| 摘要 |
The invention relates to a seamless model free of bond lines and to a method of making same. The method includes the sequential steps of providing a substructure having an exposed outer surface, applying a modeling paste to the outer surface of the substructure in the form of a continuous layer, curing the continuous layer of applied modeling paste, and machining said cured layer of modeling paste to the desired contour. The modeling paste of the invention is a mechanically frothed syntactic foam prepared by injecting inert gas with mechanical stirring into either a formed froth-forming composition, which is preferably a polyurethane or epoxy froth-forming composition containing microballoons. The polyurethane composition exemplified herein comprises (1) an organic polyisocyanate component; (2) a polyol component comprising (a) greater than 50%, by weight of a high molecular weight polyol and (b) less than 50%, by weight, of a low molecular weight polyol; and (3) a chemical thixotropic agent in an amount sufficient to induce thixotropic properties. The epoxy composition preferably comprises (1) an epoxy resin; (2) a thixotropic agent in an amount sufficient to induce thixotropic properties; and (3) a hardener comprising (a) at least one polyethyleneimine and (b) at least one other amine having at least two amino hydrogen groups, the combined amounts of (a) and (b) being sufficient to effect cure of the epoxy resin. |
