Effect of the holding pressure on the skin‐core morphology of injection‐molded polypropylene parts

Studies of Injection‐Moulded Isotactic Poly(propylene) by Synchrotron WAXD/SAXS: Effects of Nucleating Agent on Morphological Distribution

“…[8] Such an approach is simple and gives a similar shape of the distribution to that of the volume crystallinity presented here. However, it is worth pointing out that this crystallinity index is not simply related to the fraction of the crystalline phase of bulk materials and cannot be physically compared with the degree of crystallinity obtained from other methods such as differential scanning calorimetry and density measurement.…”

“…The crystalline scattering peaks in the range of scattering angles 2y from 10 to 30 degrees were assigned to the a-(monoclinic) and b-(hexagonal) phases. [8,21] The Miller indices of these crystalline reflections are a 1 (110), a 2 (040), a 3 (130), a 4 ((111) ( 1 131), and (041)), b(300), and a 5 (060), respectively. The (111) reflection of a 4 is observed at about 21.68.…”

“…Nevertheless, there is little doubt that the shear flow of industrial processing can significantly modify the crystallization and the resulting morphology of semicrystalline polymers. [8][9][10][11][12][13] Studies of the injection moulding of semicrystalline polymers such as isotactic poly(propylene) (iPP) have revealed that the hot polymer melt contacting with the cold walls of the die experiences high stresses, strain rates, and cooling rates and subsequently the final structures of articles Full Paper: The morphological distribution of injectionmoulded isotactic poly(propylene) (iPP) plates in the presence of nucleating agents was extensively investigated using synchrotron radiation. The commercial PP compound was injection-moulded under a variety of different conditions in order to explore the effects of shear flow and temperature on the morphology and morphological distribution.…”

“…[8][9][10][11][12][13] The morphology of injection-moulded semicrystalline polymers is a skincore structure in which multiple layers have been observed. The layer numbers may vary from one semicrystalline polymer to another and the structures are pronouncedly dependent on moulding conditions, including the cavity thickness, the mould temperature, the injection speed and pressure, the holding pressure, and the cooling time.…”

Combined effect of shear and nucleating agent on the multilayered structure of injection‐molded bar of isotactic polypropylene

“…[1][2][3][4][5][6][7] Although the shear flow in industrial processing is considered to be weak and may not be able to induce the extended molecular chain, many studies have revealed that the crystallization and morphology are significantly affected under shear flow in industrial processing. [8][9][10][11][12][13] It is found that a so-called ''skin-core'' structure is usually formed in injection molded semicrystalline polymers such as isotactic polypropylene (iPP) or polyethylene (PE). During the injection molding process, the hot polymer melt contacting with the cold walls of the mold experiences high shear stress, high strain and rapid cooling rate, resulting in a layer with high orientation near the wall to be the skin.…”