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SynopsisA new method has been developed for determining the total crystallinity and relative amounts of a-and y-phases in nylon-6 samples. The procedure is based on a combination of X-ray and density data and does not require complicated analytical procedures to separate overlapping reflections. The technique has been applied to study the structural changes accompanying the melt spinning, annealing, and drawing of nylon-6 fdaments. Higher spin draw ratios result in higher crystallinity, greater relative amounts of y-phase, and higher orientation. Annealing up to 2 h in boiling water or a 20% aqueous formic acid solution decreases the y-phase content, increases the a-phase content and total crystallinity, but does not e l i t e all of the y-phase in samples spun with high spin draw ratios. Annealing in vacuum also i nthe a-phase content when annealing ia carried out at temperatures above 120°C, but there is little effect below thia temperature. Drawing of ae-spun and conditioned f b e n t a at 9o°C also increases the a-phase content and decreases the y-phase content. The total crystalline content increases with draw ratio for samples with low spin draw ratia, but drawing has littie effect on the total crystalline content of samples spun with higher spin draw ratios. Drawing also resulta in substantial increases in orientation, especially for samples spun with low spin draw ratioa The effecta of these changes in structure on the mechanical properties are.also dmribed.

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Gold (III) chloride is monoclinic, in space group P21/c, with cell dimensions a = 6-57, b = 11-04, c = 6-44 A, and fl = 113-3 °. The atomic positions were determined by Patterson and electrondensity projections and were refined by Fourier and least-squares methods with three-dimensional data. The structure consists of plana molecules Au2C16 (at centers of symmetry) in which each Au has four C1 neighbors at 2-23 and 2.25 A (terminal C1) and 2.33 and 2-34 A (bridge C1), each + 0.02 A. Gold scattering factors in the least-squares refinement were modified for dispersion with little effect on coordinates but with appreciable effect on temperature and scale factors.

A new kind of acetal fiber has been discovered which has a tensile strength of 1.7 GPa (250,000 psi) and an elastic modulus of 35 GPa (5 x lo6 psi). This fiber is produced by a special two-stage drawing process in the solid state which requires careful control of deformation rate and temperature. Previously known drawn fibers are reported to consist of folded-chain blocks joined by a limited number of tie-molecules. It is hypothesized that the second stage of the novel drawing process eliminates the lamella (block) surfaces which act as strength-limiting stress concentrators. A new type of fiber is created in which any remaining chain-folds are distributed as defects in a continuous crystal matrix. It is the continuity of the crystal matrix which is believed responsible for the remarkable properties of the fiber.

An experimental study of sandwich injection molding is reported which involves sequential injection of polymer melts with differing melt viscosity into a mold. In isothermal injection molding the relative viscosity of the two melts is the primary variable determining the phase distribution in the mold. Generally the most uniform skin‐core structure occurs when the second melt entering the mold has a slightly higher viscosity than the first melt injected. Large viscosity inequalities lead to nonuniform skin thicknesses. The influence of blowing agents and non‐uniform temperature fields on the extent of encapsulation is described. Temperature fields are very important especially if the first polymer melt injected has a greater activation energy of viscous flow (or a greater temperature dependence of the viscosity function).