the casting process faster, economical and conventional is to green sand molding, where the main ligand is a moist clay (bentonite). however, due to technological requirements, are also used as binders toxic furan resin, phenolic or urethane. new technologies have been developed for the recovery and blanketing the sands, but the resins currently available are limited by its chemical origin. after use these molds are discarded, and thus the toxic binders become an environmental problem. thus, the replacement of these binders by organic compounds derived from renewable sources such as polyurethane resin derived from castor oil minimizes environmental impacts, leading the casting process towards sustainability, necessary because of the increasing stringency of environmental legislation. because of the thermal behavior of vegetable polyurethane, which decompose in a more pronounced when exposed to high temperatures compared to traditional organic binders the addition of inorganic components is required as a facilitator of the link between the grains sand and consequent cohesion of the molds during stage of fusion. in this sense, the use of phase diagrams to predict the appearance of liquid phase by the addition of inorganic components to the mix sand / resin in sand molds for casting and its effect on mechanical strength at high temperatures of the mold serves as a theoretical tool in helping to determining the composition of the molds according to its thermal stress during melting. initial tests of molding and mechanical strength at room temperature showed that the polyurethane resin derived from castor oil produces results comparable to those of commercial resins. also the addition of inorganic components and its effect when subjected to heat treatment is tested for mechanical compression and analysis of photomicrographs of the compositions, as provided in the respective phase diagrams.