کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
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5186961 | 1381117 | 2010 | 8 صفحه PDF | دانلود رایگان |
The effects of ultrasonic irradiation on conformation and crystalline structure of isotactic polypropylene (iPP) and β-isotactic polypropylene (β-iPP) were studied by means of Fourier transform infrared spectroscopy (FT-IR), differential scanning calorimetry (DSC) and wide-angle X-ray diffraction (WAXD). The results demonstrate that ultrasonic irradiation decreases the helical conformation order and changes the crystalline structures: for iPP, Tm and Tonset decrease, Tm â Tonset becomes larger; for β-iPP, the βc, (1 â λ)β and kβ increase, the intensities of α(040) plane and α(130) plane in WAXD profiles decrease evidently. For both iPP and β-iPP, the crystallinity decreases, d-spacing increases, the crystallite size L decreases and ultrasound shows a selective effect on the growth of β-crystal. Furthermore, DSC and WAXD were employed to observe the effect of ultrasound on the “melting memory effect” of β-iPP. The results indicate that ultrasonic irradiation destructs the existing “locally ordered structure” in β-iPP melt, as a result greatly inhibits the βα-recrystallization of β-iPP samples during heating.
Journal: Polymer - Volume 51, Issue 1, 6 January 2010, Pages 249-256