Morphology studies of multilayered HDPE/PS systems

Films with alternating layers of high density polyethylene (HDPE) and polystyrene (PS) were prepared by layer-multiplying coextrusion, using two HDPEs differing in molecular weight. The crystal structure of extremely thin PE layers confined between PS layers was studied by small angle X-ray scattering (SAXS), wide angle X-ray diffraction (WAXS), and also by atomic force microscopy (AFM) and differential scanning calorimetry (DSC) technique including MDSC. The morphology of HDPE in the systems studied is greatly affected by the presence of HDPE/PS interfaces. In the HDPE layers, the texture component was observed with lamellae with their basal planes normal to the interface and (200) crystallographic planes parallel to the interface. Thus, the polymer chains in this texture component are parallel to the interface between both polymers. The small fraction of lamellae parallel to the interface in thicker HDPE layers disappears with the thinning of the layers beyond 100 nm. AFM images show in these samples straight, long lamellae positioned edge-on at HDPE/PS interface. The thickness and perfection of lamellae decrease with the decrease of individual HDPE layer thickness. Those thinner and less perfect lamellae are more susceptible to reorganization during heating as it is observed by MDSC. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 597–612, 2006