最新刊期
卷 32 ， 期 12 ， 2019
- 摘要：Catalysts have dominated the molecular weight and polydispersity of resultant polyolefin as well as its microstructure in the polymerization process of olefin, therefore significantly affected their physical and mechanical properties. Nickel catalysts have promoted ethylene reactivity in generating either oligomer or polyethylene; it has been great attractive of observing elastomeric properties of polyethylenes obtained. Therefore extensive investigations would enhance catalytic activities of nickel complex catalysts and result better performances of catalytic systems, achieving novel elastomeric materials of polyethylenes in order to target the further pilot process. Herein the current review collects the new progress of nickel complexes in ethylene polymerization, illustrating correlations or regulations between structures of nickel complexes and their catalytic activities,thermo-stabilities and microstructures of resultant polyethylenes.关键词：Nickel complexes;Polyethylene;Catalytic activity;Elastomeric material
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发布时间：2022-09-05 - 摘要：Melamine formaldehyde resin has good heat resistance and high bonding strength, so it is widely used in wood processing adhesives,coating curing agents,paper wet strength agents. However,the rigid triazine ring structure of melamine causes the melamine formaldehyde resin to have defects such as hard and brittle, poor mechanical properties, low strength, and poor tensile and bending properties. The above drawbacks limit the use of melamine formaldehyde resins in certain fields. In order to expand its application range, the toughening problem of melamine formaldehyde resin has received more and more attention. This paper mainly reviews two main methods of toughening of small molecules and toughening of polymers. The toughening of small molecules includes toughening of isocyanurate, toughening of glycols, toughening of dialdehydes, toughening of amines,and varieties of small molecules synergistic toughening. Polymer toughening includes polyhydric alcohol toughening and polyurethane toughening. In addition, several other methods have been introduced, such as biomass toughening, silane toughening. At the same time,the toughening mechanism of the above method is also described.关键词：Melamine formaldehyde resin;Toughening;Mechanism
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发布时间：2022-09-05 - 摘要：The molecular weight and distribution of natural rubber (SCRWF) were changed by mechanical shearing force. Gel permeation chromatography was used to test and demonstrate that the molecular weight and molecular weight distribution of SCRWF changed apparently after treatment. The plastic properties of plasticity initial values (P0),plastic retention (PRI),Mooney viscosity and stress relaxation time of different rubber samples were compared and analyzed. The thermal stability, mechanical properties and processing properties of vulcanized rubber were analyzed. The results show that the molecular weight of natural rubber decreases with the increase of mechanical shearing force, and its single peak trend is obvious. The quality of the raw rubber and the thermal stability is greatly affected by mechanical shearing force, and the mechanical properties of the vulcanized rubber are degraded with the increase of mechanical shearing force. Rubber processing analyzer (RPA) analysis shows that the loss factor (tanδ)of the samples increases linearly and the elastic modulus (G') decreases linearly with the increase of strain in the strain sweep,the loss factor (tanδ) of the samples decreases linearly and the elastic modulus (G') increases linearly with the increase of frequency.关键词：Natural rubber;Mechanical shear force;Relative molecular mass;Performance
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发布时间：2022-09-05 - 摘要：Hydrotalcite was modified by ultrasonicandion exchange method was added to isotaticpolypropylene (PP)materialssubsequently. X-ray diffraction spectra (XRD),Fourier transform infrared spectroscopy (ATIR),differential scanning calorimetry (DSC), polarized light microscopy (POM),scanning electron microscopy and other methods were used to characterize the effect of hydrotalcite on the structure of isotaticpolypropyleneby ultrasonicandion exchange method. These results indicated that the intercalation rate of modified groups can be promoted and increased, the dispersibilityofhydrotalcite in isotaticpolypropylenecan be improved by ultrasonic ion exchange method modified whichplays a distinct heterogeneous nucleation effecton isotaticPP, and the toughness of polypropylene material was simultaneously enhance by the refined grain.关键词：Ultrasonic modification;Hydrotalcite;Polypropylene;Enhanced toughening
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发布时间：2022-09-05 - 摘要：Two different stereoregular polylactides,poly(L-lactide) (PLLA) and poly (D-lactide) (PDLA) were synthesized using water as co-initiator. The double melting behavior of PLLA/PDLA stereocomplex crystal (Sc-crystal)was studied with DSC and in situ X-ray measurements. The oscillation phenomenon of melting peak area and melting point was discovered and investigated with the increase of isothermal time at 180℃. Through DSC and situ X-ray measurements, it is found that driving force of the oscillation in melting peak area is the instability of the massive isomers in the PLLA/PDLA Sc-crystal, which comes from the adjacent folding mechanism of crystal growth.关键词：PLLA/PDLA;Stereocomplex crystal;Oscillation behavior;Lamellae;Crystal growth
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发布时间：2022-09-05 - 摘要：The priority was given to developing undergraduate education,in order to lay a good foundation for the cultivation of applied innovative talents and graduate education with Chinese characteristics for a new era. Inspiring interest in learning, improving self-learning ability, possessing innovative genes, mastering high-end and new technology,and keeping in line with international standards are the keys to the cultivation of undergraduate talents in Colleges and universities. In this paper,based on my 10-year teaching experience in polymer materials and engineering, the innovative practical experiences of teaching mode about special English, were introduced in detail, which include curriculum content adjustment, school leaders' example power, internet plus technology support, and students' self-designed final exam questions,and so on. The results showed that with innovating the content and mode of course teaching, the students' ability and enthusiasm of independent learning were effectively stimulated, and the ability of professional English understanding and application were also significantly improved.关键词：Polymer materials and engineering;Special English;Teaching mode innovation
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发布时间：2022-09-05 - 摘要：The mixed teaching based on information network teaching platform, has gradually become a popular trend with the development of Internet technology. The combination of online and offline teaching was introduced into the teaching activities of Polymer Chemistry through the learning platform named as "Chaoxing Xuexitong". The BOPPPS teaching mode with the flipping classroom as the core was successfully constructed. The application effect comparison experiment found that the final score of the observation group (Class 1) was significantly better than that of the control group(Class 2),and the online self-learning ability of the observation group was gradually enhanced. The results show that implementing mixed teaching is conducive to improving learning efficiency. The questionnaire also shows that students have high satisfaction and recognition for mixed teaching.关键词：Mixed teaching;BOPPPS;Polymer chemistry course;Practice
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发布时间：2022-09-05 - 摘要：There are many problems existing in the current curriculum evaluation system, such as summary evaluation, neglect of the learning process,mainly inspecting memory in final examination and perfunctory homework. The course evaluation system is designed based on the key concept of engineering education accreditation. It includes three main measures: organizing final examination according to the guidance of "outcome-based education",designing homework around "student-centered" and introducing formative evaluation to achieve "continuous improvement" effect. The new evaluation system has been put into practice in the Polymer Physics course. The evaluation results and questionnaire survey of students show that the reform of the evaluation system has achieved good results.关键词：Engineering education accreditation;Course evaluation system;Polymer physics;Course assessment
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发布时间：2022-09-05 - 摘要：Case teaching is an important part of the professional master's training, and a key link to cultivate the engineering practice ability and innovation ability of graduate students. This paper expounded the significance of case teaching (including standardization, inspiration, interactivity, content relevance and application), and summarized and combed,then put forward the importance of case teaching and the construction method of teaching case for polymer professional master's course. In comparison with the previous professional master's degree course teaching mode, proposed the case teaching mode and some suggestions on the guarantee of case teaching to prepare for the next putted forward case library construction. It would promote the case teaching of professional master's course for our university in to a higher level of development.关键词：Polymer;Case construction;Teaching reform
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发布时间：2022-09-05 - 摘要：To eliminate the fragmentary feelings of students in the study of polymer physics experiment,the integrated design of experiments were proposed. Two modules including the experiments about "chain structures and condensed state structures",and "mobility, crystallization structures and mechanical behaviors" were taking as examples. In these experiments, the same samples were used in the different experiments. At the same time,the theory learned in "old" experiment was used to design the "new" experiment conditions. Therefore, the integrated design of experiment contents were realized. In addition, the existed problems were also analyzed.关键词：Polymer Physics Experiment;Experiment contents;Integrated design
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发布时间：2022-09-05 - 摘要：According to the outcome-based education (OBE) concept, training engineering and technical personnel has posed a new challenge to the revision and improvement of personnel training objectives. This paper constructs a dual cycle training objective demonstration mechanism involving industry experts, enterprises and graduate representatives, and puts forward a training objective formulation procedure that considers both external and internal needs.关键词：Training objectives;Outcome-based education;Mechanism;Procedure
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发布时间：2022-09-05 - 摘要：High density polyethylene (HDPE) synthesis provides a new coordination polymerization mechanism for polymer chemistry. Ziegler was regarded as the first person to synthesize HDPE in 1953,but the historical truth is that it was not. In this paper, based on the historical facts,we discussed who first synthesized HDPE and investigated synthesis technology of HDPE described in the existing polymer chemistry textbooks at home and abroad. It was found that most textbooks did not accurately record the real situation and ignored the contributions of others (especially Hogan and Banks, etc.) to synthesis of HDPE. Finally, the history of science and technology,which was discussed in polymer chemistry course,can promote students' understanding of basic concepts,cultivate innovative ideas and stimulate their learning enthusiasm.关键词：High density polyethylene;Science and technology history;Polymer chemistry;Course teaching
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发布时间：2022-09-05
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