Polymers form when several monomers join through a process known as polymerization. These are the two classes of polymers, namely natural polymers, and synthetic polymers. The natural polymers are wool, rubber, shellac, silk, and keratin. The two examples of synthetic polymers are thermoplastic polymers and thermoset plastic. Thermoplastic polymers are solid at low temperatures but above specific temperatures are moldable. Thermoplastic polymers also melt when heated. Examples of thermoplastic polymers include Teflon, polycarbonate, and nylon. On the other hand, thermoset plastics are liquid. They become an irreversible polymer when heated as they decompose. Thermoset plastics have high molecular weights and are rigid. Thermoset plastics include polyester, epoxy, polyurethanes, and Kevlar. This research will delve into a type of thermoset plastic known as epoxy resin. It will discuss its definition, properties, classes, sources, and its commercial uses.
Epoxy Resins
Epoxy resins are a type of thermoset plastic produced synthetically. They contain more than two epoxide group. In normal circumstances, an epoxy resin contains two carbon atoms and an oxygen atom. They are produced chiefly from petroleum products and are brownish substances. There are two classes of epoxy resins, namely glycidyl group and non-glycidyl group. Glycidyl group consisting of Bisphenol A epoxy resin, Epoxy Cresol Novolac, Novolac epoxy resin, Bisphenol F epoxy resin and Glycidylamine epoxy resin. The non-glycidyl group includes Aliphatic epoxy resin and cyclo-aliphatic resin.
Novolac epoxy resin. The epoxy resins form because of the reaction of phenols and formaldehyde. A further process of glycidylation leads to the production of epoxy phenol novolacs and epoxy cresol novolac. These epoxy resins are highly viscous and have a high mean epoxide functionality.
Bisphenol A epoxy resin. Formed due to the reaction of bisphenol A with epichlorohydrin.
Bisphenol F epoxy resin. Formed by reacting bisphenol F with epichlorohydrin, a process known as epoxidation. They have a slightly lower viscosity than Bisphenol A epoxy. However, they possess a higher mean epoxide functionality that bisphenol A epoxy resin.
Aliphatic epoxy resin. The reaction of aliphatic alcohols and epichlorohydrin produce aliphatic epoxy resins. They have low viscosity and customarily used as reactive diluents.
Cyclo aliphatic epoxy resin. The reaction of peracid with cyclo-olefins produces these types of epoxy resins. They have low viscosity. As compared with aliphatic epoxy resins, they have a higher temperature resistance and favorable electrical properties at higher temperatures.
Glycidylamine epoxy resin. Formed due to the reaction of epichlorohydrin and aromatic amines. They have a medium viscosity, are very reactive, have high-temperature resistance and excellent mechanical properties.
Properties of epoxy resins
Epoxy resins possess excellent features that make it popular in industrial circles. They have excellent mechanical strength, fatigue strength and adhesive strength that are comparable to the welding process, though it is less costly and faster. As it has low shrinkage rate during curing, it eliminates chances of internal stress in materials. Also, they can withstand expansion due to temperature variations without harming the elements. Epoxy resins are also resistant to chemical reactions and solvents. Moreover, they are resistant to heat. It is the properties that make them popular to use in electrical applications. Epoxy resins are versatile in that its formulations can be altered to meet the needs one requires. Other significant properties are that epoxy resins are non-porous, can resist impact and are tough, the thickness of the applied film is controllable and is easy to use on the surfaces of materials. Epoxy resins also have a long shelf life.
Epoxy resin cure
Curing or gelation of epoxy resins is the process in which epoxy resins react with curing agents to produce cross-linked thermoset figures. This process is usually exothermic. Two common curing processes are homopolymerization and use of hardeners to form a copolymer. Homopolymerisation involves the reaction of epoxy resin with itself in the presence of an anionic or cationic catalyst. The cured product exhibits excellent thermal and chemical resistance.
Applications and commercial uses of epoxy resins
Adhesives. Engineering adhesives and structural adhesives are popular in the aircraft construction industry, vehicle manufacture, motorboat, bikes, and bicycles. Epoxy resins are useful as general purpose gel or adhesives.
Paints and coats. Due to the ability of epoxy resins to dry faster and provide tough protective layers, they are common in the paint industries. Powder coats for washers and dryers are epoxy resins.
Laboratory use. Used in the biology labs to embed electron microscope samples
Electronics and its systems. Epoxy resins are applicable in the over-molding of transistors, integrated circuit board, and printed circuit boards. Potting of transformers and inductors make use of epoxy resins.
Aerospace application. Epoxy resins are useful in the reinforcement of fiber. It is one of the structural matrix material and acts an adhesive.
Art scene. Artists use epoxy resins together with pigments to obtain varied colors in their artwork.
Cement industry. Epoxy resins act as a binder in pozzolanic cement
Petroleum industry. Epoxy resins also serve to solidify sandy surfaces during the process of oil drilling. They are also useful in the water shut-off process.
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