Effect of interactions between stabilisers and silica used for anti-blocking applications on UV and thermal stability of polyolefin film 2. Degradation studies

The first part of this series of papers (Liauw CM, Childs A, Alien NS, Edge M, Franklin KR, Collopy DG. Polymer Degradation and Stability, 1999;63:391 ) indicated that the interactions between stabilisers and silica were depen dent on both the silica type and the molecular structure of the additive. I n this second part it is shown that these interactions play a significant r ole in the enhancement of thermo-oxidative stabilisation of linear low dens ity polyethylene. Under thermo-oxidation, combinations of the Irganox 1010 with a polymeric hindered amine light stabilisers (HALS) (Chimassorb 944) a fforded strong synergism which is far stronger than when the silica is abse nt. Similar observations were apparent for photo-oxidation but were less pr onounced. On the basis of the adsorption data given in Part 1, it is propos ed that displacement of a relatively weak adsorbing stabiliser by a more st rongly adsorbing one during the product life-time constitutes a controlled release mechanism which can enhance the chemical synergy between stabiliser combinations. (C) 1999 Elsevier Science Ltd. All rights reserved.