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.

In order to identify the major fluid mechanical effects and catalog their domains of influence, an extensive study of flow behavior of reactive polyester resin systems in uniaxial, horizontal rotating systems has been undertaken. Four general flow phenomena are identified: cascading, where resin is withdrawn from the recirculating pool arid drains back; rimming, where resin is taken around the top of the cylinder by viscous forces; stable hydrocyst formation, where rings of fluid perpendicular to the axis of rotation are formed; and solid body rotation, where the resin on the mold wall is quite uniform and time‐independent. For most flow conditions, the desired region of solid body rotation apparently can be reached only by passing through each of the other flow regimes. Experimental work on polyester resin systems is compared with theoretical studies on flow stability, hydrocyst formation, and withdrawal from quiescent pools, and suitable correlations are developed. It is noted that the current correlations for stable hydrocyst formation are invalid for polyester resins and a simpler correlation is proposed.

Nylon 6 multifilament yarn is textured by both the conventional false-twist method and a new method of solventtexturing with aqueous phenol. The physical, mechanical, and structural properties of the textured yarns are compared.It is observed that the solvent-textured yarn has a considerably higher dye uptake than the conventionally-textured yarn. SEM studies reveal interesting differences in the surface characteristics of fibers textured by the two processes. ' ' ' ~ --Introduction 'The texturing process involves mechanical deformation of a filament or a bundle of filaments and dissipation of internal strain~nduced by mechanical stressing to obtain a permanent or quasipermanent, stress-free, distorted configuration. The dissipation of the elastic strain imposed on the matrix by the mechanical field is brought about by providing a thermal environment in the case of texturing of thermoplastic yarns. , The °g eneral mechanism of thermostabilization involves breaking of intermolecular bonds, chain-relaxation, and subsequent bond-reformation in energetically more favorable sites. The strain-dissipative environment need not, necessarily, be thermal in nature. It may be a suitable solvent, the suitability being dependent on the solubility parameters of the polymer and the solvent. Jacobs ~1~, from his study of nylon/phenol interactions, proposed a general mechanism involving three elementary-rate processes: intermolecular bondbreaking, chain-relaxation, and bond-reformation. It may be observed that the mechanism involved is, in principle, similar to the principle of thermosetting. ()ne of the present authors, in a previous paper ~6~, reported successfully texturing of polyester, nylon 66, and acetates -With the aid of suitable solvents. Texturing with solvents becomes all the more appealing when one realizes that setting through a re-arrangement of morphological order need no longer be confined to thermoplastic fibers. Work on nonthermoplastic fibers, carried out in our laboratory, has yielded interesting results, which have been reported elsewhere ~7, 8).. ' The present paper deals with torque-texturing of nylon 6 with aqueous phenol and compares the properties of solvent-textured yarn with the conventional false-twist yarn. ' Experimental Methods , . MATERIAL. A 3% concentration (v/v) of phenol in water was used as the solvent for texturing semi-dull nylon 6 multifilament yarn of 11.6 mg/m comprising . 24 filaments. --SOLVENT TEXTURING. A bath containing a pair of hositively-driven aluminum rollers running at. the same surface speed of the front rollers of a ring frame, was attached to the back of the frame. The rollers were completely immersed in aqueous phenol. The filament yarn from a bobbin was wrapped round the rollers by several turns to give an effective immersion time in solvent for 2 min, passed through the nip of the front pair of rollers of a draftin assembly via suitable guide, and twisted and wound o a ring bobbin. The yarn was twisted to 23.6 ~turns/cm. The twisted yarn was then transferred. onto a per...