DIFFUSION OF HINDERED AMINE LIGHT STABILIZERS IN LOW-DENSITY POLYETHYLENE AND ISOTACTIC POLYPROPYLENE

Diffusion coefficients and solubilities of some hindered amine light stabilizers (HALS) were measured in low density polyethylene (LDPE) and isotactic polypropylene(iPP). From the results obtained, activation energies and preexponential parameters of the Arrhenius equation were calculated. In the case of oligomeric HALS no measurable diffusion was found even after 10 months at room temperature. An empirical model from the literature was used for the correlation of physical parameters obtained with the available experimental data on the efficiency of HALS. According to this model the solubility value seems to be more important for stabilizer efficiency than its rate of diffusion.