Polymeric materials

Abstract

A component comprises a first part and a second part, wherein said second part is in contact with said first part, wherein: (i) said first part comprises a first polymer which is semi-crystalline and includes phenylene moieties, carbonyl moieties and ether moieties; (ii) said second part comprises a second polymer which is semi-crystalline and includes phenylene moieties, carbonyl moieties and ether moieties; (iii) the melting temperature (Tm) of the second polymer is less than the melting temperature (Tm) of the first polymer. In a preferred embodiment, said first polymer is polyetheretherketone and said second polymer is a copolymer having a repeat unit of formula VIII and a repeat unit of formula IX.

Claims

1. A component comprising a first part and a second part, wherein said second part is in contact with said first part, wherein: (i) said first part comprises a first polymer which is semi-crystalline and includes phenylene moieties, carbonyl moieties and ether moieties; (ii) said second part comprises a second polymer which is semi-crystalline and includes phenylene moieties, carbonyl moieties and ether moieties and wherein said second polymer includes a repeat unit of formula
O-Ph-O-Ph-CO-Ph-VI and a repeat unit of formula
O-Ph-Ph-O-Ph-CO-Ph-VII wherein Ph represents a phenylene moiety; (iii) the melting temperature (Tm) of the second polymer is less than the melting temperature (Tm) of the first polymer; and wherein said first part is overmoulded onto said second part such that said first part is at least partially around said second part.

2. The component according to claim 1, wherein the level of crystallinity in said first polymer is at least 25% and the level of crystallinity in said second polymer is at least 20%.

3. The component according to claim 1, wherein said first polymer is a homopolymer having a repeat unit of general formula ##STR00009## or a random or block copolymer of at least two different units of IV, wherein A and B independently represent 0 or 1, and wherein m, r, s and w independently represent zero or a positive integer, E and E independently represent an oxygen atom or a direct link, G represents an oxygen atom, a direct link or a O-Ph-O moiety where Ph represents a phenyl group and Ar is selected from one of the following moieties (i)**, (i) to (iv) which is bonded via one or more of its phenyl moieties to adjacent moieties ##STR00010##

4. The component according to claim 1, wherein said first polymer comprises a repeat unit of formula (XX) ##STR00011## where t1, and w1 independently represent 0 or 1 and v1 represents 0, 1 or 2, and optionally wherein t1=1, v1=0 and w1=0.

5. The component according to claim 1, wherein said second polymer is a homopolymer having a repeat unit of general formula ##STR00012## or a random or block copolymer of at least two different units of IV, wherein A and B independently represent 0 or 1, and wherein m, r, s and w independently represent zero or a positive integer, E and E independently represent an oxygen atom or a direct link, G represents an oxygen atom, a direct link or a O-Ph-O moiety where Ph represents a phenyl group and Ar is selected from one of the following moieties (i)**, (i) to (iv) which is bonded via one or more of its phenyl moieties to adjacent moieties ##STR00013##

6. The component according to claim 1, wherein said repeat units VI and VII are in the relative molar proportions VI:VI I of from 65:35 to 95:5.

7. The component according to claim 1, wherein the following relationship applies in relation to the second polymer:
log 10(X %)>1.500.26 MV; wherein X % refers to the % crystallinity.

8. The component according to claim 1, wherein said repeat unit of formula VI has the structure ##STR00014## and said repeat unit of formula VII has the structure ##STR00015## and optionally wherein said second polymer includes 68-82 mol % of units of formula VIII and 18-32 mol % of units of formula IX.

9. The component according to claim 1, wherein said first polymer is part of a composition which includes said first polymer and a filler means.

10. The component according to claim 1, wherein said second part comprises a second composition comprising a fabric impregnated with said second polymer.

11. The component according to claim 1, wherein said component is selected from a bracket, window frame, pipe, connector, panel and CMP ring.

12. The component of claim 1, wherein the melting temperature (Tm) of the second polymer is at least 10 C. less than the melting temperature (Tm) of the first polymer.

13. The component of claim 1, wherein the melting temperature (Tm) of the second polymer is at least 35 C. less than the melting temperature (Tm) of the first polymer.

14. An aerospace component suitable for use in aerospace applications, the aerospace component comprising the component of claim 1.

15. A method of making a component comprising a first part and a second part, wherein said second part is in contact with said first part, wherein: (i) said first part comprises a first polymer which is semi-crystalline and includes phenylene moieties, carbonyl moieties and ether moieties; (ii) said second part comprises a second polymer which is semi-crystalline and includes phenylene moieties, carbonyl moieties and ether moieties and wherein said second polymer includes a repeat unit of formula
O-Ph-O-Ph-CO-Ph-VI and a repeat unit of formula
O-Ph-Ph-O-Ph-CO-Ph-VII wherein Ph represents a phenylene moiety; (iii) the melting temperature (Tm) of the second polymer is less than the melting temperature (Tm) of the first polymer; and wherein said first part is overmoulded onto said second part, the method comprising: (a) selecting said second part comprising said second polymer; (b) selecting said first part comprising said first polymer or a precursor of said first part which comprises said first polymer; and (c) overmoulding said first part or said precursor onto said second part.

16. The method according to claim 15, wherein, in step (c), said first polymer is at a temperature which is greater than its Tm.

17. The method according to claim 15, the method including introducing said second part into a tool and contacting said second part with a precursor of said first part in said tool, and optionally wherein said tool is an injection moulding tool.

18. The method according to claim 15, wherein said first polymer and said second polymer are miscible and/or compatible.

19. The method according to claim 15, wherein said second polymer at a surface of the second part is melted after said second part is contacted with said first part, but a region of the second part inwards of said surface is not melted.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Specific embodiments of the invention will now be described, by way of example, with reference to the following drawings, in which:

(2) FIG. 1 is a representation of a gear;

(3) FIG. 2 is a perspective view of a bracket;

(4) FIG. 3 is a perspective view of a rear plate of the bracket of FIG. 4;

(5) FIG. 4 is a perspective view of a front plate of the bracket;

(6) FIG. 5 is a perspective view of a fillet of the bracket;

(7) FIGS. 6 and 7 are perspective views of alternative brackets;

(8) FIG. 8 is a schematic representation of a laminar structure including a honeycomb layer, prior to assembly; and

(9) FIG. 9 is a schematic representation of the laminar structure of FIG. 8 after assembly.

DETAILED DESCRIPTION

(10) The following materials are referred to hereinafter:

(11) Victrex 450Grefers to polyetheretherketone (PEEK) obtained from Victrex Manufacturing Limited.

(12) Victrex 90HMF40refers to PEEK having a melt viscosity of 0.09 KNsm.sup.2 with 40 wt % high modulus short carbon fibres.

(13) Preferred polymeric materials for use in embodiments described herein were prepared as described in Examples 1 to 10 and the properties assessed as described subsequently.

Examples 1 to 10Preparation of Polyetheretherketone (PEEK)-Polyetherdiphenyletherketone (PEDEK) Copolymer

(14) A 300 liter vessel fitted with a lid, stirrer/stirrer guide, nitrogen inlet and outlet was charged with diphenylsulphone (125.52 kg) and heated to 150 C. Once fully melted 4,4-diflurobenzophenone (44.82 kg, 205.4 mol), 1,4-dihydroxybenzene (16.518 kg, 150 mol) and 4,4-dihydroxydiphenyl (9.311 kg, 50 mol) were charged to the vessel. The contents were then heated to 160 C. While maintaining a nitrogen blanket, dried sodium carbonate (21.368 kg, 201.6 mol) and potassium carbonate (1.106 kg, 8 mol), both sieved through a screen with a mesh of 500 micrometers, were added. The D50 of the sodium carbonate was 98.7 m. The temperature was raised to 180 C. at 1 C./min and held for 100 minutes. The temperature was raised to 200 C. at 1 C./min and held for 20 minutes. The temperature was raised to 305 C. at 1 C./min and held until desired melt viscosity was reached, as determined by the torque rise of the stirrer. The required torque rise was determined from a calibration graph of torque rise versus MV. The reaction mixture was poured via a band caster into a water bath, allowed to cool, milled and washed with acetone and water. The resulting polymer powder was dried in a tumble dryer until the contents temperature measured 112 C.

(15) Table 1 below includes a summary of Examples 1 to 10. D50 as described herein was determined as described in Example 11.

Example 11General Procedure for Determining D50

(16) The D.sub.50 of sodium carbonate was determined by Malvern Laser Diffractometer, using the associated Mastersizer 3000 software. A Fraunhofer type process was used to eliminate the requirement of refractive index figures for the samples. Using the Mastersizer 300 software, the following instrument parameters were set:

(17) TABLE-US-00001 Scattering Model Fraunhofer Background measurement duration 10.00 s Sample measurement duration 10.00 s Number of measurements 2 Obscuration low limit 1% Obscuration high limit 6% Obscuration time out 5.00 s Air Pressure 1.5 barg Feed Rate 17% Venturi type Standard venturi disperser Hopper gap 2.00 mm Analysis model General Purpose

(18) A dried sample (<5 g) of carbonate was scooped into the hopper at the top of the machine. A background measurement was run, and then two sample measurements were taken. The feed rate was started at 17%, but was manually adjusted as the measurement was taken to ensure the obscuration measurement sat within the 1-6% limits.

(19) The quantity of potassium carbonate used in Examples 1 to 10 was 4 mole % which is defined as:

(20) $\frac{\mathrm{the}\mathrm{number}\mathrm{of}\mathrm{moles}\mathrm{of}\mathrm{potassium}\mathrm{carbonate}}{\mathrm{the}\mathrm{total}\mathrm{moles}\mathrm{of}\mathrm{hydoxy}\mathrm{monomer}\left(s\right)\mathrm{used}}100\%$

(21) Melt viscosity (MV) referred to in Table 1 may be determined as described in Example 12.

Example 12Determination of Melt Viscosity (MV) of Polymer

(22) Unless otherwise stated, this was measured using capillary rheometry operating at 340 C. at a shear rate of 1000 s.sup.1 using a tungsten carbide die, 0.5 mm3.175 mm. The MV measurement was taken 5 minutes after the polymer had fully melted, which is taken to be 5 minutes after the polymer is loaded into the barrel of the rheometer.

(23) TABLE-US-00002 TABLE 1 Example MV No. (@ 340 C.) 1 0.25 2 0.203 3 0.258 4 0.283 5 0.324 6 0.222 7 0.26 8 0.269 9 0.186 10 0.295

Example 13Differential Scanning Calorimetry of Polyaryletherketones of Examples 1 to 10

(24) Crystallinity (as reported in Table 2) may be assessed by several methods for example by density, by it spectroscopy, by x ray diffraction or by differential scanning calorimetry (DSC). The DSC method has been used to evaluate the crystallinity that developed in the polymers from Examples 1-10 using a Mettler Toledo DSC1 Star system with FRS5 sensor.

(25) The Glass Transition Temperature (Tg), the Melting Temperature (Tm) and Heat of Fusions of Melting (Hm) for the polymers from Examples 1 to 10 were determined using the following DSC method.

(26) A dried sample of each polymer was compression moulded into an amorphous film, by heating 7 g of polymer in a mould at 400 C. under a pressure of 50 bar for 2 minutes, then quenching in cold water producing a film of dimensions 120120 mm, with a thickness in the region of 0.20 mm. An 8 mg plus or minus 3 mg sample of each film was scanned by DSC as follows: Step 1 Perform and record a preliminary thermal cycle by heating the sample from 30 C. to 400 C. at 20 C./min. Step 2 Hold for 5 minutes. Step 3 Cool at 20 C./min to 30 C. and hold for 5 mins. Step 4 Re-heat from 30 C. to 400 C. at 20 C./min, recording the Tg, Tn, Tm, Hn and Hm.

(27) From the DSC trace resulting from the scan in step 4, the onset of the Tg was obtained as the intersection of the lines drawn along the pre-transition baseline and a line drawn along the greatest slope obtained during the transition. The Tn was the temperature at which the main peak of the cold crystallisation exotherm reaches a maximum. The Tm was the temperature at which the main peak of the melting endotherm reached a maximum.

(28) The Heat of Fusion for melting (Hm) was obtained by connecting the two points at which the melting endotherm deviates from the relatively straight baseline. The integrated area under the endotherm as a function of time yields the enthalpy (mJ) of the melting transition: the mass normalised heat of fusion is calculated by dividing the enthalpy by the mass of the specimen (J/g). The level of crystallisation (%) is determined by dividing the Heat of Fusion of the specimen by the Heat of Fusion of a totally crystalline polymer, which for polyetheretherketone is 130 J/g.

(29) Results are provided in Table 2.

(30) TABLE-US-00003 TABLE 2 Level of Polymer Tg Tm H.sub.m Crystallinity from Example ( C.) ( C.) (J/g) (%) 1 150.42 304.57 38.77 29.83 2 149.6 305.58 39.88 30.68 3 150.03 306.45 36.99 28.45 4 150.86 306.32 37.19 28.6 5 150.84 306.41 36.56 28.12 6 150.2 307.68 36.82 28.32 7 150.34 306.67 39.84 30.65 8 150.21 307.03 35.47 27.28 9 150.03 306.72 39.64 30.49 10 150.11 292.36 43.03 33.11

Example 14Preparation of PEEK-PEDEK Blend

(31) A dry powder blend of the polymers from Examples 6, 7 and 8 was made to produce a material of MV=0.25 KNsm.sup.2, a Tg of 149 C., a Tm of 302 C. and a crystallinity of 28.4%.

Example 15Preparation of Pre-Consolidated Fabric Based Composite Incorporating PEEK-PEDEK Copolymer

(32) A powderous blend as described in Example 14 was sprinkled onto one surface of a woven de-sized carbon fabric and the copolymer heated such that it fuses and bonds to the surface of the fabric. This was repeated for the other side of the fabric to produce a semi-preg. Layers of this material were cut, laid up and compression moulded, with the typical processing temperature being about 340 C.

Example 16Testing of Composite of Example 15

(33) Two tests (described below) were carried out on composite laminate approximately 2 mm thick of the type described in Example 15. Samples of the laminate were placed into a 150 mm150 mm4 mm plaque tool and Victrex 450G was injection moulded onto the surface of the laminate. The work was carried out using an Engel 740/220e injection moulding machine. (i) A sample of the laminate 150 mm150 mm was preheated to 250 C. in an oven and placed into the tool of the moulding machine, the tool being at 200 C. Victrex 450G was moulded onto the surface of the laminate. A section approximately 30 mm long had limited adhesion at the end of the plaque furthest away from the gate location. A screw driver was inserted into the gap between the laminate and the Victrex 450G and an attempt was made to break the bond formed. This proved to be impossible, the composite material kinking rather than any bond failing. (ii) A sample of laminate approximately 100 mm150 mm was preheated to 250 C. in an oven and inserted into the tool of an injection moulding machine, the tool being at 200 C. Victrex 450G was moulded onto the laminate such that there was a region approximately 50 mm long between the gate and the laminate. The bond formed was good over the whole surface of the laminate and attempts to break the bond resulted in the Victrex 450G layer fracturing, the fracture partially running across the bonded area with no loss of adhesion or delamination.

Examples 17Testing of Overmoulded Samples

(34) Samples for testing were made by moulding a 2 mm thick plaque from the PEEK-PEDEK copolymer of Example 14. This plaque was placed in an injection moulding tool, heated to a temperature of about 200 C., and overmoulded with a 2 mm thick layer of material comprising PEEK. In Examples 19 and 20, the PEEK-PEDEK plaque was pre-heated prior to introduction into the tool; Example 18 was introduced into the tool at ambient temperature.

(35) Strips 10 mm wide were cut from the overmoulded plaques and subjected to a three-point bend test with a span of 80 mm. Results are provided in Table 3 below. A corresponding 4 mm thick, 10 mm wide test bar of Victrex 450G was also subjected to the same test. This result is shown in Table 4 below.

(36) TABLE-US-00004 TABLE 3 Materials Flex Flex Flex Maximum Flexural Exam- PEEK- Strength Strain Modulus Stress ples PEDEK PEEK (MPa) (%) (GPa) Load (N) Strain (%) 18 Example 14 VICTREX 157 11.4 3.52 277 7.8 Material 450G 19 Example 14 VICTREX 151 17.4 3.35 268 7.7 Material 90HMF40 20 Example 14 VICTREX 194 2.4 9.30 345 2.4 Material 90HMF40

(37) TABLE-US-00005 TABLE 4 Flex Flex Flex Maximum Flexural Exam- Strength Strain Modulus Stress ple Material (MPa) (%) (GPa) Load (N) Strain (%) C1 Victrex 149 16.0 3.38 265 7.5 450G

(38) The results show the mechanical properties of Examples 18 to 20 are comparable (or in many cases improved) over the results for comparative Example C1. Furthermore, for each of Examples 18 to 20, under the conditions, there was no delamination between the first and second parts.

(39) The combination of polymeric materials described may have wide-ranging applications as described below:

(40) (i) As an alternative to the use of fabric based composite laminates as described in Example 15, composite panels may be made from unidirectional (UD) tape incorporating PEEK-PEDEK copolymer.

(41) (ii) A composite panel comprising PEEK (alone or in combination with fillers, especially fibres) could be manufactured. Initially, a composite panel comprising a PEEK-PEDEK pre-preg on one or more surfaces would be made and the combination overmoulded using a PEEK-based injection moulding compound so the PEEK forms a strong bond with the PEDEK layer as described.

(42) iii) In general terms, complex 3-D parts may be formed by inserting relatively simple composite panels and bonding them together, with the addition of stiffeners and/or other structural components, by overmoulding them. Referring to FIGS. 2 to 5, a bracket comprises a rear plate 32 and front plate 34 both of which comprise a pre-cut composite laminate which includes PEEK-PEDEK copolymer with an injection moulded fillet 36. The bracket may be made by positioning plates 32, 34 in an injection moulding tool and the fillet 36 injected using a filled or un-filled PEEK thereby joining the plates together.

(43) An alternative bracket 40, shown in FIG. 6, comprises a T-shaped composite insert 42 comprising laminated filled components 44, 46 which include PEEK-PEDEK copolymer. The insert 42 is completely overmoulded with PEEK or a PEEK-filled polymer to define the structure shown. The FIG. 7 embodiment is similar to the FIG. 6 embodiment, except that the insert 42 is only partially overmouldedthat is, it is not over-moulded on its lower face 48.

(44) (iv) The combination of materials may be used in chemical-mechanical planarization (CMP) rings. There is a problem with CMP rings in that the desired materials of construction that come into contact with the grinding media must introduce no contamination to the surface of the wafers being polished. If relatively low modulus materials are used the rings can distort under load and this tends to result in the edges of the wafer being polished more than the central regions. In order to obtain a uniform polishing process across the whole face of the wafer a stiff, high modulus, support for the low modulus material is required. This can be achieved by moulding using mechanical fits to ensure that the low modulus and high modulus materials remain as a single component or by the use of metals. An example of the ring construction can be seen in WO1999062672A1. The ability to mould PEEK onto a support part comprising filled PEEK/PEDEK would mean that the desired ring performance could be achieved in a straight forward manner. For example, the area of the ring in contact with the polishing system could be made exclusively from PEEK and other parts of the ring which need to be very stiff could be made from a filled PEEK-PEDEK copolymer. It would also be feasible to machine the PEEK surface off the PEEK/PEDEK support and remould at a later date so that the rings could easily be refurbished.

(45) (v) The combination of materials may be used in making gears. Referring to FIG. 1, a gear 20 comprises an internal support 22 which is arranged to be mounted on a shaft (not shown). The support 22 may be made from the PEEK-PEDEK copolymer incorporating 30 wt % carbon fibre. The support could be overmoulded with unfilled PEEK to define teeth 24 to produce a gear which: has a compliant tooth contact face and so noise would be reduced compared to a comparable gear which is made wholly from a carbon fibre filled polymeric material. has a stiff base tooth form which will increase the torque transmission capability of the gear; and is cheaper to produce compared to known gears which include a metal support and polymer-based teeth mechanically coupled to the support.

(46) (vi) The combination of materials may have wide-range applications for aerospace components. For example, aircraft window frames could be made from a first substantially planar part comprising fibre filled PEEK-PEDEK and more complex elements of the frame can be overmoulded using optionally-filled PEEK.

(47) In general terms, relatively simple planar laminates comprising PEEK-PEDEK copolymer and fibres may be produced; and then overmoulded with PEEK, optionally containing fillers, to define more complex 3D shapes, with the bond between the copolymer and the PEEK being extremely strong.

(48) (vii) Galvanic corrosion may be reduced. This is a problem in many large structures such as aircraft. Whilst carbon fibre composite does not in itself cause galvanic corrosion, it is a poor electrical conductor and so can carry small currents between dissimilar metals which will be subject to galvanic corrosion. The usual technique to overcome this problem is to use a layer of glass filled composite on the surface of the composite component, this acting as an electrically insulating layer. However, the use of glass fibre can be avoided. For example, in the case of a composite bracket comprising PEEK-PEDEK and carbon fibre, a glass-filled composite can be replaced by an overmoulded layer comprising 100% PEEK which is itself an excellent insulator and also serves to reduce the weight of the bracket.

(49) (viii) Thick components may be produced with limited residual stress. In this regard, known components manufactured from polyaryletherketones (PAEKs), such as PEEK, can exhibit large amounts of residual stress. This is particularly true where the components have thick cross-sections because, during manufacture, the cooling rate in the centre of a cross-section is slow which results in relatively high levels of crystallinity in the centre, leading to shrinkage.

(50) The ability to manufacture thick components in two stages could reduce the level of residual stress within the components. Examples of possible applications would be thick walled pipes where PEEK could be extruded over a pre-formed primary pipe made from PEEK-PEDEK copolymer. The physical properties of PEEK-PEDEK copolymer are not dissimilar to those of PEEK so most of the desired properties, for example chemical and abrasion resistance, would be retained but thicker walls could be produced.

(51) Many downhole connectors use PAEKs for the encapsulation of metal pins in the connector. The thickness of the PEEK around the pin can often be very thick, often greater than 10 mm, and this presents problems when manufacturing the connectors using injection moulding. The section thickness and the inability to pack out the thick sections adequately can often result in voidage within the mouldings. If the pin was overmoulded in two stages, the problem of voidage could be overcome. The initial moulding would be with PEEK-PEDEK copolymer to produce a moulding with half the insulation thickness. This would then be placed into another tool so that the PEEK-PEDEK copolymer could be overmoulded with PEEK to produce the finished component with the full thickness of insulation. The overmoulding could be configured to fully encapsulate the PEEK-PEDEK copolymer if required. The formation of a good leak-free interface between the polymer layers is essential in such components. Evidence suggests that with PEEK and PEEK-PEDEK copolymer a very good bond is formed and so there will be no leakage path between the materials.

(52) (ix) The PEEK-PEDEK copolymer may be used in the manufacture of honeycomb based structures. FIG. 8 shows a light-weight honeycomb core 50 made from PEEK-PEDEK. On opposite sides of the core 50 are shown composite structures 52 each of which comprise a composite skin 54 made from PEEK and carbon fibre and a film layer 56 made from PEEK-PEDEK. The components shown in FIG. 8 may be pressed together and heated through the skins 54 to melt the film layers 56 so that the core 50 fuses to the composite structure 52, to define a structure as shown in FIG. 9.

(53) 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.