Effects of ultrasound on the conformational and crystallization behavior of isotactic polypropylene polymerized with different Ziegler—Natta catalyst

Abstract

Using different Ziegler-Natta catalysts, we have prepared two samples of isotactic polypropylene with similar molecular weight and average isotacticity, but different stereo defect distributions. The influence of ultrasonic irradiation on the conformation and crystallization behavior of those samples were investigated by differential scanning calorimetry, wide angle X ray diffraction and Fourier transform infrared spectros copy. The ultrasonic treatment induced a decrease in the degree of crystalline perfection and a wider distri bution range of the crystalline perfection of polypropylene. Meanwhile, the crystal particles pack looser and the crystallite size decreased under the influence of ultrasonic irradiation. On the conformation aspect, the molecular movement in polypropylene became more intensive, the molecular entanglement was reduced when ultrasound was applied. Moreover, it was found that the uniformity of stereo defect distribution also played important role in determining the conformation and crystallization behavior of polypropylene sam ples irradiated by ultrasound.

Impacts of Modified Graphite Oxide on Crystallization, Thermal and Mechanical Properties of Polybutylene Terephthalate

“…SEM observation was performed on the fractured surface of the samples [ 51 , 52 , 53 , 54 ]. Dried and gold-sprayed samples were observed by FEI Inspect F scanning electron microscope (FEI Corp., New York, NY, USA) under 20 kV accelerating voltage.…”

Ultrasound‐assisted extraction of oil from hempseed (Cannabis sativa L.): Part 2

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“…US can modify the rheological and mechanical properties of a certain substrate, thus influencing its processability. 11 When applied to oilseeds, US enable the extraction of inaccessible oil by disrupting intact cell walls. 3,12 Therefore, an intensification of the oil extraction efficiency is expected.…”

Effects of melt structure on non-isothermal crystallization behavior of isotactic polypropylene nucleated with α/β compounded nucleating agents

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