Tuning Crystalline Morphology of High‐Density Polyethylene by Tailoring its Molecular Weight Distribution for Coupling with a Secondary Flow Field

Zhang, Jian Ping; Xia, Xiaochao; He, Shan; Feng, Jianmin; Yang, Ming‐Bo; Li, Yintao; Zhou, Yanyan

doi:10.1002/mame.201500008

Cited by 9 publications

(5 citation statements)

References 32 publications

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“…Therefore, in the current study, a particular flow pattern, i.e. the melt second flow with an intense shear caused by gas penetration in the GAIM process, [31][32][33] is used to control the crystalline morphology at the interface between PE and CNF, aiming a realization of our conjecture that the CNF can act as the stable ''shish'' and the PE lamellar crystal can be periodically decorated on the CNF to form a HSK structure. Meanwhile, the HSK could be formed massively in all regions of injection molded bars of HDPE/CNF composites.…”

Section: Introductionmentioning

confidence: 98%

Strong shear-driven large scale formation of hybrid shish-kebab in carbon nanofiber reinforced polyethylene composites during the melt second flow

Xia

Yang

Liu

et al. 2016

Phys. Chem. Chem. Phys.

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The formation of a hybrid shish-kebab (HSK) structure with different degrees of lamellar orientations was first observed in the solution crystallization of polyethylene (PE) in the presence of carbon nanofibers (CNFs). In this study, PE crystal lamellae were periodically decorated on the surface of CNFs and were aligned approximately perpendicular to the long axes of the CNFs, forming aligned hybrid shish-kebab nanostructures. More importantly, the fascinating structure was directly formed in all regions of the injection molded bars of HDPE/CNF composites, via a gas-assisted injection molding (GAIM), instead of the shell-core structure. In the GAIM process, an intense shear was imposed onto the melt during the melt second flow and drove PE chains to orient along the axes of the CNFs. Then the entropy penalty for PE chains deposited on the CNF surface was drastically decreased. Although the attractive van der Waals interactions were weak, the oriented PE chains could successfully adsorb on the CNF surface due to the decrease of the entropy penalty, therewith the underlayer coating was formed along the axis based on a two-dimensional mode for early nucleation on the CNF surface. Subsequently, subglobules appeared on the ordered structure, which could be regarded as the crystal nucleus. Finally, the oriented PE chains began to epitaxially grow from the subglobules with a folded-chain shape to decrease the polymer surface energy and grew perpendicular to the CNFs long axis, abiding by the "soft epitaxy" crystallization mechanism regardless of strict lattice matching.

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Section: Introductionmentioning

confidence: 98%

Strong shear-driven large scale formation of hybrid shish-kebab in carbon nanofiber reinforced polyethylene composites during the melt second flow

Xia

Yang

Liu

et al. 2016

Phys. Chem. Chem. Phys.

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Section: Recycling By Reprocessingmentioning

confidence: 99%

“…Even only considering a single polymer type within the plastic waste, the molecular weight distribution tends to be engineered to the application to meet the processing and product property demands. 132 Thus, products of nominally the same plastic may have vastly different molecular weight distributions if produced by injection molding in comparison to pultrusion or blow molding. These differences in the initial molecular weight distribution will alter the rheological performance of the recycled resin and its suitability for the variety of melt processing typically associated with the production of plastic products.…”

Section: Plastic Waste Streamsmentioning

confidence: 99%

Why is Recycling of Postconsumer Plastics so Challenging?

Vogt

Stokes²,

Kumar

2021

ACS Appl. Polym. Mater.

193

122

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The ubiquitous use of plastics has been driven by their combination of low cost and properties, but these attributes directly challenge waste management schemes for plastic recycling. Some postconsumer recycling programs are now nearly 50 years old, but a significant fraction of plastics still finds landfills or other dumping strategies at their end of life. With the growing concern regarding plastic waste, especially ocean plastics, there is a need for innovation and alternative strategies for the economic translation of plastic waste to valued product(s) that will promote their efficient circular utilization. This review first describes the technical and economic hurdles associated with the recycling of postconsumer plastics, but then it focuses on providing an overview of emergent strategies to recover plastic waste through new polymer design, new recycling processes, and chemical transformations to value-added products. Specific challenges discussed include plastic waste sorting and separations, product variability including additives, and the high efficiency/low cost in which the existing petrochemical industry can produce virgin polymers, in particular polyolefins. Although a wide variety of technical strategies have been demonstrated for recycling of plastics through both mechanical and chemical means, the commercial success of these different strategies is generally limited by either performance, including large variance in key metrics, or economics where the products can match the performance of virgin materials but the recycling process is expensive. Successful capture of postconsumer plastic waste through recycling likely will depend on economic incentives and government regulations.

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“…The molecular weight and the molecular weight distribution of polymers have a pronounced effect on the shear‐induced crystallization . It is generally believed that high molecular weight species play an important role in nucleation, melt orientation and subsequent crystallization.…”

Section: Current Researchmentioning

confidence: 99%

Overview of the Experimental Trends in Water‐Assisted Injection Molding

Liu

Pan

Zheng

et al. 2018

Macro Materials & Eng

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In recent years, a new and promising polymer processing technology known as water‐assisted injection molding (WAIM) has attracted attention not only for academic reasons but also for its industrial applications. WAIM technology provides a new way to fabricate hollow or other complicated products due to its faster cycling time and light weight. This paper aims to give an overview of the basic principles and applications of WAIM as well as the current research status in academia. The origin and development of WAIM technology are first described and then, their advantages and applications are given. This review focuses on the experimental trends of WAIM such as computer simulation, the effect of processing parameters on the WAIM samples, and the morphology as well as related WAIM–molded composites and polymer blends' work.

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Tuning Crystalline Morphology of High‐Density Polyethylene by Tailoring its Molecular Weight Distribution for Coupling with a Secondary Flow Field

Cited by 9 publications

References 32 publications

Strong shear-driven large scale formation of hybrid shish-kebab in carbon nanofiber reinforced polyethylene composites during the melt second flow

Strong shear-driven large scale formation of hybrid shish-kebab in carbon nanofiber reinforced polyethylene composites during the melt second flow

Why is Recycling of Postconsumer Plastics so Challenging?

Overview of the Experimental Trends in Water‐Assisted Injection Molding

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