Effect of additive interactions on the thermo-oxidative stabilization of a film grade metallocene LLDPE

The simultaneous effects of a range of additives and associated interactions on melt processing stability, processing discoloration, and long‐term stability of a blown film‐grade metallocene LLDPE (mLLDPE) were investigated by using a two‐level factorial experimental design. The additives investigated were a phenolic antioxidant, a phosphite processing stabilizer, a calcium stearate antacid, a synthetic silica antiblocking agent, and an erucamide slip additive. A multiple extrusion experiment was carried out to assess processing stability. Melt stabilization performance was monitored by melt flow rate (MFR) measurements, and color development was determined using yellowness index (YI) measurements. Long‐term thermal stability was assessed by monitoring the rate of formation of the non‐volatile carbonyl oxidation products using FTIR. Results were quite consistent with the literature. Therefore, the two‐level factorial experimental design proved to be a very useful tool for screening the simultaneous effects of each additive and the possible interactions between additives present in the stabilizer system investigated. J. Vinyl Addit. Technol. 10:149–156, 2004. © 2004 Society of Plastics Engineers.