How high is the melting point of resin?
Bisphenol A epoxy resins, like other polymers, are not a single molecule of relative molecular weight, but a mixture of homologous molecules with different degrees of polymerization. Therefore, not only the average relative molecular mass has a great influence on the properties of the resin, but also the relative molecular weight distribution has a great influence on the properties of the resin. The bisphenol A epoxy resin, the average molecular weight is determined by the size of the epoxy resin content, hydroxyl content, resin viscosity, softening point and solubility properties have great influence on the curing process, and the cured resin properties and applications. For example, resins with relatively low molecular weight can be dissolved in aliphatic and aromatic solvents, while resins with relatively high molecular weight can only be dissolved in strong solvents such as ketones and esters. The relative molecular weight distribution will affect the crystallinity, viscosity and softening point of epoxy resin. For example, when the average molecular weight is the same and the relative molecular weight is wide, the softening point of the resin is low. Therefore, average relative molecular mass and relative molecular mass distribution are important properties of epoxy resin.
The performance of epoxy resin is determined by the average molecular weight and molecular weight distribution and chemical properties (epoxy content, hydroxyl content, heterogeneous end group structure and content), physical properties (viscosity, softening point, solubility etc.) to determine the. A small amount of impurities (water, NaCl, free phenol, solvent, epoxy chloropropane, high boiling agent, etc.) also have a great influence on the quality of the resin.
Not a pure substance such as epoxy resin, bisphenol A type epoxy resin is composed of homologous compounds with different degree of polymerization, so it has no clear melting point, only a melting temperature range, known as the softening point, melt temperature characterization of his soft. The softening point is a temperature range. For example: because the composition and content of different softening point can be 58 degrees ~93 degrees C. epoxy phenolic resin with high viscosity semi solid, average functionality of 2.5 to 6, the softening point is less than or equal to 28 DEG C; three hydroxyphenylmethane three glycidyl ether epoxy resin as the solid red, the softening point of 72 to 78 DEG C; some crystalline epoxy resin, high purity, can also be referred to as the melting point, such as 140 + 2 C.
The epoxy group with the highest reactive epoxy group is the most important functional group of epoxy resin. The content of epoxy group is directly related to the size of the crosslink density of the curing agent. Thus become one of the main factors that affect the properties of cured products. Therefore, in the synthesis of epoxy resin, the content of epoxy resin is one of the main means to control and identify the quality of epoxy resin. When applying epoxy resin, the content of epoxy group is one of the main bases for formulation design (material selection and proportion) of epoxy resin curing system. There are usually three kinds of epoxy group content. The epoxy equivalent is defined as the quality of epoxy resin containing lmol epoxy resin (g), which is g/mol. Epoxy value - defined as the amount of the epoxy group contained in the 100g epoxy resin. The unit is mol/100g. Epoxy resin mass fraction - defined as 100g epoxy resin containing epoxy group mass (g), per unit%.
