Thermoplastic composite material, process for its preparation, composite structures made thereof and process for preparing composite structures

Abstract

The invention relates to a thermoplastic composite material comprising a thermoplastic matrix and a fibrous material impregnated with the thermoplastic matrix, wherein the fibrous material comprises carbon fibers with a weight average aspect ratio of length divided by diameter (L/D) of at least 500; the thermoplastic matrix comprises a thermoplastic polymer and a laser absorbing additive.

Claims

1. A thermoplastic composite material comprising: (i) a thermoplastic matrix, and (ii) a fibrous material impregnated with the thermoplastic matrix, wherein the fibrous material comprises at least 20 wt. %, relative to the total weight of the thermoplastic composite material, of carbon fibers with a weight average aspect ratio of length divided by diameter (L/D) of at least 500; and wherein the thermoplastic matrix comprises a thermoplastic polymer and 0.01-2 wt. %, relative to the total weight of the thermoplastic composite material, of a laser absorbing additive, and wherein the thermoplastic composite material is a tape comprising at least a layer comprising unidirectionally oriented continuous carbon fibers.

2. The thermoplastic composite material according to claim 1, wherein the composite material is a tape having a thickness in the range of 50 μm-1000 μm, and/or having a width in the range of 5 mm-50 cm.

3. The thermoplastic composite material according to claim 1, wherein the thermoplastic polymer comprises a thermoplastic polyamide.

4. The thermoplastic composite material according to claim 1, wherein the laser absorbing additive comprises carbon black.

5. The thermoplastic composite material according to claim 1, wherein the thermoplastic polymer comprises a semi-crystalline semi-aromatic polyamide.

6. A process for the preparation of the thermoplastic composite material according to claim 1, comprising steps of: (i) providing the fibrous material comprising the carbon fibers; (ii) providing a melt of a thermoplastic composition comprising the thermoplastic polymer and the laser absorbing additive; (iii) impregnating the fibrous material with the melt thereby obtaining an impregnated material; and (iv) cooling the impregnated material and solidifying the melt to thereby form the thermoplastic composite material.

7. A process for preparing a thermoplastic composite structure, comprising an assembly step which comprises consolidating at least a first piece of the thermoplastic composite material according to claim 1 onto a second piece of a second material.

8. The process according to claim 7, wherein the second material is a thermoplastic composite material, identical to or different from the thermoplastic composite material in the first piece.

9. The process according to claim 7, wherein the step of consolidating the first and second pieces is done by at least partially heating or welding.

10. The process according to claim 7, wherein the step of consolidating the first and second pieces is done by laser welding.

11. The process according to claim 7, wherein the step of consolidating the first and second pieces is done by nip-laser welding.

12. The process according to claim 7, wherein the first piece is a piece of a tape, optionally wrapped or wound around the second piece.

13. The process according to claim 12, further comprising the steps of: (a) winding the tape such that successive windings of the tape partially overlap with each other at overlapping areas; (b) consolidating the overlapping areas of the tape thereby creating a hollow body; and (c) cooling the hollow body to become solid.

14. A composite structure comprising a first piece comprising the thermoplastic composite material according to claim 1 consolidated onto a second piece of a second material.

15. The composite structure according to claim 14, wherein the first and second pieces have been consolidated by laser welding.

16. The composite structure according to claim 14, wherein the composite structure is a hollow body, a hollow pipe or a 3-dimensional part comprising a core part made of a plastic material and local reinforcement elements made of a thermoplastic composite material consolidated on the core part.

17. A process for the preparation of a composite tape material, comprising the steps of: (i) providing unidirectional continuous fibers, and (ii) impregnating the fibers with a thermoplastic material, wherein the unidirectional continuous fibers comprise carbon fibers and the thermoplastic material comprises a semi-aromatic polyamide and a laser absorbing additive dispersed in the semi-aromatic polyamide.

Description

FIGURES

(1) FIG. 1 is a schematic illustration of a tape placement process, wherein a tape is placed onto and consolidated on a substrate by use of a laser beam. As illustrated in FIG. 1, in this process the laser beam (1) is focused at or close to the nip-point (2), thus heating both a portion of one side of the tape (3) and a portion of the upper side of the substrate (4), shortly before contacting each other. Such a process can be used for local reinforcement of a part.

(2) FIG. 2 is a schematic illustration of a tape winding process. Herein the tape (3) is wound a cylinder (5) and consolidated by use of a laser beam (1), wherein the laser beam is focused at or close to the nip-point (2), thus heating simultaneously a portion of one side of the tape (3a) and another portion of the other side of the tape (3b), shortly before contacting each other. Such a process can be used for producing tubes or containers.

(3) The invention is further illustrated with the following examples and comparative experiments.

Materials

(4) TABLE-US-00001 sc-PPA-I PA 6T/4T (60 mole %/40 mole %), VN of 80, Tg 151° C. and Tm 338° C., (ex DSM) sc-PPA-II PA 6T/4T (60 mole %/40 mole %), VN of 100, Tg 151° C. and Tm 338° C., (ex DSM) am-PPA Novamid X21 F07 PA 6I/6T (70 mole %/30 mole %) semi aromatic amorphous copolyamide, Tg 127° C., (ex DSM). CB-MB Carbon black masterbatch based on sc-PPA containing 20 wt. % Black Pearls 880 and 80 wt. % sc-PPA. CF Continuous carbon fibers
Preparation Thermoplastic Polymer Compositions of Examples I and II and Comparative Experiments A and B
Polyamides compositions were prepared by melt mixing the polymers sc-PPA-I or sc-PPA-II with am-PPA in the desired ratio, and optionally the masterbatch CB-MB, on a Berstorff ZE25/48 UTX (a co-rotating twin-screw extruder) operating at 350 rpm and using a wall temperature setting of 360° C. All polymeric materials and additives were fed to the feed-throat of the extruder. The settings used resulted in a temperature of the melt exiting the die-head of approximately 370-380° C. The mean residence time of the molten polymers in the extruder was about 120 seconds. The compositions have been listed in table 1.
Test Methods
Viscosity Number (VN)

(5) The VN was measured in 96% sulphuric acid with a polymer concentration of 0.005 g/ml at 25° C. by the method according to ISO 307, fourth edition.

(6) Determination of Melting Temperature by DSC According to ISO-11357-1/3, (2011).

(7) The measurements of the melting temperature (Tm) were carried out with a Mettler Toledo Star System (DSC) using a heating and cooling rate of 20° C./min in an N2 atmosphere. For the measurements, a sample of about 5 mg pre-dried powdered polymer was used. The pre-drying was carried out at high vacuum, i.e. less than 50 mbar and at 105° C. during 16 hrs. The sample was heated from 0° C. to 360° C. with a heating rate of 20° C./min, immediately cooled to 0° C. with a cooling rate of 20° C./min and subsequently heated again at 20° C./min to 360° C. For the melting temperature Tm, the peak value of the melting peak in the second heating cycle was determined. For the melting enthalpy ΔHm the melting enthalpy of the melting peak in the second heating cycle was determined.

(8) Glass Transition Temperature by DSC (According to ISO-11357-2 (2013)

(9) The measurements of the glass transition temperature (Tg) were carried out with a Mettler Toledo Star System (DSC) using a heating and cooling rate of 20° C./min in an N2 atmosphere in the same way as described above for the Tm. Herein the Tg was determined as the temperature at the peak of the first derivative (with respect of time) of the parent thermal curve corresponding with the inflection point of the parent thermal curve for the second heating cycle.

(10) Tape and Tube Production

(11) Tapes were produced from the polymer compositions with (Examples I and II) and without carbon black (Comparative Experiments A and B) and carbon fibers. Then tubes were produced by winding the tapes around a cylinder and laser nip-welding of the wound tape. Adhesion and shear strength of the tape construct was measured after the winding and welding step. Results are shown in Table 1.

(12) TABLE-US-00002 TABLE 1 Compositions, tape and tube production and test results Thermoplastic composition CE-A CE-B EX-I EX-II Color NC NC BK BK sc-PPA-I (wt %) 65 64 sc-PPA-II (wt %) 65 64 am-PPA (wt %) 35 35 35 35 CB MB (wt %) 0 0 1 1 Tm 310 310 309 311 Tg 138 138 137 138 ΔHm 60 57 58 56 Viscosity Number PPA 80 100 80 100 Tape production Good OK Good OK CF content (wt %) 50 50 50 50 Carbon black content 0 0 0.1 0.1 in tape (wt %) 90° tensile strength Good OK Good OK Slitting Good OK Good OK Winding and nip-welding Marginally White Good Good OK foam Quality tube Bad Ugly Good Good (process feedback) Peel strength Low — High High ILSS Low — High High