Epoxy resin, epoxy resin composition, epoxy resin cured product and composite material
An epoxy resin includes a reaction product between: an epoxy compound having a mesogenic structure; and at least one selected from the group consisting of an aromatic hydroxycarboxylic acid having a carboxy group and a hydroxy group bonded to an aromatic ring and an aromatic dicarboxylic acid having two carboxy groups bonded to an aromatic group.
1. An epoxy resin, comprising at least one compound selected from the group consisting of the following General Formulae (E1) and (E2):
wherein, in General Formulae (E1) and (E2), Ar represents a substituted or unsubstituted aromatic ring; each of R1 and R2 independently represents a monovalent organic group having a glycidyl group, wherein at least one selected from the group consisting of R 1 and R2 includes a mesogenic structure; and each R3 independently represents a hydrogen atom or a monovalent organic group, at least one R3 being a monovalent organic group of the following Formula (c):
wherein, in Formula (c), R 4 represents a monovalent organic group; and * represents a bonding site to an oxygen atom.
2. The epoxy resin according to claim 1 , wherein, in General Formulae (E1) and (E2), Ar represents a substituted or unsubstituted benzene ring or naphthalene ring.
3. The epoxy resin according to claim 1 , wherein the mesogenic structure comprises a structure represented by the following General Formula (M):
wherein, in General Formula (M), X represents a single bond or a linking group that includes at least one divalent group selected from the following Group (A); each Y independently represents an aliphatic hydrocarbon group having 1 to 8 carbon atoms, an alkoxy group having 1 to 8 carbon atoms, a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, a cyano group, a nitro group or an acetyl group; each n independently represents an integer from 0 to 4; and * represents a bonding site to an adjacent atom:
wherein, in Group (A), each Y independently represents an aliphatic hydrocarbon group having 1 to 8 carbon atoms, an alkoxy group having 1 to 8 carbon atoms, a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, a cyano group, a nitro group or an acetyl group; each n independently represents an integer from 0 to 4;
k represents an integer from 0 to 7; m represents an integer from 0 to 8; and 1 represents an integer from 0 to 12.
4. The epoxy resin according to claim 1 , wherein the mesogenic structure comprises a structure represented by the following General Formula (M-2):
wherein, in General Formula (M-2), each Y independently represents an aliphatic hydrocarbon group having 1 to 8 carbon atoms, an alkoxy group having 1 to 8 carbon atoms, a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, a cyano group, a nitro group or an acetyl group; each n independently represents an integer from 0 to 4; and * represents a bonding site to an adjacent atom.
5. The epoxy resin according to claim 1 , having an epoxy equivalent weight of from 300 to 380 g/eq.
6. The epoxy resin according to claim 1 , having a melt viscosity at 100° C. of 2.0 to 50.0 Pa·s.
7. The epoxy resin according to claim 1 , wherein a cured product of the epoxy resin cured by 3,3′-diaminodiphenyl sulfone, which is a curing agent, has a fracture toughness of 2.4 MPa·m 1/2 or more measured by three-point bend testing in accordance with ASTM D5045-14.
8. The epoxy resin according to claim 1 , wherein a cured product of the epoxy resin cured by 3,3′-diaminodiphenyl sulfone, which is a curing agent, shows an interference pattern due to depolarization, when the cured product is observed with a polarized light microscope under crossed Nicols.
9. An epoxy resin composition, comprising the epoxy resin according to claim 1 and a curing agent.
10. An epoxy resin cured product, which is a cured product of the epoxy resin composition according to claim 9 .
11. A composite material comprising the epoxy resin cured product according to claim 10 and a reinforcing material.