SHAPED OBJECT COMPRISING POLYETHYLENE TEREPHTHALATE AND ALUMINIUM

Abstract

The present invention relates to a material composition comprising: (i) a polyester selected from polyethylene terephthalate, polybutylene terephthalate, or mixtures thereof; and (ii) ≥1.0 and ≤30.0 vol % of aluminium particles and to a shaped object comprising a material composition comprising such material composition. Such shaped object does demonstrate the desirable mechanical impact properties, and also demonstrates the desirable electromagnetic shielding, electrical conductivity, and thermal conductivity, given its high loading of aluminium.

Claims

1. A material composition comprising: (i) a polyester selected from polyethylene terephthalate, polybutylene terephthalate, or mixtures thereof; and (ii) ≥1.0 and ≤30.0 vol % of aluminium particles wherein the aluminium particles are present in the form of particles having an average particle size of ≥0.05 and ≤4000 μm, as determined in accordance with ISO 9276-2 (2014).

2. The material composition according to claim 1, wherein the aluminium particles are spherical particles, powdery particles, flakes, micro fibres, or rod-shaped particles.

3. Material composition according to claim 1, wherein the polyester has an intrinsic viscosity of ≥0.45 dg/l as determined in accordance with ASTM D2857-95 (2007).

4. A process for the production of the material composition according to claim 1, wherein the process involves melt mixing of the polyester and the aluminium particles in a melt extruder.

5. A process for the production of the material composition according to claim 1, wherein the process involves introduction of the aluminium particles during the polymerisation reaction to manufacture the polyester.

6. A shaped object produced using the material composition according to claim 1.

7. The shaped object, according to claim 6, comprising a material composition comprising: (a) a polyethylene terephthalate polymer; and (b) ≥10.0 wt % of aluminium, with regard to the total weight of the material composition.

8. The shaped object according to claim 6, wherein the polyethylene terephthalate has an intrinsic viscosity of ≥0.45 dl/g as determined in accordance with ASTM D2857-95 (2007).

9. The shaped object according to claim 6, wherein, in the shaped object, the aluminium is distributed to form a conductive matrix.

10. A process for manufacturing of a shaped object according to claim 6, wherein the process comprises the steps in this order of: a. providing the material composition; b. providing a compacting tool comprising a die having a cavity and a punch having an outer surface corresponding to the cavity; c. positioning a quantity of the material composition in the cavity of the die; d. exerting a force onto the punch of the compacting tool to compact the material composition so as to fuse the material composition to form a shaped object; e. releasing the force exerted onto the punch; f. removing the shaped object from the cavity; and optionally g. treating the shaped object at a temperature of between 5° C. below the melting temperature and the melting temperature for a period of between 10 and 60 minutes.

11. The process according to claim 10, wherein the material composition comprises the polyethylene terephthalate in the form of particles.

12. The process according to claim 11, wherein the polyethylene terephthalate particles have an average particle size of ≥0.5 and ≤4000 μm, and/or the aluminium particles have an average particle size of ≥0.5 and ≤4000 μm, wherein the average particle size is as determined in accordance with ISO 9276-2 (2014).

13. The process for manufacturing of a shaped object according to claim 6, wherein the process comprises the steps in this order of: a. providing a quantity of a powder comprising the material composition; b. irradiating a portion of the material composition with a radiation source such that the particles in that portion of the material composition absorb sufficient heat to reach a temperature above T.sub.p,m; c. terminating the exposure of the portion of the material composition to the radiation source so that the temperature of the particles of the material composition decreases to below T.sub.p,m; wherein steps (a) through (c) are executed in this sequence, wherein steps (a) through (c) may be repeated to form the shaped object, and wherein T.sub.p,m is the peak melt temperature determined in accordance with ISO 11357-3 (2011), first heating run.

14. (canceled)

15. The shaped object according to claim 6, wherein the shaped object is capable of conducting heat or electricity.

Description

[0043] An example of a suitable method for manufacturing of the shaped objects according to the present invention is a process comprising the steps in this order of: [0044] (a) providing the material composition; [0045] (b) providing a compacting tool comprising a die having a cavity and a punch having an outer surface corresponding to the cavity; [0046] (c) positioning a quantity of the material composition in the cavity of the die; [0047] (d) exerting a force onto the punch of the compacting tool to compact the material composition so as to fuse the material composition to form one single shaped object; [0048] (e) releasing the force exerted onto the punch; [0049] (f) removing the shaped object from the cavity; and optionally [0050] (g) treating the shaped object at a temperature of between 5° C. below the melting temperature and the melting temperature for a period of between 10 and 60 minutes.

[0051] Such process may be understood to be a compaction process. Such process allows for the manufacturing of the shaped object of the present invention in a manner that crystallisation is controlled to avoid undesirably fast crystallisation, and further does not induce a melt shear onto the material as a result of which the distribution of the filled in the shaped object is undesirable.

[0052] It is particularly preferred that prior to step (c), the die has been heated to a compaction temperature, preferably wherein the compaction temperature is ≥230° C., more preferably wherein the compaction temperature is ≥230° C. and ≤260° C. It is preferred that the temperature of the die is maintained at the compaction temperature during step (d).

[0053] It is further particularly preferred that the force exerted in step (d) is such that the material composition in the cavity is subjected to a pressure of ≥3.0 MPa, preferably ≥10.0 and/or ≤50.0 MPa. Application of such pressure results in the shaped object to have, upon release and removal from the mould, a desirably high mechanical strength.

[0054] In the compaction process according to the invention, it is preferred that exertion of the force in step (d) is maintained for ≥1 minute, preferably for ≥5 and ≤15 minutes. In a certain embodiment, the temperature of the die is maintained at the compaction temperature during step (d)

[0055] A further suitable process for manufacturing of a shaped object according to the invention comprises the steps in this order of: [0056] (a) providing a quantity of a powder comprising the material composition; [0057] (b) irradiating a portion of the material composition with a radiation source such that the particles in that portion of the material composition absorb sufficient heat to reach a temperature above T.sub.p,m of the polyethylene terephthalate polymer; [0058] (c) terminating the exposure of the portion of the material composition to the radiation source so that the temperature of the particles of the material composition decreases to below T.sub.p,m of the polyethylene terephthalate polymer; [0059] wherein steps (a) through (c) are executed in this sequence, wherein steps (a) through (c) may be repeated to form the shaped object, and wherein T.sub.p,m is the peak melt temperature determined in accordance with ISO 11357-3 (2011), first heating run.

[0060] In such process, material is selectively subjected to a source of radiation in such way that the exposed polymer quantity becomes heated to be sufficiently fluid to fuse or sinter to neighbouring polymer material that is sufficiently heated. In this way, upon cooling, a solidified object is formed having predetermined dimensions, namely according to the material subjected to the radiation. Such process may be referred to as a selective sintering process. Such process also allows for the manufacturing of an object without subjecting the material to excessive melt shear, and accordingly particularly suitable for producing the objects according to the present invention.

[0061] A suitable selective sintering process may involve the application of the radiation by means of a laser device. Such process may then be referred to as selective laser sintering. The selective sintering process according to the present invention may for example involve providing a layer of a certain thickness of a powder of the material composition onto a die bed, followed by subjecting a certain portion of the powder to the appropriate radiation, again followed by providing a further layer of powder on top of the previous powder layer in the die, and again subjecting a desired part of that powder layer to the radiation. This may be repeated multiple times to obtain an object of the dimensions at desired.

[0062] Particularly, it is desired that the temperature of the powder material that is provided onto the die bed is ≥230° C., particularly preferably ≥230° C. and ≤260° C.

[0063] The invention also encompasses an embodiment relating to the use of a shaped object according to the invention for conducting heat or electricity in an article.

[0064] The invention will now be illustrated by the following non-limiting examples.

TABLE-US-00001 PET Polyethylene terephthalate having an intrinsic viscosity of 1.09 dl/g, having a heat of fusion of 60 J/g, in powder form with average particle size 100 μm. Al1 Aluminium powder, average particle size 30 μm. Al2 Aluminium powder, average particle size 100 μm.

[0065] For the manufacturing of shaped objects of the present invention, dry powder blends were prepared by mixing PET and aluminium powder material as per the formulations of the table below. The weighed powders were mixed manually in a bottle and agitated. The powder blends according to the examples were dried at 170° C. for three hours.

TABLE-US-00002 Example PET Al1 Al2 1 100 2 90 10 3 80 20 4 70 30 5 60 40 6 75 25

[0066] The values in the above table indicate the wt % of each ingredient as compared to the total weight of the powder blend.

[0067] A cylindrical die was used as a hot compaction tool to make cylindrical compacts with a diameter of 14.5 mm and a length of ca. 5 cm. The compaction die consisted of a barrel and a piston. The walls of the barrel were provided with a heating means, wherein the heaters were covered with insulation. A pressure transducer measured the pressure applied by the piston. 15 Grams of the dried powder, at room temperature, was introduced into the barrel. Next, the piston applied a compacting pressure. A compaction temperature of 245° C. and a pressure of 25 MPa was used for all the compositions. The compaction time including the heat-up time was 10 minutes. After that, the insert at the bottom of the barrel was unscrewed and the billet was pushed out at 245° C. Properties of the prepared object were subsequently tested.

[0068] Example 1 is to be considered an example for comparative purposes. The object consisted of pure PET. The cylindrical object could be removed from the mould at 245° C. without sticking. The DSC curve of a sample of material taken from that object only barely showed a Tg, no cold crystallisation, and a melting peak at 257.7° C., with a heat of fusion comparable to that of the starting powder (55.7 J/g). The object was hard and rigid, but chipped at the edges when subjected to an impact test by dropping the object onto a ceramic surface from a height of 1.5 m. The object showed desirable properties for insulation to heat and electricity. When cooled in nitrogen at 77° K, and subjected to hammer impact testing, the object shattered into fragments. Examination of these fragments revealed consolidation with some grain boundaries.

[0069] A sample of the composition of example 3 was converted to a shaped object according to the compaction conditions set out above for example 1. A sample of the shaped object was subjected to DSC measurement, revealing a weak Tg, no cold crystallisation peak, and a single melt peak at 249.1° C., with a heat of fusion of 37.5 J/g PET. This indicated that the Pet phase of the composite was semi-crystalline, which would not have been the case if the object would have been prepared by injection moulding using the composition of example 3. When subjecting the object to drop impact test as described above for example 1, chipping at the edges occurred. Examination of the surface of a cross section obtained by liquid nitrogen fracturing revealed that the Al was evenly distributed.

[0070] Cylindrical objects based on the material of example 4, prepared according to the method described for example 1, showed a change to metal-dominated behaviour. The appearance of the object was more metallic. The DSC curve showed a single melting peak at 249.9° C. and a heat of fusion of 33.2 J/g PET. This indicated that the PET phase of the composite was semi-crystalline. When subjecting the object to drop impact test as described above for example 1, no chipping occurred, but only denting of the object. Subjecting the object to hammer impact testing under cooled conditions as with example 1 resulted in no break. The electrical and thermal conductivity showed metal-like behaviour.

[0071] The cylinder of example 4 was subjected to a further heat treatment to improve the bonding of the PET to the aluminium by placing it in an oven at 260° C. for 30 minutes. The cylinder maintained its shape and dimensions. The cylinder of example 1, i.e. from pure PET, when subjected to such treatment, did fully melt and lose its shape. The cylinder of example 4 demonstrated improved bonding between the PET and the aluminium, as observed in microscopic examination, which is understood to result in the higher impact strength at room temperature as well as in cold impact testing.

[0072] The object based on the material of example 5, also prepared according to the method described for example 1, was near aluminium-like in appearance and behaviour. The cylinder object, when tested via DSC, showed a single melting peak at 250.1° C., with a heat of fusion of 43.8 J/g PET. The composition cannot be shaped via injection moulding. When subjecting the object to drop impact test as described above for example 1, no chipping occurred, but only denting of the object. Subjecting the object to hammer impact testing under cooled conditions as with example 1 resulted in no break, even upon subjecting to multiple impacts. The electrical and thermal conductivity showed metal-like behaviour.

[0073] The compacted objects as prepared according to examples 3-5, as presented above, provided articles having a density of less than 2 g/cm.sup.3, with good impact strength at both room temperature as well as under cooled conditions, and good thermal and electrical conductivity. Further properties of the compacted objects are presented in the table below.

TABLE-US-00003 Density Heat of fusion Peak melting Example (g/cm.sup.3) (J/g PET) temperature (° C.) 1 1.35 55.7 252.7 3 1.58 37.5 249.1 4 1.81 33.2 249.9 5 2.07 43.8 250.1

[0074] Further experiments were performed using the powder formulations of examples 1, 2 and 6, which were subjected to selective laser sintering (SLS) to form tensile test bars. This method of manufacturing of objects allows for manufacturing of complex shaped without the need for external moulds to be employed. The SLS was performed using a CO.sub.2-laser powered SLS machine, wherein the process parameters were as presented in the table below:

TABLE-US-00004 Parameters (optimized) SLS 1 SLS 2 Temperature Part bed temperature 233° C. 230° C. Piston temperature 180° C. 180° C. Cylinder temperature 180° C. 180° C. Feed temperature 160° C. 160° C. Laser Laser source CO.sub.2 CO.sub.2 Power 14-18 W 18-24 W Scan speed 5 m/s 5 m/s Hatch distance 100 μm 100 μm Other Layer thickness 100 μm 100 μm

[0075] In experiment SLS1, the powder of examples 1 and 2 was used. In experiment SLS2, the powder of example 6 was used.

[0076] The tensile test bars that were produced in the SLS experiments as above had dimensions as in ASTM 0638. The bars were subjected to material testing as in the table below.

TABLE-US-00005 SLS 1 SLS 1 SLS 2 Material Testing method Ex. 1 Ex. 2 Ex. 6 Density (g/cm.sup.3) ASTM D792 1.36 1.45 1.52 Tensile Modulus (MPa) ASTM D638 2961 3558 4057 Tensile Strength (MPa) ASTM D638 66 37 29 Flexural Modulus (MPa) ASTM D790 2713 3179 3564 Flexural Strength (MPa) ASTM D790 113 79 51 IZOD Impact, notched, ASTM D256 26 22 17 23° C. (J/m)
Further experiments were conducted relating to compounding of polyester/aluminium compositions.

TABLE-US-00006 PET-B SABIC PET BC212, a polyethylene terephthalate having an intrinsic viscosity of 0.84 dl/g, obtainable from SABIC PBT Valox 310, a polybutylene terephthalate having a melt viscosity of 600 Pa .Math. s, obtainable from SABIC PC SABIC PC 0703, a polycarbonate having a melt mass-flow rate of 7.0 g/10 min at 300° C. under a load of 1.2 kg, obtainable from SABIC PP SABIC PP500P, a polypropylene having a melt mass-flow rate of 3.1 g/10 min at 230° C. under a load of 2.16 kg according to ISO 1133, obtainable from SABIC Al1B Aluminium powder, average particle size D.sub.50 of 20-50 μm, potato and carrot shaped particles, density 2.7 g/cm.sup.3 obtainable from Nanokar, Turkey Al2B Aluminium nano powder, average particle size D.sub.50 of 3 μm, potato and carrot shaped particles, density 2.7 g/cm.sup.3 obtainable from Nanokar, Turkey Al3B Aluminium flakes, average particle size D.sub.50 of 16 μm, density 2.7 g/cm.sup.3 obtainable from Nanografi, Germany Al4B Aluminium nano powder, spherical, average particle size D.sub.50 of 68 nm, density 2.7 g/cm.sup.3, obtainable from Nanografi, Germany

[0077] Using the above materials, a number of formulations were prepared by extrusion melt mixing as presented in the table below:

TABLE-US-00007 Example Polymer Aluminium 1B 100.0% PET-B — 2B 95.0% PET-B 5.0% Al1B 3B 90.0% PET-B 10.0% Al1B 4B 85.0% PET-B 15.0% Al1B 5B 80.0% PET-B 20.0% Al1B 6B 70.0% PET-B 30.0% Al1B 7B 95.0% PET-B 5.0% Al3B 8B 90.0% PET-B 10.0% Al3B 9B 85.0% PET-B 15.0% Al3B 10B 80.0% PET-B 20.0% Al3B 11B 75.0% PET-B 25.0% Al3B 12B 99.0% PET-B 1.0% Al2B 13B 97.0% PET-B 3.0% Al2B 14b 95.0% PET-B 5.0% Al2B 15B 99.0% PET-B 1.0% Al4B 16B 97.0% PET-B 3.0% Al4B 17B 95.0% PET-B 5.0% Al4B 18B 100.0% PBT-B — 19B 85.0% PBT-B 15.0% Al3B 20B 60.0% PBT, 40.0% PET-B — 21B 51.0% PBT, 34.0% PET-B 15.0% Al3B 22B 100% PC — 23B 95.0% PC 5.0% Al4B 24B 85.0% PC 15.0% Al3B 25B 100% PP — 26B 95.0% PP 5.0% Al4B 27B 85.0% PP 15.0% Al3B

[0078] In the table above, the percentages indicate the percentage by volume of each ingredient vis-á-vis the total volume of the formulation.

[0079] Using the formulations of the examples as presented above, an array of physical properties were determined, as shown in the table below.

TABLE-US-00008 Example 1B 2B 3B 4B 5B 6B 7B 8B 9B Tm 1.60/1.60* 1.75 1.95 2.07 2.08 2.32 2.82/2.62* Ts 59.94/63.31* 56.55 58.33 57.23 66.2 71.6  79.1/57.22* El 96.19/5.21*  135.73 16.09 13.65 23.26 7.41 5.13/3.15* Fm 2.47/3.49* 2.74 3.18 3.24 3.15 4.54 5.41/6.86* Fs  88.98/131.95* 88.62 92.83 90.52 103.1 116.7 126.0/100.2* Izod 22.12/30.00  26.46 39.51 51.29 43.08 31.25 45.57 44.06 43.49/26.04* κ 0.241 0.293 0.340 0.396 Example 10B 11B 12B 13B 14B 15B 16B 17B 18B Tm 3.21 3.09 1.54 1.63 1.61 1.83 1.87 1.97 Ts 76.0 72.2 55.64 56.19 55.99 62.42 52.71 40.55 El 4.08 3.39 442.13 428.27 201.89 227.4 7.35 2.37 Fm 6.71 8.03 2.52 2.65 2.78 2.82 3.00 3.17 Fs 124.2 103.4 89.39 90.14 90.34 98.71 100.51 91.37 Izod 21.25 29.37 35.00 42.19 51.25 38.75 26.25 24.68 54.06 κ 0.499 0.606 0.251 0.277 0.294 Example 19B 20B 21B 22B 23B 24B 25B 26B 27B Izod 68.13 35.94 53.75 963.4 50.9 55.0 83.44 92.50 50.63

[0080] The properties indicated with * in the table above were determined on test samples that were injection moulded into specimens at a mould temperature of 170° C., leading to crystallisation of the PET. All other measurements were performed on specimens that were injection moulded at a mould temperature of 30° C., which in the examples using PET resulted in that the PET remained amorphous in the test specimen.

[0081] In the table above, the abbreviations represent the below properties: [0082] Tm is the tensile modulus, expressed in MPa, determined in accordance with ASTM D638 (2014); [0083] Ts is the tensile strength, expressed in MPa, determined in accordance with ASTM D638 (2014); [0084] El is the elongation at break, expressed in %, determined in accordance with ASTM D638 (2014); [0085] Fm is the flexural modulus, expressed in MPa, determined in accordance with ASTM D790 (2015); [0086] Fs is the flexural strength, expressed in MPa, determined in accordance with ASTM D790 (2015); [0087] Izod is the notched Izod impact strength at 23° C., expressed in J/m, determined in accordance with ASTM D256 (2010); [0088] K is the thermal conductivity, expressed in W/m.Math.K, determined in accordance with ASTM D5930 (2017).