We successfully formed an inclusion complex between nylon-6 and R-cyclodextrin and attempted to use the formation and subsequent disassociation of the nylon-6/R-cyclodextrin inclusion complex to manipulate the polymorphic crystal structures, crystallinity, and orientation of nylon-6. Formation of the inclusion complex was verified by Fourier transform infrared (FTIR) spectroscopy, wideangle X-ray diffraction (WAXD), differential scanning calorimetry (DSC), and CP/MAS 13 C NMR. After obtaining the inclusion complex of nylon-6 and R-cyclodextrin, the sample was treated in an acid environment to remove the host R-cyclodextrin and coalesce the nylon-6 guest polymer. Examination of as-received and IC coalesced nylon-6 samples showed that the R-form crystalline phase of nylon-6 is the dominant component in the coalesced sample. X-ray diffraction patterns demonstrate that the γ-form is significantly suppressed in the coalesced sample. Along with the change in crystal form, an increase in crystallinity of ∼80% was revealed by DSC, and elevated melting and crystallization temperatures were also observed for the coalesced nylon-6 sample. FTIR spectroscopy revealed a significant degree of orientaion for the nylon-6 chains coalesced from their R-cyclodextrin inclusion complex crystals. Thermogravimetric analysis indicated that nylon-6 has an ∼30 °C higher thermal degradation temperature after modification by threading into and being extracted from its R-cyclodextrin inclusion complex.
We successfully formed a series of inclusion complexes (ICs) between an ␣-cyclodextrin (␣-CD) host and two kinds of guest polymers, nylon-6 and nylon-66. An attempt to achieve an intimate blend between nylon-6 and nylon-66 through the formation and dissociation of their common ␣-CD IC was made. The formation of all nylon ICs was verified with wide-angle X-ray diffraction, differential scanning calorimetry (DSC), and Fourier transform infrared (FTIR) and cross-polarized/magic-anglespinning 13 C NMR spectroscopy. The experimental results demonstrated that ␣-CD could only host single nylon polymer chains in the IC channels, either nylon-6 or nylon-66 in their own complexes, and presumably either nylon in neighboring channels of their common IC. The IC-coalesced blend of nylon-6 and nylon-66 was obtained after the removal of the host cyclodextrin from their common IC with dimethyl sulfoxide. The spectroscopic results (FTIR and 13 C NMR) illustrated that there was a degree of intimate miscibility existing in the IC-coalesced blend, but not in the solution-cast physical blend, although X-ray diffraction patterns showed that the crystal structure of the IC-coalesced blend was similar to that of the physical blend. DSC thermal profiles suggested that nylon-66 first formed crystals during coalescence and that the subsequent crystallization of nylon-6 was greatly affected by the nylon-66 crystallites because of the close proximity of the two components in portions of the coalesced blend. DSC observations also demonstrated that the melting of the coalesced blend did not lead to complete phase separation of the nylon-6 and nylon-66 components.
The influence of the milling conditions on phase formation and structural transitions induced by ball milling has been studied for Al&umMn15 powders by X-ray diffraction and differential scanning calorimetry. Depending on the experimental conditions, an amorphous, a quasi-crystalline, or a crystalline phase can be obtained from the layered composite of the pure elements. The various phases can be transformed into each other by further milling at suitable milling intensity. Possible mechanisms are discussed.
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