METHOD OF IMPROVING ADHESION OF CARBON FIBERS WITH A POLYMERIC MATRIX

• US 20130224470A1
• Filed: 02/28/2012
• Published: 08/29/2013
• Est. Priority Date: 02/28/2012
• Status: Active Grant

• Current Assignee: UT-Battelle LLC
• Original Assignee: UT-Battelle LLC
• Inventors: Ozcan, Soydan, Paulauskas, Felix Leonard, Vautard, Frederic
• Granted Patent: US 9,365,685 B2
• Time in Patent Office: Days
• US Class Current: 428/300.1
• CPC Class Codes: C08J 2333/04 esters
• CPC Class Codes: C08J 2363/00 Characterised by the use of epoxy resins; Derivatives of epoxy resins
• CPC Class Codes: C08J 2463/00 Characterised by the use of epoxy resins; Derivatives of epoxy resins
• CPC Class Codes: C08J 5/06 using pretreated fibrous materials
• CPC Class Codes: C08L 63/10 Epoxy resins modified by unsaturated compounds
• CPC Class Codes: Y10T 428/249948 Fiber is precoated
• CPC Class Codes: Y10T 428/2918 including free carbon or carbide or therewith [not as steel]

Abstract

A functionalized carbon fiber having covalently bound on its surface a partially cured epoxy or amine-containing sizing agent, wherein at least a portion of epoxide or amine groups in the sizing agent are available as uncrosslinked epoxide or amine groups, which corresponds to a curing degree of epoxide or amine groups of no more than about 0.6. Composites comprised of these functionalized carbon fibers embedded in a polymeric matrix are also described. Methods for producing the functionalized carbon fibers and composites thereof are also described.

Claims

1. A carbon fiber having covalently bound on its surface a partially cured sizing agent comprised of an epoxy resin, wherein at least a portion of epoxide groups in the sizing agent are available as uncrosslinked epoxide groups, which corresponds to a curing degree of epoxide groups of no more than about 0.6.

2. The carbon fiber of claim 1, wherein said epoxy resin possesses a curing degree of epoxide groups of no more than about 0.5.

3. The carbon fiber of claim 1, wherein said epoxy resin possesses a curing degree of epoxide groups of no more than about 0.4.

4. The carbon fiber of claim 1, wherein said epoxy resin is comprised of a difunctional epoxy resin.

5. The carbon fiber of claim 4, wherein said difunctional epoxy resin is selected from one or both of bisphenol A diglycidyl ether and ethylene glycol diglycidyl ether.

6. The carbon fiber of claim 1, wherein said epoxy resin is a trifunctional or a higher functional epoxy resin.

7. The carbon fiber of claim 1, wherein said partially cured sizing agent is a flexible gel.

8. The carbon fiber of claim 1, wherein said epoxy resin is covalently attached to a linking group that contains an accessible reactive group that is reactive with a carbon-carbon double bond.

9. A solid composite in which carbon fibers are embedded in a polymeric matrix, wherein said carbon fibers have covalently bonded on their surfaces a partially cured sizing agent comprised of an epoxy resin, wherein at least a portion of epoxide groups in the sizing agent are available as uncrosslinked epoxide groups, which corresponds to a curing degree of epoxide groups of no more than about 0.6.

10. The solid composite of claim 9, wherein said polymeric matrix is a thermoset.

11. The solid composite of claim 10, wherein said thermoset is derived from vinyl-addition polymerization of an unsaturated resin containing carbon-carbon double bonds.

12. The solid composite of claim 11, wherein said unsaturated resin is a vinyl ester resin.

13. The solid composite of claim 11, wherein said unsaturated resin is an unsaturated polyester resin.

14. The solid composite of claim 9, wherein said polymeric matrix is derived from an acrylate or methacrylate resin.

15. The solid composite of claim 11, wherein said unsaturated resin is in admixture with at least one unsaturated reactive diluent that is cured with the unsaturated resin.

16. The solid composite of claim 15, wherein said unsaturated reactive diluent is selected from the group consisting of styrene, divinyl benzenes, methacrylates, acrylates, and vinyl esters.

17. The solid composite of claim 9, wherein said polymeric matrix is a thermoplastic.

18. The solid composite of claim 9, wherein said epoxy resin possesses a curing degree of surface epoxide groups of no more than about 0.5.

19. The solid composite of claim 9, wherein said epoxy resin possesses a curing degree of surface epoxide groups of no more than about 0.4.

20. The solid composite of claim 9, wherein said epoxy resin is comprised of a difunctional epoxy resin.

21. The solid composite of claim 20, wherein said difunctional epoxy resin is selected from one or both of bisphenol A diglycidyl ether and ethylene glycol diglycidyl ether.

22. The solid composite of claim 9, wherein said epoxy resin is trifunctional or a higher functional epoxy resin.

23. The solid composite of claim 9, wherein said partially cured sizing agent is a flexible gel.

37. The method of claim 23, wherein said sizing agent is made to covalently bind to the surface of the carbon fiber by, first, providing a carbon fiber containing on its surface groups reactive with said sizing agent to form a covalent bond with said sizing agent, and contacting said carbon fiber with a solution or emulsion of said sizing agent under conditions that cause the sizing agent to react with surface reactive groups and form covalent bonds with the carbon fiber, wherein said solution or emulsion is comprised of said sizing agent dispersed in a solvent carrier.

38. The method of claim 37, wherein said sizing agent is in an amount of up to 10% by weight in said solution or emulsion.

39. The method of claim 37, wherein said solvent carrier is aqueous.

40. The method of claim 37, wherein the sizing agent on the carbon fiber is selectively adjusted in thickness by corresponding selective adjustment in the concentration of the sizing agent in said solution.

24. A method of making a carbon fiber having on its surface a partially cured sizing agent, the method comprising covalently binding on the surface of said carbon fiber a sizing agent comprised of an epoxy resin, and partially curing said sizing agent by contact thereof with a curing agent such that at least a portion of epoxide groups remain uncrosslinked on said surface, which corresponds to a curing degree of epoxide groups of no more than about 0.6.

25. The method of claim 24, wherein less than a stoichiometric amount of said curing agent is used.

26. The method of claim 24, wherein, prior to covalent binding of said sizing agent on the surface of the carbon fiber, said carbon fiber is surface-treated by a process that incorporates on said surface reactive functional groups that react with and form covalent bonds with said sizing agent.

27. The method of claim 26, wherein said reactive functional groups are selected from hydroxyl, carboxyl, and amine groups.

28. The method of claim 24, wherein said epoxy resin is comprised of a difunctional epoxy resin.

29. The method of claim 28, wherein said difunctional epoxy resin is selected from one or both of bisphenol A diglycidyl ether and ethylene glycol diglycidyl ether.

30. The method of claim 24, wherein said epoxy resin is a trifunctional or a higher functional epoxy resin.

31. The method of claim 24, wherein said curing agent is comprised of an organoamine containing at least two amine groups selected from primary and secondary amine groups.

32. The method of claim 24, wherein an amount of curing agent is selected that provides a curing degree of surface epoxide groups of no more than about 0.6.

33. The method of claim 24, wherein an amount of curing agent is selected that provides a curing degree of surface epoxide groups of no more than about 0.5.

34. The method of claim 24, wherein an amount of curing agent is selected that provides a curing degree of surface epoxide groups of no more than about 0.4.

35. The method of claim 24, wherein said partially cured sizing agent is a flexible gel.

36. The method of claim 24, further comprising reacting at least a portion of said epoxide groups with a bifunctional molecule that contains a first reactive group reactive with an epoxide group, which forms a covalent bond upon reacting with said epoxide groups, and a second reactive group reactive with a carbon-carbon double bond, wherein said second reactive group is unreacted and accessible for reaction with a carbon-carbon double bond of an unsaturated resin.

41. The method of claim 24, wherein the sizing agent on the carbon fiber is selectively adjusted in viscosity by corresponding selective adjustment in the amount of curing agent used.

42. A method of making a solid composite containing carbon fibers embedded in a polymeric matrix, the method comprising admixing carbon fibers with a polymer precursor resin, and curing the polymer precursor resin to form a cured polymeric matrix that contains said carbon fibers embedded therein, wherein said carbon fibers have covalently bonded on their surfaces a partially cured sizing agent comprised of an epoxy resin, wherein at least a portion of epoxide groups in the sizing agent are available as uncrosslinked epoxide groups, which corresponds to a curing degree of epoxide groups of no more than about 0.6.

43. The method of claim 42, wherein an amount of curing agent is selected that provides a curing degree of surface epoxide groups of no more than about 0.5.

44. The method of claim 42, wherein an amount of curing agent is selected that provides a curing degree of surface epoxide groups of no more than about 0.4.

45. The method of claim 42, wherein said polymeric matrix is a thermoset.

46. The method of claim 45, wherein said thermoset is derived from vinyl-addition polymerization of an unsaturated resin containing carbon-carbon double bonds.

47. The method of claim 46, wherein said unsaturated resin is a vinyl ester resin.

48. The method of claim 46, wherein said unsaturated resin is an unsaturated polyester resin.

49. The method of claim 42, wherein said polymeric matrix is derived from an acrylate or methacrylate resin.

50. The method of claim 42, wherein said polymeric matrix is a thermoplastic.

51. The method of claim 46, wherein said unsaturated resin is in admixture with at least one unsaturated reactive diluent that is cured with the unsaturated resin.

52. The method of claim 51, wherein said unsaturated reactive diluent is comprised of one or more compounds selected from the group consisting of styrene, divinyl benzenes, methacrylates, acrylates, and vinyl esters.

53. The method of claim 46, wherein said unsaturated resin is admixed with an unsaturated polymerizable monomer that includes a group reactive with epoxide in order for said carbon fibers to become covalently bonded with said unsaturated resin on curing the unsaturated resin.

54. The method of claim 53, wherein said group reactive with epoxide is a primary, secondary, or tertiary amine.

55. The method of claim 42, wherein the sizing agent includes reactive groups that react with and form covalent bonds with the carbon-carbon double bonds of the unsaturated resin.

56. A carbon fiber having covalently bound on its surface a partially cured amine-containing sizing, wherein at least a portion of amine groups in the sizing agent are available as uncrosslinked amine groups, which corresponds to a curing degree of amine groups of no more than about 0.6.

57. The carbon fiber of claim 56, wherein said amine-containing sizing agent possesses a curing degree of amine groups of no more than about 0.5.

58. The carbon fiber of claim 56, wherein said amine-containing sizing agent possesses a curing degree of amine groups of no more than about 0.4.

59. The carbon fiber of claim 56, wherein said amine-containing sizing agent is comprised of an organoamine moiety containing at least two amine groups selected from primary and secondary amine groups.

60. The carbon fiber of claim 56, wherein said partially cured amine-containing sizing agent is a flexible gel.

61. A solid composite in which carbon fibers are embedded in a polymeric matrix, wherein said carbon fibers have covalently bonded on their surfaces a partially cured amine-containing sizing agent, wherein at least a portion of amine groups in the sizing agent are available as uncrosslinked amine groups, which corresponds to a curing degree of amine groups of no more than about 0.6.

62. The solid composite of claim 61, wherein said polymeric matrix is a thermoset.

63. The solid composite of claim 62, wherein said thermoset is an acrylate resin, vinyl ester resin, or polyester resin that covalently bonds with amine groups of the amine-containing sizing agent.

64. The solid composite of claim 63, wherein said resin is an acrylate, a vinyl sulfone, a vinyl ester, a polyester, or an unsaturated resin containing an acrylate monomer or a vinyl ester monomer in admixture with at least one unsaturated reactive diluent.

65. The solid composite of claim 64, wherein said unsaturated reactive diluent is selected from the group consisting of styrene, divinyl benzenes, methacrylates, and vinyl esters.

66. The solid composite of claim 61, wherein said polymeric matrix is a thermoplastic derived from a monomer containing a functionality that covalently bonds with the uncrosslinked amine groups of the sizing agent.

67. The solid composite of claim 66, wherein said functionality is selected from an ester, a carboxylic acid, a urethane, an aldehyde, and a ketone.

68. The solid composite of claim 66, wherein said thermoplastic is selected from polyether ether ketone (PEEK), polycarbonates, polymethacrylic acids, polyesters, polylactic acids, polyglycolic acids, polymethacrylates, polymethylacryaltes, Nylon 6, Nylon 6,6, polysulfones, polyvinylalcohols, polyimides and thermoplastic polyurethanes.

69. A method of making a carbon fiber having on its surface a partially cured sizing agent, the method comprising covalently binding on the surface of said carbon fiber an amine-containing sizing agent, and partially curing said sizing agent by contact thereof with a curing agent such that at least a portion of amine groups remain uncrosslinked on said surface, which corresponds to a curing degree of amine groups of no more than about 0.6.

70. The method of claim 69, wherein less than a stoichiometric amount of said curing agent is used.

71. The method of claim 69, wherein, prior to covalent binding of said sizing agent on the surface of the carbon fiber, said carbon fiber is surface-treated by a process that incorporates on said surface reactive functional groups that react with and form covalent bonds with said amine-containing sizing agent.

72. The method of claim 71, wherein said reactive functional groups are selected from carboxylic acid, carboxylic acid ester, aldehyde, and ketone functionalities.

73. The method of claim 69, wherein said amine-containing sizing agent is comprised of an organoamine containing at least two amine groups selected from primary and secondary amine groups.

74. The method of claim 69, wherein curing agent is comprised of a difunctional epoxy resin.

75. The method of claim 74, wherein said difunctional epoxy resin is selected from bisphenol A diglycidyl ether, ethylene glycol diglycidyl ether, and mixtures thereof.

76. The method of claim 69, wherein said epoxy resin is a trifunctional or a higher functional epoxy resin.

77. The method of claim 69, wherein an amount of curing agent is selected that provides a curing degree of surface amine groups of no more than about 0.6.

78. The method of claim 69, wherein an amount of curing agent is selected that provides a curing degree of surface amine groups of no more than about 0.5.

79. The method of claim 69, wherein an amount of curing agent is selected that provides a curing degree of surface amine groups of no more than about 0.4.

80. The method of claim 69, wherein said partially cured sizing agent is a flexible gel.

81. The method of claim 69, wherein said amine-containing sizing agent is made to covalently bind to the surface of the carbon fiber by, first, providing a carbon fiber containing on its surface groups reactive with said amine-containing sizing agent to form a covalent bond with said amine-containing sizing agent, and contacting said carbon fiber with a solution or emulsion of said amine-containing sizing agent under conditions that cause the amine-containing sizing agent to react with surface reactive groups and form covalent bonds with the carbon fiber, wherein said solution or emulsion is comprised of said amine-containing sizing agent dispersed in a solvent carrier.

82. The method of claim 81, wherein said amine-containing sizing agent is in an amount of up to 10% by weight in said solution or emulsion.

83. The method of claim 81, wherein said solvent carrier is aqueous.

84. The method of claim 69, wherein the amine-containing sizing agent on the carbon fiber is selectively adjusted in thickness by corresponding selective adjustment in the concentration of the amine-containing sizing agent in said solution.

85. The method of claim 69, wherein the amine-containing sizing agent on the carbon fiber is selectively adjusted in viscosity by corresponding selective adjustment in the amount of curing agent used.

86. A method of making a solid composite containing carbon fibers embedded in a polymeric matrix, the method comprising admixing carbon fibers with a polymer precursor resin, and curing the polymer precursor resin to form a cured polymeric matrix that contains said carbon fibers embedded therein, wherein said carbon fibers have covalently bonded on their surfaces a partially cured amine-containing sizing agent, wherein at least a portion of amine groups in the sizing agent are available as uncrosslinked amine groups, which corresponds to a curing degree of amine groups of no more than about 0.6.

87. The method of claim 86, wherein an amount of curing agent is selected that provides a curing degree of surface amine groups of no more than about 0.5.

88. The method of claim 86, wherein an amount of curing agent is selected that provides a curing degree of surface amine groups of no more than about 0.4.

89. The method of claim 86, wherein said polymeric matrix is a thermoset.

90. The method of claim 86, wherein said thermoset is an acrylate resin, a vinyl sulfone resin, a vinyl ester resin, or a polyester resin that covalently bonds with amine groups of the sizing agent.

91. The method of claim 90, wherein said resin is an acrylate, a vinyl sulfone, a vinyl ester, a polyester, or an unsaturated resin containing an acrylate or a vinyl ester monomer in admixture with at least one unsaturated reactive diluent.

92. The method of claim 91, wherein said unsaturated reactive diluent is selected from the group consisting of styrene, divinyl benzenes, methacrylates, and vinyl esters.

93. The method of claim 86, wherein said polymeric matrix is a thermoplastic derived from a monomer containing a functionality that covalently bonds with the uncrosslinked amine groups of the sizing agent.

94. The solid composite of claim 93, wherein said functionality is selected from an ester, a carboxylic acid, a urethane, an aldehyde, and a ketone.

95. The solid composite of claim 93, wherein said thermoplastic is selected from polyether ether ketone (PEEK), polycarbonates, polymethacrylic acids, polyesters, polylactic acids, polyglycolic acids, polymethacrylates, polymethylacryaltes, Nylon 6, Nylon 6,6, polysulfones, polyvinylalcohols, polyimides, and thermoplastic polyurethanes.