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On the Structure and free volume Properties of Poly（3-hydroxybutyrate-co-3-hydroxyvalerate） Membranes via Various Crystallization Conditions

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On the Structure and Free Volume Properties of Poly（3-hydro...

A Thermodynamic Perspective on Polymer Glass Formation

2009年全国高分子学术论文报告会

作者：程美玲孫一明 Department of Chemical Engineering and Materials Science Yuan Ze University

＜正＞The crystalline structure and the free volume properties within the amorphous phase of poly（3-hydroxybutyrate-co-3-hydroxyvalerate）（PHBV） membranes depend on the preparation conditions.The difference of free volume properties among various PHBV membranes was created according to the crystalline structure of the polymer from different thermal history.free volume properties in the amorphous region of a series of PHBV membranes,which were prepared by cold-and melt-crystallization processes,were investigated using

关键词： positron annihilation lifetime free volume crystallization temperature rigid amorphous fraction long period

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Chinese Journal of Polymer Science 2023年第9期41卷 1329-1341,I0004页

作者： Wen-Sheng Xu Zhao-Yan Sun State Key Laboratory of Polymer Physics and Chemistry Changchun Institute of Applied ChemistryChinese Academy of SciencesChangchun130022China

The dynamics of polymeric and other glass-forming liquids dramatically slows down upon cooling toward the glass transition temperature without any obvious significant change in their static structure.A quantitative understanding of this extraordinary dynamic slowdown remains one of the most significant challenges in condensed matter physics.Historically,extensive efforts have been devoted to explaining the dynamics of glass-forming liquids in terms of thermodynamic properties,leading to a number of semi-empirical models emphasizing distinct thermodynamic properties.Here,a thermodynamic perspective is provided on the glass formation of polymeric and other materials.We begin with an overview of the thermodynamic models of glass formation,including the intuitively appealing“free volume”models,enthalpy models originally emphasized by Goldstein and later by others,and the highly influential configurational entropy-based models.The review of these models is followed by a discussion of the advances that attempt to bring together some of the seemingly disparate thermodynamic viewpoints on glass formation by revealing a close interrelation between thermodynamic properties.We conclude this review with remarks on several key topics in this field,along with our viewpoint for future work.

关键词： Glass formation Entropy free volume Enthalpy

Bending behavior of as-cast and annealed ZrCuNiAl bulk metallic glass

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Journal of Materials Science & Technology 2017年第10期33卷 1153-1158页

作者： Yongjiang Huang Zhiliang Ning Zhe Shen Weizhong Liang Haicao Sun Jianfei Sun School of Materials Science and Engineering Harbin Institute of Technology Harbin 150001 China National Key Laboratory of Precision Hot Processing of Metals Harbin Institute of Technology Harbin 150001 China Shenyang Engine Research Institute Aero Engine Corporation of China Shenyang 110000 China School of Materials Science and Engineering Heilongjiang University of Science and Technology Harbin 150027 China

Here ZrCuNiAl bulk metallic glass samples were annealed below its glass transition temperature. The bending behaviors and thermal properties of the as-cast and the annealed samples were studied. The increase of annealing time leads to the transition from ductile to more brittle behavior during bending tests. Meanwhile, prolonging the annealing causes a gradual decrease in the free volume content. Based on free volume theory, the change in the microstructure and mechanical properties induced by annealing treatment has been interpreted in detail.

关键词： Bulk metallic glasses Annealing Bending Fracture free volume

A Facile Strategy for Non-fluorinated Intrinsic Low-k and Low-loss Dielectric Polymers: Valid Exploitation of Secondary Relaxation Behaviors

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Chinese Journal of Polymer Science 2020年第3期38卷 213-219,I0005页

作者： Chao Qian Zhen-Guo Fan Wei-Wen Zheng Run-Xin Bei Tian-Wen Zhu Si-Wei Liu Zhen-Guo Chi Matthew P.Aldred Xu-Dong Chen Yi Zhang Jia-Rui Xu PCFM Lab GD HPPC LabGuangdong Engineering Technology Research Centre for High-performance Organic and Polymer Photoelectric Functional FilmsState Key Laboratory of Optoelectronic Materials and TechnologiesSchool of ChemistrySun Yat-sen University

High-performance low-k and low-loss circuit materials are urgently needed in the field of microelectronics due to the upcoming FifthGeneration Mobile Communications Technology(5 G Technology).Herein,a facile design strategy for non-fluorinated intrinsic low-k and low-loss polyimides is reported by fully considering the secondary relaxation behaviors of the polymer chains.A new amorphous non-fluorinated polymer(TmBPPA)with a k value of 2.23 and a loss tangent lower than 3.94×10^-3 at 104 Hz has been designed and synthesized,which to the best of our knowledge is the lowest value amongst the non-fluorinated and non-porous polymers reported in literature.Meanwhile,TmBPPA exhibits excellent overall properties,such as excellent thermostability,good mechanical properties,low moisture absorption,and high bonding strength.As high-performance flexible circuit materials,all these characteristics are highly expected to meet the present and future demands for high density,high speed,and high frequency electronic circuit used in 5 G wireless networks.

关键词： Polyimides Low-k free volume Secondary relaxation

Effect of thermo-oxidation on the dynamical and physical properties of ethylene-propylene-diene monomer elastomer

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2021年第7期22卷 499-513页

作者： Ya-jian WANG Yu-you YANG Lin-bing WANG School of Engineering and Technology China University of Geosciences(Beijing)Beijing 100083China Joint USTB-Virginia Tech Lab on Multifunctional Materials USTBBeijing 100083China Department of Civil and Environmental Engineering Virginia TechBlacksburgVA 24061USA

Understanding the underlying processes associated with the thermo-oxidative performance of the ethylenepropylene-diene monomer(EPDM)is essential for assessing and improving its waterproofing performance in underground infrastructures.To explore the fundamentals of EPDM degradation behavior during thermal oxidation,this paper investigates the effects of hydrocarbon free chain,carbon crosslink,chain scission,hydroxyl,and ether crosslinks,on its kinetics and mechanical properties through molecular dynamics(MD)simulations.Several EPDM thermo-oxidative models were built and verified by comparing the simulation results of oxygen diffusivity,glass transition temperature,and mechanical properties with reported experimental ones.Then the radius of gyration,free volume,density,transport,glass transition,and uniaxial compression performance were investigated via MD simulations.The results show that crosslinking in the thermal oxidation process has a significant influence on the free volume,glass transition temperature,and mechanical properties of the system;the hydroxyl and chain scission mainly interfere with the transport properties;all of these affect the structural conformation.

关键词： Ethylene-propylene-diene monomer(EPDM)elastomer Thermo-oxidation Glass transition temperature free volume Crosslinking

POSITRON LIFETIME STUDY OF THERMALLY INDUCED MICROSTRUCTURAL CHANGES IN NISTARI SILK FIBER

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Chinese Journal of Polymer Science 2003年第3期21卷 325-332页

作者： C.Ranganathaiah Department of Studies in Physics University of Mysore Manasagangotri Mysore-570 006 India

Positron lifetime measurements have been made in natural polymer-Nistari silk fibers as a function of isochronalannealing temperature in the range of 27℃ to 280℃. The variations in the positron results indicate the structural changesoccurring in the Nistari silk fibers and determine the glass transition temperature as 170℃. Activation energies weremeasured separately for the crystalline and amorphous regions indicating the versatility of the technique. These values areclose to the N--H bond dissociation energy, suggesting N--H bond dissociation as the most probable process occurringduring thermal treatment As an extension of the positron results, the molecular weight of the Nistari silk fibers wasdetermined to be 10.7×10~5 based on free volume, which lies within the range suggested for the silk fibers. There seems to bean indication that cross-linking changes the spiral structure of cotton fibers to network type. However, this needs to be validated by other techniques.

关键词： Nistari silk fiber Positronium free volume Molecular weight Activation energy

Investigation of SPPO Membranes by Positron Annihilation Lifetime Spectroscopy

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Plasma Science and Technology 2006年第5期8卷 573-576页

作者： Htwe Htwe Yin 阴泽杰唐世彪黄环 Department of Modern Physics University of Science and Technology of China Hefei 230026 China Department of Chemistry University of Science and Technology of China Hefei 230026 China

Positron annihilation lifetime spectroscopy （PALS） is a powerful technique to study the free volume in polymers. The lifetime of ortho-positronium （o-Ps）, a bound state of an electron and a positron, can be used to assess the pore size while the intensity can be used to characterize the number of pores. On the basis of the values of the long-lived o-Ps components in the lifetime spectra, the radii and fractional free volumes in the sulfonated poly （2,6-dimethyl-1,4- phenyleneoxide）（SPPO） membranes with different amounts of LiCl were calculated. It was found that, with the increasing amount of LiCl, the free volume radius and the fractional free volume firstly increased and then decreased. After immersing the membranes in distilled water, the free volume radius and the fractional free volume changed with different water concentrations in the membrane.

关键词： positron annihilation pore size free volume SPPO polymer water concentration

INVESTIGATION OF MICROSTRUCTURE AND CONDUCTIVE MECHANISM OF HIGH DENSITY POLYETHYLENE/CARBON BLACK PARTICLE COMPOSITE BY POSITRON ANNIHILATION LIFETIME SPECTROSCOPY

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Chinese Journal of Polymer Science 2002年第3期20卷 243-252页

作者： Yang-mei Fan Xian-feng Zhang Bang-jiao Ye Xian-yi Zhou Hui-min Weng Jiang-feng Du Rong-dian Han Shao-jin Jia Zhi-cheng Zhang Department of Modern Physics, University of Science and Technology of China, Hefei 230027, China Department of Polymer Science and Engineering University of Science and Technology of China, Hefei 230027 China Department of Modern Physics University of Science and Technology of China Hefei 230027 Department of Modern Physics University of Science and Technology of Chin Hefei 230027 Department of Polymer Science and Engineering University of Science and Technology of China Hefei 230027

The microstructure and conductive mechanism of high density polyethylene/carbon black (HDPE/CB) composite were investigated by positron annihilation lifetime spectroscopy (PALS). The PALS were measured in two series of samples, one with various CB contents in the composites and the other with various gamma-irradiation doses in HDPE/CB composite containing 20 wt% CB. It was found that CB particles distribute in the amorphous regions, the CB critical content value in HDPE/CB composite is about 16.7 wt% and the suitable gamma-irradiation dose for improving the conductive behavior of HDPE/CB composite is about 20 Mrad. The result observed for the second set of samples suggests that gamma-irradiation causes not only cross-linking in amorphous regions but also destruction of the partial crystalline structure. Therefore, a suitable irradiation dose, about 20 Mrad, can induce sufficient cross-linking in the amorphous regions without enhancing the decomposition of crystalline structure, so that the positive temperature coefficient (PTC) effect remains while the negative temperature coefficient (NTC) effect is suppressed. A new interpretation of the conductive mechanism, which might provide a more detailed explanation of the PTC effect and the NTC effect has been proposed.

关键词： conductive mechanism PALS free volume HDPE/CB

Effect on microstructure and plastic deformation behavior of a Zr-based amorphous alloy by cooling rate control

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Journal of Materials Science & Technology 2021年第23期82卷 1-9页

作者： Feilong Wang Dawei Yin Jingwang Lv Shan Zhang Mingzhen Ma Xinyu Zhang Riping Liu State Key Laboratory of Metastable Materials Science and Technology Yanshan UniversityQinhuangdao066004China

In this study,Zr_(41.2)Ti_(13.8)Cu_(12.5)Ni_(10)Be_(22.5) amorphous alloys samples with the same diameter(8 mm)were prepared by using self-designed molds(viz.refractory steel,pure graphite,and copper molds)with different cooling capacities.Moreover,by eliminating the size effect,the effect of the cooling rate on the microstructure and compression deformation behavior of Zr_(41.2)Ti_(13.8)Cu_(12.5)Ni_(10)Be_(22.5) amorphous alloys was investigated.Differentiation of the cooling curves revealed that the instantaneous cooling rates of the alloy melt at the glass transition temperature(Tg)are 45,52,and 64 K·s^(-1) for refractory steel,pure graphite,and copper molds,respectively.X-ray diffraction,differential scanning calorimetry,and highresolution transmission electron microscopy analysis revealed that with the decrease in the cooling rate,trace icosahedral-like atomic clusters and nanocrystals appear in local areas of the amorphous alloy and that the amount of free volume decreases with the increase in the amount of icosahedra-like atomic clusters and nanocrystals.Compression test results revealed that the elastic strain,yield strength,and compressive strength of the amorphous alloy marginally change with the decrease in the cooling rate,while the plastic strain gradually increases.By fitting,the effective size of the vein-like pattern was linearly related to the enthalpy released during structural relaxation and plastic strain,indicating that at a low cooling rate,the trace nanocrystals in the amorphous alloy could not effectively improve its plasticity and that the amount of free volume mainly affects its plasticity.

关键词： Bulk amorphous alloy Cooling rate Compression plasticity free volume