Effects of ultrasound on the conformation and crystallization behavior of isotactic polypropylene and β-isotactic polypropylene

✍ Scribed by Jian Kang; Jinyao Chen; Ya Cao; Huilin Li

• Publisher: Elsevier Science
• Year: 2010
• Tongue: English
• Weight: 703 KB
• Volume: 51
• Category: Article
• ISSN: 0032-3861
• DOI: 10.1016/j.polymer.2009.11.018

✦ Synopsis

The effects of ultrasonic irradiation on conformation and crystalline structure of isotactic polypropylene (iPP) and b-isotactic polypropylene (b-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, T m and T onset decrease, T m À T onset becomes larger; for b-iPP, the b c , (1 À l) b and k b increase, the intensities of a(040) plane and a(130) plane in WAXD profiles decrease evidently. For both iPP and b-iPP, the crystallinity decreases, d-spacing increases, the crystallite size L decreases and ultrasound shows a selective effect on the growth of b-crystal. Furthermore, DSC and WAXD were employed to observe the effect of ultrasound on the ''melting memory effect'' of b-iPP. The results indicate that ultrasonic irradiation destructs the existing ''locally ordered structure'' in b-iPP melt, as a result greatly inhibits the ba-recrystallization of b-iPP samples during heating.