Structure and Properties of the Welded Joints of Single-Type Polyethylenes Formed Under the Action of Constant Magnetic
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STRUCTURE AND PROPERTIES OF THE WELDED JOINTS OF SINGLE-TYPE POLYETHYLENES FORMED UNDER THE ACTION OF CONSTANT MAGNETIC FIELDS V. L. Demchenko1,2 and M. V. Yurzhenko3
UDC 621.791: 678.029.43
We study the structural features and the thermomechanical and operating properties of the welded joints of PE-80–PE-80 with PE-100–PE-100 made with and without the action of constant magnetic fields ( B ∼ 1 T). By using the wide-angle X-ray diffraction method, it is shown that the action of a transverse constant magnetic field on the melts of polyethylene specimens of the same type in the course of their welding causes the formation of an oriented structure of the welded joint. The axis of its texture coincides with the direction of the magnetic field, which improves the thermomechanical and operating properties of welded joints. The formation of a welded joint under the action of a longitudinal magnetic field leads to the deterioration of its physicomechanical characteristics, which is explained by the opposing action of the force field that formed in the process of welding and compensating the effect of the magnetic field. Keywords: polyethylene, welded joint, structural organization, thermomechanical properties, operating characteristics.
Due to the progress attained in the contemporary materials science of polymers, the application of thermoplastic polymers is rapidly intensified in various branches of industry, including the building, chemical, medical, radioengineering, electronic, and food industries [1]. These polymers are readily shaped and easily painted. They have low density, high chemical stability, and satisfactory dielectric properties. For complex structures made of thermoplastic polymers, the procedure of joining of separate parts is of high importance. At present, among the contemporary highly efficient methods of joining the elements of polymeric structures, the procedure of contact-heating welding (capable of guaranteeing the high reliability and long service life of the product) proves to be one of the most promising and extensively used methods [2]. The process of making welded joints passes through a series of physicochemical transformations of polymers: the fluidity of the melt changes and we observe the phenomena of orientation crystallization, repeated crystallization, recrystallization, and even partial destruction. This results in the formation of the structure of welded joint. In view of the complexity of these processes, it is clearly practically impossible to make a joint whose morphology is completely identical to the morphology of the source material. Therefore, the physicomechanical properties of welded joints always differ from the similar characteristics of the source polymeric materials [3]. At present, leading researchers in this field, both in Ukraine and abroad, continue their work aimed at finding the methods designed to improve the quality of welded joints of thermoplastic polymers and enhance their 1 2 3
Institute of Chemistry of High-Molecular Compounds, Ukrainian National Academy o
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