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A NEURAL NETWORK STUDY ON glass transition temperature OF POLYMERS

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Chinese Journal of Polymer Science 2002年第1期20卷 25-30页

作者：章林溪 Department of Physics Zhejiang University Hangzhou 310028

In this paper, an artificial neural network model is adopted to study the glass transition temperature of polymers. In our artificial neural networks, the input nodes are the characteristic ratio C-infinity, the average molecular weight M-e between entanglement points and the molecular weight M-mon of repeating unit. The output node is the glass transition temperature T-g, and the number of the hidden layer is 6. We found that the artificial neural network simulations are accurate in predicting the outcome for polymers for which it is not trained. The maximum relative error for predicting of the glass transition temperature is 3.47%, and the overall average error is only 2.27%. Artificial neural networks may provide some new ideas to investigate other properties of the polymers.

关键词： neural network glass transition temperature

Prediction of glass transition temperatures of Polyarylates Using a Support Vector Machine Model

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Chinese Journal of Structural Chemistry 2011年第7期30卷 943-950页

作者：张仕华谭正德 Network Information Center Hunan Institute of Engineering Key Laboratory of Environmentally Friendly Chemistry and Applications of Ministry of Education College of ChemistryXiangtan University College of Chemistry and Chemical Engineering Hunan Institute of Engineering

A three-descriptor quantitative structure-property relationship （QSPR） model, based on the support vector machine （SVM） algorithm, was constructed to predict the glass transition temperatures （Tgs） ofpolyarylates with complex structures. A total of 50 polyarylates were randomly divided into three sets, viz., the training set （30 polymers）, validation set （10 polymers） and prediction set （10 polymers）. By adjusting various parameters by trial and error, the final optimum SVM model based on Austin Model 1 （AM1） calculation is a polynomial kernel with the parameters C of 100, ε of 1.00E-05 and d of 2. The root-mean-square （RMS） errors obtained from the training set, validation set and prediction set are 19.4, 12.8 and 15.5 K, respectively. Research results show that the proposed SVM model has better statistical quality than the previous models. Thus, applying the SVM algorithm to predict Tgs of polymers is feasible.

关键词： glass transition temperature structure-property relations support vector machine

Nanoparticle Dispersion and glass transition Behavior of Polyimide-grafted Silica Nanocomposites

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Chinese Journal of Polymer Science 2020年第1期38卷 100-108,I0008页

作者： Sha-Ni Hu Yu Lin Guo-Zhang Wu Shanghai Key Laboratory of Advanced Polymeric Materials School of Materials Science and Engineering East China University of Science and Technology

How to control the spatial distribution of nanoparticles to meet different performance requirements is a constant challenge in the field of polymer *** studies have been focused on the flexible polymer chain *** this study,the rigid polyimide(PI) chain grafted silica particles with different grafting chain lengths and grafting densities were prepared by "grafting to" method,and the influence of polymerization degree of grafted chains(N),matrix chains(P),and grafting density(a) on the spatial distribution of nanoparticles in the PI matrix was *** glass transition temperature(Tg) of PI composites was systematically investigated as *** results show that silica particles are well dispersed in polyamic acid composite systems,while aggregation and small clusters appear in PI nanocomposites after thermal ***,the particle size has no impact on the spatial distribution of *** σ·N0.5<<(N/P)2,the grafted and matrix chains interpenetrate,and the frictional resistance of the segment increases,resulting in restricted relaxation kinetics and Tg increase of the PI composite *** addition,smaller particle size and longer grafted chains are beneficial to improving Tg of composites These results are all propitious to complete the microstructure control theory of nanocomposites and make a theoretical foundation for the high performance and multi-function of PI nanocomposites.

关键词： Polyimide grafted nanoparticle Dispersion morphology glass transition temperature

Multi-scale Studies of glass transition and Uniaxial Tensile Properties of a Commercially Available Epoxy Adhesive Using Experimental Measurements and Molecular Dynamics Simulation

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Chinese Journal of Polymer Science 2015年第3期33卷 465-474页

作者：姚力 State Key Laboratory of Automotive Safety and Energy Department of Automotive EngineeringTsinghua University

In this study, the glass transition and uniaxial tensile properties of a commercially available epoxy adhesive were investigated using experimental measurements and molecular dynamics （MD） simulation. Differential scanning calorimetry （DSC） was used to study the change of glass transition temperature （Tg） with cross-link density （CLD）. Uniaxial tensile test was performed to measure the Young＇s modulus （E）, Poisson＇s ratio （v） and yielding strength （tyv）. In MD simulation, the complicated epoxy system was simplified as the mixture of two kinds of simple molecules, with the key information well preserved and the less important details omitted. The molecular model of the cross-linked epoxy network was constructed and its mechanical properties were calculated using MD simulation. Overall, the MD simulation results agreed with experimental ones, which proved the validity of the molecular model and justified the simplification method of the industry- level epoxy system.

关键词： Epoxy adhesive glass transition temperature Uniaxial tension Experiment Molecular dynamics simulation.

Molecular Dynamics Simulation of glass transition Behavior of Polyimide Ensemble

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Chinese Chemical Letters 2001年第9期12卷 827-828页

作者： Tai Ning LIANG Xiang Yu ZHANG Xiao Zhen YANG State Key Laboratory of Polymer Physics and Chemistry Center for Molecular ScienceInstitute of ChemistryChinese Academy of SciencesBeijing 100080 Institute of Chemistry&Engineering Heilongjian UniversityHarbin 150089

The effect of chromophores to the glass transition temperature of polyimide ensemble has been investigated by means of molecular dynamics simulation in conjunction with barrier analysis. Simulated Tg results indicated a good agreement with experimental value. This study showed the MD simulation could estimate the effect of chromophores to the Tg of polyimide ensemble conveniently and an estimation approach method had a surprising deviation of Tg from experiment. At the same time, a polyimide structure with higher barrier energy was designed and validated by MD simulation.

关键词： glass transition temperature molecular dynamics simulation

Understanding the alkyl effect of geminal dinitropropyl ester energetic plasticizers on hydroxyl terminated polybutadiene(HTPB):Simultaneous tuning on low temperature behavior and processability

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Chinese Journal of Chemical Engineering 2023年第2期54卷 364-371页

作者： Baodong Zhao Yinglei Wang Fulei Gao Yajing Liu Weixiao Liu Feng Ding Xi'an Modern Chemistry Research Institute Xi'an 710065China State Key Laboratory of Fluorine&Nitrogen Chemicals Xi'an 710065China

Geminal dinitropropyl ester plasticizers(DNPEPs) possess excellent energetic performances which provide good potentials as insensitive plasticizer. In this study, we design and synthesize DNPEPs with different alkane chain parts, and systematically investigate their structure-property *** show that DNPEPs have impact sensitivities all higher than 25.2 J, thermal decomposition temperatures all higher than 254 ℃, and glass transition temperatures(T_(g)) lower than-90 ℃.Furthermore, the effects of DNPEPs as plasticizer are studied on hydroxyl terminated polybutadiene(HTPB) in detail, including the viscosity, glass transition temperatures and others. It is noteworthy that 2,2-dinitropropyl nonanoate(DNPNc) among these DNPEPs exhibits the most expected simultaneous tuning effects on both viscosity and T_(g) of HTPB systems, providing favorable potentials to replace the conventional plastizers as dioctyl sebacate(DOS) in the HTPB based propellants and explosives.

关键词： Molecular simulation Experimental validation Preparation Energetic plasticizer glass transition temperature Viscosity

STUDIES ON PARTIAL COMPATIBILITY OF PP AND PS

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Chinese Journal of Polymer Science 2010年第4期28卷 647-656页

作者：傅强 College of Polymer Science & Engineering Sichuan UniversityState Key Laboratory of Polymer Materials Engineering

Blends of polystyrene （PS） and polypropylene （PP） were prepared through melt compounding. With an increase of PS content up to 30 wt%, the tensile strength of PP/PS blends increased from 37.4 MPa to 42.2 MPa, although the blends were widely regarded as immiscible. The DSC results showed that there＇s slight decrease in melting temperature of PP, showing insufficient evidence for partial compatibility between PP and PS. Almost no variation of distinct characterization peaks were observed in FTIR spectra of PS/PP blends compared with those of neat PP and PS, indicating there is no chemical interactions between PP and PS. Since the morphology investigation showed a droplet structure as PS content was up to 30 wt%, the improvement of tensile strength could be simply considered as due to the reinforcing effect of dispersed rigid PS particles on the PP, combining with partial compatibility between them as evaluated by change of Cp at glass transition for both PS and PP. More interestingly, DSC and DMA results showed that the blending of PS and PP could lead to a substantial decrease of the glass transition temperature （Tg） of PP, and increase of Tg of PS. The annealing experiment was carried out to understand the change of Tg in PP/PS blends. It is believed that the compressive stress generated by the contracting PP should be the dominant mechanism for the Tg elevation of PS. On the other hand, the Tg decrease of PP is likely owing to the creation of a large amount free interface of PP and the dilatation of the PP phase resulting from the corresponding tension exerted by PS during cooling.

关键词： Polypropylene Polystyrene Tensile strength glass transition temperature Compatibility Interaction

LITHIUM ION CONDUCTING POLYMER ELECTROLYTES BASED ON ALTERNATING MALEIC ANHYDRIDE COPOLYMER WITH OLIGO-OXYETHYLENE SIDE CHAINS

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Chinese Journal of Polymer Science 1996年第3期14卷 240-247页

作者：丁黎明 Changchun Institute of Applied Chemistry Academia Sinica Changchun 130022

A comb polymer with oligo-oxyethylene side chains of the type -(CH2CB2O)(12)CH3 was prepared from methyl vinyl ether/maleic anhydride copolymer and poly (ethylene glycol) methyl ether. The polymer can dissolve LiClO4 salt to form homogeneous amorphous polymer electrolyte. The ac ion conduction was measured using the complex impedance method, and conductivities were investigated as functions of temperatures and salt concentration. The complexes were first found to have two classes of glass transition which increase with increasing salt content, The optimum conductivity attained at 25 degrees C is in the order of 5.50 x 10(-6)Scm(-1). IR spectroscopy was used to study the cation-polymer interaction.

关键词： comb polymer lithium perchlorate ionic conductivity polymer electrolyte glass transition temperature

Reinforcement of natural rubber latex with silica modified by cerium oxide:preparation and properties

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Journal of Rare Earths 2016年第2期34卷 221-226页

作者：张福全廖禄生王永周汪月琼黄红海李普旺彭政曾日中 Chinese Agricultural Ministry Key Laboratory of Tropical Crop Product Processing Agricultural Product Processing Research InstituteChinese Academy of Tropical Agricultural SciencesZhanjiang 524001China Agriculture Ministry Key Laboratory of Biology and Genetic Resources of Rubber TreeRubber Research InstituteChinese Academy of Tropical Agricultural SciencesDanzhou 571731China

Variable masses of nano cerium oxide (CeO2) were added into nano silica (SiO2) to prepare the well-dispersed SiO2-CeO2 suspension (SiO2-CeO2), cetyltrimethyl ammonium bromide (CTAB) was used to adjust the compatibility of SiO2-CeO2 with rubber matrix, then SiO2-CeO2 modified by CTAB and curing formulas were mixed with fresh natural rubber (NR) latex to prepare NR/SiO2-CeO2 nanocomposites that contained 0–10 parts of CeO2 by a new emulsion compounding method. The morphologies, cure characteristics, mechanical properties and thermal-oxidative stability of NR/SiO2-CeO2 nanocomposites were investigated. The re-sults revealed that the presence of CeO2 in NR/SiO2-CeO2nanocomposites was favorable for enhancing the interaction between NR matrix and fillers, helped to get smaller SiO2-CeO2 particles with narrower particle size distribution, further improved the crosslink densities and mechanical properties of NR/SiO2-CeO2 nanocomposites vulcanizates. Meanwhile, the addition of CeO2 increased the active energy at least 4.66%, obviously improved the thermal-oxidative aging-inhibiting properties of NR/SiO2-CeO2 nanocomposites. Additionally, nanocomposites containing CeO2 promotedTg shift to high temperature direction, causing the nanocomposites featured higher tanδ at 0 oC and lower tanδ at 60 oC and exhibited comparable wet grip and lower rolling resistance when NR/SiO2-CeO2nano-composites were used in tire tread compound.

关键词： cerium oxide silica natural rubber latex emulsion compound reinforcement aging-inhibiting property glass transition temperature rare earths