1, the calculation of the amount of amine curing agent The calculation method for the amount of amine curing agent is based on the consideration of an active hydrogen on the amine group and an epoxy group. The amount of various primary amines and secondary amines was obtained by the following formula: W=(M/Hn)×E; Where: W—the mass of an amine curing agent per 100 g of epoxy resin, g; M—the molecular weight of the amine curing agent; Hn—The number of active hydrogen atoms on the amine group in the curing agent molecule; E—the epoxy value of the epoxy resin. Example: Use ethylenediamine as the curing agent to cure the E-44 epoxy resin. Determine the amount of ethylenediamine required for each loog epoxy. Solution: The molecular formula of ethylenediamine is H2N-CH2-NH2, the molecular weight of ethylenediamine is M=60, and the number of active hydrogen atoms of ethylenediamine is Hn=4. E-44 Epoxy resin epoxy value from the table found E = 0.40 ~ 0.47, then the maximum W = 60/4 × 0.47 = 7.05 (g), W minimum = 60/4 × 0.40 = 6 (g); That is, 6-7g of ethylenediamine curing agent is required for every 100g of E-44 epoxy resin. In fact, with the size of the amine molecule, as well as the difference in reaction ability and volatilization, it is generally more than 10% more than the theoretically calculated value. 2, the amount of anhydride curing agent usage The amount of anhydride curing agent is usually determined by the following formula: W = AE · E · K, Where: W—the mass of an anhydride curing agent per 100 g of epoxy resin, g; AE-anhydride molar mass, kg/mol; K - the amount of anhydride required per mole of epoxy, mol. Empirical data, which varies from 0.5 to 1.1, generally takes 0.85. Example: For a 100 g epoxy resin with an epoxy value of 0.43, if a neighboring phthalic anhydride (PA) is used as its hardener, what amount is appropriate to use? Solution: Phthalic anhydride molecular formula: its molecular weight M = 148; E = 0.43 empirical value to take K = 0.85 so the appropriate amount is: W = 148 × 0.43 × 0.85 × = 54.1 (g); That is, 100 g of epoxy resin with an epoxy value of 0.43 is suitable, and about 54 g of phthalic anhydride is used as a curing agent. The actual usage is also higher than the theoretical calculation. There are two reasons why the amount of curing agent is generally higher than the theoretical value: one is that during the preparation process and during the operation there will be volatilization losses; the second is that it is not easy to mix with the resin. However, when the amount of hardener is too large, it will cause the resin chain to stop growing, reduce the molecular weight of the hardened material, and make the cured resin brittle. The above calculated values ​​all refer to the pure curing agent, that is, the content is 100%. When this purity is not reached, a conversion adjustment should be made.
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