| abstract |
PURPOSE:To prevent the production of sink mark due to the hardening and contraction of a thermosetting resin by a method in which the hardening rate of the resin is partly changed by varying the concentration of a hardening accelerator in the thermosetting resin. CONSTITUTION:One hundred pts.wt. bisphenol-A type epoxy resin (Epikote 828), for example, is mixed with about 80pts.wt. 4-methyl-hexahydrophthalic anhydride as an acid anhydride hardening agent, together with an inorganic filler, e.g., silica, etc., as needed. Twenty five (25)g of the mixture is mixed with 0.05-0.15g of 2-ethyl-4-methylimidazole as a hardening accelerator, whereby preventing the production of sink marks due to hardening contraction of the resin. |