The word "unvulcanized" refers to a state where a material, typically rubber, has not undergone the process of vulcanization, which is intended to improve its strength and elasticity. Antonyms of the word "unvulcanized" include "vulcanized," "cured," "hardened," "stabilized," and "strengthened." Vulcanization is a crucial step in the manufacturing of tires, hoses, belts, and other rubber products, as it increases their durability and resistance to weathering, chemicals, and abrasion. Hence, the antonyms of "unvulcanized" signify a material that has undergone this process and possesses the desirable properties of strength, flexibility, and longevity.