The influence of types and amounts of wax on the thermal and mechanical properties of PE/Wax blends
Mpanza, Highness Sebenzile
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The influence of three different waxes on the thermal and mechanical properties of lowdensity (LOPE) and linear low-density (LLDPE) polyethylenes was investigated. The samples were prepared through melt blending in a Brabender mixer. The thermal properties of the samples were determined using differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). Surface free energy analysis was used to confirm the miscibility of wax with polyethylene. The tensile and flow properties of all the samples were determined and compared. The observations are discussed in terms of possible morphological changes when wax is mixed with polyethylene. The polymer-wax miscibilities differed with the type of wax and polyethylene used, and with the amount of wax mixed into the polymer. These miscibilities, and accompanying morphologies, had a strong influence on the flow properties, thermal stabilities and tensile properties of the corresponding blends. Based on my observations, Wax 2 may be regarded as the best processing agent for LOPE. Both Wax 1 and Wax 2 have a similar influence on the tensile properties of LOPE, but Wax 2 increases the melt flow rate more than Wax 1, which was specifically designed as a polyethylene processing agent. As far as thermal stability is concerned, the blends seem to be thermally more stable in the presence of Wax 1 than in that of Wax 2. Although Wax 3 improves the melt flow rate in a similar way than Wax 2, it has a strong negative impact on the tensile properties of LOPE. In the case of LLD PE, either Wax 2 or Wax 3 can be used. Wax 3 has the strongest influence on the melt flow rates of the blends, and it has the least influence on the tensile properties of LLDPE. It does, however, strongly reduce the thermal stability of LLDPE. Wax 2, on the other hand, has only a small influence on the thermal stability of LLDPE, but like Wax 1 it strongly increases the modulus. Again Wax 1, which was specifically designed as a polyethylene processing agent, seems not to be the best wax to use for this purpose.