Evaluation of novel 4,4-dimethyloxazolidine derivatives as thermal and UV stabilisers in linear low density polyethylene (LLDPE) film

Abstract

Three novel doxyl derivatives have been synthesised and characterised as thermal and light stabilisers for linear low density polyethylene (LLDPE). The three additives (C2, C3, U2) when mixed with a commercial phenolic antioxidant Irganox 3114, gave rise to good thermal antioxidant activity, similar to that of a commercial HALS (Hindered Amine Light Stabiliser), Chimassorb 944. Furthermore, when the additives are mixed with a mixture of a commercial antioxidant and HALS synergism is observed. On the other hand whilst the three additives exhibit a light stabilising function they are not as exceptional as the commercial mixture of HALS and phenolic antioxidant. Using FTIR analysis interesting comparisons are made between the respective growths in various functionalities. During thermal oxidation the hydroxyl and double bond vinyl and trans-vinylene absorbances (909 and 966 cm −1) begin to growth at the same time and rate as the carbonyl groups. In the case of samples under UV oxidative conditions the ratio of the 1718/1774 keto/peracid value in is lower than that observed on thermal oxidation. Inferences are made form the relative rates of growth and decay in the double bond and carbonyl group concentrations and how these relate to the relative stabilities of the stabilised films.