Quantification of shish–kebab and β‐crystal on the mechanical properties of polypropylene

Abstract

ABSTRACT:The oriented "shish-kebab" structure and b-crystal can enhance the mechanical properties of polypropylene products. In this regard, equipment and b-nucleation agents have been developed or modified to form shish-kebab and b-crystal. However, the effect of shish-kebab/b-crystal proportion on the mechanical properties of polypropylene remains unclear. The answer is crucial but remains a challenge because of the difficulty in manipulating the shish-kebab proportion. In this work, we used a self-made multiflow vibrate-injection molding, which can provide a controllable shear flow, to produce samples with different shear-layer thicknesses. The shish-kebab proportion was represented by R, which is the thickness ratio of the shear layer to that of the whole sample. Results showed that the tensile strength exponentially increased, whereas the elongation at break exponentially decreased, with R. The impact strength remained constant with R, indicating that the shish-kebab and b-crystal possessed similar toughening effects. This work proposes a schematic to interpret the strengthening mechanism involved and presents a method of establishing and controlling the mechanical properties of polypropylene samples by using shish-kebab structures and b-crystals. V C 2017 Wiley Periodicals, Inc. J. Appl.Polym. Sci. 2017, 134, 45052.

A novel combination of sandwich and co‐continuous structure based on polypropylene and styrene‐butadiene‐styrene block copolymer formed with wide range of polypropylene content

“…Since the crystallinity of each blend is contributed by crystalline polymer PP, the data of X C in Table indicates that the X C of different SBS/PP blends is lower than pure PP, which can be ascribed to the lower volume content of PP as a crystallizable component replaced by amorphous polymer SBS. The diffractograms of all samples mainly exhibit peaks of the stable monoclinic a ‐form of the isotactic PP crystalline phase which are at about 2θ = 14.5°, 17.4°, 19.1°, 21.6°, and 22.2° can be responsible for the crystal plane of (110), (040), (130), (131), (111), indicating that there is no change in crystal form with the addition of SBS and no evidence of β‐form of the isotactic PP crystalline phase forming from the melt under this crystallization condition . Pure PP with sharp characteristic diffraction peaks has a X C value of 65.41%.…”

Differential scanning calorimetry/small-angle X-ray scattering analysis of ultraviolet sensible polypropylene filaments

“…The formation of the "Shish-Kebab" in iPP has been reported in the literature. [34][35][36][37] It is noteworthy that almost isotropic donut-shaped ring peaks overlapped in the two-spot pattern in Figures 4(a) and 5(a), while no such peak was discernible in the others. This result suggests that the lamellar stacks ("Kebab" without "Shish") with random orientation co-exist with the preferentially oriented "Shish-Kebab" parallel to the fiber axis in the initial miPP filament.…”

Effect of high‐temperature annealing on the microstructure and mechanical properties of polypropylene with shish kebab or spherulite structure

“…After several flows, the shear layer thickness increased to 2.9 mm. The details of the preparation method and theory have been described previously . The specimens were annealed in an air‐circulating oven at different temperatures, 150, 160, 165, and 170 °C, for different time periods.…”

“…The details of the preparation method and theory have been described previously. 29,30 The specimens were annealed in an air-circulating oven at different temperatures, 150, 160, 165, and 170 8C, for different time periods. When the annealing temperature was close to T m , the inhomogeneous cooling easily caused a warping dimensional change.…”

“…For the CIM sample, annealing at 150, 160, 165, and 170 8C enabled the impact strength to be increased to 13, 17, 23, and 28 kJ/m 2 , respectively. For the MFVIM sample, the impact strength can be increased to30,35, 48 and 50 kJ/m 2 , respectively. The impact strength increased sharply in the first 10 min regardless of the crystal structure and annealing temperature.…”