The optimal ratio of diisocyanate and polyol for the synthesis of polyurethane with desired mechanical and thermal properties depends on the specific application and requirements of the final product. In general, the stoichiometric ratio of diisocyanate to polyol is 1:1, which means one isocyanate group reacts with one hydroxyl group.However, this ratio can be adjusted to achieve specific properties in the final polyurethane product. For instance, increasing the diisocyanate content can lead to a more rigid and thermally stable material, while increasing the polyol content can result in a more flexible and softer material.It is essential to consider the molecular weight and functionality of the diisocyanate and polyol, as well as the presence of any additives or catalysts, when determining the optimal ratio for a specific application. Ultimately, the ideal ratio should be determined through experimentation and testing to achieve the desired mechanical and thermal properties for the specific polyurethane product.