The in-phase modulus and coefficient of diffusion of nylon 6 fibers are analyzed in terms of wide-and small-angle X-ray diffraction data. Both properties are examined in directions parallel and perpendicular to the fiber axis. The anisotropy in diffusion and mechanical coupling between the crystalline and amorphous phase reaches its maximum at relatively low draw ratios of about 2.5 to 3.0X. With increasing draw ratio the anisotropy in these properties decreases monotonically and reaches its minimum value with the fibers of the highest draw ratio (5.35X). The diffusion analysis yields a heretofore undetermined structural parameter, the separation of the microfibrils. The results indicate that increases in draw ratio lead t o an increase in the distance between the microfibrils, a decrease in the diameter to length of the crystallite, and a decrease in the diffusion constant of the permeable phase. The longitudinal structure of the microfibril is not affected significantly during this phase of drawing. These observations cannot be explained by the microfibrillar fiber model derived from studies of polyethylene and polypropylene fibers. A new structural model is proposed in which the strength, diffusion, and modulus are controlled by the densely packed matrix. The model is corroborated by transmission electron micrographs from thin fiber cross sections. be reproduced o r transmitted in any lormor by any means. electronic or mechanical, including photocopying. microfilming. and recording, or hy any information storage and retrieval system, without permission in wiling from the publisher.

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A piston‐cylinder‐type high‐pressure dilatometer has been built and the effect of pressure on melting behavior of poly(ethylene terephthalate) (PET) has been studied. The melting temperature increases but the rate of change of the melting temperature decreases with increasing pressure. Poly(ethylene terephthalate) crystallized from the melt at elevated pressure and temperature was studied by thermal analysis, and wide‐angle and small‐angle x‐ray diffraction and electron microscopy. Chain‐extended PET crystals were observed for the first time and some of their properties are described. A similarity to extended‐chain polyethylene is suggested.

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The glass transition temperature of nylon 6–inorganic salt mixtures has been investigated. Tg not only increases monotonically with the salt content but the rate of increase depends on the type of salt. Infrared measurements indicate that metal ions form adducts with the amide group, and, as a result, the nylon chains are stiffened. This effect appears to be a major cause of the Tg increase. The adduct formation between the ions and the amide group is very similar to hydration of ions and the observed effect of ions on the Tg of nylon 6 is similar to the effect of the same ions on hydration. The effect is also shown well correlated to Q/R of the ion, the ratio of the oxidation number to ionic radius of the ion.

The advent of high speed spinning of PET fibers has brought on a higher degree of "frozen-in" orientation in quenched amorphous fibers. Since these fibers are amorphous by x ray, birefringence measurements have constituted, until recently, the only independent characterization method for determining the frozen-in orientation. The amorphous orientation function is then calculated from the well-known equation'

Small-angle x-ray scattering from amorphous polyethylene terephthelate (PET) has been detected. It is very weak, more than an order of magnitude less intense than is usually obtained from partially crystallized specimens. It is also of a continuous nature with the absence of any distinct interference peak. Based on the assumption of spherical particles, the diameters are in the range of 30-40 A. This is somewhat smaller in size than is seen in electron microscopy, but reasonable since it is more a measure of the actual electron density fluctuation and not physical size. The scattering is sensitive to thermal treatment below the glass transition temperature and also depends on the source of the amorphous PET, e.g., films or fibers. When these data are combined with other analyses, parameters such as size, number density, and electron density of the particles can be segregated. The effects of the state of the amorphous material on subsequent crystallization is also presented and discussed.