The ratio between the molecular weight of the polystyrene block and that of the butadiene affects the morphology of the elastomer and determines the final characteristics of the product. With a low content of polystyrene, the elastomer represents the continuous phase in which the polystyrene is dispersed. As the polystyrene content increases, the morphology of the rigid dispersed phase (polystyrene) changes from a structure with spheres to a structure with cylinders; the further increase in the quantity of polystyrene at first causes the formation of a lamellar structure, followed by a phase reversal during which the cylinders and then the polydiene spheres are dispersed in a polystyrene matrix. The mechanical properties of the co-polymers with styrene blocks are very similar (at ambient temperature) to those of vulcanized rubber, with typical ultimate strengths of 30 MPa and elongations up to 800%. SBS compounds are commonly used in applications where resistance to chemical agents and aging is not a decisive factor.