Role of β-cyclodextrin nanosponges in polypropylene photooxidation

The interactions between β-cyclodextrin nanosponges and two different UV stabilizers (namely, 2-hydroxy-4(octyloxy)-benzophenone and triphenyl phosphite) in the photooxidation of polypropylene exposed to UV light have been investigated. A significant decrease of the oxidation induction time (OIT) has been observed in presence of β-cyclodextrin nanosponges. On the contrary, the combination of the above nanosponges with 2-hydroxy-4(octyloxy)-benzophenone turned out to be very efficient and advantageous since a remarkable increase of OIT has been registered, namely a threefold increase of polypropylene OIT. This result has indicated a possible synergistic effect between the two species due to the occurring of some chemical or physical interactions, verified by comparing the experimental results and data calculated on the basis of simple additivity rule. Some hypotheses on the interaction mechanism between the two species have been given. Conversely, no effect has been found for the triphenyl phosphite-nanosponge pair.