Plasticizer diffusion rate and the methods of study

Plasticizers diffusion is important in many practical applications. These include  

Diffusion of small molecules in polymeric materials is too diverse to be described by a simple relationship applicable to all of the above eases. There are several types of diffusion  

The differences in these processes lies in the availability of the penetrant (whether an unlimited pool of liquid or a limited-supply), the eoncentration gradient, the reaction of surrounding molecules (relaxation rate), and physical conditions (temperature, amount of free volume, interactions, etc.). These diverse inflnences make aity description complex. Fick s first law is given by the equation  

D diffusion coefficient c concentotion of diffusant X depth of penetration. 

The flux of the diffusant is proportional to the gradient of concentration of the diffusant with the diffusion coefficient being a proportionahty constant. In this model it was assumed that there is some diffusion front which advances with diffusion time. The concentration difference between the pure liquid and the concentration of the same liquid in the material is the driving force of the process and the diffusion rate is determined by the properties of solid body and of the penetrant. These are expressed by a numerical value of the diffusion coefficient. A constant diffusion rate is assumed. 

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