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Time and Temperature Dependence of the Structural Evolution for Polyamide 1012

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Chinese Journal of Polymer Science 2020年第9期38卷 993-998,I0007页

作者： Xin-Ran Liu Yu wang Li-Yuan Liu Xia Dong du-jin wang CAS Key Laboratory of Engineering Plastics CAS Research/Education Center for Excellence in Molecular SciencesBeijing National Laboratory for Molecular SciencesInstitute of ChemistryChinese Academy of SciencesBeijing 100190China University of Chinese Academy of Sciences Beijing 100049China Shenzhen Key Laboratory of Polymer Science and Technology College of Materials Science and EngineeringShenzhen UniversityShenzhen 518060China

The rheological property evolution of polyamide 1012(PA1012)in the isothermal process in molten state has been *** results show that the viscosity increases and crosslinking reaction occurs simultaneously together with the increase of temperature,thus causing the variation of storage modulus(G')and loss modulus(G")in the repeated frequency sweeps with residual *** research has pointed out that the superposition is valid for monitoring the complex behavior composed of the viscosity increasing and crosslink occurring process by tracing the variation behavior of the crossover points of G'and G"with time,revealing the same time-temperature dependence of the two reactions in the isothermal process.A normalized master curve has been proposed to describe the melt behavior at a given temperature.

关键词： Polyamide 1012 Rheology Crosslinking Viscosity increasing Time-temperature superposition

Controllable Synthesis of a Well-defined Polypropylene grafted Silica Nanoparticles and Its Effect on Crystallization Behavior of Polypropylene

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Chinese Journal of Polymer Science 2022年第11期40卷 1411-1421页

作者： Wei-Long Ju Shao-Fan Li Yun-Lan Su du-jin wang Key Laboratory of Engineering Plastics Beijing National Laboratory for Molecular SciencesInstitute of ChemistryChinese Academy of SciencesBeijing100190China University of Chinese Academy of Sciences Beijing100049China

Well-defined polypropylene grafted silica nanoparticles(PP-g-SiO_(2))were prepared through the reaction of maleic anhydride grafted polypropylene(PP-g-MAH)with amino-functionalized silica(SiO_(2)-NH_(2))by the'grafting-to'*** grafting density of PP-g-SiO_(2) is found to be controlled by the concentration of silane coupling agent 3-[2-(2-aminoethylamino)ethyl amino]propyl trimethoxy silane(TAMS).The maximum grafting density of grafted PP-g-MAH chains with molecular weight of 9100 g/mol could reach 0.34 chains/nm~2,when the critical concentration of TAMS was 0.0194 mol/*** critical concentration of TAMS can be explained by the maximum amounts of primary amino groups,which can totally react with PP-g-MAH on the surface of SiO_(2)-NH_(2),when the silane monolayer is *** synthesized PP-g-SiO_(2)with different molecular weights was mixed with PP by solution mixing to form a series of *** crystallization temperature(T_(c))of nanocomposites increased significantly with the particle *** PP-g-SiO_(2) with high molecular weight of grafted chains exhibits a high nucleation ability at 1 wt%nanoparticle loading in PP/PP-g-SiO_(2)*** summary,we provide an effective method to synthesize the well-defined PP-g-SiO_(2)with controlled grafting density,which shows excellent nucleation ability.

关键词： Polypropylene grafted silica nanoparticles Grafting density Grafting to Crystallization behavior

Stress-induced Solid-Solid Crystal Transition in Trans-1,4-polyisoprene

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Chinese Journal of Polymer Science 2022年第3期40卷 256-265,I0006页

作者： Chun-Bo Zhang Lei wang Bo Yang Hui Zhao Guo-Ming Liu du-jin wang Shenzhen Key Laboratory of Polymer Science and Technology College of Materials Science and EngineeringShenzhen UniversityShenzhen 518060China CAS Key Laboratory of Engineering Plastics Beijing National Laboratory for Molecular SciencesInstitute of ChemistryChinese Academy of SciencesBeijing 100190China University of Chinese Academy of Sciences Beijing 100049China School of Materials Science&Engineering Beijing Institute of Fashion TechnologyBeijing 100029China

The polymorphic transition of trans-1,4-polyisoprene(TPI) during stretching was investigated by in situ wide-angle X-ray diffraction and Fourier transform infrared spectroscopy. The influences of the initial structure, stretching temperature, and strain rate on the contents of different crystal modifications(α, β) were explored. The results confirm that the α-β transition occurs during stretching of TPI that only contains αcrystal(α-TPI). When the stress is relaxed, the β crystal formed during stretching remains, which indicates that the transition is irreversible. On the other hand, stretching of TPI that only contains β crystal(β-TPI) results in orientated β crystal. No β-α transition occurs during stretching. The different structures of stretched α-TPI and β-TPI exclude the previously proposed "melting-recrystallization mechanism". The α-β transition depends significantly on temperature and strain rate, indicating the transition is governed both by thermodynamics and kinetics. Our results support a solid-solid transition mechanism rather than a melting-recrystallization mechanism. The irreversible nature of the transition is attributed to the metastability of the β phase in the unstretched state. Different from the "β phases" that appear in polymers with stress-induced reversible transitions, e.g. poly(butylene terephthalate) and poly(butylene succinate), the stability of β phase in TPI is high that can be *** strain rate dependence of α-β transition hinders the determination of critical stress for the transition. It further indicates that the local stress within the sample is more heterogeneous at higher strain rates.

关键词： Trans-1 4-polyisoprene Crystal transition Deformation Crystallization

High Performance Long Chain Polyamide/Calcium Silicate Whisker Nanocomposites and the Effective Reinforcement Mechanism

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Chinese Journal of Polymer Science 2016年第8期34卷 991-1000页

作者： Li-li wang 董侠 Xing-rui wang Gan-yu Zhu Hui-quan Li du-jin wang Beijing National Laboratory for Molecular Sciences CAS Key Laboratory of Engineering PlasticsInstitute of ChemistryChinese Academy of SciencesBeijing 100190China Key Laboratory of Green Process and Engineering and National Engineering Laboratory for Hydrometallurgical Cleaner Production Technology Institute of Process EngineeringChinese Academy of SciencesBeijing 100190China

PA1012/calcium silicate whisker nanocomposites with contents of whisker ranging from 10 wt% to 40 wt%, are prepared by twin screw extruder without any additions of coupling agent. The effect of whisker on the matrix is analyzed by the studies of morphology, the mechanical properties, water absorption and thermal stabilities. SEM micrographs obviously demonstrate, even under the high filler content of 40 wt% and without surface treatment, calcium silicate whisker can be homogeneously dispersed in polyamide, directly leading to the enhanced mechanical properties. The mechanism of higher efficiency of reinforcement is needle-like shape whisker, having access to be intercalated, and mutual affinity caused by hydrogen bonding interaction between carbonyl group in polyamide chain and hydroxyl group in whisker surface. Both aspects attach matrix with excellent stress-transfer properties. In addition, with the assistance of whisker, the nanocomposite favors an improved water absorption as well as thermal stability, which is intimately associated with physical performance.

关键词： PA1012 Calcium silicate whisker No coupling agent Homogeneous dispersion Enhanced properties.

DEFORMATION INVESTIGATION ON iPP/SiO_2 COMPOSITES: INFLUENCE OF STRETCHING TEMPERATURE AND PARTICLE SIZE ON MORPHOLOGY EVOLUTION AND CRYSTALLINE STRUCTURE OF THIN FILMS

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Chinese Journal of Polymer Science 2013年第2期31卷 275-284页

作者： Xiu-qin Zhang Qian Xing Rong-bo Li 王锐 du-jin wang Beijing Key Laboratory of Clothing Materials R & D and Assessment Department of Materials Science & Engineering Beijing Institute of Fashion Technology Beijing National Laboratory for Molecular Sciences Key Laboratory of Engineering Plastics Institute of Chemistry Chinese Academy of Sciences

In the present work, structure changes during （SiO2） composites have been investigated systematically stretching of isotactic polypropylene （iPP） and iPP/silicon dioxide The or-form crystal structure of both iPP and iPP/SiO2 composites is destroyed and transforms into the mesophase as the samples are stretched at a low temperature （35℃）, while stretching at high temperatures （90℃ and 120℃） can restrain the appearance of defects and keep the perfection of crystal structure. FTIR results reveal that the stretching temperatures show no obvious difference of the effect on the orientation of pure iPP, however, the orientation of iPP/SiO2 composites is greatly changed by the tensile temperature. In the case of micron-sized SiO2 particles （average particle diameter d 〉 1 μm）, the orientation of the composites is lower than that of pure iPP at all stretching temperatures. The above results suggest that the stretching temperature and the SiO2 particle size have great influence on the structure variation and orientation behavior of iPP/SiO2 composites.

关键词： iPP/SiO2 composites Stretching Morphology Structure variation.

Phase Behavior Actuating Morphology and Rheological Response of Polybutadiene/Polyisoprene Blends under Small Amplitude Oscillatory Shear

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Chinese Journal of Polymer Science 2014年第6期32卷 718-730页

作者： Fa-sheng Zou 董侠 Wei Liu du-jin wang Charles C.Han Beijing National Laboratory for Molecular Science CAS Key Laboratory of Engineering Plastics Joint Laboratory of Polymer Science and MaterialsInstitute of Chemistry Chinese Academy of Sciences

The morphology evolution and the corresponding linear viscoelastic behavior of the phase-separating polybutadiene （PB）/low vinyl content polyisoprene （LPI） blend have been investigated by phase contrast optical microscopy （PCOM）, small-angle light scattering （SALS） and rheometxy. Two kinds of structure evolutions and rheological responses have been observed. It is found that the co-continuous structure generally gives a power law behavior of the dynamic storage modulus versus frequency and the coarsening of co-continuous structure leads to a decrease of the storage modulus. For the droplet-matrix structure, a platform modulus is observed at the mediate frequencies, followed by the typical terminal relaxation behavior of storage modulus at the extremely low frequencies. The decreasing platform modulus and increasing terminal modulus with the growth of droplets are observed and can be well interpreted by the simplified Palieme model. The platform modulus and terminal modulus at a given frequency are found to be scalable with the phase separation time. Besides, the characteristic relaxation time and domain size of the droplets have been obtained by theology. And it seems that the theologically determined droplet dimensions are consistent with the ones determined by PCOM and SALS.

关键词： Phase separation Structure evolution Rheology.

Experimental and Data Fitting Guidelines for the Determination of Polymer Crystallization Kinetics

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Chinese Journal of Polymer Science 2022年第6期40卷 658-691页

作者： Ricardo Arpad Perez-Camargo Guo-Ming Liu du-jin wang Alejandro J.Muller Beijing National Laboratory for Molecular Sciences CAS Key Laboratory of Engineering PlasticsInstitute of ChemistryChinese Academy of SciencesBeijing 100190China University of Chinese Academy of Sciences Beijing 100049China POLYMAT and Department of Polymers and Advanced Materials:Physics Chemistry and TechnologyFaculty of ChemistryUniversity of the Basque Country UPV/EHUDonostia-San Sebastián 20018Spain IKERBASQUE Basque Foundation for ScienceBilbao 48013Spain

The crystallization kinetics of semicrystalline polymers is often studied with isothermal experiments and analyzed by fitting the data with analytical expressions of the Avrami and Lauritzen and Hoffman(LH)*** correctly carry out the analysis,precautions in both experiments and data fitting should be ***,we systematically discussed the factors that influence the validity of the crystallization kinetics *** basic concepts and fundamentals of the Avrami and LH theories were introduced at ***,experimental protocols were discussed in *** clarify the impact of various experimental parameters,selected common polymers,i.e.,polypropylene and polylactide,were studied using various experimental techniques(i.e.,differential scanning calorimetry and polarized light optical microscopy).Common mistakes were simulated under conditions when non-ideal experimental parameters were ***,from a practical point of view,we show how to fit the experimental data to the Avrami and the LH theories,using an Origin■App developed by us.

关键词： Isothermal crystallization Avrami equation Lauritzen and Hoffman theory Thermal analysis Step-crystallization

PREPARATION AND SURFACE PROPERTIES OF ACRYLIC COPOLYMERS CONTAINING FLUORINATED MONOMERS

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Chinese Journal of Polymer Science 2006年第6期24卷 575-578页

作者： Tai-jiang Gui Hao Wei Ying Zhao Xiu-lin wang du-jin wang duan-fu Xu Chemistry and Chemical Engineering College Ocean University of China Qingdao 266003 China State Key Laboratory of Polymer Physics and Chemistry Joint Laboratory of Polymer Science and Materials Institute of Chemistry Chinese Academy of Sciences Beijing 100080 China Marine Research Institute of Chemical Industry Qingdao 266071 China

A series of copolymers comprising butylmethacrylate, styrene, butylacrylate, hydroxypropyl acrylate and perfluoroalkyl methacrylate were synthesized by the free radical polymerization using BPO as an initiator. The surface property of the copolymer films was subsequently characterized. The contact angle measurements and energy dispersive analysis of X-ray （EDAX） show that the length and content of perfluoroalkyl side chains in the copolymers are crucial for the preparation of the film with low surface energy. At a given content of fluorinated monomers in the copolymers, the longer the perfluoroalkyl side chain, the larger the water contact angle of the copolymer films will be. On the other hand, the higher the content of fluorinated monomers, the lower the surface energy is. The water contact angle increases with the increase of the fluorinated monomer content and reaches a plateau at 3 wt% of fluorinated monomer content.

关键词： Acrylate copolymers Fluorinated monomers Surface property Contact angle X-ray energy dispersive analysis.

Dynamic Bonds Mediate π-π Interaction via Phase Locking Effect for Enhanced Heat Resistant Thermoplastic Polyurethane

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Chinese Journal of Polymer Science 2021年第2期39卷 154-163,I0005页

作者： Yue Lai Xiao Kuang Wen-Hong Yang Yu wang Ping Zhu jing-Pu Li Xia Dong du-jin wang CAS Key Laboratory of Engineering Plastics CAS Research/Education Center for Excellence in Molecular SciencesInstitute of ChemistryChinese Academy of SciencesBeijing 100190China University of Chinese Academy of Sciences Beijing 100049China The George W.Woodruff School of Mechanical Engineering Georgia Institute of TechnologyAtlantaGeorgia 30332United States College of Materials Science and Engineering Shenzhen UniversityShenzhen 518060China

Stimulus-responsive polymers containing dynamic bonds enable fascinating properties of self-healing,recycling and reprocessing due to enhanced relaxation of polymer chain/network with labile ***,we study the structure and properties of a new type of thermoplastic polyurethanes(TPUs)with trapped dynamic covalent bonds in the hard-phase domain and report the frustrated relaxation of TPUs containing weak dynamic bond andπ-πinteraction in hard *** detected by rheometry,the aromatic TPUs with alkyl disulfide in the hard segments possess the maximum network relaxation time in contrast to those without dynamic bonds and alicyclic *** situ FTIR and small-angle scattering results reveal that the alkyl disulfide facilitates stronger intermolecular interaction and more stable micro-phase morphology inπ-πinteraction based aromatic *** dynamics simulation for pure hard segments of model molecules verify that the presence of disulfide bonds leads to strongerπ-πstacking of aromatic rings due to both enhanced assembling thermodynamics and *** enhancedπ-πpacking and micro-phase structure in TPUs further kinetically immobilize the dynamic *** kinetically interlocking between the weak dynamic bonds and strong molecular interaction in hard segments leads to much slower network relaxation of *** work provides a new insight in tuning the network relaxation and heat resistance as well as molecular self-assembly in stimulus-responsive dynamic polymers by both molecular design and micro-phase control toward the functional applications of advanced materials.

关键词： Thermoplastic polyurethane Disulfide bond Stimuli-responsive rearrangement π-πStacking Phase locked effect