Wide‐angle X‐ray diffraction studies of nylon–ionomer blends

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Abstract
Blends of nylon 6 with poly(acrylic acid) polyacrylamide, poly(ethylene‐co‐acrylic acid), poly(ethylene‐co‐vinyl alcohol), poly(acrylamide‐co‐acrylic acid), and polypropylene were prepared by melt blending. Annealing treatments included treatments in Vacuum, in water, and in 20% formic acid at various temperatures. WAXS (wide‐angle X‐ray scattering) patterns of melt chips and of undrawn, drawn and textured yarns were obtained. The melt chips of 100% nylon 6 crystallize in the α form while the chips of all the blends exhibit a single diffracton ring. All the blends behave similarly during different annealing treatments. When annealed in 20% formic acid at 102°C, the α structure results. The as‐spun fibers of nylon 6 and of the blends with poly(acrylamide‐co‐acrylic acid) and poly(ethylene‐co‐vinyl alcohol) exhibit a broad diffraction maximum in the region 2θ = 19–25°. The α content and its purity increase with increasing severity of the annealing treatment. The as‐spun fibers of the blend with poly(acrylic acid), on the other hand, exhibit a highly oriented γ structure which is highly resistant to conversion to the α from during the annealing treatments. Only when treated in 20% formic acid at 102° does the pure α form result. The drawn textured yarns of nylon 6 exhibit both the α and the γ forms. However, the γ content of the textured yarns from the blends varies with the type and concentration of the additives. The textured yarns from the blends with low levels (0.125%) of poly(acrylic acid) have a very high α content. It is very unusual that the as‐spun fibers with almost pure γ structure, when drawn, produce a structure with a high α content.