Polymeric material and use thereof

Abstract

A polyaryletherketone PAEK polymeric material and use thereof is disclosed, the polymeric material comprising a homopolymer and/or a copolymer, suitable for use in an additive manufacturing process to make an object. The PAEK polymeric material has a shear viscosity, SV, of at least 145 Pa.Math.s and less than 350 Pa.Math.s, measured using capillary rheometry operating at 400 C. at a shear rate of 1000 s.sup.1 using a circular cross-section tungsten carbide die, 0.5 mm (capillary diameter)8 mm (capillary length). The PAEK polymeric material has an isothermal crystallinity half life, T.sub.1/2, of greater than 12 minutes at a temperature of 280 C., measured by Differential Scanning Calorimetry, DSC.

Claims

1. A polyaryletherketone PAEK polymeric material comprising a homopolymer and/or a copolymer, suitable for use in an additive manufacturing process to make an object, wherein the PAEK polymeric material has a shear viscosity, SV, of at least 145 Pa.Math.s and less than 350 Pa.Math.s, measured using capillary rheometry operating at 400 C. at a shear rate of 1000 s.sup.1 using a circular cross-section tungsten carbide die, 0.5 mm (capillary diameter)8 mm (capillary length), and wherein the PAEK polymeric material has an isothermal crystallinity half life, T.sub.1/2, of greater than 12 minutes at a temperature of 280 C., measured by Differential Scanning Calorimetry, DSC.

2. A PAEK polymeric material according to claim 1, wherein a co-monomer unit with a phenyl group is incorporated into the PAEK homopolymer.

3. A PAEK polymeric material according to claim 1, wherein the PAEK polymeric material is a PAEK copolymer.

4. A PAEK polymeric material according to claim 3, wherein, the PAEK copolymer is a polyetherketoneketone, PEKK.

5. A PAEK polymeric material according to claim 3, wherein the copolymer comprises repeat units of formula ##STR00006## and a repeat unit of formula ##STR00007## wherein Ph represents a phenylene moiety, wherein at least 95 mol % of the copolymer repeat units are repeat units of formula I and of formula II; wherein the repeat units I and II have a molar ratio I:II from 60:40 to 80:20.

6. A PAEK polymeric material according to claim 3, wherein the copolymer comprises repeat units of formula ##STR00008## and repeat units of formula ##STR00009## wherein at least 95 mol % of the copolymer repeat units are repeat units of formula III and of formula IV; wherein the repeat units III and IV have a molar ratio III:IV from 60:40 to 80:20.

7. An automated fibre placement process, AFP, comprising applying sequential layers of fibre to form a composite part, wherein the fibre comprises the PAEK polymeric material of claim 1, wherein the PAEK polymeric material has a shear viscosity, SV, of at least 200 Pa.Math.s and less than 280 Pa.Math.s, measured using capillary rheometry operating at 400 C. at a shear rate of 1000 s.sup.1 using a circular cross-section tungsten carbide die, 0.5 mm (capillary diameter)8 mm (capillary length), and wherein the PAEK polymeric material has an isothermal crystallinity half life, T.sub.1/2, of greater than 20 mins and less than 50 mins at 290 C.

8. A powder bed fusion process comprising forming a component from a polymeric material in a layer by layer process, wherein the polymeric material is the PAEK polymeric material of claim 1, wherein the PAEK polymeric material has a shear viscosity, SV, of at least 240 Pa.Math.s and less than 350 Pa.Math.s, measured using capillary rheometry operating at 400 C. at a shear rate of 1000 s.sup.1 using a circular cross-section tungsten carbide die, 0.5 mm (capillary diameter)8 mm (capillary length), and wherein the PAEK polymeric material has an isothermal crystallinity half life, T.sub.1/2, of greater than 40 mins and less than 80 mins at 290 C.

9. The process according to claim 8, wherein the PAEK polymeric material is a copolymer and has a repeat unit ratio of at least 62:38 and less than 68:32.

10. The process according to claim 9, wherein the copolymer has a particle size distribution, PSD, with a D50 range from 45 to 60 m, a D10>14 m and a D90<136 m.

11. A filled filament fusion fabrication process comprising extruding a filament in layers to form a three-dimensional component, wherein the filament comprises the PAEK polymeric material of claim 1 and further comprises a filler, wherein the PAEK homopolymer or copolymer has a shear viscosity, SV, of at least 145 Pa.Math.s and less than 205 Pa.Math.s, measured using capillary rheometry operating at 400 C. at a shear rate of 1000 s.sup.1 using a circular cross-section tungsten carbide die, 0.5 mm (capillary diameter)8 mm (capillary length), and wherein the PAEK polymeric material has an isothermal crystallinity half life, T.sub.1/2, of greater than 35 mins and less than 75 mins at 290 C.

12. An unfilled filament fusion fabrication process comprising extruding a filament in layers to form a three-dimensional component, wherein the consists essentially of the PAEK polymeric material of claim 1, wherein the PAEK homopolymer or copolymer has a shear viscosity, SV, of at least 200 Pa.Math.s and less than 280 Pa.Math.s, measured using capillary rheometry operating at 400 C. at a shear rate of 1000 s.sup.1 using a circular cross-section tungsten carbide die, 0.5 mm (capillary diameter)8 mm (capillary length), and wherein the PAEK polymeric material has an isothermal crystallinity half life, T.sub.1/2, of greater than 15 mins and less than 45 mins at 290 C.

13. An additive manufacturing process comprising forming an object from a polymeric material according to claim 1 in a layer by layer process.

14. A PAEK polymeric material according to claim 4, wherein the PEKK copolymer comprises a combination of PEKK repeat units whereby a proportion of the PEKK repeat units include-1,4-linkages and a proportion of the PEKK repeat units include-1,3-linkages.

Description

(1) FIG. 1 provides isothermal crystallinity half life values for a number of examples.

EXAMPLE 1PREPARATION OF POLYETHERETHERKETONE (PEEK) POLYETHERDIPHENYLETHERKETONE (PEDEK) COPOLYMER AT 75:25 REPEAT UNIT RATIO

(2) A 0.5 litre flanged Hastelloy pot fitted with a ground glass lid, stirrer/stirrer guide, nitrogen inlet and outlet was charged with 4,4-diflurobenzophenone (110.95 g, 0.508 mol), 1,4-dihydroxybenzene (41.29 g, 0.375 mol), 4,4-dihydroxydiphenyl (23.28, 0.125 mol) and diphenylsulphone (275.00 g) and purged with nitrogen for 1 hour. The contents were then heated under a nitrogen blanket to 160 C. to form an almost colourless solution. Whilst maintaining a nitrogen blanket, dried sodium carbonate (53.00 g, 0.500 mol) and potassium carbonate (2.75 g, 0.020 mol), both sieved through a screen with a mesh size of 500 micrometres, were added. The temperature was raised to 200 C. at a rate of 0.75 C./min and then to 240 C. at a rate of 0.5 C./min before finally being heated to 305 C. at 1 C./min and held for approximately 200 minutes or until the desired SV was reaches as indicted by the torque rise on the stirrer. The required torque rise was determined from a calibration graph of torque rise versus SV. The reaction mixture was then poured into a metal tray, allowed to cool, milled and washed with 2 litres of acetone and then with warm water at a temperature of 40-50 C. until the conductivity of the waste water was <2 S. The resulting polymer powder was dried in an air oven for 12 hours at 120 C.

(3) The resulting polymer had a Shear Viscosity (SV) of 290 Pa.Math.s at a temperature of 400 C. and a shear rate of 1000 s.sup.1, as measured by capillary rheometry.

EXAMPLE 2PREPARATION OF POLYETHERETHERKETONE (PEEK) POLYETHERDIPHENYLETHERKETONE (PEDEK) COPOLYMER AT 70:30 REPEAT UNIT RATIO

(4) A 0.5 litre flanged Hastelloy pot fitted with a ground glass lid, stirrer/stirrer guide, nitrogen inlet and outlet was charged with 4,4-diflurobenzophenone (110.95 g, 0.508 mol), 1,4-dihydroxybenzene (38.55 g, 0.350 mol), 4,4-dihydroxydiphenyl (27.95, 0.150 mol) and diphenylsulphone (275.00 g) and purged with nitrogen for 1 hour. The contents were then heated under a nitrogen blanket to 160 C. to form an almost colourless solution. Whilst maintaining a nitrogen blanket, dried sodium carbonate (53.00 g, 0.500 mol) and potassium carbonate (0.35 g, 2.5310.sup.3 mol), both sieved through a screen with a mesh size of 500 micrometres, were added. The temperature was raised to 200 C. at a rate of 0.75 C./min and then to 240 C. at a rate of 0.5 C./min before finally being heated to 305 C. at 1 C./min and held for approximately 200 minutes or until the desired SV was reaches as indicted by the torque rise on the stirrer. The required torque rise was determined from a calibration graph of torque rise versus SV.

(5) The reaction mixture was then poured into a metal tray, allowed to cool, milled and washed with 2 litres of acetone and then with warm water at a temperature of 40-50 C. until the conductivity of the waste water was <2S. The resulting polymer powder was dried in an air oven for 12 hours at 120 C.

(6) The resulting polymer had a Shear Viscosity (SV) of 122 Pa.Math.s at a temperature of 400 C. and a shear rate of 1000 s.sup.1, as measured by capillary rheometry.

EXAMPLE 3PREPARATION OF POLYETHERETHERKETONE (PEEK) POLYETHERDIPHENYLETHERKETONE (PEDEK) COPOLYMER AT 70:30 REPEAT UNIT RATIO

(7) A 0.5 litre flanged Hastelloy pot fitted with a ground glass lid, stirrer/stirrer guide, nitrogen inlet and outlet was charged with 4,4-diflurobenzophenone (110.95 g, 0.508 mol), 1,4-dihydroxybenzene (38.55 g, 0.350 mol), 4,4-dihydroxydiphenyl (27.95, 0.150 mol) and diphenylsulphone (275.00 g) and purged with nitrogen for 1 hour. The contents were then heated under a nitrogen blanket to 160 C. to form an almost colourless solution. Whilst maintaining a nitrogen blanket, dried sodium carbonate (53.00 g, 0.500 mol) and potassium carbonate (2.75 g, 0.020 mol), both sieved through a screen with a mesh size of 500 micrometres, were added. The temperature was raised to 200 C. at a rate of 0.75 C./min and then to 240 C. at a rate of 0.5 C./min before finally being heated to 305 C. at 1 C./min and held for approximately 200 minutes or until the desired SV was reaches as indicted by the torque rise on the stirrer. The required torque rise was determined from a calibration graph of torque rise versus SV. The reaction mixture was then poured into a metal tray, allowed to cool, milled and washed with 2 litres of acetone and then with warm water at a temperature of 40-50 C. until the conductivity of the waste water was <2 S. The resulting polymer powder was dried in an air oven for 12 hours at 120 C.

(8) The resulting polymer had a Shear Viscosity (SV) of 131 Pa.Math.s at a temperature of 400 C. and a shear rate of 1000 s.sup.1, as measured by capillary rheometry.

EXAMPLE 4PREPARATION OF POLYETHERETHERKETONE (PEEK) POLYETHERDIPHENYLETHERKETONE (PEDEK) COPOLYMER AT 65:35 REPEAT UNIT RATIO

(9) A 0.5 litre flanged Hastelloy pot fitted with a ground glass lid, stirrer/stirrer guide, nitrogen inlet and outlet was charged with 4,4-diflurobenzophenone (110.95 g, 0.508 mol), 1,4-dihydroxybenzene (35.82 g, 0.325 mol), 4,4-dihydroxydiphenyl (32.58, 0.175 mol) and diphenylsulphone (275.00 g) and purged with nitrogen for 1 hour. The contents were then heated under a nitrogen blanket to 160 C. to form an almost colourless solution. Whilst maintaining a nitrogen blanket, dried sodium carbonate (53.00 g, 0.500 mol) and potassium carbonate (2.75 g, 0.020 mol), both sieved through a screen with a mesh size of 500 micrometres, were added. The temperature was raised to 200 C. at a rate of 0.75 C./min and then to 240 C. at a rate of 0.5 C./min before finally being heated to 305 C. at 1 C./min and held for approximately 200 minutes or until the desired SV was reaches as indicted by the torque rise on the stirrer. The required torque rise was determined from a calibration graph of torque rise versus SV. The reaction mixture was then poured into a metal tray, allowed to cool, milled and washed with 2 litres of acetone and then with warm water at a temperature of 40-50 C. until the conductivity of the waste water was <2 S. The resulting polymer powder was dried in an air oven for 12 hours at 120 C.

(10) The resulting polymer had a Shear Viscosity (SV) of 186 Pa.Math.s at a temperature of 400 C. and a shear rate of 1000 s.sup.1, as measured by capillary rheometry.

(11) Measurement of Shear Viscosity

(12) The shear viscosity, SV, was measured according to a Standard method as defined in ISO11443:2014 using capillary rheometry operating at 400 C. at a shear rate of 1000 s.sup.1 using a circular cross-section tungsten carbide die, 0.5 mm (capillary diameter)8 mm (capillary length). The range of SV of the polymeric material selected was from around 100 Pa.Math.s to around 400 Pa.Math.s, at 400 C.

Comparative Examples

(13) Preparation of polyetheretherketone (PEEK)-polvetherdiphenyletherketone (PEDEK) Copolymer on a 200 mol Scale

(14) A 300 litre 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 micrometres, were added.

(15) 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 then raised to 305 C. at 1 C./min and held until desired melt viscosity was reached, as determined by the rise in torque required to rotated the agitator. The required torque rise was determined from a calibration graph of torque rise versus SV. 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.

(16) The resulting polymer had a Shear Viscosity (SV) of 250 Pa.Math.s at a temperature of 400 C. and a shear rate of 1000 s.sup.1, as measured by capillary rheometry.

(17) Victrex PEEK 151 and Victrex PAEK AM 200 were obtained from Victrex Manufacturing Limited, Thornton Cleveleys, United Kingdom.

(18) Measuring Crystallinity Half Life of the PAEK Materials

(19) Crystallisation study was carried out using Differential Scanning Calorimetry, DSC. Isothermal crystallisation half life is defined as the time consumed to reach half of the final crystallinity and is determined by integration of isothermal heat flow measurements.

(20) The isothermal crystallisation half-life was determined using the following DSC method.

(21) 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:

(22) The sample was first heated to 30 C. and allowed to equilibrate for 15 mins. It was then heating to 400 C. at 20 C./minute, and held at this temperature for 15 minutes. The sample was then cooled at 20 C./minute to the desired isotherm temperature (typically 270-290 C.) and held isothermally for up until 3 hours, until crystallisation was complete. It was then cooled back to ambient temperature at 20 C./minute.

(23) From the DSC trace resulting from the scan the heat flow data at the isothermal crystallisation temperature were obtained and plotted. Crystallisation half-life was taken to be the time from the start of the isothermal hold (at the crystallisation temperature) to the time when the crystalline level reached one half of its ultimate level.

(24) The modified crystallisation kinetics may be defined by a set of Avrami kinetics. The Avrami equation describes how solids transform from one phase to another at a constant temperature. In this example it is employed to study the crystallisation kinetics of various polyaryletherketone polymers. The Avrami exponent and rate constant for the isothermal crystallisation process can be determined experimentally using differential scanning calorimetry.

(25) The Avrami equation is presented below

(26) $X_t=\left[1-\exp \left(-{\mathrm{Zt}}^n\right)\right]$ Z=rate constant incorporating growth rate and characteristics of crystallite growth Xt=the volume of fraction crystallised material at time t n=the Avrami exponent which adopts different values depending on the crystallisation mechanism involved

(27) The standard Avrami equation can then be expressed as the equation of a straight line where the components are representative of y=mx+c respectively

(28) $\log \left[-\ln \left(1-\frac{X_t}{X_{}}\right)\right]=n\log t+\log Z$

(29) This is then then be used to experimentally determine the kinetic data for the rate constant (Z), half-life (t), and the Avrami constant (n).

DISCUSSION

(30) The materials of the present invention are particularly useful in additive manufacturing processes because the crystallisation behaviours are modified to suit such processes. In conventional polymer processing in operations such as injection moulding, all of the polymeric material that later goes on to form the article or object is molten at the same time. This means that the melt is a homogenous mixture, with the backbone chains in the polymer evenly dispersed. As the article cools and crystallises, this homogeneity of the polymer chains is locked into the morphology of the article.

(31) In an additively manufactured article however, the layer wise manufacturing processing and resultant structure means that polymer chains are not homogenously dispersed, and do not traverse the boundaries between subsequent layers well. This is because the new layer is typically added to a now solid layer and cannot mix with the preceding layer. We have surprisingly found that one way of overcoming this problem is to use a slow-crystallising polymer which remains molten for sufficient time after being printed for example, for the following layer to be printed onto it. This has been shown to improve mixing at the interface between layers, in turn resulting improved mechanical properties on the article.

(32) The described and illustrated embodiments are to be considered as illustrative and not restrictive in character, it being understood that preferred embodiments have been shown and described and that all changes and modifications that come within the scope of the inventions as defined in the claims are desired to be protected. It should be understood that while the use of words such as preferable, preferably, preferred or more preferred in the description suggest that a feature so described may be desirable, it may nevertheless not be necessary and embodiments lacking such a feature may be contemplated as within the scope of the invention as defined in the appended claims. In relation to the claims, it is intended that when words such as a, an, at least one, or at least one portion are used to preface a feature there is no intention to limit the claim to only one such feature unless specifically stated to the contrary in the claim.