Epoxies

1
Epoxies

• A. Brent Strong

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Epoxies

• Second most widely used family of thermosets
  (after polyesters)
• Large portion of uses are non-reinforced
  (adhesives, paints, etc.)
• Circuit boards are the largest reinforced
  application (low conductivity, low volatiles)
• Advanced composites use epoxies because of
• Thermal stability
• Adhesion
• Mechanical properties

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Epoxy Structure
Epoxy ring
Epoxy ring
(
C
C
)n
C
C
O
O
Polymer portion
Number of repeat units
4
Epoxy - specific molecules
c
c
n
a) Diglycidyl Ether of Bisphenol A (DGEBPA)
(
)n
b) Tetraglycidylmethylenedianiline (TGMDA)
c) Epoxidized phenolic resin (Epoxy Novalac)
5
Properties - chain length (n)
6
Epoxy - specialty molecules
Toughened Epoxy Resin
High Temperature Epoxy Resins
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Epoxies - HDT and structure
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Curing Epoxies

• Epoxies use hardeners instead of initiators for
  curing
• Hardeners can be almost any molecule that will
  react with (open) the epoxy ring

9
Epoxy Crosslink Mechanism
C
C
H
Epoxy
H
Cured Polymer
Hardener
The other end can also react.
10
Curing
Epoxy ring
Epoxy ring
(
C
C
)n
C
C
O
O
H
H
N
N
H
H
Hardener molecules have two reactive ends, so
they can each react with two epoxy molecules.
N
N
H
H
H
H
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Effects of various hardeners
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Epoxy and Polyester Comparison
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Polyester and Epoxy - Properties
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Epoxy
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Thank you

• Brent Strong