Relationship between molecular structure, crystallization behavior, and mechanical properties of long chain branching polypropylene

Zhou, Shuai; Wang, Weixia; Xin, Zhong; Zhao, Shicheng; Shi, Yaoqi

doi:10.1007/s10853-016-9856-0

Cited by 32 publications

(27 citation statements)

References 46 publications

(54 reference statements)

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“…64,65 While co-monomers hinder crystallization into α-phase effectively, they extend mesophase formation toward lower cooling rates. 66,67 As chain structural feature, LCBs affect iPP crystallization, as they enhance the α-phase nucleation process and increase crystallization temperature of iPP by up to 20 K. [68][69][70][71][72] In turn, spherulitic growth rate of LCB PP is less than for linear PP as found by several authors, also confirmed via unpublished data from our laboratories according to a method described elsewhere. 54 The LCB PP α-nucleation effect is active up to the cooling rate of about 1000 KÁs −1 , and like heterogeneous nucleation, it inhibited mesophase formation.…”

supporting

confidence: 63%

A DSC study of polypropylene chain branching effects on structure formation under rapid cooling and reheating from the amorphous glass

Gloger

Mileva

Zhuravlev

et al. 2020

Polymer Crystallization

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Isotactic polypropylene, iPP, exists as linear polymer or with side chains, long-chain branches, LCB. In the melt state, LCBs increase physical interactions between different chains, the entanglements. Under melt deformation, entanglements provide melt strength, a useful property for conversion processes like blow molding or extrusion foaming. LCBs also increase the crystallization temperature of iPP, from about 385 K to above 393 K, comparable to heterogeneous α-nucleating agents. Here, LCB PP crystallization in fast scanning differential calorimeters was investigated under cooling with rates up to 60,000 KÁs −1. Results show that LCB PP crystallized via α-phase up to a cooling rate of 1000 KÁs −1 , vitrified as amorphous glass at cooling rates above 2000 KÁs −1 and hindered mesophase formation upon cooling and via cold crystallization upon heating. This effect increased with branch content and melt elasticity, that is, with chain immobilization in the entanglement network. This melt state enhances α-nucleation but limits ordering processes at strong undercooling. Results highlight melt structure effects on polymer crystallization, possibly affecting LCB PP processing behavior and product quality.

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supporting

confidence: 63%

A DSC study of polypropylene chain branching effects on structure formation under rapid cooling and reheating from the amorphous glass

Gloger

Mileva

Zhuravlev

et al. 2020

Polymer Crystallization

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“…The curve of PP1PE1B shows that structural modification improves the crystallization ability of the PP‐phase, which separates from the PE crystallization peak. Zhou et al and Tian et al explain the higher T c of LCB‐PP with the structure of the polymer itself that acts as nucleating agent and Tabatabei et al connects it with residuals from the production process . Furthermore the melting peak of the modified sample PP1PE1B becomes broader; Δ H m increased at the same time slightly.…”

Section: Resultsmentioning

confidence: 99%

“…Long chain branching (LCB) of PP for example can turn out as an innovative concept to give PP post‐consumer waste a second life with improved material properties, especially considering its melt rheology . LCB causes strain hardening and improves the melt strength of the PP.…”

Section: Introductionmentioning

confidence: 99%

Upcycling of polypropylene—the influence of polyethylene impurities

Kamleitner

Duscher

Koch

et al. 2017

Polymer Engineering & Sci

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Long chain branching (LCB)—a well‐known industrial process—is shown as an innovative tool for the treatment of PP post‐consumer waste. The introduction of LCB by reactive extrusion does not only compensate the degradation during product life (e.g., thermally and UV‐induced chain scission), it also improves the melt properties (e.g., melt strength, strain hardening). Thus, not only a re‐cycling process, even a real “up‐cycling” can be achieved. Compared with virgin material, PP from post‐consumer waste contains impurities like other polyolefines (PE‐HD, PE‐LD, PE‐LLD, copolymers), the total removal is economically not viable. Hence, the focus of this work was the influence of PE‐HD on the LCB formation of PP. Based on model mixtures with virgin PP and 10% PE‐HD, it is shown that PE‐HD influences the mechanical properties and gel content of the chemically modified blend but has no detrimental effect on the improved melt properties. POLYM. ENG. SCI., 57:1374–1381, 2017. © 2017 Society of Plastics Engineers

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“…Nowadays, polypropylene has been widely used in various applications because of its good mechanical properties, low density, good chemical, and heat resistance . As an important industrial catalyst, the fourth‐generation Ziegler–Natta catalyst has been widely used to produce polypropylene .…”

Section: Introductionmentioning

confidence: 99%

Polypropylene with high melt flow rate and high isotacticity prepared by phosphate‐mixed external donors

Zhou

Wang

et al. 2017

J of Applied Polymer Sci

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High melt flow rate (MFR) of polypropylene can improve its processability and its high isotacticity is favor of keeping good mechanical properties of polypropylene. In this study, as a convenient and effective method, the mixture of phosphate and alkoxysilane as mixed external donors for Ziegler-Natta catalyst is used to improve MFR of polypropylene. The MFR of polypropylenes prepared by mixed external donors is three to five time higher than that prepared by dicyclopentyl dimethoxysilane (Donor-D) alone, which is attributed to broad molecular weight distribution and low molecular weight of polypropylene prepared by mixed external donors. In addition, isotacticity and lamella thickness of polypropylene prepared by mixed external donors containing triisopropyl phosphate or phenyl-phosphonic acid dipentyl ester are very close to that prepared by Donor-D, which lead to keep high thermal properties and good mechanical properties for the polypropylenes.

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Relationship between molecular structure, crystallization behavior, and mechanical properties of long chain branching polypropylene

Cited by 32 publications

References 46 publications

A DSC study of polypropylene chain branching effects on structure formation under rapid cooling and reheating from the amorphous glass

A DSC study of polypropylene chain branching effects on structure formation under rapid cooling and reheating from the amorphous glass

Upcycling of polypropylene—the influence of polyethylene impurities

Polypropylene with high melt flow rate and high isotacticity prepared by phosphate‐mixed external donors

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