In various application fields of epoxy resin, its final performance is provided by cured epoxy resin. The taxi performance of the cured epoxy resin depends on the molecular structure of the cured product. The molecular structure and formation of the cured product depends on the structure and performance of the epoxy resin, the structure and performance of the curing agent, the structure and performance of the additive, and the curing history of the epoxy resin. Here, we first introduce the influence of the structure of bisphenol A epoxy resin on the performance of epoxy resin and its cured product.
1. The macromolecular structure of bisphenol A epoxy resin has the following characteristics:
(1) Both ends of the macromolecule are epoxy groups with strong reactivity.
(2) There are many ether bonds on the main chain of the molecule, which is a linear polyether structure.
(3) A large number of secondary hydroxyl groups appear regularly on the resin molecular chain with a large n value and far apart, which can be regarded as a long-chain polyol.
(4) There are also a large number of benzene rings, methine groups and isopropyl groups on the main chain.
2. Each structural unit of bisphenol A epoxy resin gives the resin the following functions: epoxy group and hydroxyl group give the resin reactivity, which makes the cured resin have strong cohesion and adhesion. Ether Jian and hydroxyl groups are polar groups, which help to improve infiltration and adhesion. Ether Jian and C-C bond make macromolecules flexible. The benzene ring imparts heat resistance and rigidity to the polymer. Isopropyl also imparts certain rigidity to large molecules. The bond energy of the -C-O- bond is high, thereby improving alkali resistance. Therefore, the molecular structure of bisphenol A epoxy resin determines its performance with the following characteristics:
(1) It is a thermoplastic resin, but with thermosetting properties, it can form a variety of cured products with excellent properties with a variety of curing agents, catalysts and additives, and can almost meet various requirements.
(2) The resin has good manufacturability. It does not generate small molecular volatiles during curing, and can be molded at low pressure. Soluble in many solvents.
(3) The cured product has high strength and bonding strength.
(4) The cured product has high corrosion resistance and electrical properties.
(5) The cured product has certain toughness and heat resistance.
(6) The main disadvantages are: low heat resistance and toughness, poor humidity resistance and weather resistance.