NYLON-65 HAS A UNIQUE STRUCTURE WITH 2 DIRECTIONS OF HYDROGEN-BONDS

A new type of polyamide structure has been found for nylon 65 and it i s reported here. The structure and morphology of nylon 65 lamellar cry stals have been investigated using transmission electron microscopy, s elected-area electron diffraction, and X-ray diffraction. Additional d ata have been obtained from uniaxially oriented fibers. The deduced un it cell parameters (a = 4.60 Angstrom, b = 30.95 Angstrom, c = 8.62 An gstrom, alpha = beta = 90 degrees, and gamma = 114 degrees) and the sp ace group symmetry indicate a different structure for nylon 65 than th e conventional alpha and gamma-forms of nylons. Each molecule is linke d to its four neighbors by a network of hydrogen bonds made by amide g roups in two different orientations. Structural modeling has been carr ied out using the linked-atom least-squares (LALS) methodology. The re sults obtained point to a particular conformation for the glutaryl uni ts which play a decisive role in establishing such a unique structure. The temperature-induced structural changes have also been studied. A pseudohexagonal packing is found at 190 degrees C. Modifications are b elieved to occur without changes in the hydrogen bond system, in a way that is similar to that found in nylon 66. Fiber diffraction patterns of nylon 66 at 220 degrees C are also presented in order to confirm s uch conclusion.