Efficiency of processing stabilizers using a micro-oxygen uptake technique

Abstract

The thermooxidative stability of various low density polyethylene (LDPE) film formulations was investigated using the technique of micro oxygen uptake measurement following multiple extrusions. The results show that the micro oxygen uptake technique is more sensitive than conventional test methods. High molecular weight hindered phenolic stabilizers are more effective in reducing gel formation during polymer film production than are lower molecular weight species such as butylated hydroxytoluene (BHT). The antioxidant 2,2′-ethylidene-bis-(4,6-di-tert-butylphenol) is an effective stabilizer, but it forms a highly coloured complex with transition metal impurities. The hindered phenol/organic phosphite system, comprising a combination of 0.008% (wt/wt) octadecyl-3-(3,5-di-tert-butyl)-4-hydroxy-phenol propionate and 0.032% (wt/wt) tris-(2,4-di-tert-butyl)phenyl phosphite, is effective in suppressing the formation of coloured products but does not provide adequate thermal stability.