Effect of phase transitions on the volatility of UV absorbers from polypropylene

The volatility of 2-hydroxy-4-methoxybenzophenone and 2-(2′-hydroxy-5′-methylphenyl) benzotriazole from isotactic polypropylene was studied by thermal methods in the temperature range that included the melting point of one of the stabilizers and the fusion of the polymer. The process proceeds according to the first order of kinetics. The rate constants of the stabilizers' volatility were calculated and the Arrhenius plots were constructed. The observed discontinuities in the Arrhenius dependences are interpreted as the result of the phase transitions of the polymer (melting) and the stabilizer. The activation energies for all zones were calculated. © 1993 John Wiley & Sons, Inc.