ABSTRACT:As a means of better understanding the role of amorphous chains on the deformation behavior of crystalline polymers, we prepared high density polyethylene (HDPE) having various chain densities by extracting the petroleum resin dissolved in the interlamellar amorphous region of HDPE/petroleum resin blends. The small angle X-ray scattering intensity increased by increasing the amount of petroleum resin extracted, suggesting that the density of the amorphous chain in the interlamellar amorphous region decreases with an increase in the extracted petroleum resin. The yield stress and Young's modulus decreased while the drawing property was improved by decreasing the amorphous chain density in the interlamellar amorphous region. TEM observation of the stretched specimen revealed that the decrease in overall stress is ascribed to the enhancement of the lamellar separation associated with a large void formation and lamellar deflection due to the low number density of tie chains, which act as transmitters of the external force in the interlamellar amorphous region. The tensile properties of crystalline polymers are elucidated by a lamellar structure of alternating crystalline and amorphous regions.1 Crystalline polymers are considered composite materials consisting of a crystalline phase with high strength and an amorphous phase with low strength. It is often reported that the modulus and yield stress simply increase as the crystallinity increases.2-4 However, the mechanical properties of crystalline polymers are not simple and can be different even if the crystallinity is the same. 5The differences in the mechanical properties are ascribed to differences in the amorphous structure by various chain conformations, e.g., an adjacent crystalline phase is linked by tie chains that are entangled with loop chains, cilia chains, or floating chains in the amorphous phase. By taking into account tie chains, the Takayanagi model has explained the modulus of the crystalline polymers and of revised ones in which the crystalline phase and amorphous phase are joined in series and/or parallel according to the morphological features of the crystalline polymers.6-9 The stress-strain relationship of crystalline polymers is predicted by a primitive molecular theory based on the change in the conformational free energy of tie chains, and the calculated results suggest that the overall stress increases with an increase in the fraction of tie chains. [10][11][12][13] To date, the role of amorphous chains on the mechanical properties of crystalline polymers has not been confirmed experimentally.In this paper, to better understand the role of amorphous chains on the deformation behavior of crystalline polymers from an experimental viewpoint, we prepared high density polyethylene (HDPE) having various amorphous chain densities by extracting the petroleum resin, which dissolves in the interlamellar amorphous region of HDPE/petroleum resin blends. After the extraction, the mechanical properties of the blends were investigated by tensile t...

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ABSTRACT:A new technique is presented to measure the concentration of fluorine in a reaction gas consisting of fluorine, nitrogen, and oxygen in a reaction chamber. The method is described as follows: The gas is directly taken from the chamber using a peristaltic pump and dissolved in a TISAB (total ionic strength adjusted buffer) solution. The concentration of fluorine ion is measured using the selected fluorine ion electrode, the output voltage of which is monitored. The concentration of the fluorine ion and the output voltage follow the Nernst relation so that the measurement of the output voltage of the system enables us to know the concentration of fluorine gas. This technique was applied to monitor the concentration of fluorine gas in the chamber in which a sheet of polyethylene nonwoven fabric was continuously oxy-fluorinated. The monitored concentration of the fluorine gas as a function of time coincided with the variation of the incorporated fluorine in the sheet measured by X-ray fluorescence (XRF) spectroscopy after the treatment. This technique can be best used for process control of the continuous oxy-fluorination of polymeric materials. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 684 -691, 2002

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