COMPOSITION COMPRISING CARBON FIBERS AND AN ADDITIVE AGENT

Abstract

The invention relates to a composition comprising carbon fibers and an additive agent having a molecular weight of at least 200 g/mol and comprising at least one functional group (A) which is an ethylenically unsaturated polymerizable group, and at least one functional group (B) comprising at least one group selected from secondary amine, tertiary amine, salt of secondary or tertiary amine, and quaternary ammonium, and wherein groups (A) and groups (B) are connected via covalent bonds, and wherein the covalent bonds include at least one ester group.

Claims

1. A composition comprising carbon fibers and an additive agent having a molecular weight of at least 200 g/mol and comprising at least one ethylenically unsaturated polymerizable group (A), and at least one functional group (B) comprising one or more of a secondary amine, a tertiary amine, a salt of a secondary ora tertiary amine, and a quaternary ammonium, and wherein the at least one ethylenically unsaturated polymerizable group (A) and the at least one functional group (B) are connected via at least one covalent bond, and wherein the at least one covalent bond includes at least one ester group.

2. The composition according to claim 1, wherein the ethylenically unsaturated polymerizable group comprises one or more of an acrylic acid ester, a methacrylic acid ester, a maleic acid ester, a fumaric acid ester, an itaconic acid ester, a vinyl ester, a vinyl ether, a vinyl aromatic group, an allyl ester, an allyl ether, and combinations thereof.

3. The composition according to claim 1-e2, wherein the additive agent has a molecular weight of at least 300 g/mol.

4. The composition according to claim 1, wherein the additive agent has at least two functional groups (B1) and (B2), wherein (B1) comprises at least one of a secondary amine and a tertiary amine, and (B2) comprises at least one group selected from a tertiary amine and a hydroxyl.

5. The composition according to claim 1, wherein the additive agent is represented by formula (I)
A-R.sup.1O(CO)CR.sup.2R.sup.3CR.sup.4R.sup.5NR.sup.6R.sup.7 (I) wherein A represents an ethylenically unsaturated polymerizable group, R.sup.1 represents an organic linking group, R.sup.2, R.sup.3, R.sup.4, and R.sup.5 independent of each other represent hydrogen or an alkyl group having 1 to 6 carbon atoms, with the proviso that at least one of R.sup.2, R.sup.3, R.sup.4, and R.sup.5 is hydrogen, and R.sup.6 and R.sup.7 independently of each other represent hydrogen or an organic group.

6. The composition according to claim 5, wherein the additive agent is represented by at least one of formulae (II) and (III) ##STR00003## wherein the groups A and R.sup.1 to R.sup.7 are defined as for the formula (I), and n represents an integer from 1 to 15.

7. The composition according to claim 1, wherein the additive agent comprises at least one segment selected from a polyalkylene oxide segment, a polyester segment and combinations thereof, and the at least one segment is located between the at least one ethylenically unsaturated polymerizable group (A) and the at least one functional group (B).

8. The composition according to claim 7, wherein the polyalkylene oxide segment is based on polymerized units selected from ethylene oxide, propylene oxide, and combinations thereof.

9. The composition according to claim 1, wherein the composition further comprises a curable resin or prepolymer component having at least one ethylenically unsaturated polymerizable group.

10. The composition according to claim 1, wherein the carbon fibers are present as filament fibers, staple fibers or chopped fibers.

11. The composition according to claim 10, wherein the carbon fibers are present as filament fibers in the form of a woven- or non-woven fabric or a roving.

12. The composition according to claim 1, wherein the additive agent is present in an amount of 0.1 to 15.0% by weight, calculated on the weight of the carbon fibers.

13. A process of manufacturing a carbon fiber composite material, the process comprising: providing a composition comprising a) carbon fibers, b) an additive agent having a molecular weight of at least 200 g/mol and comprising at least one ethylenically unsaturated polymerizable group (A), and at least one functional group (B) comprising one or more of a secondary amine, a tertiary amine, a salt of a secondary ora tertiary amine, and a quaternary ammonium, and wherein the at least one ethylenically unsaturated polymerizable group (A) and the at least one functional group (B) are connected via at least one covalent bond, and wherein the at least one covalent bond includes at least one ester group, and c) a curable resin or prepolymer component having ethylenically unsaturated polymerizable groups, and curing the composition by radical polymerization to produce a carbon fiber composite material.

14. The process according to claim 13, wherein the additive agent is added to the carbon fibers prior to including the curable resin or prepolymer component in the composition.

15. The process according to claim 13, wherein the additive agent is added to the carbon fibers together with or after the curable resin or prepolymer component.

16. A carbon fiber composite material obtained by the process of claim 13.

17. A method comprising forming a carbon fiber composite material that includes an additive agent, the additive agent having a molecular weight of at least 200 g/mol and comprising at least one functional ethylenically unsaturated polymerizable group (A), and at least one functional group (B) comprising one or more of a secondary amine, a tertiary amine, a salt of a secondary ora tertiary amine, and a quaternary ammonium, and wherein the at least one ethylenically unsaturated polymerizable group (A) and the least one functional group (B) are connected via at least one covalent bond, and wherein the at least one covalent bond includes at least one ester group, the additive agent being provided in the composite material in an amount effective to increase the transverse tensile strength thereof.

Description

EXAMPLES

[0083] Preparation of Additive Agents

[0084] Raw Materials

TABLE-US-00001 Name Description PEG200DA diacrylate of polyethylene glycol of average molecular weight 200 PEG400DA diacrylate of polyethylene glycol of average molecular weight 400 Sartomer SR 9003 Propoxylated neopentyl glycol diacrylate HDDA 1,6-hexanediol diacrylate Tone M100 Reaction product of 1-hydroxyethylacrylate and 1.8 mol of epsilon-caprolactone HDI 1,6-hexamethylene diisocyanate Sartomer CN tetrafunctional aromatic urethane 9165A acrylate ex Arkema

[0085] Molecular weights (M.sub.n and M.sub.w) were determined by means of gel permeation chromatography (GPC) according to DIN 55672 part 1 (2016-03). Tetrahydrofuran (THF+1 vol. % dibutyl amine) was used as the eluent. The calibration was achieved using narrowly distributed polystyrene standards of molecular weights between 162 and 1,000,000 g/mol. The temperature of the column system was 25 C.

[0086] Additive Agent AA1

[0087] In a flask equipped with stirrer, thermometer, dropping funnel and reflux condenser were placed 226.5 g (0.75 mol) of the diacrylate of polyethylene glycol of average molecular weight 200, and 298.7 g of propylene glycol methyl ether acetate. 1.04 g of 2,6-Di-tert-butyl-4-methylphenol were dissolved in the mixture. During a period of 15 minutes 48.2 g (0.45 mol) of benzyl amine was added dropwise. The mixture was stirred for 4 hours at a temperature of 30 C. A clear, colorless, low viscous product was obtained (M.sub.n=1144 g/mol, M.sub.w=2122 g/mol).

[0088] Further additive agents were prepared in an analogous manner as described for additive agent AA1 from the raw materials indicated in the Table below. All products were obtained as 48 wt. % solutions in propylene glycol methyl ether acetate (AA14 was prepared as 48 wt. % solution in methoxypropanol as the solvent).

TABLE-US-00002 Raw material 1 Raw material 2 M.sub.n M.sub.w Name (mol) (mol) (g/mol) (g/mol) AA1 PEG200DA Benzylamine (0.450) 1144 2122 (0.750) AA2 PEG200DA N-[3-(Dimethylamino)propyl]- n.d. n.d. (0.375) N,N-dimethylpropane-1,3- diamine (0.225) AA3 PEG200DA 1,3-Bis(aminomethyl)- n.d. n.d. (0.750) benzene (0.230) AA4 PEG400DA 3-Aminopropyldimethylamine 2976 8218 (0.500) (0.300) AA5 Dipropyleneglycol 3-Aminopropyldimethylamine 1040 1912 diacrylate (0.830) (0.495) AA6 Sartomer SR 3-Aminopropyldimethylamine 1535 2889 9003 (0.610) (0.360) AA7 HDDA (0.880) 3-Aminopropyldimethylamine 1003 1974 (0.530) AA8 Reaction product 3-Aminopropyldimethylamine 3616 7347 of 2 mol Tone (0.160) M100 and 1 mol HDI (0.269) AA9 Sartomer CN N-[3-(Dimethylamino)propyl]- 1148 2146 9165 A (0.088) N,N-dimethylpropane-1,3- diamine (0.260) AA10 PEG200DA N,N-diethylethylenediamine 1314 2576 (0.750) (0.450) AA11 PEG200DA Diethanolamine (0.750) 582 1088 (0.750) AA12 PEG200DA 3-Aminopropyldimethylamine 1335 2725 (0.750) (0.450) AA13 Sartomer SR Diethanolamine (0.610) 630 721 9003 (0.610) AA14 PEG200DA Tris(hydroxymethyl)aminomethane n.d. n.d. (0.750) (0.290) AA15 PEG200DA Ethanolamine (0.600) 1616 3913 (0.750) AA16 PEG200DA Ethanolamine (0.45) 1240 2834 (0.750) AA17 PEG200DA Diethanolamine (0.660) n.d. n.d. (0.750) AA18 PEG200DA Diethanolamine (0.880) 756 2211 (0.750) AA19 PEG200DA n-Butylamine (0.450) 1251 2832 (0.750) (n.d. = not determined)

[0089] Preparation of compositions comprising carbon fibers and an additive agent

[0090] Raw Materials

TABLE-US-00003 Name Description N-C-416 g/m.sup.2 1270 mm Unidirectional carbon fiber sheets ex Saertex

[0091] N-C-416 g/m.sup.2 1270 mm unidirectional carbon fiber sheets were cut into square shaped sheets having an edge length of 600 mm. The various additives solutions described above were spray applied to both sides of the square shaped sheets with a spray gun SAT Jet 30 HVLP Digital, using a 1.3 mm spray nozzle. The amount of additive (non-volatile content) applied was 3.12 g per sheet (8.64 g per m.sup.2), corresponding to 2.2 weight % of additive, calculated on the weight of the carbon fibers.

[0092] The carbon fiber compositions were stored for 24 hours at 23 C., before impregnating with a curable resin.

[0093] Preparation of resin impregnated carbon fiber stacks

[0094] Raw Materials

TABLE-US-00004 Name Description Palapreg 2681-01 Polyester resin in styrene ex Aliancys Palapreg P 17-02 Unsaturated polyester resin in styrene ex Aliancys Atlac XP 810X Vinylester resin in styrene ex Aliancys Trigonox 117 Tert-butylperoxy-2ethylhexyl carbonate ex AkzoNobel Coathylene HA 1681 Polyethylene based polymer powder ex Axalta Luvatol MK 35 NV Thickener ex Lehmann & Voss Luvatol EK 100KM Thickener ex Lehmann & Voss BYK P 9065 Release agent ex BYK-Chemie BYK P 9085 Release agent ex BYK-Chemie

[0095] A first composite resin material CRM1 was prepared by mixing the following materials with a dissolver at a maximum temperature of 35 C.:

TABLE-US-00005 Name Amount (parts by weight) Atlac XP 810 X 92.50 Palapreg 2681-01 7.50 BYK-P 9085 5.00 Trigonox 117 1.50 Coathylene HA 1681 2.50 Luvatol EK 100KM 8.00

[0096] Resin impregnated carbon fiber stacks were prepared from the additive agent treated unidirectional carbon fiber sheets and the composite resin material CRM1 described above. Resin impregnation was carried out using a SMC machine (Schmidt & Heinzmann, model HM-LB-23). For every type of additve agent 4 individual sheets were combined in a stack before impregnation. The stacks were cut to dimensions of 390 mm290 mm and were stored for 24 h at 35 C. before curing.

[0097] Preparation of Carbon Fiber Composite Sheets

[0098] The stacks described above were pressed and cured at a pressure of 133 bar at 150 C. for 120 s using a press model PYXZ ex Zeulenroda.

[0099] Measurement of Mechanical Properties

[0100] For measurement of transverse tensile strength according to DIN EN ISO 527-5, the carbon fiber composite sheets were cut into specimen of 250 mm25 mm edge length. For measurement of flexural strength according to DIN EN ISO 14130, the carbon fiber composite sheets were cut into specimen of 80 mm15 mm edge length. The flexural strength measurement was carried out parallel to the fiber direction. Prior to measurement of mechanical properties, the specimen were stored at 23 C. and a relative humidity of 50% for a period of 24 h.

[0101] The results are summarized in the Table below:

TABLE-US-00006 Transverse tensile Flexural strength Fiber content Additive Agent strength in MPa in MPa in weight-% None 18.0 33.8 55.0 AA1 28.1 47.6 55.0 AA2 27.6 45.4 55.0 AA3 26.6 45.2 55.0 AA4 26.7 46.4 55.0 AA5 29.7 49.5 55.0 AA12 32.7 55.4 53.2 AA6 33.1 49.5 55.0 AA7 32.4 52.3 55.0 AA8 29.6 48.1 55.0 AA9 28.5 45.7 53.5 AA10 31.3 61.5 55.0 AA11 31.8 57.0 55.0 AA13 26.8 43.2 53.5 AA15 28.8 46.5 53.5 AA16 29.4 50.6 53.5 AA19 26.3 42.4 53.5 AA17 28.6 44.8 53.5 AA16 27.3 44.7 53.5 AA14 28.5 53.5 55.0

[0102] The data in the table above clearly demonstrate that with carbon fiber compositions according to the invention significant improvements of mechanical properties of resulting carbon fiber composite materials can be obtained, in particular with respect to transverse tensile strength and flexural strength, compared to a composite material without using an additive agent.

[0103] A further composite resin material CRM2 was prepared by mixing the following materials with a dissolver at a maximum temperature of 35 C.:

TABLE-US-00007 Name Amount (parts by weight) Palapreg P 17-02 92.00 Palapreg 2681-01 10.50 BYK-P 9065 2.50 Trigonox 117 1.50 Coathylene HA 1681 2.50 Luvatol EK 35 NV 8.00

[0104] Resin impregnated carbon fiber stacks were prepared from the additive agent treated unidirectional carbon fiber sheets and the composite resin material CRM2 as described above. Curing and mechanical testing was carried out as described above. The results are summarized in the Table below:

TABLE-US-00008 Transverse tensile Flexural strength Fiber content Additive Agent strength in MPa in MPa in weight-% None 8.1 17.9 52 AA12 25.7 46.1 52 2-(Dimethyl- 20.9 38.9 52 amino)ethyl methacrylate

[0105] From the data it can be inferred that the additive agent according to the invention provides a more pronounced improvement of mechanical strength of the carbon fiber composite material than the comparative additive agent 2-(dimethylamino)-ethyl methacrylate.