DETERMINATION OF PROPORTION OF EPOXY RESIN BY USING ITS WPE NUMBER
PROCURE 812 replaces Epon 812, which is no longer available. The proportions of DDSA, NMA, and DMP-30 in PROCURE 812 are the same as in Epon 812.
Since W.P.E. (Weight per Epoxide Equivalent) values of the epoxies vary from lot to lot, the only reliable way to ensure reproducible hardness of the blocks is by using the W.P.E. supplied with each bottle. According to Luft's formula, the following equation is used, with the ratio of anhydride equivalent to epoxy being 0.7:1.
Wt of Anhydride req 100g of Embed 812 Anhydride Ratio of anhydride =(-----------------) x ( M.W. ) x (to epoxy resin equivalent) (DDSA and NMA) W.P.E.
Using 100g of PROCURE 812 and Anhydride M.W. of 266 for DDSA, 178 for NMA, and the ratio of anhydride to epoxy resin Equivalent is 0.7.
With the Above equation and 100g PROCURE 812 being used, with a W.P.E. of 149:
Weight of DDSA = 100g X 266 X .7 = 124.96g 149 Mixture A: 100g PROCURE 812 125g DDSA
Weight of NMA = 100g X 178 X .7 = 83.26g 149 Mixture B: 100g PROCURE 812 = 84 g NMA
Immediately before use, the two mixtures A and B are blended, and the accelerator DMP-30 is added in the proportion of 1.5% - 2%. Increasing the amount of DMP-30 will increase the cure rate.