Advantage of Preserving Bi-orientation Structure of Isotactic Polypropylene through Die Drawing

Light‐weight and high‐strength PP/CaCO3 composites by die drawing: Effect of drawing ratios

“…It is the process of passing the sample through a converging die under tensile force. [16,17] During the die drawing process, the crystal areas are broken into smaller crystal blocks and the crystal blocks tilted and slide along the drawing direction under the action of tensile stress to rearrange and recrystallize to form new orientation structure. [18] Molecular chains in the amorphous regions are disentangled along the drawing direction.…”

Morphological Characteristics of β-Nucleating Agents Governing the Formation of the Crystalline Structure of Isotactic Polypropylene

“…Isotactic polypropylene (iPP), one of the typically versatile semicrystalline polymers, exhibits complex polymorphic behaviors. iPP crystallizes into four forms, namely, monoclinic α, trigonal β, orthorhombic γ, and a mesomorphic form, under different thermal and mechanical conditions and the usage of nucleating agents (NAs). − Among the various crystalline modifications, the α form is readily obtained under common melt processing conditions. , Owing to better toughness and improved heat resistance, the thermodynamically metastable β form has attracted much attention in both academic and industrial research. − β - crystals form in abundance exclusively with the addition of efficient β-nucleating agents (β-NAs). − Several organic compounds, inorganic compounds, and polymers were investigated with respect to their β-nucleation capability. The first reported efficient β-NA was γ-quinacridone that could dramatically enhance the relative fraction of the β-crystal ( K β value) in iPP even at an extremely low content range. − A series of metal salts of dicarboxylic acid such as calcium pimelate were demonstrated to show a sole nucleation capability for β-crystal. ,− Several aromatic bisamide compounds (e.g., N,N′ -dicyclohexylterephthalamide (DCHT) and N,N′ -dicyclohexyl-2,6-naphthalenedicarboxamide (DCHN)) − and rare-earth compounds (WBG, Ca x La 1– x (LIG1) m (LIG2) n , where LIG1 and LIG2 represent a dicarboxylic acid and an amide-type ligand, respectively), ,, showing a dual selectivity for β- and α-crystals, could improve the nucleation efficiency and enhance the K β value in the iPP homopolymer.…”

A Simple Way to Control Small-Strain Cavitation in Die-Drawn Isotactic Polypropylene

“…Similar to the ones of the cross-hatched structure, ,− the diffraction signals of lamellae with their normal along different directions were expected to appear at different positions along the characteristic diffraction ring of the (110) α -lattice plane. The diffraction signal for the lamellae with normal along the deformation direction (designated as the parallel lamellae in the following discussion) appeared at the equator region of the pattern, as shown in the S2 WAXD pattern in Figure , while the one for lamellae with normal perpendicular to the deformation (referred as the perpendicular lamellae) was at the meridional position, as shown in the S3 WAXD pattern in Figure .…”

“…Hence, the acquisition time was set as 300 s to achieve a balance between the structure relaxation and the signal quality. The orientation of the molecular chains in the (040) α -lattice plane, S (040)α , could be evaluated through Hermans equation, and the crystallinity was determined via peak fitting which was introduced in our previous work. , …”

“…The orientation of the molecular chains in the (040) α -lattice plane, S (040)α , could be evaluated through Hermans equation, 35 and the crystallinity was determined via peak fitting which was introduced in our previous work. 36,37 The in situ small-angle X-ray scattering (SAXS) experiments were performed at Beamline 1W2A Beijing synchrotron radiation facility (BSRF), Beijing, China, to monitor the evolution of the long spacing of the crystalline stacks. A Pilatus 1 M detector, with dimensions of 1043 × 981 pixels (pixel size = 172 × 172 μm 2 ), was employed to collect the 2D SAXS patterns.…”