Relationship between molecular characteristics and physical properties of linear low density polyethylenes

Furumiya, A.; Akana, Yoshinori; Ushida, Y.; Masuda, Toshio; Nakajima, Akira

doi:10.1351/pac198557060823

Cited by 23 publications

(8 citation statements)

References 9 publications

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“…The influence of the molecular composition, which controls the relaxation times at long times, is also revealed in G ′ and G ″ at low frequencies 63. According to earlier results by Furumiya et al,64 the frequency‐dependence curves of ZN LLDPE melts are clearly different from those of LDPE in their shapes: Both G ′ and G ″ curves for LLDPE are much steeper than those for LDPE, which indicates that the distribution of relaxation times is broader in LDPE than in ZN LLDPE. On account of the similarity in MWD of their studied samples, the differences in curve shapes were related to branching effects rather than MWD.…”

Section: Resultsmentioning

confidence: 73%

Thermal and rheological studies on the molecular composition and structure of metallocene‐ and Ziegler–Natta‐catalyzed ethylene–α‐olefin copolymers

Starck¹,

Malmberg²,

Löfgren³

2001

J of Applied Polymer Sci

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ABSTRACT:The relationship between the molecular structure and the thermal and rheological behaviors of metallocene-and Ziegler-Natta (ZN)-catalyzed ethylene copolymers and high-density polyethylenes was studied. Of special interest in this work were the differences and similarities of the metallocene-catalyzed (homogeneous) polymers with conventional coordination-catalyzed (heterogeneous) polyethylenes and low-density polyethylenes. The short-chain branching distribution was analyzed with stepwise crystallization by differential scanning calorimetry and by dynamic mechanical analysis. The metallocene copolymers exhibited much more effective comonomer incorporation in the chain than the ZN copolymers; they also exhibited narrower lamellar thickness distributions. Homogeneous, vanadium-catalyzed ZN copolymers displayed a very similar comonomer incorporation to metallocene copolymers at the same density level. The small amplitude rheological measurements revealed the expected trend of increasing viscosity with weight-average molecular weight and shear-thinning tendency with polydispersity for the heterogeneous linear low-density polyethylene and very-low-density polyethylene resins. The high activation energy values (34 -53 kJ/mol) and elevated elasticity found for some of our experimental metallocene polymers suggest the presence of long-chain branching in these polymers. This was also supported by the comparison of the relationship between low shear rate viscosity and molecular weight.

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Section: Resultsmentioning

confidence: 73%

Thermal and rheological studies on the molecular composition and structure of metallocene‐ and Ziegler–Natta‐catalyzed ethylene–α‐olefin copolymers

Starck¹,

Malmberg²,

Löfgren³

2001

J of Applied Polymer Sci

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“…In general, a wide range of properties can be accessed by properly tuning the density and the melt flow rate, MFR, used in industrial environment as a proxy to molecular weight distribution (MWD). Density is related to the microstructure of the polymer, that is, to short chain branching and comonomer content, therefore being a PE characteristics that can be substantially influenced via polymer design. Increasing density provides stiffness at the expense of toughness, which on the other hand can be imparted by higher MFR .…”

Section: Polymer‐based Crystallinity Modificationsmentioning

confidence: 99%

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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“…The property and functionality of polymeric materials can be regulated in a wide range. First of all, the basic properties and functionalities are determined by their chemical structure, such as chemical composition, chain configuration, molecular weight and distribution, and so forth. − On the other hand, structures of a certain polymer at diverse scales have a prominent effect on their performance, which is more evident for semicrystalline polymers. First, the crystalline morphology, for example, single crystals or polycrystals and crystal orientation, exhibits a remarkable impact on the physical and mechanical properties of semicrystalline polymers. , Moreover, specific crystal modification can even endow a polymer with distinct functionalities.…”

Section: Introductionmentioning

confidence: 99%

Temperature-Dependent Reversibility of Epitaxy between Isotactic Polystyrene and Polypropylene

et al. 2021

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Epitaxial crystallization of isotactic polystyrene (iPS) on the oriented isotactic polypropylene (iPP) substrate and the reverse process, that is, epitaxial growth of iPP crystals on the oriented iPS film initially generated by epitaxy of it on iPP, have been investigated through transmission electron and atomic force microscopies. Epitaxy of iPS on the ordered iPP substrate was achieved by cold crystallization of an amorphous thin film at 130 °C for 2 h. The results indicate that epitaxy of iPS on the iPP substrate has parallel chain relationship. Epitaxial growth of iPP on the oriented iPS film was realized by selective melting of the iPP in the epitaxial iPP/iPS system at 190 °C for 5 min and then crystallizing at varied temperatures. It was found that oriented recrystallization of iPP on the itself-induced iPS epitaxially oriented substrate occurs at temperatures below 30 °C and produces exactly the same parallel mutual chain alignment, indicating the reversibility of epitaxy between iPP and iPS. It does, however, not happen at temperatures over 60 °C, reflecting a temperature-dependent epitaxial growth of iPP on iPS oriented films. This was explained by secondary nucleation and indicates that a larger dimension of substrate crystals than the depositing epitaxial ones is necessary for the occurrence of polymer epitaxy. This provides a theoretical basis for the substrate selection of polymer epitaxies.

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Relationship between molecular characteristics and physical properties of linear low density polyethylenes

Abstract: Abstract

Cited by 23 publications

References 9 publications

Thermal and rheological studies on the molecular composition and structure of metallocene‐ and Ziegler–Natta‐catalyzed ethylene–α‐olefin copolymers

Thermal and rheological studies on the molecular composition and structure of metallocene‐ and Ziegler–Natta‐catalyzed ethylene–α‐olefin copolymers

Designing polymer crystallinity: An industrial perspective

Temperature-Dependent Reversibility of Epitaxy between Isotactic Polystyrene and Polypropylene

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