The transformation behaviors of nylon 12 were investigated using wide-angle X-ray diffraction (WAXD), X-ray fiber patterns and differential scanning calorimetry. The γ' form could be distinguished from the γ form in spite of their very similar WAXD patterns, because the γ form cannot be transformed into the α form, while the γ form can be so transformed under high pressure. The γ' to γ transformation occurs on annealing above 110°C at atmospheric pressure. The γ to γ' and α to γ' transformations occur on drawing at atmospheric pressure above 50°C and above 70°C, respectively. The transformation behaviors presented in this paper and in a previous paper [N. Hiramatsu, S. Hashida and S. Hirakawa: Jpn. J. Appl. Phys. 21 (1982) 651] are summarized.
ABSTRACT:Thermal behavior under high pressure of the y form nylon 6 obtained by iodine treatment was investigated by means of a high pressure differential thermal analysis. The crystalline structures which resulted in the endo-and exo-thermic peaks in the thermogram were examined with the wide angle X-ray diffraction measurement. Under relatively low pressure kg em-2 ), two endothermic peaks were found. With increasing pressure, the lower temperature side endotherm due to the melting of the y form crystal became small, while the higher one due to the melting of the converted rx form crystal became large. Under high pressure (above 2000 kg em -z) an endotherm due to the melting of the converted rx form crystal and an exotherm were observed. This exotherm is attributed to they to rx form transformation. In this case, the transformation occurred without melting the y form crystal, in contrast to the situation at atmospheric pressure. The pressure dependences of the melting peak temperatures of the rx form and they form were almost the same and equal to !Soc per 1000 kg em-2 •
For poly(ethylene terephthalate) crystallized and/or annealed under elevated pressure, the melting behavior was studied, using a differential scanning calorimetry technique at atmospheric pressure. The melting point of the sample crystallized from the melt by slow cooling under elevated pressure is lower than that of the sample crystallized at atmospheric pressure, although the former sample has a slightly thicker lamella than the latter one. This implies that the fold surface energy is much larger in the elevated pressure crystallized sample. The atmospheric pressure melting point increases greatly by annealing under elevated pressure. In particular, a remarkable increase in melting point is observed at the early stage of the annealing for the elevated pressure crystallized sample, which may be due mainly to the decrease in fold surface energy in addition to lamella thickenning. An electron micrograph of the sample annealed for a long period after the melt crystallization under elevated pressure shows a morphology of a band structure composed of extended-chain-like crystal.
The first small-angle X-ray scattering (SAXS) measurements were carried out
in order to examine the mesoscopic structure in the
N-isopropylacrylamide/sodium acrylate (NIPA/SA) gel.
By the SAXS measurements, a prominent peak was found in the
dehydrated gel around 0.026 Å-1.
Taking into account of the cross section magnitude against X-ray,
the concentration fluctuation of Na+ ions was a probable candidate for
making contrast for the SAXS profile, which depends on the distribution of
the hydrophilic group.
Therefore, it was concluded that the mesoscopic structure found in the present
study is due to the hydrophilic domains in the dehydrated gel which capture
the Na+ ions and the remnant water inside the gel.
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