Plastic component comprising a carbon filler

Abstract

A composite material containing carbon and a plastic includes: a) provision of a pulverulent composition with one or more components of amorphous carbon, graphite and mixed forms thereof, b) provision of a liquid binder, c) planar deposition of a layer consisting of the material provided in step a) and local deposition of droplets of material provided in step b) onto this layer and any number of repetitions of step c), the local deposition of the droplets in the successive repetitions of this step being adapted according to the desired shape of the component to be produced, d) at least partial curing or drying of the binder to obtain a green body that has the desired shape of the component, e) impregnation of the green body with a liquid synthetic resin and f) curing of the synthetic resin to produce a synthetic resin matrix.

Claims

1. A method for producing a three-dimensional component consisting of a composite material containing carbon and plastics material, which method comprises the following steps: a) providing a powdered composition comprising one or more constituents selected from the group consisting of amorphous carbon, graphite and hybrid forms thereof, b) providing a liquid binder, c) planarly depositing a layer of the powdered composition provided in a) and locally depositing droplets of the liquid binder provided in b) on said layer, and repeating step c) any number of times, wherein the step of locally depositing the droplets in subsequent repetitions of said step is adjusted according to the desired shape of the three-dimensional component to be produced, d) at least partially hardening or drying the liquid binder and obtaining a green body that has the desired shape of the three-dimensional component, e) impregnating the green body with a liquid synthetic resin, and f) hardening the liquid synthetic resin so as to form a synthetic resin matrix.

2. The method according to claim 1, wherein step d) comprises carbonising the green body at a temperature of between 500° C. and 1300° C.

3. The method according to claim 1, wherein the green body is subject to a recompaction process on one or multiple occasions between steps d) and e), which process comprises the following steps: d1) impregnating the green body with a carbon source, d2) carbonising the green body at a temperature of between 500° C. and 1300° C.

4. The method according to claim 1, wherein the powdered composition comprises acetylene coke, flexicoke, fluid coke, shot coke, hard coal tar pitch coke, petroleum coke, carbon black coke, anthracite, synthetic graphite, spheroidal graphite, microcrystalline natural graphite, carbonised ion-exchange resin beads or a coke granulate.

5. The method according to claim 1, wherein the powdered composition comprises graphite particles or graphitised coke particles, and step d) comprises carbonising the green body at a temperature of between 500° C. and 1300° C.

6. The method according to claim 1, wherein the powdered composition comprises particles in a particle size range of a d50 value, on average, a shape factor (width/length) of at least 0.5.

7. The method according to claim 1, wherein the liquid binder in step b) comprises phenolic resin, furan resin or liquid glass.

8. The method according to claim 1, wherein the liquid synthetic resin is selected such that the component has a porosity of at most 2%.

9. The method according to claim 1, wherein the liquid binder in step b) and the liquid synthetic resin in step e) belong to the same class of resins.

10. The three-dimensional component which consists of a composite material containing carbon and plastics material and is produced using a method according to claim 1.

Description

EXAMPLE 1

(1) Calcinated hard coal tar pitch coke was ground and had, after grinding and sieving, a particle size distribution of d10=130 μm, d50=230 μm and d90=390 μm and an average shape factor of 0.69 (in the particle size range of d50+/−10%). The coke was first mixed with 1 wt. % of a sulphuric liquid activator for phenolic resin, based on the total weight of the coke and activator, and processed using a 3D printing powder bed machine. A scraper unit was used to apply a thin coke powder layer (approximately 0.3 mm thick) onto a planar powder bed and a type of inkjet printing unit was used to print an alcoholic phenolic resin solution onto the coke bed according to the desired component geometry. Then, the printing table was lowered by the layer thickness, another layer of coke was applied and phenolic resin was locally printed again. By the procedure being repeated, cuboid test pieces were formed that had the measurements 168 mm (length)×22 mm (width)×22 mm (height). Once the complete “component” had been printed, the powder bed was put into an oven that had been preheated to 140° C. and was kept there for approximately 6 hours. Even if a “component” has already been mentioned before this point, it goes without saying that this is not meant to refer to the finished component according to the invention. To produce said finished component, the phenolic resin was hardened and formed a dimensionally stable green body. The excess coke powder was sucked up after cooling, and the green body of the component was removed.

(2) The density of the green body after the binder had been hardened was 0.88 g/cm.sup.3. The density was determined geometrically (by weighing and determining the geometry). The green body had a resin proportion of 5.5 wt. %, which was determined by carbonisation treatment. The procedure was such that the carbon yield of the hardened resin components used was determined in advance by means of thermogravimetric analysis (TGA) as being 58 wt. %. The original resin proportion in the green body could be calculated from the loss in mass of the green body after it had been subsequently carbonised for one hour at 900° C. in a protective gas atmosphere.

(3) The green body was subsequently impregnated with phenolic resin and carbonised again at 900° C. The density was thereby increased to 1.1 g/cm.sup.3. The carbon body that had been recompacted in this manner was then subject to vacuum pressure impregnation with phenol formaldehyde resin (manufacturer: Hexion) having a viscosity of 700 mPas at 20° C. and a water content according to Karl Fischer (ISO 760) of approximately 15%. The procedure was as follows: the carbon bodies were put in an impregnating pressure cylinder. The cylinder pressure was reduced to 10 mbar, and increased to 11 bar after the resin had been introduced. After a dwell time of 10 hours, the carbon test pieces were removed from the impregnating pressure cylinder and heated to 160° C. at a pressure of 11 bar in order to harden the resin. The heating time was approximately 2 hours, and the dwell time at 160° C. was approximately 10 hours. After hardening, the cooled test pieces had a density of 1.45 g/cm.sup.3 (example 1).

EXAMPLE 2

(4) Example 2 differed from example 1 in that the recompacted carbonised carbon body was additionally subject to graphitisation treatment at 2400° C. in a protective gas atmosphere before the subsequent phenol formaldehyde impregnation. The subsequent resin impregnation carried out in the same manner as in example 1 resulted in a test piece density of 1.58 g/cm.sup.3 (example 2).

EXAMPLE 3

(5) Calcinated acetylene coke was mixed in an unground form and with a particle size distribution of d10=117 μm, d50=190 μm and d90=285 μm and an average shape factor of 0.82 (in the particle size range of d50+/−10%) with 0.35 wt. % of the liquid activator according to example 1 and processed so as to form a green body in the same manner as in example 1.

(6) The green body had a resin proportion of 3.0 wt. %. The density of the green body was 0.98 g/cm.sup.3 and was thus significantly higher than in the case of the hard coal pitch coke from example 1. Furthermore, this green body was stronger than that from example 1, which made handling easier. Therefore, it was not necessary to recompact this green body, and this reduced the production costs.

(7) The green carbon bodies produced in this manner were subsequently subject to the resin impregnating and hardening procedure from example 1. The density of the hardened plastics material/carbon test pieces was determined as being 1.43 g/cm.sup.3 (example 3).

EXAMPLE 4

(8) Example 4 differed from example 3 in that the green carbon test pieces were impregnated with epoxy resin instead of being impregnated with phenolic resin. The procedure was as follows:

(9) The samples were provided in a plastics container and an epoxy resin mixture which was prepared in advance and consisted of 100 parts EPR L20 resin (manufacturer: Hexion) and 34 parts EPH 960 hardener (manufacturer: Hexion) was poured thereover. A vacuum of 100 mbar was then applied to the immersed samples for one hour. Infiltration was then continued at normal air pressure for 30 minutes. The sample pieces were completely immersed in the solution for the entire infiltration time (at room temperature). After infiltration of the epoxy resin, the samples were removed and the surface thereof was cleaned using a cellulose cloth. The samples impregnated with resin were then hardened in the drying cabinet in air and at normal pressure initially for 2 hours at 100° C. and then for 3 hours at 150° C. After the resin had been hardened, the sample pieces had an average density of 1.40 g/cm.sup.3 (example 4). Since epoxy resin hardens by a polyaddition reaction, there was no measurable loss in mass after the hardening step.

EXAMPLE 5

(10) Example 5 differs from example 3 in that the green carbon test pieces were impregnated with furan resin by being immersed therein instead of being impregnated with phenolic resin. The advantage of furan resin impregnation over phenolic resin impregnation is the extremely low viscosity of the furan resin system, namely of less than 100 mPas, as a result of which simple impregnation without applying any pressure can be carried out easily. The procedure was as follows:

(11) The samples were provided in a glass container and a solution which was prepared in advance and consisted of one part maleic acid anhydride (manufacturer: Aug. Hedinger GmbH & Co. KG) and 10 parts furfuryl alcohol (manufacturer: International Furan Chemicals B.V.) was poured thereover. The sample pieces were completely immersed in the solution for the entire infiltration time of two hours (at room temperature). After infiltration of the furfuryl alcohol/maleic acid anhydride solution, the samples were removed and the surface thereof was cleaned using a cellulose cloth. The samples impregnated with resin were then hardened in the drying cabinet. In the process, the temperature was gradually increased from 50° C. to 150° C. The actual hardening procedure was as follows: 19 hours at 50° C., 3 hours at 70° C., 3 hours at 100° C. and then 1.5 hours at 150° C. The average density of the test pieces impregnated with furan resin was determined as being 1.31 g/cm.sup.3 following hardening (example 5).

(12) A characterisation of materials was performed for all test pieces from examples 1-5. The results of these tests are summarised in the following table:

(13) TABLE-US-00001 Ex- Ex- Ex- Ex- Ex- ample 1 ample 2 ample 3 ample 4 ample 5 (averages) (averages) (averages) (averages) (averages) AD (g/cm.sup.3) 1.45 1.58 1.43 1.40 1.31 ER (ohmμm) 350 35 500,000 100,000 120,000 YM 3p (GPa) 6 6 6 6 5 FS 3p (MPa) 30 15 20 45 25 CTE 27 12 24 40 24 RT/150° C. (μm/(m*K)) TC 2 40 <1 <1 <1 (W/(m*K)) AD (g/cm.sup.3): (geometric) density in accordance with ISO 12985-1 ER (ohmμm): electrical resistance in accordance with DIN 51911 YM 3p (GPa): elastic modulus (stiffness), determined from the 3-point flexural test FS 3p (MPa): 3-point flexural strength in accordance with DIN 51902 CTE RT/150° C. (μm/(m*K)): coefficient of thermal expansion measured between room temperature and 150° C. in accordance with DIN 51909 TC (W/(m*K)): thermal conductivity at room temperature in accordance with DIN 51908 Example 1: hard coal tar pitch coke, green body additionally impregnated with phenolic resin, carbonised at 900° C., and subsequently finally compacted by phenolic resin in the vacuum pressure impregnation process. Example 2: hard coal tar pitch coke, green body not impregnated with phenolic resin, carbonised at 900° C., then graphitised at 2400° C., subsequently finally compacted by phenolic resin in the vacuum pressure impregnation process. Example 3: acetylene coke, green body finally compacted directly by phenolic resin in the vacuum pressure impregnation process. Example 4: acetylene coke, green body finally compacted directly by an epoxy resin system by means of vacuum impregnation. Example 5: acetylene coke, green body finally compacted directly by a furan resin system by means of impregnation by immersion.

(14) In examples 1 and 2, there is thus a continuous carbon network, since the coke particles are connected to amorphic carbon, or the graphitised coke particles are connected to carbon that is similar to graphite. By comparison with examples 3, 4 and 5, examples 1 and 2 demonstrate a significant reduction in the electrical resistance, the graphitisation of the green body (example 2) further reducing the electrical resistance. Similarly, the thermal conductivity of the components is also increased as a result of the thermal treatment.

(15) The epoxy matrix (example 4) is stronger than phenolic resin and furan resin; however, phenolic resin and furan resin are more temperature and chemically stable. With regard to the complexity involved in the impregnation, impregnation with furan resin can occur simply by means of impregnation by immersion, whereas impregnation with phenolic resin and epoxy resin has to occur by means of a vacuum impregnation process or a vacuum pressure impregnation process, owing to the viscosity usually being higher.