Epitaxial crystallization of polyethylene and paraffin on oriented polypropylene

Abstract

Epitaxial growth of polymers on various substrates has been reported on numerous occasions1-10J6J6; however, in most investigations ionic salts or organic crystals were used as substrates. The interest in these systems arises from the use of the crystals as nucleation agents for the polymers. On the other hand, there is considerable interest in coupling agents for polymer blends and multilayered films. Epitaxy in blended polymers can substitute for or replace the adhesive because epitaxially oriented interfaces may provide strong bonding? It is the purpose of this note to report epitaxies of polyethylene and paraffin on oriented polypropylene, polybutene-1, and isotactic polystyrene substrates. EXPERIMENTAL MaterialsThe materials used for the experiments were polypropylene, type PPN and PPH, from Hkhst; polyethylene, Lupolen 6021 DX from BASF wax A409 and polybutene-1 (PRl), Vestolen BT, both from Chemische Werke Hills; isotactic polystyrene (ips) from Polyscience, Inc., and paraffin, T,,, = W C (n-aa) from Merck. This paraffin has a much shorter chain length than wax A409, which has a number-average molecular weight of about 2 x 1W. ProcedureThin oriented substrate films of polypropylene, polybutene-1, and isotactic polystyrene were prepared according to the method of Petermann and Cohil.'' The thin films were cut into 3x 3 mm pieces and mounted on electron microscope grids. Thin unoriented films of polyethylene, wax, and paraffin were cast from 0.1% solutions in o-xylene. These films were then cut to the same size as the oriented films, floated on distilled water, and then transferred to the oriented films. Subsequently, the layered films were heated in an air oven to well above the melting point of the unoriented films for 15 min (polypropylene-polyethylene: 160°C. polypropylene-wax: 13OT, polypropylene-paraffin: 90T, polybutene-l -wax: 130"C, polybutene-1-paraffin: WC). The drawn films of isotactic polystyrene were first crystallized a t 180'C for 30 min and subsequently heat treated with polykhylene at 1WC and paraffin at 90°C. The heat-treated samples were examined in a Phillips 400 T electron microscope a t 100 kV using electron diffraction, dark-field, and bright-field techniques. RESULTS AND DISCUSSIONIn Table I the morphologies and crystal orientations of substrates and recrystallized layered polymers are documented. Figure 1 shows a bright-field TEM photograph of the PP-PE morphology. A sketch of PP-PE is inserted in this figure. Figure 2 is an electron diffraction pattern of this specimen. The molecular axis (c axis) of the PP substrate film is horizontal. This f w r e exhibits two sets of diffraction patterns of PE with both molecular axes in the same plane, but displaced by f5(Y from the molecular axis of the PP. All the diffraction spots of the PE can be indexed as OM. In Figure 3 the electron diffraction pattern of the PE together with the PP substrate is illustrated. For clarity only one set of PE diffraction spots is shown in Figure 3. The two sets of diffraction patterns arise from two differe...

Polyethylene–isotactic polypropylene epitaxy: Analysis of the diffraction patterns of oriented biphasic blends

“…Finally, Broza et al, in a most recent report, indicate that the situation becomes even more complex when the PE films become thicker, since "an additional rotation of the PE lamellae around the c axis of the PP as well as a twisting of the PE lamellae around the [020] direction in the PE" occur. 5 Sherman'O investigated the structure of oriented crystalline blends of iPP and PE obtained by extrusion. The x-ray diffraction pattern is characterized by a set of sharp iPP reflections indicative of a fiber orientation (chain axis parallel to the extrusion direction) and by strong, more spread out reflections due to PE.…”

Surface-Induced Polymer Crystallization and the Resultant Structures and Morphologies

“…Epitaxy, meaning “on arrangement”, is most generally defined as the crystals of one phase (guest crystal) growing on the surface of a crystal of another phase (host crystal) in one or more strictly defined crystallographic orientations . The epitaxial crystallization phenomenon was first recognized by mineralogists in various natural minerals, and the study on polymer epitaxy was started in the 1950s with the pioneer work of Willems and Fischer. , It has been well documented that polymer epitaxy could be realized on inorganic, − organic, − and polymeric − substrates from solution, melt, and vapor phases. We will not summarize all of the work to date, as there are already several excellent reviews on these topics, − but rather provide a context as to how the surface-induced epitaxy influences the crystal structure and morphology of polymers as shown in recent new developments.…”

Effect of Molecular Weight on the Structure and Morphology of Oriented Thin Films of Regioregular Poly(3‐hexylthiophene) Grown by Directional Epitaxial Solidification

“…Whereas epitaxy of PE on oriented substrates of poly(propylene) and polybutene-1 leads mainly to an edge-on lamellar orientation, the epitaxy of paraffins can lead to either flat-on or edge-on orientations. [34][35][36] Following the same reasoning, the difference in orientation mechanism between the P3HT-LowMw and the P3HT-HighMw samples on TCB must reflect the difference in the crystallization modes of both weight fractions. The P3HT-LowMw samples (M w of ca.…”