Investigating the disentanglement of long chain branched polypropylene under different shear fields

Liu, Mingjin; Chen, Jin; Luo, Jiaxu; Min, Jie; Fu, Qiang; Zhang, Jie

doi:10.1002/app.51642

Cited by 7 publications

(11 citation statements)

References 29 publications

(26 reference statements)

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“…Therefore, based on the idea of a complex shear field, a novel polymer melt disentanglement machine (PMDM) that can impose not only rotational and vibrational shear fields on the polymer melt but also a unique complex shear field (superposition of rotational and vibrational shear fields) has been designed, and it can prepare disentangled materials continuously. Experimental results on polycarbonate and long-chain branched polypropylene prove that the PMDM has a good disentanglement effect and the disentangled state can be maintained in pellet for the next secondary processing.…”

Section: Introductionmentioning

confidence: 94%

Regulation of Entanglement Networks under Different Shear Fields and Its Effect on the Properties of Poly(l-lactide)

Chen

Tao

et al. 2023

Ind. Eng. Chem. Res.

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Entanglement will lead to a sharp increase in viscosity and a decrease in flowability of polymers and affect their crystallization behavior adversely. Thus, it seems that disentanglement becomes a feasible way to improve the flowability and crystallization ability of polymers without adding other substances. Poly(L-lactide) (PLLA), as a renewable polymer material, has attracted increasing attention in the past decades. Accelerating crystallization of PLLA is extremely important to improve its performance. The present study utilizes a self-designed polymer melt disentanglement machine (PMDM) with PLLA as the experimental material, which can effectively promote polymer disentanglement by applying a unique complex shear field (superposition of rotational and vibrational shear fields) to a polymer melt. The experimental results show that compared with the untreated material, the disentangled ones have a lower viscosity and a higher melt flow rate and can fill the mold cavity at a lower pressure and a lower melt or mold temperature during the injection molding process. Simultaneously, the crystallization kinetics of the disentangled materials is accelerated, the crystallinity is higher under the same secondary processing conditions, and the heat resistance and mechanical properties of prepared products are better. This study provides new ideas for resolving the conflict between mechanical properties and processing flowability, improving the heat resistance of PLLA, and expanding its application range.

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Section: Introductionmentioning

confidence: 94%

Regulation of Entanglement Networks under Different Shear Fields and Its Effect on the Properties of Poly(l-lactide)

Chen

Tao

et al. 2023

Ind. Eng. Chem. Res.

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“…The effects of polymer shear application are studied on a small scale using rheometers [55][56][57][58]. To process larger amounts of polymer, processing machines such as extruders are modified.…”

Section: Figurementioning

confidence: 99%

“…The melt shear process is performed either in a rheometer, on a laboratory scale, or using specially modified extruders. The effectiveness of melt shear procedures, i.e., steady-state shear (5 s −1 ) and ramping up shear (0-10 s −1 ) for disentangling iPP was examined by Liu et al [57]. The application of shear in the rheometer resulted in increase in M e from 11,442 g/mol to 18,974 g/mol for the steady-shear treated polymer and 67,181 g/mol for the ramping up-shear treated iPP, meaning that the later approach was most effective.…”

Section: Crystallization During Process Of Disentanglingmentioning

confidence: 99%

Crystallization of Polymers with a Reduced Density of Entanglements

Pawlak

2024

Crystals

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Since methods for reducing macromolecule entanglements have been developed, it has become possible to better understand the impact of polymer chain entanglement on the crystallization process. The article presents basic information about the disentangling of macromolecules and the characterization of the degree of entanglement. The basic knowledge of polymer crystallization was also presented. Then, it was discussed how polymers crystallize during their disentangling. Non-isothermal and isothermal crystallization experiments using disentangled polymers, and for comparison using entangled polymers, are described in more detail. The influence of disentangling on both nucleation and crystal growth is highlighted. It is also shown how the crystallization of polymers changes when macromolecules re-entangle.

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“…Based on the idea of compound stress fields, we designed a polymer melt disentanglement machine (PMDM), which has been used to treat polycarbonate and long-chain branched polypropylene in our previous studies. , The results show that it has a good disentanglement effect and can effectively retain the disentanglement in the pellets for secondary processing. In the current work, we used the PMDM to prepare disentangled PLLA to accelerate its crystallization kinetics.…”

Section: Introductionmentioning

confidence: 99%

Novel Strategy to Improve the Performance of Poly(l-lactide): The Synergistic Effect of Disentanglement and Strong Shear Field

Zhang

Chen

et al. 2023

ACS Sustainable Chem. Eng.

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As a biobased and biodegradable material that can replace traditional petrochemical-based polymers, poly(L-lactide) (PLLA) shows great application potential. However, its widespread application still faces some obstacles, mainly associated with the poor thermal resistance, because the molecular chains of PLLA are semirigid and of poor regularity. Therefore, the crystallization rate is low, making it difficult to crystallize during the molding process, and the finally obtained PLLA is almost amorphous. In this work, the entanglement density of molecular chains was reduced to promote the molecular chain mobility. Then, PLLA was processed in combination with a strong shear field provided by the vibration injection molding technology. The results show that the synergistic effect of disentanglement and strong shear field can significantly accelerate the crystallization kinetics of PLLA. In addition, due to the better mobility, molecular chains of PLLA tend to be more regularly arranged along the flow direction under strong shear field, resulting in thicker shear layers as well as the generation of denser and more perfect shish-kebab structures. As a result, PLLA material with enhanced performance is obtained, which favors to broaden the application range of PLLA.

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Investigating the disentanglement of long chain branched polypropylene under different shear fields

Abstract: Many experimental results have revealed that entanglement networks of molecular chain would undergo the orientation, deformation, and breakdown under the condition with shear field, forming a new conformation with much reduced entanglement interactions with the surrounding medium. In this

Cited by 7 publications

References 29 publications

Regulation of Entanglement Networks under Different Shear Fields and Its Effect on the Properties of Poly(l-lactide)

Regulation of Entanglement Networks under Different Shear Fields and Its Effect on the Properties of Poly(l-lactide)

Crystallization of Polymers with a Reduced Density of Entanglements

Novel Strategy to Improve the Performance of Poly(l-lactide): The Synergistic Effect of Disentanglement and Strong Shear Field

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