The optimal ratio of diisocyanate to polyol for the synthesis of polyurethane with optimal mechanical properties depends on the specific types of diisocyanate and polyol being used, as well as the desired properties of the final product. In general, the ratio is determined by the stoichiometry of the reaction, which requires one isocyanate group NCO to react with one hydroxyl group OH from the polyol.A common guideline is to use an equivalent ratio of 1:1 NCO:OH , which ensures that all the reactive groups are consumed, and the resulting polyurethane has a balanced network structure. However, this ratio can be adjusted depending on the desired properties of the polyurethane. For example, increasing the amount of diisocyanate can lead to a more crosslinked and rigid structure, while increasing the amount of polyol can result in a more flexible and elastic material.It is important to note that the optimal ratio may vary depending on the specific application and desired properties of the polyurethane. Therefore, it is recommended to perform experiments and characterization tests to determine the best ratio for a given system.