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Dive into the research topics where Yanping Liu is active.

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Featured researches published by Yanping Liu.


Review of Scientific Instruments | 2011

Extensional rheometer for in situ x-ray scattering study on flow-induced crystallization of polymer

Yanping Liu; Weiqing Zhou; Kunpeng Cui; Nan Tian; Xiao Wang; Liangbao Liu; Liangbin Li; Yingui Zhou

We designed and constructed an extensional rheometer for in situ small and wide angle x-ray study on flow-induced crystallization of polymer. Two rotating drums with an axis distance of 20 mm are employed to impose extensional deformation on the samples. With a constant angular velocity, the two drums generate a constant Henkcy strain rate as sample length for testing keeps constant during deformation. An ionic liquid is used as heating medium to prevent polymer melt from bending downward due to gravity, which is excellent in terms of high thermal stability, low viscosity, and relative low adsorption on x-ray. Flow-induced crystallization experiments are conducted with this apparatus on x-ray scattering station in Shanghai Synchrotron Radiation Facility (SSRF), which allows us to collect rheological and structural data simultaneously and may lead to a better understanding on flow-induced crystallization of polymer.


Journal of Materials Science | 2014

A novel way to monitor the sequential destruction of parent-daughter crystals in isotactic polypropylene under uniaxial tension

Yanping Liu; Zhihua Hong; Liangui Bai; Nan Tian; Zhe Ma; Xiangyang Li; Liang Chen; Benjamin S. Hsiao; Liangbin Li

The cross-hatched structural evolution of isotactic polypropylene (iPP) during uniaxial tensile deformation was investigated with in situ synchrotron radiation wide angle X-ray scattering. An effective way was developed to study parent and daughter lamellae separately with in situ environment. iPP sample was preoriented to generate a bimodal orientation of lamellae for distinguishing the parent and daughter lamellae, which will orient in orthogonal directions under flow-induced crystallization. The dumbbell samples were prepared along different angles with respect to preorientation direction to achieve multisided stretching. The structural evolution of parent and daughter lamellae was followed by recording the scattering from (110) crystallographic plane. It was observed that the parent lamellae were destroyed earlier than daughter ones, no matter which the tensile direction was. Mesophase was observed at very small strain of 0.3, immediately after the damage of cross-hatched structure, which may be attributed to the destruction of parent lamellae. Deformation induced mesophase was proved to be the small crystal cluster which was transformed from parent and daughter lamellae.Graphical Abstract


Chinese Journal of Polymer Science | 2015

The spatial correlation between crystalline and amorphous orientations of isotactic polypropylene during plastic deformation: An in situ observation with FTIR imaging

Wei Chen; Xiangyang Li; Yanping Liu; Jing Li; Weiming Zhou; Liang Chen; Liangbin Li

On the basis of research method in FTIR imaging, we made a heterogeneous thin film of isotactic polypropylene (iPP) that contains a few large spherulites (∼150 μm) which are surrounded by small spherulites (∼15 μm) for tensile testing. The evolution processes of crystalline and amorphous orientations of iPP are monitored with its characteristic peaks at 998 and 973 cm−1, respectively. By introducing the correlation images, the analysis demonstrates the relationships between the orientation evolutions of crystalline and amorphous phases in a space of 250 μm × 250 μm detecting area. During the plastic deformation, crystalline orientation is higher than amorphous orientation outside the large spherulite, while that is opposite inside the region. In addition, the evolutions of crystalline and amorphous orientations almost keep a positive correlation.


Polymers | 2018

Simultaneous Enhancement of Strength and Toughness of PLA Induced by Miscibility Variation with PVA

Yanping Liu; Hanghang Wei; Zhen Wang; Qian Li; Nan Tian

The mechanical properties of poly (lactic acid) (PLA) nanofibers with 0%, 5%, 10%, and 20% (w/w) poly (vinyl alcohol) (PVA) were investigated at the macro- and microscale. The macro-mechanical properties for the fiber membrane revealed that both the modulus and fracture strain could be improved by 100% and 70%, respectively, with a PVA content of 5%. The variation in modulus and fracture strain versus the diameter of a single electrospun fiber presented two opposite trends, while simultaneous enhancement was observed when the content of PVA was 5% and 10%. With a diameter of 1 μm, the strength and toughness of the L95V5 and L90V10 fibers were enhanced to over 3 and 2 times that of pure PLA, respectively. The structural evolution of electrospun nanofiber was analyzed by differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FTIR). Although PLA and PVA were still miscible in the concentration range used, the latter could crystallize independently after electrospinning. According to the crystallization behavior of the nanofibers, a double network formed by PLA and PVA—one microcrystal/ordered structure and one amorphous structure—is proposed to contribute to the simultaneous enhancement of strength and toughness, which provides a promising method for preparing biodegradable material with high performance.


Macromolecules | 2012

Stretch-Induced Crystal–Crystal Transition of Polybutene-1: An in Situ Synchrotron Radiation Wide-Angle X-ray Scattering Study

Yanping Liu; Kunpeng Cui; Nan Tian; Weiqing Zhou; Lingpu Meng; Liangbin Li; Zhe Ma; Xiaolin Wang


Macromolecules | 2012

Self-Acceleration of Nucleation and Formation of Shish in Extension-Induced Crystallization with Strain Beyond Fracture

Kunpeng Cui; Lingpu Meng; Nan Tian; Weiqing Zhou; Yanping Liu; Zhen Wang; Jie He; Liangbin Li


Macromolecules | 2011

Extension Flow Induced Crystallization of Poly(ethylene oxide)

Nan Tian; Weiqing Zhou; Kunpeng Cui; Yanping Liu; Yuye Fang; Xiao Wang; Liangbao Liu; Liangbin Li


Polymer Testing | 2014

A novel apparatus combining polymer extrusion processing and x-ray scattering

Kunpeng Cui; Yanping Liu; Lingpu Meng; Xiangyang Li; Zhen Wang; Xiaowei Chen; Liangbin Li


Polymer | 2013

Disentanglement decelerating flow-induced nucleation

Weiqing Zhou; Kunpeng Cui; Nan Tian; Dong Liu; Yanping Liu; Lingpu Meng; Xiangyang Li; Jie He; Liangbin Li; Xiuhong Li; Feng Tian


Journal of Applied Polymer Science | 2014

In Situ microscopic infrared imaging study on deformation‐induced spatial orientation and phase transition distributions of PA12

Liang Chen; Wei Chen; Weiming Zhou; Jing Li; Yanping Liu; Zeming Qi; Liangbin Li

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Liangbin Li

University of Science and Technology of China

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Kunpeng Cui

University of Science and Technology of China

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Nan Tian

University of Science and Technology of China

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Weiqing Zhou

University of Science and Technology of China

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Xiangyang Li

University of Science and Technology of China

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Lingpu Meng

University of Science and Technology of China

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Dong Liu

University of Science and Technology of China

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Liang Chen

University of Science and Technology of China

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Zhen Wang

University of Science and Technology of China

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Jie He

University of Science and Technology of China

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