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

Abstract

Shish‐kebab, which is endowed with superior strength and modulus, provides the potential to fabricate self‐reinforced polymer products. However, the injection‐molded product usually exhibits a typical skin–core structure, and the shish‐kebab is only located in an extremely thin shear layer. Therefore, the controlling and tailoring of crystal structures in complex flow field to improve the mechanical properties of the injection‐molded sample are still a great challenge. Herein, for the first time, high‐density polyethylene sample with a novel macroscopic alternating skin–core structure is achieved using a melt multi‐injection molding technique. Results show that, with increasing the amount of melt injection, the layers of skin–core structure increase in the form of arithmetic progression, and therefore the tensile strength of the samples progressively increases due to an increase of shish‐kebab content. This study demonstrates a new approach to achieve multilayer homogeneous materials with excellent tensile strength via macroscopic structural design during the practical molding process.

Thermally Assisted Electrohydrodynamic Jet High‐Resolution Printing of High‐Molecular Weight Biopolymer 3D Structures

“…Numerous fabrication techniques have been used to process high‐molecular weight biopolymers to form biostructures, such as gas foaming, injection molding, and freeze‐drying . Among the fabrication techniques, in particular, printing has been paid more attention due to its additive manufacture capabilities on demand, fast fabrication of complex structures, and no need of mold .…”

Facile Thermally Impacted Water‐Induced Phase Separation Approach for the Fabrication of Skin‐Free Thermoplastic Polyurethane Foam and Its Recyclable Counterpart for Oil–Water Separation

“…Low density and high porosity polymer foam with controllable micro‐/nano‐structures could be formed through this simple and template‐free method. However, the obtained polymer foam usually has a skin structure, like some injection‐molded parts . This special structure will lead to the decline of the adsorption capacity and wetting properties.…”

“…However, the obtained polymer foam usually has a skin structure, like some injection-molded parts. [23][24][25][26][27] This special structure will lead to the decline of the adsorption capacity and wetting properties. In this study, we developed a facile thermally impacted water-induced phase separation, which is a combination of thermally and nonsolvent induced phase separation to form hydrophobic and superoleophilic foam with a skin-free structure.Our method for making polymer foam starts with the preparation of a precursor solution of water and thermoplastic polyurethane (TPU) in dioxane (Scheme 1).…”

Overview of the Experimental Trends in Water‐Assisted Injection Molding

“…It is well known that iPP is a polymorphic material with several crystal modifications, including monoclinic α‐phase, trigonal β‐phase, orthorhombic γ‐phase, and smectic mesophase . Thus, iPP is always used as a representative template to study the crystalline evolution during the injection molding process.…”

“…[92] It is well known that iPP is a polymorphic material with several crystal modifications, including monoclinic α-phase, trigonal β-phase, orthorhombic γ-phase, and smectic mesophase. [93][94][95][96][97][98] Thus, iPP is always used as a representative template to study the crystalline evolution during the injection molding process. Wang and Huang [99] suggested that lowering the melt temperature is favorable for the formation of β-form in the WAIM PP part (Figure 9a,b).…”