Crystallization behavior of some unimodal and bimodal linear low‐density polyethylenes at moderate and high supercooling

Krumme, Andres; Lehtinen, Ari; Adamovsky, Sergey; Schick, Christoph; Roots, Jaan; Viikna, Anti

doi:10.1002/polb.21494

Cited by 22 publications

(10 citation statements)

References 30 publications

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“…On the other hand, Zhang et al showed via molecular dynamics simulations that the behavior of the simulated blend was influenced by the total branch content of the system, which in view of the results mentioned above co‐crystallize, as well as by the actual branch content of the branched fraction. Proofs of this behavior were shown by Tian et al, by Hubert et al, and Krumme et al Krishnaswamy et al in particular showed how the introduction of SCB in the longest chains favors the formation of tie chains.…”

Section: Polymer‐based Crystallinity Modificationsmentioning

confidence: 85%

Designing polymer crystallinity: An industrial perspective

Mileva

Tranchida

Gahleitner

2018

Polymer Crystallization

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More than 50% of the thermoplastic polymers applied globally are semi‐crystalline, making crystallization part of the material and component design process for these materials. The mechanical and optical performance, but also the long‐term stability of the final articles and applications will depend upon three major groups of influence factors: Polymer structure and monomer composition, additive addition (especially nucleation) and blending with secondary components, and processing parameters. In the present review, we try to establish a connection between these three areas, the resulting combination of crystallinity and morphology, and the final application properties. Examples are drawn from the two major polyolefins, polyethylene and polypropylene, technical polymers like polyamide and polyester, but also polymers from renewable sources like poly(lactic acid).

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Section: Polymer‐based Crystallinity Modificationsmentioning

confidence: 85%

Designing polymer crystallinity: An industrial perspective

Mileva

Tranchida

Gahleitner

2018

Polymer Crystallization

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show abstract

“…The reorganization kinetics in PET and iPS was studied in combination with conventional DSC at scanning rates Brought to you by | Stockholms Universitet Authenticated Download Date | 7/7/15 5:06 AM covering 8 orders of magnitude [69][70][71]. Isothermal and non-isothermal crystallization and the formation of different crystal polymorphs were analyzed in a wide range of temperatures and scanning rates applying DSC and the fast scanning setup in PE, iPP and PVDF [54,[72][73][74][75][76][77][78][79]. The complex behavior in the temperature range between glass transition and melting temperature was investigated in PBT [80].…”

Section: Fast Scanning Calorimetric Techniquesmentioning

confidence: 99%

1. Influence of Thermal Prehistory on Crystal Nucleation and Growth in Polymers

Schick¹,

Zhuravlev²,

Androsch³

et al. 2014

Glass

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Observations regarding the effect of thermal history of crystallizing polymer melts onto the outcome of crystal nucleation and growth processes are investigated experimentally. Some results can be at least on a qualitative basis explained by classical nucleation theory (CNT) while others are not easy to understand in the framework of CNT. The origin of the respective problems and possible extensions of CNT to overcome them are briefly discussed. We chose polymers as model systems because they allow one a separate investigation of nucleation and growth processes in a wide temperature and time range. Furthermore they are well suited to be analyzed experimentally by the recently developed fast scanning calorimetry. In particular, by applying fast scanning calorimetry we are able to investigate processes in bulk samples and do not need to use droplets to study homogeneous nucleation kinetics. Fast scanning calorimetry enables us to observe homogeneous nucleation in materials crystallizing relatively fast like most of the industrial relevant semicrystalline polymers. Quantitative analysis allowed us to judge the nucleation efficiency of additives in the whole range of temperatures, where polymers crystallize. Besides the observed nucleation and growth below the glass transition information about the nucleation activity of small crystals grown at different temperatures relative to the cold-crystallization temperature range were obtained. Finally we show how relaxation of the under-cooled melt (glass) influences homogeneous nucleation. These data may serve as input for a more general description of the interplay of nucleation-growth and relaxation processes within the framework of a structural order-parameter model.

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“…The use of Ziegler-Natta (ZN) type catalysts when synthesizing LLDPEs makes them heterogeneous both in intermolecular and intramolecular terms [1], i.e. compared to materials synthesized by single-site catalysts, the ZN materials have a broad ethylene sequence length (ESL) distribution with considerable quantities of long sequences [1,2,3]. If unimodal LLDPEs are traditionally produced by a single reactor-catalyst system then bimodal polymer materials can be produced, besides using dual catalyst systems in a single reactor [4], in two cascaded reactors at different reaction conditions and feeds [5], which is comparable to blending two polymers of a different structure, resulting in a broad molar mass distribution (MMD).…”

Section: Introductionmentioning

confidence: 99%

The effect of modality on linear low-density polyethylene crystallization behaviour at high and very high supercoolings

Märtson

Krumme²,

Gavrilkina³

et al. 2009

Proc. Estonian Acad. Sci.

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Isothermal crystallization rates of uni-and bimodal linear low density polyethylenes having similar average molar mass and branching content were analysed at various temperatures in a very high supercooling range by means of a novel methodchip nanocalorimetry. At a particular crystallization temperature within the lower range of temperatures the bimodal material crystallized slower than the unimodal one, whereas at moderate supercooling temperatures bimodal polyethylene materials have earlier been reported to crystallize faster. Comparison to a high and moderate range of supercoolings was also made using an inhouse built hot stage polarized light microscopy system. The difference gives evidence of a different crystallization mechanism caused by modality, which can have a strong impact on the application properties of the material.

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Crystallization behavior of some unimodal and bimodal linear low‐density polyethylenes at moderate and high supercooling

Cited by 22 publications

References 30 publications

Designing polymer crystallinity: An industrial perspective

Designing polymer crystallinity: An industrial perspective

1. Influence of Thermal Prehistory on Crystal Nucleation and Growth in Polymers

The effect of modality on linear low-density polyethylene crystallization behaviour at high and very high supercoolings

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