Plasticizers are added to polymers to reduce brittleness. They decrease intermolecular forces between polymer chains, thus increasing flexibility and extendibility. Generally, plasticizers act by entering between polymeric molecular chains, physical-chemically associating with the polymer, reducing cohesion within the film network, and effectively extending and softening the film structure (Arnold, 1968, Banker, 1966 and Guilbert and Gontard, 1995a).