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The characteristic curve and deformation band with yield points were investigated in off-axis angle stretching of strip-biaxially stretched poly (ethylene terephthalate) (PET) and isotactic polypropylene (it-PP) films. As the yield strain in polymers are much greater than those of metals, the change of orientation angles must be corrected for elastic-plastic deformation. The re-orientation mechanisms of chain axes during off-axis angle stretching may be divided into inter-lamella slippage and intra-lamella chain slip. The orientation of molecular chain axes by chain slip was much greater than that of inter-lamella slip.

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Strip-biaxially stretched syndiotactic polypropylene and syndiotactic 1, 2-polybutadiene films have been characterized by crystallinity and birefringence. Birefringence values for the polypropylene and polybutadiene films indicated positive and negative values, respectively. A good correlation between birefringence measurements by Abbe, polarization microscope and optical biregringence analyzer was obtained. Moreover, we confirmed the correlation between birefringence by Abbe and microwave measurements for the polypropylene film.

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This study is a part of an effort to develop precision injection molding of LCP. With the objection of replacing die-casted aluminum with injection molded LCP in an HDD actuator E-block application, modified design of experiment methods were used to investigate the significant factors involved both the injection machine operation process and the mold design. The preciseness was defined by the standard deviation (σ) of the arm tip heights of the E-block as measured on a laser scan micrometer, and values were compared with that of the die-casted aluminum E-block used in the HDD market. Among the machine process factors cut-off pressure was the most important one. Among the mold factors a cavity having a one-point gate located behind the carriage portion and a bridge connecting three arm tips, which functions as a slug-well and provides distortion resistance, gave the highest precision. For the purposes of high precision the mold geometry should permit molten LCP to flow with high symmetry. The value of the σ under the optimized process gave equal or better than that of aluminum E-block.

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