最新刊期
卷 33 ， 期 5 ， 2020
- 摘要：Group 4 non-metallocene catalyst is an important type of catalyst for olefin polymerization. It not only possesses advantages of high catalytic activity and wide scope of comonomers, but also can obtain poly-olefins with controllable structure. Besides, the synthesis and cost of this type of catalyst are easier and lower compared with metallocene catalyst. These advantages help group 4 non-metallocene catalyst enriching the catalyst structure and developing new polyolefin products. The research process of group 4 non-metallocene catalyst in recent ten years has been reviewed according to the structure of ligands. The structure characteristics and catalytic performance in olefin homo- and copolymerization of this kind of catalyst has been discussed, focusing on the electronic and steric effect within ligands on the catalytic activity of complexes and properties of resultant polyolefins. Finally, some suggestions on the future development of the related fields are put forward.关键词：Group 4 metal;Non-metallocene catalyst;Olefin polymerization;Dentate ligand
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发布时间：2022-08-31 - 摘要：Injectable hydrogel has attracted much attention in the field of biomedicine due to its unique properties. Chitosan is the only cationic polysaccharide found in nature, which has the advantages of abundant content, low price, good biocompatibility and biodegradability, and is often used to prepare injectable hydrogel. In recent years, with the further development of research, injectable chitosan hydrogels with excellent properties were springing up by using various chemical or physical modification and functionalization methods, introducing various biological functional molecules or using various cross-linking methods. Their application scope has been expanding and they have played an increasingly important role in practical applications. In this article, the common preparation methods of injectable chitosan hydrogel with chemical crosslinking and physical crosslinking were introduced. The applications in drug carrier, gene vector, cell scaffold and wound repair were reviewed, and the existing problems and development trends were analyzed and prospected, which provided guidance and reference for the further development of injectable chitosan hydrogels.关键词：Chitosan;Hydrogel;Injectable
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发布时间：2022-08-31 - 摘要：The physical mechanical properties and dynamic mechanical properties of NBR and BNBR during thermaloxidative aging were compared,The effects of molecular structure on thermal-oxidative aging and dynamic mechanical properties were discussed. The results showed that the physical mechanical properties of NBR and BNBR were similar,and BNBR exhibited better mechanical properties after thermal oxidative aging test. In the dynamic mechanical properties test, the polarity of NBR is stronger than BNBR,the interaction force is greater,the rotation of single bond is more difficult,and the flexibility of chain is worse. At the same time,the BNBR has flexibility. The dynamic mechanical properties of BNBR at low temperature are better than that of NBR due to these two factors. The degree of crosslinking of the NBR and BNBR is further improved after thermal aging resulting in an increase in the shear modulus. The larger loss factor of NBR is due to the fact that the NBR has a more polar side nitrile group, The internal friction is further increased and the loss factor is further improved after thermal aging.关键词：BNBR;Glass transition temperature;Thermo-oxidative aging;Dynamic mechanical properties
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发布时间：2022-08-31 - 摘要：DOPO-based aluminum phosphinate, named as DOPO-Al, was synthesized from 10-hydroxy-9-oxa-10- phosphorphenanthrene-10-oxide (DOPO-OH) and aluminum chloride hexahydrate. Its structure was characterized by the infrared spectrum, scanning electron microscope, energy spectrum, phosphorus nuclear magnetic resonance spectrum and thermogravimetry. The flame-retardant epoxy resin based on DOPO-Al was prepared, and it flame-retardant and thermal properties were analyzed using limiting oxygen index (LOI), cone calorimetry, thermogravimetry and differential scanning calorimetry. The results showed that DOPO-Al was a high-temperature flame retardant, and its initial thermal decomposition temperature (T5% ) was as high as 595.5℃. The flame-retardant property and heat resistance of epoxy resin were improved by incorporation of DOPO-Al. When 7.5% (wt) DOPO-Al was introduced into the epoxy resin, the LOI value of epoxy resin was increased from 24.1% to 31.3%, and during the combustion, its peak heat release rate, average heat release rate, total heat release, total smoke release and total smoke production were all reduced, and the increase rate of the residue was up to 135%. The analysis of carbon layer suggested that DOPO-Al existed the condensed-phase flameretardant mechanism. Its T5% and glass transition temperature were up to 368.9℃ and 161.8℃, respectively. The prepared flame-retardant epoxy resin had the good thermal properties.关键词：DOPO-Based aluminum phosphinate;Epoxy resin;Flame-retardant properties;Thermal properties;Flame-retardant mechanism
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发布时间：2022-08-31 - 摘要：PLA-g-BF grafting copolymer was prepared by alkali-treated modified bamboo fiber and lactic acid. PLA-g- BF grafts were compounded with chitosan(CS) and polyvinyl alcohol(PVA) as raw materials to prepare bamboo fiber composite hydrophilic membranes. The effects of mass concentration of chitosan solution and mass ratio of PLA-g-BF grafting copolymer/CS(PVA) solution on the structure, tensile strength, morphology, hydrophilicity, adhesion and degradability of the prepared bamboo fiber composite hydrophilic membrane were investigated. The results show that when the concentration of CS solution was 1∶40 (g/mL), the quality ratio of grafting copolymer/CS solution was 2∶40, the tensile strength of the film was 4.93 MPa, the contact angle was 72.9°, the hardness value was 2H, and was basically nondegradable. When the concentration of PVA solution was 7%, the quality ratio of grafting copolymer/PVA solution was also 2∶40, the tensile strength was 17.2 MPa, the contact angle was 53.2°, the hardness value was 5H and was degraded within 6 days.关键词：PLA-g-BF grafting copolymer;Polyvinyl alcohol;Chitosan;Hydrophilcity
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发布时间：2022-08-31 - 摘要：Mechanical performance test and aspect ratio measurement were performed on Pennisetum stalk, and X-ray diffraction pattern, infrared spectrum and thermogravimetric analysis were performed. 40 mesh, 60 mesh and 80 mesh Pennisetum stalk fibers were used as filling materials, and polypropylene (PP) was used as the matrix material. Three different sizes of Pennisetum/PP composites were prepared by compression molding. The prepared composites were measured for contact angle, water absorption and mechanical properties, and the microstructure of the tensile section of the composites was observed with a scanning electron microscope (SEM). The results showed that the stem cellulose type of Pennisetum was type I and the relative crystallinity was 44%; the 40-mesh, 60-mesh, and 80-mesh pennisetum/PP composites had 24-hour water absorption thickness expansion rates of 7.7%, 4.2% and 4.4% respectively; 40 mesh pennisetum/PP composite material has better combining interface and high mechanical properties, its tensile strength, flexural strength, flexural modulus, and impact strength are 10.47MPa, 15.98MPa, 1.9GPa, and 3.7kJ/m2, respectively. It was finally learned that 40-mesh Pennisetum/PP composite material has the best mechanical properties but strong water absorption; 60-mesh Pennisetum/PP composite material has good mechanical properties and certain water absorption resistance, and its comprehensive performance is the best.关键词：Hybrid pennisetum fiber;PP;Mechanical properties;Molding process
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发布时间：2022-08-31 - 摘要：The effects of untreated aramid pulp (UAP), surface chemical treated aramid pulp (TAP) and the amount of TAP on the static mechanical properties, tensile fatigue life and dynamic thermomechanical properties of NR were studied. The results show that the effect of TAP is better than UAP, a small amount of TAP can significantly improve the comprehensive mechanical properties of rubber, adding 1.5 phr can increase the tear strength of rubber by 59.7%, adding 0.5 phr can increase the 100% tensile fatigue life of rubber by 20.3%, adding 1.5 phr or 2 phr can increase the dynamic storage modulus of rubber above 0℃ by 50%~88.4%, and reduce the loss factor by 13.1%~26.0%.关键词：Aramid pulp;Natural rubber;Mechanical properties;Tensile fatigue;Dynamic hysteresis
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发布时间：2022-08-31 - 摘要：As for application-oriented undergraduate colleges and universities which pay special attention to the graduation practice and thesis, which is also the most important practical teaching after the theoretical course learning. In order to overcome the problems of disconnection between production and teaching, and the separation between universities and enterprises, resulting in which application-oriented talents are not good at analyzing and solving problems.Therefore, based on overseas and domestic research status, it had been proposed in the paper to perform the reform of integration of university-enterprise cooperation according to the existing problems of graduation practice and thesis, which the two teams of full-time teachers and technical experts carry it out together in the two main positions of schools and enterprises.At present, the reform has been implemented in the major of polymer materials and engineering of chizhou university, and achieved the initial results.关键词：Fusion of production and education;Applied;Graduation practice;Graduation thesis;Integration
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发布时间：2022-08-31 - 摘要：Under the key competencies, the instructional design of the section "Thermal stability of ideal mixing reactor" in the textbook of polymerization reaction engineering is taken as an example to explore the educational value in the teaching process of engineering. Through the analysis and discussion of the principle of thermal stability and the analysis of the examples of thermal stability in industry, the students are guided to understand the concept of principle with the scientific thinking of engineering. Driven by probing into problems, inquiry-based learning is carried out to cultivate students' awareness of engineering problems and practical application ability, and to implement the cultivation and development the key competencies of undergraduates in the course of teaching.关键词：Polymerization reaction engineering;Key competencies;Instructional design
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发布时间：2022-08-31 - 摘要：The internalization of knowledge is a process in which an individual digests and absorbs the received knowledge and convert it to discipline thought. The students' knowledge internalization and application ability can be trained by sorting out the main line of research, finding out the basic research methods and the interconnection of knowledge modules, building interchange knowledge system. Taking the teaching of "Polymerization Dynamics" as an example, the specific teaching design of the above ideas is introduced: The equal reactivity hypothesis as research principal line runs through the knowledge system of polymerization kinetics. Differential and integral are used as the basic methods of related calculation for chain polymerization and stepwise polymerization, respectively. Dynamic chain length is regarded as the bridge between the degree of polymerization and the rate of polymerization, and the reactivity ratio as the bridge of the composition, segment sequence of copolymers between copolymerization rate.关键词：Polymer chemistry;Polymerization kinetics;Equal reactivity hypothesis;Kinetic chain length;Reactivity ratio
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发布时间：2022-08-31 - 摘要：In the past two decades, due to the influence of major adjustments and state-owned corporate reforms, there are very few companies willing and capable of accepting students of the entire major to set up a system to conduct a onemonth graduation practice, making graduation practice a difficult point for many universities. In this paper, we discussed the exploration of the graduation practice course in recent years based on the model of "multiple-group in the same period" for the polymer material and engineering major of South China University of Technology, in which, the construction of undergraduate teaching practice base, appointments of off-campus tutor, management and evaluation of graduation practice were discussed in detail.关键词：Graduation practice;Reform on practice teaching;Engineering education accreditation
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发布时间：2022-08-31
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