Epoxy Resins

Epoxy

Epoxy resins are one of the most important thermosetting polymers, which are extensively used as the structural adhesives and coatings, and other plastic engineering materials because of their high modulus and thermal stability properties. Also, epoxy resins are widely used in the electronics industry as moulding and sealing compounds for electronic packaging. Especially, these thermosetting resins have a variety of useful properties, including excellent insulating characteristics, good adhesive properties, outstanding chemical resistance, retention of properties under severe operating conditions, low moisture adsorption, and no reaction by-products that could cause void formation or act as plasticizers [17,18]. { Preparation and Characterization of Poly(amide imide)-based Carbon Nanofibers/Epoxy Nanocomposites, Min-Kang Seo1, Kyeong-Eun Choi2, Sang-Hee Park3, Young-Taik Hong4 and Soo-Jin Park1  }

Epoxies are polymer resins where the resin molecule contains one or more epoxide groups. The chemistry can be adjusted to perfect the molecular weight or viscosity as required by the end use. There are two primary types of epoxies, glycidyl epoxy and non-glycidyl. Glycidyl epoxy resins can be further defined as either glycidyl-amine, glycidyl-ester, or glycidyl-ether. Non-gylcidyl epoxy resins are either aliphatic or cyloaliphatic resins. One of the most common glycidyl epoxy resins is created using Bisphenol-A, and is synthesized in a reaction with epicholrohydrin. The molecular structure of this is shown below in Figure 1.

[pic 1]

Figure 1:

Initially, the viscosity of these resins is low; however, thermoset resins undergo chemical reactions that crosslink the polymer chains and thus connect the entire matrix together in a three-dimensional network. This process is called curing. Epoxy resins are cured with the addition of a curing agent, which is commonly called a hardener. Perhaps the most common type of curing agent is amine based such as Triethylenetetramine (TETA) as shown in Figure 2. Unlike in polyester or vinyl ester resins where the resin is catalyzed with a small (1-3%) addition of a catalyst, epoxy resins usually require the addition of the curing agent at a much higher ratio of resin to hardener, often 1:1 or 2:1.