- Structurally, epoxy resin consists of two main parts: long polymer chains of bisphenol A and epichlorohydrin molecules, and polyamine molecules that links these polymer chains into a net-like sheet From a manufacturing standpoint, the two tubes of liquid in a retail epoxy dispenser are filled with separate solutions of epichlorohydrin-bisphenol polymers and polyamine molecules. When mixed together, the hardening or "curing" that results is actually the multiple amine (-NH2) groups in the polyamines breaking open the epicholorhydrins' trigular epoxy (C-C-O) groups to form a nitrogen-carbon bond. In this way, several different epichlorohydrin-bisphenol polymers are linked via the polyamine molecules.
- Even on the retail level, few manufacturers actually synthesize and package the epoxy polymers in-house. Rather, certain companies special in creating special polymer "formulas" from raw materials, which they then sell to manufacturers. Because epoxy resins are used for a vast range of applications (maritime, aerospace, home repair, manufacturing), producers have developed additives that lend special properties such as flexibility, viscosity, color, adhesiveness, and faster curing.
To begin, producers add a strong sodium hydroxide (NaOH) solution to a tank containing bisphenol A solution. The basic hydroxide ions strip hydrogens from the bisphenol to create water. Meanwhile, the Na+ ions help stabilize the bisphenol's negatively-charged oxygen atoms. Next, a concentrated epichlorohydrin solution (approximately 3 times that of the original bisphenol A solution), is added to the mixture. The charged oxygen atoms on the bisphenol A, knock the chlorine atoms away to bond with the epichlorohydrin molecules. The resulting chloride ions (Cl-) are then neutralized by the sodium ions (Na+) in solution.
Once this polymer formation is complete, the producers will add the specific minerals, chemicals, solvents and/or catalysts which give their formulation its special character. - Although triethylenetetramine (TETA) is sold as a mixture four different isomers, they are all synthesized through the same procedure. First, ethylene dichloride is dissolved in ammonia and heated under high pressure for a few hours. The result is an acidic mixture of diethyleneamine and ethyleneamine hydrochloride, which is then neutralized with a strong NaOH solution.
These compounds polymerize in many different ways, forming a wide variety of ethyleneamine-type molecules. Once this mixture is separated through heating and distillation, the 4 TETA isomers are diverted and packaged for shipment.
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