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SynopsisThe details of an infrared technique standardized to analyze cotton-polyester blends of different compositions are reported. It is observed that particle size plays a very important role in the peak intensity of the 1725 cm-' band (C=O stretching) in polyester, the absorption band recommended for analysis of cotton-polyester blends. However, the product of the band width and peak intensity is found to be dependent on particle size to a lesser extent and hence is a more reliable parameter in the measurement of percentage composition. It has further been shown that the method of sample preparation can affect the band width and hence the results. A suitable sample preparation procedure is, therefore, described whereby an accuracy of f3% in the estimation of polyester content in a given blend can be achieved.

SYNOPSISIn the present investigation, we have made a systematic study of the induced crystallization in never-dried cotton fiber, by allowing it to desiccate under different conditions of humidity and temperature. The resulting structural changes have been followed using x-ray diffraction and infrared absorption techniques. A slow rate of drying coupled with a high temperature was more conducive for maximum crystallization. Analysis of the effect of temperature on the induced crystallization showed possible existence of a thermal transition in cellulose around 3OOC. The induced crystallization brought about by slow drying as well as those produced using intercrystalline swelling agents, have been shown to be resulting from a proper channelization of the interfibrillar mobility existing in the never-dried fibers.* Part of the results reported here were presented as poster in Session 9 "Crystallisation Phenomena"

Investigations in the recent past have led to the opinion that the spiral angle of fibrils in different genetic varieties of cotton is more or less the same and that the differences found in X-ray orientation angle measured on fiber bundles are due largely to the influence of convolutions formed during the initial desiccation of fibers in the cotton bolls. It was Meredith,1,2 who observed for the first time that the spiral angle deduced from refractive indices is nearly the same (ca. 21") for all varieties of cotton when the effect of convolutions is corrected for. An extension of this work by Betrabet et al.3 to Indian cottons also led to the same conclusion.More recently, Hebert4 measured the spiral angle by Hakshorne's optical method6 and confirmed the earlier observation that spiral angle of cotton is a constant at around 21". Duckett and Tripp6 using a single-fiber X-ray technique showed that the variation in spiral angle among different varieties is small. Morosoff and Ingram7 examined the interconvolution tracts by X-ray diffraction as well as by Hartshorne's method and found that the spiral angle is a constant in the range 20-23". De Luca and Orr? on the other hand, have reported a range of values for the sprial angle (12-18") among different varieties on the basis of a modified Xray method.One thing common to all earlier investigations on the true spiral angle of cotton discussed above has been the use of naturally dried, convoluted fibers for the measurement.