Flow-induced crystallization: from the beginning to the end
Citation for published version (APA):
Ma, Z., & Peters, G. W. M. (2012). Flow-induced crystallization: from the beginning to the end. Poster session
presented at Mate Poster Award 2012 : 17th Annual Poster Contest.
Document status and date:
Published: 01/01/2012
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Accepted manuscript including changes made at the peer-review stage
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Results
1) During flowFlow-induced crystallization:
from the beginning to the end
Z. Ma, G.W.M. Peters
Materials technology, Department of Mechanical Engineering, TU/e
/ Department of Mechanical Engineering
Introduction
Flow-induced crystallization is one of the fundamental issues in polymer physics and also one of the most important determining factors in polymer processing. This is because flow can significantly vary the formed crystal structures (e.g. from isotropic to oriented) [1] and consequently determine the ultimate mechanical properties [2]. Therefore, a full understanding on how crystallization is altered by flow and further develops after cessation of flow is of importance for both academic and industrial societies. In this work, we are aiming at tracking the entire process of flow-induced crystallization from start-up of flow (the beginning) to completion of solidification (the end).
Material and methods
The material used is an commercial iPP (Borealis HD601CF) with a molecular weight, Mw = 365,000 g/mol and a polydispersity, Mw/Mn = 5.4.
2) Growth kinetics of crystallization
Fig. 1 The combination of Multi-Pass Rheometer (MPR) and synchrotron X-ray.
Fig. 2 SAXS and WAXD results during and just after flow.
Conclusions
References
3) Orientation during crystallization.
[1] van Erp, T. B. (2012) PhD thesis, Eindhoven University of Technology, NL [2] Schrauwen, B.A.G. (2003) PhD thesis, Eindhoven University of Technology, NL
Orientation is very high (low FWHM value) at the beginning and decreases (FWHM increases) with crystallization.
By combining slit flow with ultra-fast X-ray, the entire flow-induced crystallization is tracked from the start-up of flow until the end of crystallization. It is found that shish nuclei can be generated during flow. Growth of parent lamellae is effectively started by shish nuclei, but daughter lamellae appear later. Moreover, orientation decreases with crystallization. Fig. 3 Area of equatorial and daughter (110) diffraction during crystallization. Selected 2D patterns are shown in the right column. Flow direction is vertical.
Crystallization is effectively triggered by shish nuclei.
X-ray MPR BM26B@ESRF Pilatus time 0.17s 0.20s 0.13s 0.27s flow cessation (110) (110) (110) (040) (130) WAXD SAXS streak 1.7s 6.7s
Daughter lamellae appear later than parent lamellae.
Crystal-shish nuclei are formed during flow.
Fig. 4 FWHM evolution of equatorial (110) diffraction during crystallization. Selected 2D pattern is shown. Flow direction is vertical.
Experimental conditions:
apparent wall shear rate = 560s-1, flow time = 0.20s
temperature for shear and isothermal crystallization = 145oC
Experimental equipments:
Multi-Pass Rheometer executes a very strong flow field.
European Synchrotron Radiation Facility provides a high intensity X-ray source. The “Pilatus” detector provides a high-speed acquisition of 30 frame/s.
Peak area of (110) diffraction (Area110) can be used to indicate
the amount of crystal.
Full width at half maximum (FWHM) of equatorial (110) diffraction can be used to indicate orientation.
