最新刊期
卷 36 ， 期 2 ， 2023
- 摘要：Poly(3-hydroxybutyrate) (PHB) and poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) undergo an ageing process on storage at room temperature which renders them increasingly mechanical property deterioration, which has been attributed to the development of secondary crytallisation. The formation of β crystals by tensile induction can effectively inhibit the secondary crystallization and improve the mechanical properties. This paper reviews the β crystal structure of PHB and PHBV, and the formation and transformation mechanism of β crystal. The influence of β crystal structure on mechanical properties and the research progress of toughening mechanism are summarized emphatically. The relationship between β crystal structure and degradation properties was briefly reviewed. Finally, the gaps in the research of β crystal structure are analyzed.关键词：Poly(3-hydroxybutyrate);Poly(3-hydroxybutyrate-co-3-hydroxyvalerate);β Crystal;Mechanical property;Toughening mechanism
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发布时间：2022-12-29 - 摘要：As a water-soluble polymeric material based on a polysaccharide, carboxymethyl chitosan (CMCTs) has been widely used in the fields of medicine and industry in virtue of their excellent properties such as biocompatibility, biodegradability, moisturizing, hemostasis, antibacterial and absorbability. After being implanted, CMCTs could be degraded while involved in enzyme, oxygen, microbial, water and other suitable environments through absorption, metabolism and excretion. The rate of in vivo degradation mainly depends on the size, degree of deacetylation, degree of substitution and molecular weight of the sample. Exploring the degradation and metabolism behavior of CMCTs in vivo was essential for the quality control and clinical application of CMCTs. Up to now, the mechanism of the degradation and metabolism of CMCTs in organs in terms of its absorption, distribution, metabolism and excretion patterns in vivo is not well elucidated, which would limit its application in the field of biomaterials. Therefore, this review aims to summarize the degradation and metabolism behavior of CMCTs based biomaterials reported in recent years. The biological properties, degradation mode and metabolic process of CMCTs were reviewed. The in vivo distribution of metabolism and pathway of excretion during the degradation of CMCTs were interpreted. Meanwhile, the key factors, such as size of implants, degree of deacetylation, degree of substitution, molecular weight, degree of crosslinking and composition, which influence the degradation of CMCTs were also summarized. This work is expected to provide a reference for the research and development of CMCTs based biomaterials.关键词：Chitosan;Carboxymethyl chitosan;Absorbable implants;Degradation;Metabolism
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发布时间：2022-12-29 - 摘要：In recent years, natural polymer hydrogels have developed rapidly and have fully demonstrated their potential applications as drug delivery systems. Polysaccharide is a kind of multifunctional macromolecules, which is involved in many biological interactions that are vital to life. Due to their advantages like biocompatibility, biodegradability, wide source and low material cost, polysaccharides have good application prospect in drug delivery, wound healing and some other fields, and they are ideal materials for the preparation of drug loaded hydrogels. In this paper, the application progress of cellulose, chitosan, hyaluronic acid and sodium alginate as drug loaded hydrogel carriers was reviewed. The existing problems and future development directions in this field were also discussed.关键词：Biomaterials;Natural polymers;Polysaccharides;Hydrogels;Drug delivery
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发布时间：2022-12-29 - 摘要：In recent years, transition metal carbides and nitrides (MXenes), as a new type of two-dimensional materials, have attracted more and more attention due to their unique crystal and structural characteristics, especially in the fields of energy, catalysis and biomedicine. The unique crystal structure and surface properties of MXenes endow them with excellent electronic, optical, magnetic and other physical and chemical properties. Moreover, the large specific surface area and high photothermal conversion efficiency of MXenes make them widely used in the biomedical field, especially in tumor treatment. In this paper, the synthesis methods and photothermal properties of MXenes are introduced, as well as the applications and research progress of MXenes’ photothermal properties in cancer therapy. In addition, the potential challenges and prospects of MXenes in cancer therapy are proposed.关键词：Transition metal carbides and nitrides (MXenes);Two-dimensional materials;Photothermal properties;Cancer therapy
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发布时间：2022-12-29 - 摘要：Due to its excellent physical and chemical properties such as air tightness, heat aging resistance, and good damping, butyl rubber (IIR) is widely used in tires, shock absorption products, waterproof building materials, etc. In 2018, the China’s production capacity of butyl rubber ranked first in the world. However, the import volume is still very high because of some problems such as few brands and poor product performance. In this paper, research work on the fatigue properties of butyl rubber is reviewed. According to the mechanism of rubber fatigue, factors affecting the fatigue aging resistance and fatigue failure performance of butyl rubber, such as: raw rubber structure, formula composition, external environment, etc. are introduced. It provides reference for the molecular structure and application formula design of butyl rubber and helps the development of the butyl rubber industry.关键词：Butyl rubber;Fatigue;Aging;Lifetime
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发布时间：2022-12-29 - 摘要：Poly(butyleneadipate-co-terephthalate) (PBAT) is a biodegradable aliphatic aromatic linear copolyester. The foamed material based on PBAT has the characteristics of light weight, high porosity, good flexibility, high energy absorption and heat insulation, as well as excellent biodegradability and biocompatibility. Therefore, it has great application prospects in packaging, transportation, aerospace, biomedicine and other fields. Aiming at the shortcomings of low melt strength and narrow processing temperature window in the foaming process of PBAT, this paper introduces in detail the research on PBAT modification method and foaming technology in recent years, and elaborates the structural characteristics of PBAT foam material and its preparation method, focusing on the regulation of foaming performance via different modification methods. It is expected to provide a reference for the further research of PBAT foaming materials.关键词：PBAT;Biodegradation;Modification;Foaming;Foaming property
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发布时间：2022-12-29 - 摘要：Guar gum fracturing fluid is the most widely used working fluid in fracturing operation at present, but it has the problems of high dosage of guar gum, large residue and serious reservoir damage. Organic boron crosslinking agent is the main research direction of crosslinking agent of guar gum fracturing fluid system because of its excellent crosslinking performance, easy regulation of delayed crosslinking, complete gel breaking of fracturing fluid, reducing guar gum dosage and reducing reservoir damage caused by guar gum residue. This paper introduces the research progress of organic boron crosslinking agent in guar gum fracturing fluid system, discusses the crosslinking mechanism of organic boron crosslinking agent, focuses on the synthesis of organic boron crosslinking agent, and prospects the development direction. From the synthesis research, the organic boron crosslinking agent mainly has three methods: the composite preparation of various ligands, the preparation of long-chain multi head polar organic amine boron and the preparation of nano crosslinking agent, which has excellent performance in reducing the amount of guar gum and improving the sand carrying performance of fracturing fluid. In the future research, the key is to improve the crosslinking efficiency. The long-chain multi head polar structure is the main research direction. The optimization of organic ligands and reaction design will be the core problems.关键词：Guar gum fracturing fluid;Organic boron crosslinking agent;Crosslinking mechanism;Synthesis;Nanostructures
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发布时间：2022-12-29 - 摘要：This paper explores the feasibility of preparing different micro-structures of desulfurization waste rubber powder (WRP) by using mechanochemical and thermochemical, and its effect on the properties of modified asphalt. The results show that different micro-structures of desulfurization WRP can be prepared by the two methods. Due to the different desulfurization mechanism, the micro morphology of desulfurization WRP prepared by the two methods is different. With increasing reaction temperature, the crosslink density and sulfur content of desulfurization WRP decrease, and the oxygen content increases. The content and PDI of sol component in the desulfurization WRP increase, and the Mn decreases. With the reaction temperature increases, the processing workability of desulfurized WRP modified asphalt is enhanced with the reduced in its high-temperature performance and resilience. The storage stability of desulfurized WRP modified asphalt is weakened first and then enhanced. The low-temperature performance of mechanochemical desulfurized WRP modified asphalt is reduced first and then increased, while it is reduced for thermochemical desulfurized WRP modified asphalt. With the particle size of WRP decreases, the crosslink density and sulfur content of thermochemical desulfurized WRP decrease, and the oxygen content increases. The content and PDI of sol component increase, and the Mn decreases. It is reversed for mechanochemical desulfurized WRP. With the particle size of WRP decreases, the storage stability of desulfurization WRP modified asphalt was enhanced. The high and low temperature properties and resilience of mechanochemical desulfurized WRP modified asphalt are enhanced, while these are reversed for thermochemical desulfurized WRP modified asphalt.关键词：Mechanochemical desulfurization;Thermochemical desulfurization;Desulfurization waste rubber powder;Desulfurization waste rubber powder modified asphalt;Pavement performance
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发布时间：2022-12-29 - 摘要：In the industrial production of polyglycolide (PGA) perpared via ring-opening polymerization (ROP) of glycolide (GL), the catalysts used play a significant role in controlling the polymerization reaction and the molecular weights of the resultant PGA products. In this study of ring-opening polymerization of glycolide using various metal compound catalysts and hydroxyl initiators, the effects of different metal centers (tin, aluminum, zinc and zirconium) and different ligand structures (alkoxy, carboxylate, acetylacetonate and halogen) on the ring-opening polymerization reaction of glycolide and the coloring issues of the resulting polymer were investigated. It was found that the metal used dominantly determined its catalytic activity and the color of the PGA products obtained, while the anionic ligands showed only limited influence. Among the catalyst systems studied, the tin metal center catalysts exhibited the highest catalytic activity, enabling rapid and complete conversion of the GL monomer even at very low concentration. Moreover, the PGA products obtained from the tin or zirconium metal center catalysts possessed the most desirable color attributes.关键词：Polyglycolide;Metal compound catalysts;Ring-opening polymerization;Product color
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发布时间：2022-12-29 - 摘要：Photocatalytic degradation of organic dyes is considered as an ideal strategy to solve the dye pollution problem. In this study, melamine, graphene oxide (GO), and hollow ZnFe2O4 were used as precursors to construct a 3D ZnFe2O4/g-C3N4/rGO skeleton by heat treatment. Then, the silver (Ag) as a co-catalyst was immobilized on the ZnFe2O4/g-C3N4/rGO skeleton to prepare the 3D ZnFe2O4/g-C3N4/rGO@Ag composite photocatalyst. The structure, morphology, and chemical composition of the obtained materials were characterized with Fourier transform infrared (FT-IR),X-ray diffraction patterns (XRD)and scanning electron microscopy (SEM). The experimental results showed that the degradation activity of ZnFe2O4/g-C3N4/rGO@Ag composite catalyst for Rhodamine B (RhB) was significantly enhanced, and the degradation rate of RhB reached 97% within 20 min under visible light irradiation, which was twice as high as that of ZnFe2O4/g-C3N4/rGO. In addition, the introduction of ZnFe2O4 endowed the ZnFe2O4 @g-C3N4/GO@Ag composite with good magnetic properties, which can be easily separated from the reaction system under the action of an external magnetic field. After repeated use for 5 times, the photocatalytic activity did not decrease significantly, indicating that the catalytic material has excellent stability and recyclability.关键词：ZnFe2O4;g-C3N4;Graphene oxide;Photodegradation;Rhodamine B
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发布时间：2022-12-29 - 摘要：Poly(methyl methacrylate) (PMMA) was prepared through free-radical polymerization using BPO as the initiator. Size-exclusion chromatography and several NMR analysis methods, including 1H-NMR, 13CNMR, DEPT135-NMR, heteronuclear multiple-bond correlation, and heteronuclear single quantum correlation NMR were used to analyze the structure of the end vinyl group from disproportionation termination to disclose the mechanism. 1H-NMR measurement indicates that there are two NMR proton resonances at δ=6.20 and 5.47 ppm, the other NMR methods confirm that there is only one type of vinyl group formed from disproportionation and the transferred hydrogen radical comes from the side methyl group at the chain end. The polymerization behavior of the end vinyl group in PMMA provides further evidence to support the conclusion from NMR measurements. In addition, there is also marked primary termination besides disproportionation in the polymerization.关键词：Methyl methacrylate;Free-radical polymerization;Disproportionation
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发布时间：2022-12-29 - 摘要：The integration of teaching and scientific research is the development direction of teaching reform. Here, a case of teaching promoting scientific research is presented. An innovative idea has been extracted from thinking and systematic digest of teaching contents. Polymer crystallization is one of the core contents of the "Polymer Physics" course. Therein, it is widely considered that molecular weight shows a great influence on polymer crystallization process and aggregated structure. First, fractional segregation is observed during crystallization based on molecular weight. Second, different molecular weights lead to different aggregation structures. Hence, it is speculated that there would be a distribution of aggregation structure in polymers due to the polydispersity of molecular weight. The speculation promotes the discovery of a novel nested spherulite texture and provides key guidance for the study of its formation mechanism. By showing the feasibility and superiority of the teaching promoting scientific research, this paper provides an example of the integration of teaching and scientific research.关键词：Polymer physics;Polymer crystallization;Integration of teaching and scientific research
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发布时间：2022-12-29 - 摘要：Face to the demand of the engineering education accreditation, the evaluation method of the major’s courses should be refined and revised. According the 8 indexes of requirement for graduation, a comprehensive scoring method named S.M.A.R.T is constructed. In this evaluation system, we aim to strengthen the process evaluation, make the process evaluation more practicable and design a scoring algorithm. This system will analyze and evaluate students' learning process data with a proper weight, implement the implementation basis and calculation method of process evaluation, comprehensively reflecting students' participation process and learning effect of this course. This system will effectively evaluate the students’ study efficiency and the objective achievement scale of requirement for graduation in this course. Combined with the online learning platform and offline courses, collect complete student learning data, and realize the efficient statistics and analysis of students' corresponding learning data through Excel, so as to automatically process students' learning data in batch through software.关键词：Course evaluation;Engineering Education Accreditation;Comprehensive scoring method;Objective achievement scale;MOOC
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发布时间：2022-12-29 - 摘要：Polymer processing rheology is a comprehensive theoretical and practical course that is based on polymer physics and serves as a foundation for the polymer molding process and the design of plastic molding die. It acts as a bridge between undergraduate polymer materials and engineering courses. In response to the course’s current teaching status, in this paper, the engineering education professional certification concept is as a guide and combined with our school's professional characteristics, the idea of curriculum reform is proposed, and the reform of teaching content, experiment teaching and teaching methods are also discussed. A more reasonable and perfect course teaching system has been developed, and the reformed teaching content structure has been further optimized. The online micro-experiment course is designed to compensate for the lack of rheology experimental teaching, and the teaching method is more diversified with dynamic and static combinations. Students' theoretical knowledge of rheology has been strengthened via reform and practice, their ability to analyze and solve problems utilizing rheological knowledge has been enhanced, and the quality of course teaching has been significantly improved.关键词：Engineering education professional certification;Polymer rheology;Undergraduate teaching;Microexperiment course;Teaching reform
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发布时间：2022-12-29 - 摘要：The core quality elements are organically combined with the teaching of Polymer Chemistry to enable students to learn professional knowledge and master professional skills. At the same time, the character and key ability to meet the needs of social development are formed. In this paper, taking "three dimensional polycondensation and gel" as an example, the classroom teaching is designed around the knowledge and ability training objectives of this section. Through analogy and association, analysis and comparison, perception and experience, it integrates the "humanistic quality, scientific research spirit, responsibility" and other literacy elements that are consistent with professional knowledge. At the same time, the implementation effect of the integration of core literacy and polymer chemistry teaching was analyzed, and how to cultivate core literacy in the curriculum of teaching was discussed and reflected.关键词：Polymer chemistry;Core literacy;Polycondensation and gelation;Teaching design
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发布时间：2022-12-29
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