Durability of a reference material over diverse conditions

A polyethylene film with phenolic antioxidant and phosphite synergist, has been proposed to be a standard reference material for the oxidative inducti on time measurement by DSC (differential scanning calorimetry) [R.L. Blains , A proposed reference material for oxidative induction time by differentia l scanning calorimetry, in: A.T. Riga, G.H. Patterson (Eds.), ASTM Special Technical Publications, STP 1326, ASTM, W. Conshohocken, PA, 1997, pp. 193- 204.], ASTM D-3895 [ASTM D-3895-92, Test Method for Oxidative Induction Tim e of Polyolefins by Differential Scanning Calorimetry]. We have examined th e oxidative stability of this material over diverse conditions. These inclu de oxidative induction time in air, over broad temperatures; induction time in pressurized oxygen in a pressure DSC, circulating oven. and samples sub jected to different doses of ionizing radiation. It appears that when the l ifetime is presented in the Arrhenius form, a progressively diminishing act ivation energies toward room temperature was observed. After combining expe rimental OIT (oxidative induction time) data of up to about 8 years, a cons ervative estimate of durability of about 30 years was obtained. (C) 2000 Pu blished by Elsevier Science B.V.