Experimental diffusivity and solubility of carbon dioxide and nitrogen in polyproplene

In this work, we determined the concentration-dependent diffusivity and solubility of environmentally benign blowing agents, carbon dioxide and nitrogen in polypropylene. For this purpose, experiments were carried out to obtain pressure decay data in the range 170-190°C and 0.29-7.32 MPa. For each experimental run, the mass of gas absorbed as a function of time led to the calculation of diffusion coefficient. The equilibrium pressure at sufficiently long time enabled the calculation of solubility.  The calculus of variation was used to establish the necessary conditions for the determination of concentration-dependent diffusivity such that the model-predicted mass of gas absorbed in polymer matches with the experimental counterpart. The value of diffusivity was found to lie in the ranges 2.67-9.13xlO-9 and 3.88-12.94xlO-9 m2 S- I for carbon dioxide and nitrogen, respectively.