The dewetting behavior of thin polystyrene (PS) films on top of an amorphous polyamide (PA) layer is investigated at two different annealing temperatures (119 and 195 °C). While PS is liquid at both temperatures, the PA layer remains solid at 119 °C and becomes highly viscous at 195 °C. At a constant thickness of the PA layer, the thickness and the molecular weight of the PS top layer were varied. With optical microscopy and optical phase interference microscopy ex situ the hole growth was measured during the dewetting of the PS layer. A statistical analysis of the data shows evidence for a change in the dewetting mechanism from a spinodal process into a nucleation and growth process as a function of film thickness. For very thin films the effect of a geometrical constraint is discussed. The retardation of the observed dewetting process was achieved by adding a styrene maleic anhydride random copolymer (SMA). The influence of the amount of SMA added and its molecular weight are shown for each given temperature. SMA with a low weight percentage content of maleic anhydride shows an increased retardation as compared to a higher weight percentage irrespective of the amount of SMA added.
A ternary system polypropylene (PP)/calcium carbonate (CaCO 3 )/high molar mass polysiloxane has been investigated with respect to its processing, crystallization, and dynamic mechanical properties. The filling level of PP varied from 2.5 vol % to 6.5 vol % CaCO 3 and 0.6 vol % to 2.5 vol % polysiloxane, and the mixing was done in a single screw extruder. The polysiloxane molecules had different functionalities added (epoxy and methacrylate reactivity, respectively). However, the functionality did not influence processing, crystallinity, or mechanical properties. It was found that the polysiloxane molecules tended to surround the CaCO 3 particles, thus forming a coreshell structure. This structure was achieved without surface treatment of the filler. The polysiloxane also provided a lubrication effect in the melt and thus enabled an easier processing of the composite. A nucleating effect of the filler could be detected. The mechanical properties were similar to those found in other core-shell structured samples, where the structure was achieved by surface treatment. It was found that the polysiloxane exhibited a lubricant effect only if it was mixed with PP together with CaCO 3 . If polysiloxane was added to the PP matrix alone, screw slippage occurred and the polysiloxane molecules agglomerated. The mechanical properties of these composites were similar to those of pure PP. No influence on the matrix crystallisation could be detected in this case.
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