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The wide-angle X-ray diffraction (WAXD) patterns of isothermally crystallized Nylon 1212 show thatγ-form crystals form below 90℃and the a-form crystals can exist above 140℃. In the temperature range of 90-140℃, theα-form andγ-form crystals coexist. Variable-temperature WAXD exhibits that the nylon 1212γ-form does not show crystal transition on heating, whileα-form isothermally crystallized at 160℃exhibits Brill transition at a little higher than 180℃on heating. The multiple melting behaviors of Nylon 1212 isothermally crystallized from melt come from a complex mechanism of different crystal structures, dual lamellar population and melting-recrystallization. In polarized optical microscope (POM) observations, Nylon 1212 isothermally crystallized at 175℃shows the ringed banded spherulites. However, at temperatures below 160℃the ringed banded image disappears, and cross-extinct spherulites are formed.
The wide-angle X-ray diffraction (WAXD) patterns of isothermally crystallized Nylon 1212 show that γ-form crystals form below 90 ° C. and the a-form crystals can survive above 140 ° C. In the temperature range of 90-140 ° C., form-and-form crystals coexist. Variable-temperature WAXD exhibits that the nylon 1212 γ-form does not show crystal transition on heating, while α-form isothermally crystallized at 160 ° C. exhibits Brill transitions at a little higher than 180 ° C on heating. The multiple melting behaviors of Nylon 1212 areothermally crystallized from melt come from a complex mechanism of different crystal structures, dual lamellar population and melting-recrystallization. In polarized optical microscope (POM) observations, Nylon 1212 isothermally crystallized at 175 ° C. at temperatures below 160 ℃ the ringed banded image disappears, and cross-extinct spherulites are formed.