Suppression of the hierarchical structure of water-assisted injection moulded iPP in the presence of a β-nucleating agent and lamellar branching of a β-crystal

Abstract

Unexpected lamellar branching of the β-crystal structure is observed in water-assisted injection molded iPP parts with a high content of β-nucleating agent.

An Alternating Skin–Core Structure in Melt Multi‐Injection‐Molded Polyethylene

“…That is to say, the twisted kebabs are formed in the depth of 50 µm, which is in good agreement with our previous work . Obviously, except for the depth of 2000 µm, the M3 sample shows a small peak width at the height of the half of the peak, which is indicative of high molecular orientation …”

“…Evidently, arc‐like diffraction patterns emerged in the depths of 50 µm of the M1 sample (Figure a) and 50, 800, and 1500 µm of the M3 sample (Figure a'–c') where the shish‐kebab superstructure formed (Figure ), indicating that the shear provided by melt injection can induce the shish‐kebabs effectively in the inner layer of MMIM samples. It is well known that the molecular orientation is manifested by the diffraction arcs on the patterns, and a decrease in molecular orientation corresponds to the weakening of the arcs into circles …”

“…It is well known that the molecular orientation is manifested by the diffraction arcs on the patterns, and a decrease in molecular orientation corresponds to the weakening of the arcs into circles. [29,30] The azimuthal profiles of the (110) reflections are illustrated in Figure 7. It had been observed that, for the depth of 50 µm, the scattering intensities of (110) reflections appear with two maxima on the off-axis, while in other depths, (110) reflections show one maximum.…”

“…[24] Obviously, except for the depth of 2000 µm, the M3 sample shows a small peak width at the height of the half of the peak, which is indicative of high molecular orientation. [29] The melting curves of M1 and M3 samples at selected depths are shown in Figure 8. Clearly, there is a dominant peak around 131 °C, which is attributed to the melting of HDPE lamellae.…”

Annealing Induced Mechanical Reinforcement of Injection Molded iPP Parts

“…As well known, the microstructures of semicrystalline materials strongly affect their mechanical properties. [1][2][3][4][5][6][7][8][9][10][11] Annealing semicrystalline polymers at temperature between glass transition temperature and melting temperature is considered to be an effective method to modify the microstructure and promote the mobility of molecular chains toward a more thermodynamically stable state, resulting in a pronounced enhancement of the physical properties. [4][5][6][7][8][9] Especially for injection molded parts, owing to the uneven thermomechanical conditions lead to the development of imperfect microstructure, it is conceivable that pronounced changes should take place during annealing process.…”