The present invention is a high modulus bio-based polymer plastic composition or mixture and methods of preparing the same. The composition is formed from the reaction of a bio-based epoxidized triglyceride oil, an energy activated catalyst and a bio-based non-aromatic cross-linking compound to form a structural polymer plastic. The bio-based epoxidized triglyceride oil is selected from a bio-based epoxidized triglyceride or a bio-based acrylated epoxidized triglyceride. The non-aromatic cross-linking compound is selected from itaconic acid or itaconic anhydride, and the energy activated catalyst is activated by UV radiation or heat.