Solvent resistant thermoplastic toughened epoxy
View Patent ↗Thermoplastic toughened epoxy resin for use in making prepreg for aerospace applications. The resin includes an epoxy resin component comprising a tri functional epoxy resin and/or tetra functional epoxy, a thermoplastic component and 4,4′-Bis(p-aminophenoxy) biphenyl (BAPB) as the curing agent. The use of BAPB as a curative was found to increase the resistance of the cured resin to attack by solvents.
1. An uncured thermoplastic-toughened epoxy resin which is curable to form a cured resin, wherein said cured resin resists cracking when exposed to a solvent, said uncured resin comprising:
an epoxy resin component comprising from 27 to 38 weight percent triglycidyl-m-aminophenol based on the total weight of the uncured resin and from 10 to 20 weight percent tetra functional para-glycidyl amine based on the total weight of the uncured resin;
a thermoplastic component comprising a soluble component and an insoluble component wherein said soluble component comprises 10 to 20 weight percent polyether sulfone based on the total weight of the uncured resin and said insoluble component comprises from 5 to 15 weight percent polyamideimide particles based on the total weight of the uncured resin and from 2 to 10 weight percent polyamide particles based on the total weight of the uncured resin and wherein said insoluble component and said uncured resin do not comprise elastic particle; and
a curing agent consisting essentially of 4,4′-Bis(p-aminophenoxy)biphenyl and/or isomers thereof, wherein said curing agent is present in an amount of from 20 to 30 weight. percent based on the total weight of the uncured resin.
2. An uncured resin according to claim 1 wherein the molecular weight of said polyethersulfone is between 15,000 and 25,000 g/mole.
3. An uncured resin according to claim 1 wherein said polyamide particles range in size from 5 to 60 microns.
4. An uncured resin according to claim 1 wherein the average particle size of said polyamideimide particles ranges from 8 to 20 microns.
5. An uncured resin according to claim 1 wherein said polyamide particles comprise polyamide 6.
6. An uncured resin according to claim 1 wherein the weight ratio of polyamideimide particles to polyamide particles is 3.2 to 1.
7. An uncured resin according to claim 3 wherein the average particle size of said polyamideimide particles ranges from 8 to 20 microns.
8. An uncured resin according to claim 7 wherein said polyamide particles comprise polyamide 6.
9. An uncured resin according to claim 8 wherein the weight ratio of polyamideimide particles to polyamide particles is 3.2 to 1.
10. An uncured resin according to claim 1 wherein said epoxy resin component comprises from 32 to 34 weight percent triglycidyl-m-aminophenol based on the total weight of the uncured resin and from 14 to 16 weight percent tetra. functional para-glycidyl amine based on the total weight of the uncured resin, said soluble component comprises from 13 to 15 weight percent polyether sulfone based on the total weight of the uncured resin, said insoluble component comprises from 5 to 10 weight percent polyamideimide particles based on the total weight of the uncured resin and from 2 to 10 weight percent polyamide particles based on the total weight of the uncured resin and wherein said curing agent is present in an amount of from 23 to 26 weight percent based on the total weight of the uncured resin.
11. An uncured resin according to claim 10 wherein the molecular weight of said polyethersulfone is between 15,000 and 25,000 g/mole.
12. An uncured resin according to claim 10 wherein said polyamide particles range in size from 5 to 60 microns.
13. An uncured resin according to claim 10 wherein the average particle size of said polyamideimide particles ranges from 8 to 20 microns.
14. An uncured resin according to claim 10 wherein said polyamide particles comprise polyamide 6.
15. An uncured resin according to claim 10 wherein the weight ratio of polyamideimide particles to polyamide particles is 3.2 to 1.
16. An uncured resin according to claim 12 wherein the average particle size of said polyamideimide particles ranges from 8 to 20 microns.
17. An uncured resin according to claim 16 wherein said polyamide particles comprise polyamide 6.
18. An uncured resin according to claim 17 wherein the weight ratio of polyamideimide particles to polyamide particles is 3.2 to 1.