The optimum ratio of diisocyanate to polyol in the synthesis of polyurethane to achieve maximum mechanical strength depends on the specific types of diisocyanate and polyol being used, as well as the desired properties of the final product. In general, a stoichiometric ratio of 1:1 one diisocyanate molecule to one polyol molecule is often used as a starting point.However, this ratio can be adjusted to fine-tune the properties of the resulting polyurethane. For example, increasing the amount of diisocyanate relative to the polyol can lead to a more rigid and stronger material, while increasing the polyol content can result in a more flexible and softer material.It is important to note that the specific ratio will depend on the molecular weights and functionalities of the diisocyanate and polyol being used. To determine the optimum ratio for a specific application, it is recommended to perform a series of experiments with varying ratios and evaluate the mechanical properties of the resulting polyurethane materials.