SYNOPSISThe neck-like deformation process occurring in high-speed melt spinning of polyamide 66 and polyamide 6 filaments was investigated at take-up speeds of 4200 to 5500 m/min by on-line laser light scattering, thermographic contrast compensation, and wide-angle X-ray scattering ( WAXS ) measurements. New information about the onset of crystallization along the spinline was obtained by measuring simultaneously diameter and temperature profiles in the neighborhood of the neck. Crystallization rates, as a function of take-up speed, are estimated for both polyamides. Based on the present experimental results of diameter profiles, temperature profiles, and WAXS patterns, a picture of the physical mechanism responsible for the neck-like deformation of high-speed melt spun polyamides is proposed.
Binary polycrystalline alloys of B2 NiAl, ranging from 47 to 51.5 at% Al, were prepared by casting and extrusion. These were tested in tension at temperatures ranging from 300 K to 873 K. Significant tensile ductility is observed in the near-stoichiometric alloy at room temperature as well as at 473 K in spite of the presence of only <100> dislocations. This anomaly appears to be related to the recrystallized texture, to the lower yield strength and to the presence of residual dislocations at grain boundaries in this alloy.
Super-tall buildings of over 100 stories are coming to Korea. To prove its economic prosperity, which was developed over the last 50 years after the Korean War, Korea is willing to have super-tall buildings as a symbol of its success. Locally, structural silicone glazing has become very common to achieve aesthetically pleasing and high utilization of small land for both residential and commercial building. Because there has been no industry-wide guideline or specification for structural silicone sealants in Korea, it is worthwhile to look at the performance of locally available structural silicone sealants. In this paper, several weathering techniques were adapted from various global industry standards. Artificial weathering using filtered xenon arc radiation was applied to specimens prepared in accordance with ASTM C1135. Comparative evaluations for temperature variations and salt spraying exposure were conducted as well. Silicones in general are known to have excellent resistance to such exposure. However, since the weathering performance of a sealant can be affected by its overall composition (not just the polymer type), some silicone products showed noticeable changes in our testing when compared to their initial properties.
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