Beschreibung
Linear low density polyethylene (LLDPE) stretch wrap film plays an essential role in the packaging industry, where it is used for the transport protection of goods. From an economic point of view, a high speed of the extrusion line and hence a high die throughput is desired. Therefore, this work aims to produce LLDPE stretch films at high production speeds. At higher production speeds, film quality control is more complicated and quality can decrease significantly. In order to monitor and evaluate the influence of different processing conditions on film properties, five-layer LLDPE films with varying conditions of processing in terms of line speed, air-gap, and frost-line are produced. First and foremost, the mechanical properties of the layers are investigated. The influence of processing parameters on the crystal morphology in the LLDPE films is investigated using scanning electron microscopy (SEM) and atomic force microscopy (AFM). The results show no significant differences in the crystal structure of the films. In addition, they show a lower roughness for the film produced at the higher line speed. Furthermore, the orientation of the films is investigated by different measuring methods such as 2D wide-angle X-ray scattering (2D-WAXS), shrinkage and polarized Fourier transform infrared spectroscopy (FTIR). It is found that although there is no significant orientation in the crystal phase, the amorphous phase has a higher orientation in the higher line speed condition. In addition, the polylactic acid (PLA) material is investigated from the point of view of melt strength and tensile properties. The melt strength is increased by compounding PLA with polymethyl methacrylate (PMMA). The tensile strength can be significantly improved by stretching the films.
