Translation and Rotation of Spherulites during the Crystallization of Isotactic Polypropylene with Reduced Chain Entanglements

Wang, Xuehui; Wang, Zhigang; Luo, Kuntian; Huang, Yong

doi:10.1021/ma1025913

Cited by 17 publications

(17 citation statements)

References 33 publications

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“…The isothermal growth of iPP spherulites observed by light microscopy was faster from a disentangled melt (see Figure ), and the whole crystallization process was finished much earlier . The shift of crystallization regimes was observed in the examined transition between regimes II and III, leading to a more perfect lamellar structure obtained at higher undercooling ( Figure ) …”

Section: Properties Of Polymers With Limited Density Of Entanglementsmentioning

confidence: 91%

“…[128] and the whole crystallization process was finished much earlier. [115,117,148] The shift of crystallization regimes was observed in the examined transition between regimes II and III, leading to a more perfect lamellar structure obtained at higher undercooling (Figure 11). [117] When iPP, previously freeze-extracted, was crystallized at low temperatures (119-127 °C) the half-time of the melt conversion in solid phase was shorter and the Avrami coefficient was lower.…”

Section: Crystallizationmentioning

confidence: 95%

“…The disentangled polymers after solidification can be used for studies of crystallization from liquid state (melt, solution) or crystallization in the solid state (i.e., cold crystallization). The crystallization from disentangled melt was examined for iPP, sPP, PLA, iPS, PEO, and UHMWPE . Cold crystallization was examined for PC, PET, PEO, and iPS .…”

Section: Properties Of Polymers With Limited Density Of Entanglementsmentioning

confidence: 99%

“…The polymer crystallization from the melt is sensitive to the concentration of entanglements, so crystallization studies can be used to characterize the process of reentangling. [115,133,148] The experiments concentrated on the isothermal nucleation and growth of spherulites, examined by using a hot stage connected to a polarizing light microscope, and on the analysis of nonisothermal crystallization or melting using DSC. Often in crystallization studies the desired initial concentration of entanglements was obtained by controlling the time of annealing the polymer in the melt.…”

Section: Crystallization and Re-entanglingmentioning

confidence: 99%

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The Entanglements of Macromolecules and Their Influence on the Properties of Polymers

Pawlak

2019

Macro Chemistry & Physics

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Macromolecules form entanglements, the presence of which determines many of the polymer's properties; in solution, melt, and solid state. In this review, how the properties of polymers (rheological, thermal, and mechanical), depend on the concentration of the entanglements, is discussed. Although a typical polymer is characterized by the equilibrium density of entanglements, there are methods that can be applied for the reduction of this density. The methods used most often include dissolving a polymer and rapid freezing, crystallization during polymerization, and crystallization from a cooled dilute solution. The properties of disentangled polymers are significantly different from the properties of fully entangled polymers. These properties are discussed in relation to their dependence on the density of the entanglements. The disentangled material can be re‐entangled by the annealing of the polymer; however, reaching the equilibrium density of the entanglements is usually a slow process. It means that a polymer may be processed without losing its disentanglements. The properties of the re‐entangled polymer are usually close to the properties of the initial polymer.

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Section: Properties Of Polymers With Limited Density Of Entanglementsmentioning

confidence: 91%

Section: Crystallizationmentioning

confidence: 95%

Section: Properties Of Polymers With Limited Density Of Entanglementsmentioning

confidence: 99%

Section: Crystallization and Re-entanglingmentioning

confidence: 99%

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The Entanglements of Macromolecules and Their Influence on the Properties of Polymers

Pawlak

2019

Macro Chemistry & Physics

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“…The second way of preparation of partially disentangled polypropylene was by dissolution of PP in hot oil. The procedure proposed by Wang et al was essentially followed . A 2 wt % of PP was dissolved in hot mineral oil at 190 °C during 1 h. The solution was cooled down to 100 °C, with the rate of 30 °C/h, followed by faster cooling (∼50 °C/h) to 40 °C.…”

Section: Methodsmentioning

confidence: 99%

Deformation of disentangled polypropylene crystalline grains into nanofibers

Krajenta

Pawlak

Gałęski

2016

J Polym Sci B Polym Phys

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It was shown that a solid‐state deformation of polypropylene (PP) being in the form of partially disentangled powder is possible by blending with another molten polymer. During mixing of disentangled polypropylene powder with polystyrene at the temperature below melting of polypropylene crystals the shear forces deform powder grains into nanofibers. All disentangled powder particles larger than 0.7 µm underwent deformation into nanofibers having the mean thickness between 100 and 200 nm. Polypropylene nanofibers got entangled during blending and form a network within polystyrene matrix, reinforcing it. Network of entangled nanofibers can be further deformed with pronounced strain hardening and strength reaching 70 MPa at 135 °C. Blending resulted in generation of PP nanofibers and formation of PP nanofibers entangled network, thus formation of “all‐polymer nanocomposites” in one step compounding. The crucial feature for ultra‐deformation of PP grains by shearing during mixing is disentanglement of macromolecules. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016, 54, 1983–1994

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The all‐polymer composites and blends made of ethylene–octene copolymer and partially disentangled polypropylene using a new processing approach

Krajenta,

Pawlak

2024

J of Applied Polymer Sci

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All‐polymer composites and blends of ethylene–octene copolymer (EOC) and polypropylene (PP) were produced in the extrusion process. They had the same composition (96:4 wt.%), but five different entanglement densities of PP macromolecules. Depending on the processing temperature, below or above the melting point of PP, fibers or spherical inclusions were formed inside the EOC matrix. The production of PP fibers directly during mixing was possible by reducing the entanglement of macromolecules in this polymer. During fiber formation by solid‐state plastic deformation, the crystallinity of PP decreased, especially for the less entangled polymers. The presence of fibers influenced the mechanical properties of the composites, which were different from those of the blends. Both in blends and composites, the matrix was reinforced, but in the composites the effect was stronger and the measured stresses increased with the lower degree of PP entanglement. SAXS and microscopic observations showed that cavitation occurred in the deformed composites. All‐polymer composites, in which the reinforcement was created as a result of polymer deformation with limited entanglements, have properties that are advantageously different from traditional ones, which opens the prospect of their application.

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Translation and Rotation of Spherulites during the Crystallization of Isotactic Polypropylene with Reduced Chain Entanglements

Cited by 17 publications

References 33 publications

The Entanglements of Macromolecules and Their Influence on the Properties of Polymers

The Entanglements of Macromolecules and Their Influence on the Properties of Polymers

Deformation of disentangled polypropylene crystalline grains into nanofibers

The all‐polymer composites and blends made of ethylene–octene copolymer and partially disentangled polypropylene using a new processing approach

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