Isotactic Poly(propylene) Crystallization: Role of Small Fractions of High or Low Molecular Weight Polymer
✍ Scribed by Aadil Elmoumni; Ramon A. Gonzalez-Ruiz; E. Bryan Coughlin; H. Henning Winter
- Publisher
- John Wiley and Sons
- Year
- 2005
- Tongue
- English
- Weight
- 238 KB
- Volume
- 206
- Category
- Article
- ISSN
- 1022-1352
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✦ Synopsis
Abstract
Summary: Two well‐characterized metallocene isotactic poly(propylene) (iPP) samples, one of high and one of low molecular weight, were blended together for studying the effects of a second component on quiescent and shear‐induced crystallization. A small amount of added high molecular weight (HMW) (up to 10 wt.‐%) polymer increases the quiescent crystallization rate. This was observed as a decrease in characteristic halftime of transmitted light intensity. The crystallization halftime increases again when adding more than 10 wt.‐% of HMW polymer. The crystallization halftime of pre‐sheared samples decreases with increasing HMW fraction and is lowest for the HMW sample by itself. For the specific shearing conditions (γ = 600, T~x~ = 145 °C), wide‐angle X‐ray diffraction (WAXD) images show the presence of the gamma (γ) crystalline phase of iPP for samples containing 25 wt.‐% of HMW and higher. DSC thermograms demonstrated higher crystalline fractions with increasing HMW fraction in pre‐sheared samples.
Optical micrograph of an iPP sample after quiescent crystallization at 145 °C.
magnified imageOptical micrograph of an iPP sample after quiescent crystallization at 145 °C.