Influence of Shear on i-Polypropylene Crystallization and Morphology†

doi:10.7503/cjcu20150675

Abstract

Abstract:

The shear-induced crystallization behavior of isotactic polypropylene(iPP) was investigated by synchrotron small angle X-ray scattering, wide angle X-ray diffraction and differential scanning calorimetry. The results showed that the β-crystallinity were found after shearing and the total crystallnity kept almost constant. The β-crystallinity increased with the shear rate up to 10 s^-1and then decreased at higher shear rates indicating the existence of competing processes of developing α- and β-crystallinities. At the shear rates between 10 s^-1 and 32 s^-1, two populations of long spacing were observed with the larger one attributed to the β-crystallinity.

Key words: Isotactic polypropylene, Shear tate, Synchrotron small angle X-ray scattering

CLC Number:

O631

TrendMD:

TANG Yujing, MEN Yongfeng. Influence of Shear on i-Polypropylene Crystallization and Morphology^†[J]. Chem. J. Chinese Universities, 2016, 37(2): 367.

Figures/Tables 12

Scheme 1 Schematic representation of the shear and temperature conditions for sample preparation

Fig.1 Room temperature WAXD patterns of iPP samples crystallized at 130 ℃ after being sheared under different rates indicated on the patterns Shear rate/s-1: (A) 0; (B) 2; (C) 5; (D) 10; (E) 16; (F) 32.

Fig.2 Integrated WAXD intensity profiles of iPP samples crystallized at 130 ℃ after being sheared under different rates indicated on the graph Curves shifted vertically for sake of clarity. Shear rate/s-1: a. 0; b. 2; c. 5; d. 10; e. 16; f. 32.

Fig.3 Crystallinity of α-crystal(a), β-crystal(b) and total crystallinity(c) as a function of shear rate

Fig.4 DSC melting curves of iPP samples crystallized at 130 ℃ after being sheared under different rates indicated on the graph Heat rate: 10 K/min. Curves shifted vertically for the sake of clarify. Shear rate/s-1: a. 0; b. 2; c. 5; d. 10; e. 16; f. 32.

Fig.5 Room temperature SAXS patterns of iPP samples crystallized at 130 ℃ after being sheared under different rates indicated on the patterns Shear rate/s-1: (A) 0; (B) 2; (C) 5; (D) 10; (E) 16; (F) 32.

Fig.6 SAXS intensity distribution of iPP samples crystallized at 130 ℃ after being sheared under different rates indicated on the graph along the orientation direction(A) and the corresponding long spacing(B) Shear rate/s-1: a. 0; b. 2; c. 5; d. 10; e. 16; f. 32.

Fig.7 DSC curves for iPP subjected to different shear rates Heating to a temperature where β-crystals were completely molten at a heat rate of 10 K/min, and then cooling down to 30 ℃ at a rate of 50 K/min.

Fig.8 Room temperature WAXD patterns of iPP after melting the β-crystal Shear rate/s-1: (A) 0; (B) 2; (C) 5; (D) 10; (E) 16; (F) 32.

Fig.9 Corresponding integrated WAXD intensity profiles

Fig.10 SAXS patterns of iPP after melting the β-crystal Shear rate/s-1: (A) 0; (B) 2; (C) 5; (D) 10; (E) 16; (F) 32.

Fig.11 Integrated SAXS intensity distribution along the orientation direction(A) and corresponding long spacing(B) Shear rate/s-1: a. 0; b. 2; c. 5; d. 10; e. 16; f. 32.

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