Recrystallization of biaxially oriented polyethylene film from partially melted state within crystallite networks

Ren, Ming‐Xun; Tang, Yujing; Gao, Dali; Ren, Yueming; Yao, Xuerong; Shi, Hongwei; Zhang, Taoyi; Wu, Changjiang

doi:10.1016/j.polymer.2020.122291

Cited by 6 publications

(2 citation statements)

References 34 publications

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“…This inversion of the recrystallization rate is a peculiar feature associated with LLPS, which has been observed in other broadly distributed copolymers. [13][14][15][16]34 As we showed by direct analysis of the melt using small-angle neutron scattering (SANS) 14,15 and light scattering (SALS), 15 the inversion demarcates the onset of LLPS. Lastly, Region D corresponds to relatively low T melt , very close to or at the end of the observed melting peak, where a small fraction of crystals remain unmolten and serve as true self-seeds to accelerate recrystallization.…”

Section: Resultsmentioning

confidence: 99%

Comparative Effects on Recrystallization of Melt-Memory and Liquid–Liquid Phase Separation in Ziegler–Natta and Metallocene Ethylene Copolymers with Bimodal Comonomer Composition Distribution

Ren

Chen

Sang

et al. 2020

Ind. Eng. Chem. Res.

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Herein, we study comparatively melt-memory effects on recrystallization of two sets of linear low-density polyethylenes (LLDPE) synthesized with Ziegler–Natta (ZN-LLDPE) and with metallocene catalysts (M-LLDPE), respectively. All copolymers have M w ∼ 120,000 g/mol, M w/M n ∼ 4, and very similar average comonomer content (∼2 mol % branches) but different comonomer composition distribution (CCD). While all types of copolymers display the strong melt-memory effect of the initial crystallites enhancing the recrystallization rate from melt temperatures (T melt) up to ∼160 °C, a subsequent retardation of the rate associated with liquid–liquid phase separation (LLPS) is found mainly in ZN-LLDPEs. Only one M-LLDPE displays the retardation of the recrystallization rate. The conclusion from a detailed quantitative analysis of the TREF profiles is that copolymers with inversion of crystallization rate, characteristic of LLPS, have CCD comprising 15–25 wt % molecules in the 12–6 mol % comonomer range and <50 wt % in the 6–1.5 mol % comonomer range. The rest (30–50 wt %) are lowly branched molecules (<1.5 mol %) that comprise the high-crystallinity component. Characterization of the spherulitic crystalline morphology with polarized optical microscopy allows us to extract the exponential variation of the number of residual clusters (self-nuclei) in the melt as a function of decreasing T melt within the melt-memory range. The comparative CCD-crystallization analysis carried out in this work serves as a guideline to design LLDPEs with distributions prone to LLPS during processing.

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Section: Resultsmentioning

confidence: 99%

Comparative Effects on Recrystallization of Melt-Memory and Liquid–Liquid Phase Separation in Ziegler–Natta and Metallocene Ethylene Copolymers with Bimodal Comonomer Composition Distribution

Ren

Chen

Sang

et al. 2020

Ind. Eng. Chem. Res.

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“…Melting enthalpies are normalized according to block content in each of the samples. Table S4: Crystallinity values (%) of the samples calculated from DSC heating scans taking into account the mass fractions of each of the blocks and using X c = (ΔH m /ΔH m,100% )·100 and enthalpy of fusion of 100% crystalline polymers (ΔH m,100% ) is taken from literature: 293 J/g for PE [ 107 ], 139 J/g for PCL [ 108 ] and 214 J/g for PEO [ 109 ]. Table S5: WAXS indexation for all the samples [ 19 , 92 ].…”

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Crystallization and Morphology of Triple Crystalline Polyethylene-b-poly(ethylene oxide)-b-poly(ε-caprolactone) PE-b-PEO-b-PCL Triblock Terpolymers

et al. 2021

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The morphology and crystallization behavior of two triblock terpolymers of polymethylene, equivalent to polyethylene (PE), poly (ethylene oxide) (PEO), and poly (ε-caprolactone) (PCL) are studied: PE227.1-b-PEO4615.1-b-PCL3210.4 (T1) and PE379.5-b-PEO348.8-b-PCL297.6 (T2) (superscripts give number average molecular weights in kg/mol and subscripts composition in wt %). The three blocks are potentially crystallizable, and the triple crystalline nature of the samples is investigated. Polyhomologation (C1 polymerization), ring-opening polymerization, and catalyst-switch strategies were combined to synthesize the triblock terpolymers. In addition, the corresponding PE-b-PEO diblock copolymers and PE homopolymers were also analyzed. The crystallization sequence of the blocks was determined via three independent but complementary techniques: differential scanning calorimetry (DSC), in situ SAXS/WAXS (small angle X-ray scattering/wide angle X-ray scattering), and polarized light optical microscopy (PLOM). The two terpolymers (T1 and T2) are weakly phase segregated in the melt according to SAXS. DSC and WAXS results demonstrate that in both triblock terpolymers the crystallization process starts with the PE block, continues with the PCL block, and ends with the PEO block. Hence triple crystalline materials are obtained. The crystallization of the PCL and the PEO block is coincident (i.e., it overlaps); however, WAXS and PLOM experiments can identify both transitions. In addition, PLOM shows a spherulitic morphology for the PE homopolymer and the T1 precursor diblock copolymer, while the other systems appear as non-spherulitic or microspherulitic at the last stage of the crystallization process. The complicated crystallization of tricrystalline triblock terpolymers can only be fully grasped when DSC, WAXS, and PLOM experiments are combined. This knowledge is fundamental to tailor the properties of these complex but fascinating materials.

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Molecular dynamics simulation of H2 in amorphous polyethylene system: H2 diffusion in various PE matrices and bubbling during rapid depressurization

Zhao

Wang

Yang

et al. 2022

International Journal of Hydrogen Energy

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Recrystallization of biaxially oriented polyethylene film from partially melted state within crystallite networks

Cited by 6 publications

References 34 publications

Comparative Effects on Recrystallization of Melt-Memory and Liquid–Liquid Phase Separation in Ziegler–Natta and Metallocene Ethylene Copolymers with Bimodal Comonomer Composition Distribution

Comparative Effects on Recrystallization of Melt-Memory and Liquid–Liquid Phase Separation in Ziegler–Natta and Metallocene Ethylene Copolymers with Bimodal Comonomer Composition Distribution

Crystallization and Morphology of Triple Crystalline Polyethylene-b-poly(ethylene oxide)-b-poly(ε-caprolactone) PE-b-PEO-b-PCL Triblock Terpolymers

Molecular dynamics simulation of H2 in amorphous polyethylene system: H2 diffusion in various PE matrices and bubbling during rapid depressurization

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