The optimal ratio of diisocyanate to polyol for the synthesis of polyurethane with maximum tensile strength and elongation at break 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 isocyanate group per hydroxyl group is used to achieve a complete reaction and balanced properties.However, this ratio can be adjusted to achieve specific properties in the final polyurethane product. For example, increasing the diisocyanate content can lead to higher crosslink density and improved tensile strength, while increasing the polyol content can result in greater flexibility and elongation at break.To determine the optimal ratio for a specific application, it is necessary to conduct experiments with varying ratios of diisocyanate and polyol, and then test the resulting polyurethane samples for their mechanical properties. This will allow you to identify the ratio that provides the best balance of tensile strength and elongation at break for your specific needs.