Synergistic enhancement of crystallization and mechanical performance of polypropylene random copolymer by strong shear and β‐nucleating agent

Abstract

Investigation of microstructure and properties is critical for the development and application of polymer materials. Polypropylene random copolymer (PPR) and -nucleated PPR are widely used in water pipe production. The effect of melt shear flow on the crystalline structure and mechanical properties of PPR containing -nucleating agent needs in-depth understanding. In this paper, we demonstrated the preparation of PPR and PPR containing 0.1 wt% calcium pimelate (Ca-Pim) samples by conventional injection molding (CIM) and oscillation shear injection molding (OSIM). The multilayer structures and morphologies of the samples were characterized by SEM, two-dimensional X-ray scattering and DSC. The mechanical properties and the microstructures of samples prepared by these two injection molding methods were compared. Compared with samples prepared by CIM, the stronger shear provided by OSIM induced the formation of a thicker layer of a shish-kebab structure and a higher content of crystals, and dramatically suppressed the -nucleating effect of Ca-Pim. The OSIM samples have more shish-kebab structures and higher crystallinities than CIM samples and therefore the former exhibit better rigidity than the latter. The crystals in the core layer and the thicker layer of shish-kebab structure endow OSIM-PPR/0.1 wt% Ca-Pim with excellent impact toughness.

β-Nucleated Polypropylene: Preparation, Nucleating Efficiency, Composite, and Future Prospects

“…The loose lattice structure makes the rubber phase more dispersed, and it can further accommodate the hard segments of the toughened rubber phase. The increase in the β-crystal content and the thickening of lamellae also contribute to energy absorption [ 170 , 171 , 172 ]. On the other hand, β-grain refinement reduces the stress concentration in the crystal region, while the rubber phase improves the impact toughness.…”

Morphological evolution ofTMB‐5/ethylene–vinyl alcohol copolymer blends under biaxial‐stretching field and its effect on the crystallization and gas barrier properties of isotactic polypropylene

“…Huang and co‐workers proposed water‐assisted injection molding (WAIM) to impose high shear and elongational stress on a polymer melt by penetration of high‐pressure water into the core of the melt 10 . Similar to WAIM, other novel injection molding technologies, such as oscillating injection molding (OSIM), 11 loop oscillating push–pull molding (LOPPM), 12 gas‐assisted injection molding 13 and dynamic packing injection molding, 14 can also impose strong flow field on a polymer melt until the gate freezes. In addition to injection molding, various attempts have been made to endow traditional extrusion with strong flow field via proper design.…”

Improved impact property of long glass fiber‐reinforced polypropylene random copolymer composites toughened with beta‐nucleating agent via tunning the crystallization and phase

“…Adding β ‐nucleating agent ( β ‐NA) has been considered to be an economical and efficient approach to induce the formation of β ‐crystal. [ 16,23 ] Many previous studies focused on the crystallization behavior and/or mechanical properties of nanocomposites containing β ‐NA, such as PPR/ β ‐NA, [ 24–28 ] PPR/SiO 2, [ 20 ] PPR/MWCNTs, [ 29 ] PPR/nano‐CaCO 3, [ 30 ] PPR/nano‐ZnO‐supported zeolite, [ 19 ] and so forth. However, these studies only discussed the influence of nanomaterials on the crystallization temperature when discussing the influence of nanomaterials on the crystallization behavior of the PPR matrix; moreover, they did not only reveal the changes in the size distribution of crystallites from the perspective of crystallization and nucleation mechanisms, but also did not establish the relationship between crystallization parameters and mechanical properties.…”