Method of tuning physical properties of thermosets

Patent metadata

Field	Value
Publication number	US-12065562-B2
Application number	US-202217577111-A
Country	US
Kind code	B2
Filing date	Jan 17, 2022
Priority date	Jan 17, 2022
Publication date	Aug 20, 2024
Grant date	Aug 20, 2024

Abstract

Polymerization-induced phase separation enables fine control over thermoset network morphologies, yielding heterogeneous structures with domain sizes tunable over 1-100 nm. However, the controlled chain-growth polymerization techniques exclusively employed to regulate morphology at these length scales are unsuitable for most thermoset materials typically formed through step-growth mechanisms. By employing binary mixtures in place of the classic constituents of phase-separating thermosets—resin, curing agent, and secondary polymer—facile tunability over morphology can be achieved through a single compositional parameter. Indeed, this method yields morphologies spanning nano-scale to macro-scale, controlled by the relative reactivities and thermodynamic compatibility of the network components. Due to the connection between chain dynamics and microstructure in these materials, the tunable morphology enables exquisite control over glass transition and other physical and mechanical properties.

First claim

We claim:

1. A method of forming a thermoset, comprising:
mixing a binary mixture of epoxy resins comprising a first epoxy resin and a second epoxy resin, wherein the first epoxy resin favors phase separation compared to the second epoxy resin and wherein a compositional parameter e of the binary mixture is equal to a fraction of the second epoxy resin in the binary mixture, an amine curing agent, and a rubber reactive with either the binary mixture of epoxy resins or the amine curing agent to provide a liquid mixture; and
curing the liquid mixture, whereby the liquid mixture phase separates to form a thermoset with phase separated domains, wherein a domain size of the phase separated domains is continuously variable from less than 200 nm when e equals 1 to greater than 1 μm when e equals 0, and wherein e is selected to tune a domain size and composition of the phase separated domains.

2. The method of claim 1 , wherein the size and composition of the phase separated domains determines a physical property of the thermoset, and wherein the physical property is a glass transition temperature, toughness, modulus, strength, fracture strain, impact and/or shock resistance, hardness, permeability, porosity, pore size, transparency, thermal expansion, or conductivity.

3. The method of claim 1 , wherein the binary mixture of epoxy resins comprises a bisphenol A- or bisphenol F-based, aliphatic or cycloaliphatic, or novolac resin.

4. The method of claim 1 , wherein the rubber comprises an amine-functionalized rubber that reacts with the binary mixture of epoxy resins.

5. The method of claim 4 , wherein the amine-functionalized rubber comprises a polyether triamine based on a trifunctional polyoxypropylene backbone, amine-functionalized butadiene, nitrile, isoprene, chloroprene, styrene-butadiene, silicone, butyl, or ethylene-propylene-diene rubber.

6. The method of claim 1 , wherein the amine curing agent comprises a polyether diamine based on a polyoxypropylene backbone, triethylenetetramine, m-phenylenediamine, 3-aminobenzylamine, or m-xylylenediamine.

7. The method of claim 1 , wherein the first epoxy resin comprises diglycidyl ether of bisphenol A and the second epoxy resin comprises an epoxide-functionalized poly(propylene oxide).

8. The method of claim 1 , wherein the rubber comprises polyether triamine or poly(ethylene glycol).

9. The method of claim 1 , wherein the phase-separated domains comprise a rubber domain and an epoxy matrix domain.

10. A method of forming a thermoset, comprising:
mixing an epoxy resin, a binary mixture of amine curing agents comprising a first amine curing agent and a second amine curing agent, wherein the second amine curing agent favors phase separation compared to the first amine curing agent and wherein a compositional parameter n of the binary mixture is equal to a fraction of the second amine curing agent in the binary mixture, and a rubber reactive with either the epoxy resin or the binary mixture of amine curing agents to provide a liquid mixture; and
curing the liquid mixture, whereby the liquid mixture phase separates to form a thermoset with phase separated domains, wherein a domain size of the phase separated domains is continuously variable from less than 200 nm when n equals 0 to greater than 1 μm when n equals 1, and wherein n is selected to tune a domain size and composition of the phase separated domains.

11. The method of claim 10 , wherein the size and composition of the phase separated domains determines a physical property of the thermoset and wherein the physical property is a glass transition temperature, toughness, modulus, strength, fracture strain, impact and/or shock resistance, hardness, permeability, porosity, pore size, transparency, thermal expansion, or conductivity.

12. The method of claim 10 , wherein the first amine curing agent comprises a polyether diamine based on a polyoxypropylene backbone and the second amine curing agent comprises triethylenetetramine.

13. The method of claim 10 , wherein the first amine curing agent comprises m-phenylenediamine and the second amine curing agent comprises m-xylylenediamine.

14. The method of claim 10 , wherein the first amine curing agent comprises 3-aminobenzylamine and the second amine curing agent comprises m-xylylenediamine.

15. The method of claim 10 , wherein the phase-separated domains comprise a rubber domain and an epoxy matrix domain.

16. A method of forming a thermoset, comprising:
mixing an epoxy resin, an amine curing agent, and a binary mixture of rubbers comprising a first rubber and a second rubber, wherein the second rubber favors phase separation compared to the first rubber and wherein a compositional parameter R of the binary mixture is equal to a fraction of the second rubber in the binary mixture, wherein the first and second rubbers are reactive with either the epoxy resin or the amine curing agent to provide a liquid mixture; and
curing the liquid mixture, whereby the liquid mixture phase separates to form a thermoset with phase separated domains, wherein a domain size of the phase separated domains is continuously variable from less than 200 nm when R equals 0 to greater than 1 μm when R equals 1, and wherein R is selected to tune a domain size and composition of the phase separated domains.

17. The method of claim 16 , wherein the size and composition of the phase separated domains determines a physical property of the thermoset and wherein the physical property is a glass transition temperature, toughness, modulus, strength, fracture strain, impact and/or shock resistance, hardness, permeability, porosity, pore size, transparency, thermal expansion, or conductivity.

18. The method of claim 16 , wherein the binary mixture of rubbers comprises at least one amine-functionalized rubber that reacts with the epoxy resin.

19. The method of claim 18 , wherein the at least one amine-functionalized rubber comprises a polyether triamine based on a trifunctional polyoxypropylene backbone.

20. The method of claim 18 , wherein the at least one amine-functionalized rubber comprises an amine-functionalized butadiene, nitrile, isoprene, chloroprene, styrene-butadiene, silicone, butyl, or ethylene-propylene-diene rubber.

21. The method of claim 16 , wherein the first rubber comprises poly(ethylene glycol) and the second rubber comprises a polyetheramine based on a polyoxypropylene backbone.

22. The method of claim 16 , wherein the phase-separated domains comprise a rubber domain and an epoxy matrix domain.

Assignees

• Nat Tech & Eng Solutions Sandia Llc

Inventors

• Jones Brad Howard
• Leguizamon Samuel

Classifications

• C08L2205/035

  containing four or more polymers in a blend · CPC title

• C08L63/00 Primary

  Compositions of epoxy resins; Compositions of derivatives of epoxy resins · CPC title