Thermal fractionation and properties of different PE/wax blends
Hato, Mpitloane Joseph
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The influence of paraffin wax type and content on the properties of its blends with HDPE, LOPE and LLDPE was investigated. Differential scanning calorimetry, thermal fractionation and surface free energy results were used to clarify the morphology of the blends. Melt-mixing of HOPE with wax gave rise to completely miscible blends for both 10 and 20 % wax contents. This miscibility must be the result of co-crystallization of the wax with HOPE. This fraction, however, melts at increasingly lower temperatures with increasing amounts of wax in the blend. This is probably the result of the formation of thinner lamellae in the presence of the wax. A wax content of 30 % gave rise to a partially miscible blend. Complete miscibility was observed for all the LLDPE/Wax B blends. This indicates cocrystallization of Wax B with LLDPE, which was also evident from the thermal fractionation curves. LLDPE/Wax A blends were, however, partially miscible for all wax contents. Melt mixing of LOPE with Wax A gave rise to a partially miscible blend for all wax contents investigated, while complete miscibility was observed for the 90/10 w/w LOPE/Wax B blend, but not for the blends containing higher Wax B contents. The main fraction of LLDPE, however, melted at increasingly lower temperatures with increasing amounts of wax in the blend. It is further clear from the thermal fractionation results that the presence of wax changed the crystallization behaviour of LOPE. All these observations were supported by the surface free energy results. Changes in the tensile properties are explained in terms of the miscibility and proposed morphologies of the different blends.