Ying Zhao

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Name: 赵莹

Organization: Institute of Chemistry, Chinese Academy of Sciences , China

Department: Institute of Chemistry

Title: Associate Researcher/Associate Professor(PhD)

Chemicals
References

New insights into the beta-form crystal toughening mechanism in pre-oriented PHBV films

Co-reporter:Jian Yang, Haijin Zhu, Ying Zhao, Qianhong Jiang, Haiming Chen, Guoming Liu, Peng Chen, Dujin Wang

European Polymer Journal 2017 Volume 91(Volume 91) pp:

Publication Date(Web):1 June 2017

DOI:10.1016/j.eurpolymj.2017.03.017

•Pre-oriented PHBV films with or without β-form structures were prepared by annealing.•PHBV film with β-form shows better ductility and toughness than that without β-form.•A new β-form toughening mechanism in pre-oriented PHBV films was proposed.Tensile deformation behaviors of pre-oriented poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) films annealed at different temperatures with or without β-form structures were investigated using the in-situ small and wide-angle X-ray scattering techniques, as well as DSC and SEM. The sample with β-form structure showed better ductility. It is convinced that the system can be viewed as a highly stretched and entangled network embedded in highly oriented fibrils being composed of shish-kebabs. Compared with sample without β structure, a tentative deformation mechanism for the sample with β structure was proposed in this paper, which we believe would shed light on the relationship between β structure and mechanical property of PHBV film. The important role of β-form played in the stretching process of pre-oriented film was also proposed for the first time, in which we stress the role of β-form structure in stabilizing the ordered microstructures and thereby improving the mechanical properties of the material.Download high-res image (116KB)Download full-size image

Correlation between the fracture toughness and -crystal fraction in a -nucleated propylene-based propyleneethylene random copolymer

Co-reporter:Chunbo Zhang;Guoming Liu;Qianhong Jiang;Dujin Wang

Journal of Applied Polymer Science 2016 Volume 133( Issue 5) pp:

Publication Date(Web):

DOI:10.1002/app.42930

ABSTRACT

Propylene-based propylene–ethylene random copolymer (PPR) has been widely used in the production of hot-water pipes. To further improve its toughness and thermal resistance, β-nucleating agents (β-NAs) are frequently incorporated. In this study, PPR containing 5.6 mol % ethylene units was modified by two kinds of β-NAs, that is, calcium pimelate and N,N′-dicyclohexylterephthalamide. The notched Izod impact strength of PPR increased with the addition of the β-NAs. Drastically different toughening effects were found between the two β-NAs. The structure of PPR with and without a β-NA was investigated by calorimetry, X-ray diffraction, and thermomechanical analysis. The results indicated that the relative fraction of β crystals (k_β) in the injection-molded specimens was determined by the type and content of β-NA. The relationship between k_β and the impact toughness was summarized. A critical value for k_β (0.68) was identified for the brittle–ductile transition of PPR. PPR with β-NA having a k_β greater than 0.68 displayed a higher impact strength than the other mixtures. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 42930.

Investigation on the overlapping bands of syndiotactic polystyrene by using 2D-IR spectroscopy

Co-reporter:Qianhong Jiang, Ying Zhao, Chunbo Zhang, Jian Yang, Dujin Wang

Journal of Molecular Structure 2016 Volume 1124() pp:98-102

Publication Date(Web):15 November 2016

DOI:10.1016/j.molstruc.2016.03.103

•2DIR spectra was applied to investigate highly overlapping bands of sPS.•A sample-specific experiment was designed and conducted in the study.•The ∼900 cm−1 band is composed of two sub-bands.•The trans-planar conformation band at 1223 cm−1 turned out to consist of two bands.In this work, WAXD and FTIR spectroscopy were utilized to investigate the phase transition of syndiotactic polystyrene (sPS) from amorphous phase to mesophase during the isothermal annealing process at 130 °C. Two dimensional (2D) correlation infrared spectroscopy was applied to reveal the sub-bands from the highly overlapping bands. The ∼900 cm−1 band is shown to be composed of two sub-bands. One band located around 906 cm−1 corresponds to the amorphous phase, another peak that occurs around 900 cm−1 is associated with mesophase. The trans-planar conformation band at 1223 cm−1 turns out to consist of two bands which might be related to trans-planar conformation with different sequence lengths.

In-situ investigation on the structural evolution of mesomorphic isotactic polypropylene in a continuous heating process

Co-reporter:Qianhong Jiang, Ying Zhao, Chunbo Zhang, Jian Yang, Yizhuang Xu, Dujin Wang

Polymer 2016 Volume 105() pp:133-143

Publication Date(Web):22 November 2016

DOI:10.1016/j.polymer.2016.10.004

•Microstructural variation of mesomorphic iPP in the heating process was revealed.•Microstructural change in the temperature range from 20 and 60 °C was detected.•Plausible structural evolution mechanism in the meso-α transformation was proposed.The microstructural changes of mesomorphic iPP from mesophase to α transition at a molecular level in a continuous heating process have been studied by in-situ Fourier-transform infrared (FT-IR) spectroscopy, in-situ X-ray scattering using synchrotron radiation, differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA). Microstructural change corresponding to helical conformation variation in the temperature range between 20 and 60 °C was detected by IR spectroscopy, which may originate from the glass transition of rigid amorphous fraction (RAF). The helical sequence with 12 monomer units is found to exist in RAF. The contents of helical sequences with different number of monomers exhibit different variation trends in the course of meso-α transition and the following process of partial melting and perfection of α crystal. A plausible mechanism was proposed that RAF experiences glass transition firstly at low temperature, and then serve as α nuclei to trigger the meso-α transition at higher temperature. This work provides a new insight into the mechanism of microstructural evolution of the meso-α transformation of iPP.

Transesterification induced mechanical properties enhancement of PLLA/PHBV bio-alloy

Co-reporter:Jian Yang, Haijin Zhu, Chunbo Zhang, Qianhong Jiang, Ying Zhao, Peng Chen, Dujin Wang

Polymer 2016 Volume 83() pp:230-238

Publication Date(Web):28 January 2016

DOI:10.1016/j.polymer.2015.12.025

•A green and industrially viable process was demonstrated for toughening PLLA/PHBV bio-alloy.•The biocompatible and biodegradable nature of bio-alloy is not compromised with addition of zinc acetate.•The miscibility and mechanical properties of PLLA/PHBV bio-alloy were improved prominently.•A new mechanism of transesterification accompanied by decomposition competition was proposed.In order to improve the miscibility and mechanical properties of poly(l-lactic acid) (PLLA) and poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) bio-alloy, small amount of transesteriﬁcation catalyst, zinc acetate was added in the melt blending process. We show that the PLLA-PHBV copolymer generated during the melt blending significantly improves the miscibility and therefore enhances the mechanical properties of the product. Dynamic mechanical analysis (DMA), scanning electron microscopy (SEM), and tensile tests were performed to study the miscibility and mechanical properties of the blends. Fourier transform infrared spectroscopy (FTIR) and gel permeation chromatography (GPC) were used to reveal the molecular structural, and molecular weight changes of PLLA and PHBV after melt mixing with zinc acetate. SEM and FTIR results have clearly shown that the PLLA-PHBV copolymer generated from transesterification reaction acted as a compatibilizer and therefore resulted in an improved interfacial miscibility and ductility of PLLA/PHBV blend. In our mechanistic study, a competition between the PLLA/PHBV transesterification reaction and the thermal decomposition of PHBV was identified for the first time. On the basis of these observations, a new mechanism of transesterification reaction was proposed.

A WAXS/SAXS study on the deformation behavior of β-nucleated propylene–ethylene random copolymer subjected to uniaxial stretching

Co-reporter:Chunbo Zhang, Guoming Liu, Qianhong Jiang, Jian Yang, Ying Zhao and Dujin Wang

RSC Advances 2015 vol. 5(Issue 55) pp:44610-44617

Publication Date(Web):11 May 2015

DOI:10.1039/C5RA04952K

Copolymerization for making propylene-based random copolymers is an important strategy to broaden the applications of polypropylene, such as propylene random copolymer with β-nucleating agent as hot water pipes. In the present work, a β-nucleated propylene–ethylene random copolymer (P–E copolymer) containing a low content of ethylene (5.6 mol%) was subjected to uniaxial stretching at 30 and 100 °C. The structural evolution during deformation was investigated by in situ X-ray scattering using synchrotron radiation. An interesting temperature dependence of the deformation feature of β-crystal was observed. The β-crystal in the sample transformed to mesophase at 30 °C and to α-crystal at 100 °C. Molecular chains in β-crystal stretched at 30 °C was identified to be perpendicular to the stretching direction, while they tended to be parallel to the direction at 100 °C. On the other hand, cavitation was observed in β-nucleated P–E copolymer when stretched at 30 °C. As the tensile temperature reached 100 °C, no cavities could be detected. A deformation model of the β-nucleated P–E copolymer combining crystal transition, cavitation and orientation depending on the drawing temperature was described.

Investigation on structural changes of isotactic polypropylene mesophase in the heating process by using two-dimensional infrared correlation spectroscopy

Co-reporter:Qian-Hong Jiang, Chun-Bo Zhang, Jian Yang, Ying Zhao, Yi-Zhuang Xu, Du-Jin Wang

Chinese Chemical Letters 2015 Volume 26(Issue 2) pp:197-199

Publication Date(Web):February 2015

DOI:10.1016/j.cclet.2015.01.015

Two-dimensional FT-IR correlation spectroscopy was used to reveal the structural changes of isotactic polypropylene (iPP) mesophase during the heating process. The co-relationship among the regular helical bands of iPP was discussed according to synchronous spectrum. The results show that the segments with different length-helixes were found to undergo a disordered process in the temperature range of 25–60 °C.Synchronous two-dimensional (2D) infrared correlation spectrum of quenched iPP in the range of 1000–800 cm−1.

Correlation between chain microstructure and mechanical properties of two polypropylene/poly (ethylene-co-propylene) in-reactor alloys

Co-reporter:Rongbo Li;Qian Xing;Dujin Wang;Xuteng Hu

Colloid and Polymer Science 2015 Volume 293( Issue 4) pp:1011-1021

Publication Date(Web):2015 April

DOI:10.1007/s00396-014-3483-6

This study concentrated on evaluating the structure-property correlation of two polypropylene/poly (ethylene-co-propylene) in-reactor alloys (A and B). Systematic investigation and comparison have been performed on the molecular structure and phase morphology of the polypropylene (PP)-based alloys. Especially, the bivariate distribution of chemical composition and molecular weight for each fraction was obtained simultaneously by adopting cross fractionation chromatography. The results illustrated the following structure difference which determines the ultimate mechanical properties of the PP in-reactor alloys. It has been found that the relative content of components polypropylene homopolymer (HPP) and ethylene-co-propylene random copolymer (EPR) is a little more in sample A than those in sample B, and meanwhile both of them in sample A show higher molecular weight and broader molecular weight distribution. Furthermore, the fraction of HPP in sample A eluted at a higher temperature, meaning that this fraction possesses better stereo-tacticity and can form more perfect crystals with higher crystallinity. These advantages in structure characteristics endow sample A with better rigidity-toughness balance than sample B.

The dynamic crystallization and multiple melting behavior of polypropylene in the in-reactor alloy: A differential scanning calorimetry study

Co-reporter:Haijin Zhu;Hengrui Yang;Dujin Wang

Journal of Applied Polymer Science 2011 Volume 121( Issue 3) pp:1372-1383

Publication Date(Web):

DOI:10.1002/app.33469

Abstract

The isothermal and nonisothermal crystallization and the subsequent melting behaviors of the polypropylene (PP) component in the in-reactor alloy were studied systematically by a series of thermal analysis techniques. The alloy sample used in the present study is a newly invented in situ blend of polypropylene with high ethylene–propylene rubber content. The effect of annealing temperatures on the subsequent crystallization and melting process of PP was explained by the different molecular behavior in the three “temperature domains.” Multiple melting endotherms were also obser-ved for the nonisothermally crystallized sample, and were attributed to the dynamic melting process which consists of three steps: melting, recrystallization, and remelting. The melting temperature of initial mesomorphic phase is found to be very close to the temperature of recrystallization or reorganization. To separate the recrystallization process from the overlapping processes, the difference spectra of fast and slow heated DSC endotherms were used, which is based on a straight forward but reasonable assumption. In addition, temperature modulated differential scanning calorimetry (TMDSC) has also been used to study the melting of PP component. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Investigation on the melt spinning fibers of PP/organoclay nanocomposites prepared by in-situ polymerization

Co-reporter:Chaowei Hao;Aihua He;Xiuqin Zhang;Dujin Wang;Qingfang Ma;Yizhuang Xu

Journal of Applied Polymer Science 2010 Volume 116( Issue 3) pp:1384-1391

Publication Date(Web):

DOI:10.1002/app.30392

Abstract

Fibers prepared by melt spinning process from the PP (polypropylene)/organoclay nanocomposite were characterized in details with the aid of SEM, FTIR, XRD, DSC, and mechanical measurements. The results suggested that the lower content of organoclay (0.1%) added to the PP matrix increased the crystallinity and mechanical property (tensile strength) of the PP/organoclay nanocomposite fiber. With increasing the content of organoclay (≥ 0.3%), the crystallinity and the tensile strength both a little decreased, and the fiber containing organoclay exhibited multi-peaks at the same draw ratio during the heating process. Furthermore, the degree of orientation of the fiber increased a little with lower content of organoclay (0.1%) introduction to PP during the infrared dichroism measurement. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

Interactions between metal chlorides and poly(vinyl pyrrolidone) in concentrated solutionsand solid-state films

Co-reporter:Chaowei Hao;Yong Zhou;Lijuan Zhou;Yizhuang Xu;Dujin Wang;Duanfu Xu

Journal of Polymer Science Part B: Polymer Physics 2007 Volume 45(Issue 13) pp:1589-1598

Publication Date(Web):23 MAY 2007

DOI:10.1002/polb.21138

The rheological behavior of poly(vinyl pyrrolidone) (PVP)/N,N-dimethylformamide (DMF) solutions containing metal chlorides (LiCl, CaCl₂, and CoCl₂) were investigated, and the results showed that the nature of the metal ions and their concentration had an obvious effect on the steady-state rheological behavior of PVP–DMF solutions with different molecular weights. The apparent viscosity of the PVP–DMF solutions increased with an increasing metal-ion concentration, and the viscosity increment was dependent on the metal-ion variety_. For a CaCl₂-containing PVP–DMF solution, for example, the critical shear rate at the onset of shear thinning became smaller with increasing CaCl₂ concentration. It was believed that multiple interactions among metal ions, carbonyl groups of PVP, and amide groups in DMF determined the solution properties of these complex fluids; therefore, ¹³C NMR spectroscopy was used to detect the interactions in systems of PVP–CaCl₂–DMF and PVP–LiCl–DMF solutions. NMR data showed that there were obvious interactions between the metal ions and the carbonyl groups of the PVP segments in the DMF solutions. Furthermore, IR spectra of the PVP/metal chloride composites demonstrated that the interaction between the metal ions and carbonyl groups in the PVP unit occurred and that the PVP chain underwent conformational variations with the metal-ion concentration. DSC results indicated that the glass transition temperatures of the PVP/metal chloride composites increased with the addition of metal ions. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 1589–1598, 2007