said polymeric material is of the type which includes:

(i) phenyl moieties; (ii) ketone and/or sulphone moieties; and (iii) ether and/or thioether moieties.

9. A material according to any preceding claim, wherein said polymeric material is a homopolymer having a repeat unit of formula

or a homopolymer having a repeat unit of general formula

V

or a homopolymer having a repeat unit of general formula

homopolymer having a repeat unit of general formula

or a random or block copolymer of at least two different units of IV and/or V; or at least two different units of IV* and/or V*; wherein A, B, C, D independently represent 0 or 1 and wherein m,r,s,t,v,w and z independently represent zero or a positive integer, E and E' independently represent an oxygen or a sulphur atom or a direct link, G represents an oxygen or sulphur atom, a direct link or a -O-Ph-0- moiety where Ph represents a phenyl group and Ar is selected from one of the following moieties (i)*, (i)**, (i) to (x) which is bonded via one or more of its phenyl moieties to adjacent moieties

10. A material according to any preceding claim, wherein said polymeric material is selected from polyetheretherketone, polyetherketone, polyetherketoneketone, polyetherketoneetherketoneketone, polyetheretherketoneketone, polyethersulphone and polysulphone .

11. A method according to any preceding claim, wherein said polymeric material is a homopolymer or copolymer which includes a repeat unit selected from: ether-phenyl-ether-phenyl-ketone-phenyl - ether-phenyl-ketone-phenyl- ether-phenyl-ketone-phenyl-ketone-phenyl- ether-pheny1-ketone-phenyl-ether-phenyl-ketone pheny1-ketone-phenyl- ether-phenyl-ether-phenyl-ketone-phenyl-ketone -phenyl- ether-pheny1-sulphone-phenyl- ether-phenyl-C (CH₃) ₂-phenyl-ether-phenyl-sulphone- phenyl .

12. A method according to any preceding claim, wherein said polymeric material is a homopolymer or copolymer which includes a repeat unit selected from ether-phenyl- ether-phenyl-ketone-phenyl, ether-phenyl-ketone-phenyl and ether-phenyl-sulphone-phenyl units .

13. A method according to any preceding claim, wherein said solvent is a strong acid.

14. A mixture formed in step (b) of the method of any preceding claim.

15. A mixture according to claim 14 which comprises nanoparticles, at least one polymeric material selected from polyetheretherketone, polyetherketone and polyethersulphone and a solvent which includes a -SO₃H moiety.

16. A composite material which includes a polymeric material, nanoparticles and residual solvent.

17. A method of making a second composite material which comprises:

(i) selecting a composite material (herein referred to as "said first composite material") prepared according to any of claims 1 to 13; and

18. A composite material comprising a first polymeric material which is amorphous and/or is a polyetherimide or polyethersulphone and a further polymeric material which has some crystallinity and is a polaryletherketone.

19. A composite material comprising polyetherketherketone and at least 0.1 wt% of nanoparticles.

20. A composite material comprising a first polymeric material, a further polymeric material and nanoparticles.