What is Plasticizers? Plasticizer or also known as dispersants are additives that increase the plasticity or fluidity of the material to which they are added. Plasticizers are relatively low molecular weight materials which have a capacity to alter the physical properties of a polymer to render it more useful as film forming agents.Polymers are widely used as film forming material as they : Produce transparent films Produce intact films They have lower values for water vapor permeability rate They have lower values for oxygen transmission rates.The polymers cellulose (derivates or cellulose related compounds like HPMC, MC, EC, HPMCP) used as film forming agents are relatively brittle in nature at room temperature and pressure do to their complex structure. When such a material is applied as a film coat on to tablet a smooth film is not be obtained. This condition necessitated the addition of plasticizers to the coating dispersions. Thats why we add plasticizer to film coating. The function of plasticizer is to make the polymer more liable and soft and thereby enhancing the flexibility and plasticity to the films.The addition of plasticizers to polymeric material causes them to diffuse within the polymers and cause polymer deformation and coalescence into homogenous films. The effectiveness of plasticizers on polymeric dispersion depends upon polymer compatibility and the permanence of plasticizer during the course of shelf life, or when it comes in contact with physiological fluids.Plasticizer Function in Film Coating Tablet Plasticizer modify the physical and mechanical properties of film by enhancing the mobility of the polymeric chain. Plasticizer reduce the glass transition temperature, plasticizer facilities the thermal stability of the drug and other ingredients. The intensity of particle coalescence and the quality of the resulting final film so formed entirely depends on the type and the concentration of plasticizer added to the coating dispersion. The efficiency of a plasticizer is intensely related to its chemical structure and the extent and rate of interaction with the polymeric material present in the formulation. Physicochemical properties of the films mainly the water uptake and erosion, solid-state crystallinity, thermal behavior and water vapor and drug permeability are modified to a greater extend.