The effects of a range of additives on thermal stability of a common rotational molding grade of polyethylene produced using a titanium-based Z-N catalyst
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1MSc in Polymer Engineering, Department of Chemical Engineering, Arak University, Arak, Iran
2Senior Catalyst Researcher, R&D Center, Shazand Petrochemical Company, Arak, Iran
3Head of Polymer Research, R&D Center, Shazand Petrochemical Company, Arak, Iran
In the present study, the effects of seven commercial additives such as Irganox 1076, DSTDP, Irgafos 168, Irganox 1010, calcium stearate, zinc stearates and Chimassorb 944 at several weight ratios to the powder of industrial rotational molding grade of polyethylene (PE), namely HD3840UA were investigated on thermal stability via analysis of granules producd by oxidation induction time (OIT), thermal gravimetric analysis (TGA) and melt flow index (MFI) tests. The aim was to evaluate perfomance of the additives when used in blend for protection of the PE in the melt. If synergism or additive interactions is observed, the goal has been to determine the best combination ratio of the additives to product regarding the best results. The results showed the additive package containing Irganox 1010, Irgafos 168, zinc stearate and Chimassorb 944 along with nanoclay had the best effect on enhancement of the thermal stability of the used PE. This formulation has exhibited the phenomenon of synergism, which results in a higher overall efficiency. Phosphite antioxidants (AOs) such as Irgafos 168 not only protect the polymer from degradation, but also diminish the consumption of phenolic AOs such as Irganox 1010, which is advantageous in terms of long-term stabilization. In addition, there is likely either hydrogen-bonded complexation with the ZnSt or direct displacement of the stearate groups to form a coordinated Zn complex of the AO, i.e. Zn phosphite.