The influence of the supermolecular structure type of linear polyethylene films on the relationship between the strengthening process and loss of strength at drawing has been studied by the infrared spectroscopy technique. It has been found that the progress of the strengthening process (which is connected with the macromolecular segments orientation in the microfibril amorphous region), as well as the loss of strength process (which is caused by macromolecules scissions), is strongly influenced by the initial supermolecular structure.
The influence of supermolecular structure on the mechanical properties of linear polyethylene has been studied. The change in film structure has been realized by means of variation of isothermal crystallization conditions. The films obtained had either lamellar structure, or consisted of spherulites. It has been shown that the tensile strength of unoriented films with small spherulite structure is twice as great as that of films with well developed lamellae. This mechanical difference remained after 20‐fold drawing of the specimens at high‐temperature (102°C) for short times. The study of the structure of oriented films showed that in all the cases the transverse size of microfibrils remained constant. However, with the help of infrared spectroscopy it has been found that the amorphous phase orientation here was different, while the degree of elongation was the same.
Th0e relief of fracture surfaces of oriented monofilaments of nylon 66 has been studied with the help of both transmission and scanning electron microscopy. It has been shown that at different speeds of macrocrack propagation the relief of the so‐called mirror zone can show the original structural features of the material (e.g., the existence of supermolecular structures of the order of a micron, the influence of annealing, the distribution of micropores in the fibrillar amorphous regions) as well as effects connected with deformation processes at the tip of the crack, with discrete and auto‐oscillatory mechanisms of crack growth, the interaction of the macrocrack with the secondary fracture processes, etc.
Annotation
The X-ray analysis of a virgin particle taken directly from the synthesis products of an ultra-high molecular weight polyethylene (UHMWPE) and not subjected to any external stresses was carried out using nanofocus beamline ID13 European Synchrotron Radiation Facility (ESRF, Grenoble,France). In the X-ray diffraction curves obtained by scanning an arbitrarily selected portion of a particle with a size of (100 x 20) μm2 by a microbeam (0.3 x 0.3) μm2 with a step of 2 μm horizontally and 0.5 μm vertically, along with reflections from the orthorhombic phase, reflexes from the metastable monoclinic phase were observed.
It is believed that the cause of its occurrence may be stresses that develop during specific structure formation in slurry synthesis and persist when cooled to room temperature and the solvent evaporates. The possibility of localization of the monoclinic phase in various morphological formations is discussed.
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