最新刊期
卷 26 ， 期 2 ， 2013
- 摘要：In this work the features and influences of entropy in the lytropic condensation of macromolecules were discussed. In an irregular condensation, in that the amorphous polymers were generated, just the entropy increase causes a decrease of Helmholtz’s free energy, and so that the condensation process can go on. In a regular condensation, in that the crystalline polymers were generated, the change of entropy induces very complex effects for polymer crystallization. Due to the competition between entropy and internal energy, a folded chain lamellae with loose structure was prior generated in the lytropic crystal process;and a two phases structure with crystal and amorphous region was generated in the crystal process from polymer melts. Two different change’s ways of entropy were distinguished: a jump change of entropy can induce a thermodynamic phase transition-entropy induced phase transition;but a gradual change of entropy can change only the mechanical property or initiate a mechanical state transition of polymers.关键词：Macromolecules;Lytropic condensation;Change of entropy;Entropy induced phase transition
- 2
- |
- 10
- |
- 2
发布时间：2022-09-18 - 摘要：The supercritical anti-solvent (SAS) technology, as a novel technology for the preparation of micro- and nano-particles, has been widely applied in variety of different fields including: superconductors, color matter, polymers, explosives and pharmaceutical compounds. The review discusses the process and how to simultaneously adjust and control the particle size and its distribution, morphology, crystallinity and so on with this facile approach. And the effects of polymer structure on preparation of fine particles is illustrated. In the present review, the application of SAS in the preparation of composite particles with the polymers as the continuous solid phase or coating solid phase were also focused on. The particle formation mechanism in the SAS process was summarized. The problems in these areas are presented, and the future development are proposed as well.关键词：Supercritical fluid;Anti-solvent;Composite particles;The regulation and control of the process
- 2
- |
- 10
- |
- 1
发布时间：2022-09-18 - 摘要：The interface has a particularly important role in fiber-reinforced composite material. It is not only a link between the reinforced phase and the matrix phase, but also a transfer bridge of stress and other information. Good interfacial adhesion makes the properties of fibers into full play, and improves mechanical properties of fiber-reinforced composite materials. It’s important to assess interface adhesion and interface microstructure of fiber reinforced composites. The paper summarizes characterizing methods of the interfacial shear strength in fiber reinforced composites, including single fiber pulling-out test, fiber fragmentation and fiber pushing-in test and etc. In addition, the paper particularly emphasizes on characterization of the interfacial adhesion and microstructure in fiber reinforced composites by using Raman spectrum.关键词：Fiber reinforced composites;Interfacial shear strength;Interface microstructure;Raman spectrum
- 2
- |
- 13
- |
- 9
发布时间：2022-09-18 - 摘要：Block copolymer is becoming one of the most promising candidates for proton exchange membranes applications owing to two distinguish advantages. Microphase separation of block copolymers easily occur to form proton conductivity channel due to thermodynamic incompatibility between their own blocks, and an abundant topologies of block copolymers could be synthesized through controlled living polymerization. This review briefly introduce the microphase separation thermodynamics theories of block copolymers, and analyze the various factors influencing the microphase separation of block copolymers, including sulfonation degree, copolymers topologies, block length, block sequence distribution, micro-aggregated structure and the surface morphology. Finally, the future research tendency in these fields is also prospected.关键词：Block copolymers;Microphase separation;Proton exchange membrane;Proton conduction
- 4
- |
- 12
- |
- 1
发布时间：2022-09-18 - 摘要：Wholly aromatic polymers exhibit excellent heat resistance and outstanding mechanical properties. As high-performance specialty engineering materials, their application continues to extend. However, due to the stack of large moiety of aromatic units, these aromatic polymers are usually insoluble in common organic solvents and infusible leading to poor processability as well as limitation on extensive applications. To overcome such a difficulty, much effort has been achieved in designing and synthesizing ether unit containing aromatic dicarboxylic acid, dianhydride and diamine monomers to produce soluble and processable aromatic polymers. In this article, the progress of synthesizing aromatic dicarboxylic acid, dianhydride and diamine monomers from bisphenol precursors by Williamson nucleophilic substitution reaction are summarized. Meanwhile, developments in the syntheses of corresponding high-performance aromatic polymers are presented. Finally, the future developing trend in this field is prospected.关键词：Aromatic polymer;Nucleophilic substitution;Bisphenol;Aryl ether
- 2
- |
- 9
- |
- 1
发布时间：2022-09-18 - 摘要：Polymer materials has a wide range of application value in pharmaceutic preparation pharmaceutical processes.The research and development of new pharmaceutical manufacturing is intimately related to the property of pharmaceutic polymer materials,especially amphiphilic high molecular materials are widely used in the research and development of new pharmaceutical manufacturing and they are also the research hotspots, such as polymeric micelles.The common hydrophilic segments of amphiphilic pharmaceutic polymer materials are summarized in this paper, on the basis of size of hydrophilic segments, hydrophilic modification of pharmaceutic polymer materials is divided three classes——water-soluble micromolecules modified, water-soluble polymers modified and water-soluble high molecular materials modified.in order to give references to colleagues and discuss, the characteristics of the modifier and modified products and modification methods from the hydrophilic modification of pharmaceutic polymer materials and the advantages and disadvantages of modifier are reviewed as comprehensive as possible in this paper, at the same time, it is discussed and prospected.关键词：Pharmaceutic polymer materials;Water-soluble polymers;Hydrophilic modification;Micelles
- 2
- |
- 10
- |
- 0
发布时间：2022-09-18 - 摘要：This research investigated the metal-coating method of carbon fibers (CF). Nickel-coated carbon fibers (NiCF) were fabricated by electroless plating, and ABS composites filled with CF and NiCF were prepared by kneading method. The influence of CF and NiCF contents on the electrical conductivity and electromagnetic shielding effectiveness of ABS based composites was studied. The results indicated that an even and intact nickel coating could be plated on carbon fibers under a suiltable pretreatment and plating conditions, and the electrical resistivity of CF decreased 2 orders of magnitude when the plating time was 5min. The electrical resistivity of composites decreased with CF and NiCF content increasing. The corresponding electromagnetic shielding effectiveness of composites increased as filler content increasing, and the value reached 51 dB for the composite containing 25wt% (13.3vol%) NiCF.关键词：Carbon fiber;Electroless nickel plating;Electromagnetic interference;ABS
- 2
- |
- 10
- |
- 1
发布时间：2022-09-18 - 摘要：PAN films were prepared by either isothermal heating or double diffusion to expel the solvent in the polymer solution. We used X-ray diffraction, FT-IR, UV spectrometer to investigate the effect of the polarity of the precipitant on the crystallization of PAN in the solutions. The results show that in the process of solidification, the effect of precipitant on PAN crystallization is achieved by the close association between precipitant and cyanogroup. The stronger polarity precipitants hold, the stronger association they form. Therefore, polymer chains are restricted more tightly to block the crystallization of PAN polymers. Addition of electrolyte can help to weaken the association and to improve PAN crystallinity.关键词：PAN films;Crystallinity;Polarity;Expelling the solvent
- 3
- |
- 9
- |
- 2
发布时间：2022-09-18 - 摘要：Chitosan modified attapulgite is used as the flocculant for precipitating Chlorella vulgaris with adding CaCl2 as the coagulant. For Chlorella vulgaris, the optimal flocculation conditions showed as following: flocculant is 0.4g/L, the ratio of chitosan and attapulgite in flocculant is 1∶12, CaCl2 coagulant dosage is 0.2g/L, and pH of the solution is 9.0. Under the best conditions, the flocculation rate of Chlorella vulgaris can reach up to 95%. The scanning electron micrographs and the BET specific surface area data(BET) of flocculant show that the modified attapulgite adsorbs and connects with chitosan to a certain degree of spatial structure, which effectively increases the surface area of flocculant and is conducive to the adsorption of Chlorella.The raw materials used in this article could have the advantages of low cost, safety and low impact on the environment. And the high efficiency of flocculation can obtain with sample method of preparing the flocculant, which can be widely used for the harvest of microalgae in industrial production.关键词：Chlorella;Chitosan;Attapulgite;Coagulant;Flocculation
- 2
- |
- 9
- |
- 2
发布时间：2022-09-18 - 摘要：In this paper, poly(acrylamido-azobenzene) (PAAAB) was synthesized by reversible addition-fragmentation chain transfer (RAFT) polymerization of acrylamido-azobenzene (AAAB) in DMF solvent, using benzyl dithiobenzoate (BDTB) as RAFT agent and α,α'-azobis(isobutyronitrile) (AIBN) as initiator. The effects of reaction temperature and the concentration of BDTB on the polymerization of AAAB were investigated. The structures of BDTB and PAAAB were characterized by FT-IR, 1H-NMR, and GPC. The results showed that the kinetic curves of the polymerization reveal good linear relationship, and the molecular weight distribution was narrower;when the ratio of [BDTB] to [AIBN] increases, the polymerization rate and molecular weight of PAAAB were decreased and the molecular weight distribution becomes narrow.关键词：Acrylamido-azobenzene(AAAB);Benzyl dithiobenzoate(BDTB);RAFT polymerization;Synthesis
- 2
- |
- 10
- |
- 0
发布时间：2022-09-18 - 摘要：Drug delivery system (DDS) mainly includes two parts: drug and carrier. Microsphere which is made from suitable polymer materials is a new drug carrier with a more extensive application. This paper studies the preparation method of polysucrose microspheres and the feasibility of drug control-released carrier. Taking Span-80 as surfactant, epichlorohydrin as cross linker, aqueous solution of Ficoll-400 as water phase (W), chlorobenzene as the oil phase (O), the experiment has made a series of spherical polysucrose microspheres within 100um particle size by adopting the method of inverse suspension polymerization. Taking bovine serum albumen ( BSA) as model drug, it studies the function of control-released when it is the drug carrier. Release experiment shows that the maximum release rate is 95% and appropriately increasing the degree of cross linking is helpful for BSA slow release.关键词：Polysucrose microsphere;Control-released carrier;Research
- 2
- |
- 10
- |
- 0
发布时间：2022-09-18 - 摘要：Ploy(glycolic) acid (PGA), as a biodegradable material, was synthesized via melt/solid polycondensation with glycolic as starting material. A general procedure for preparation was as follows: At first, oligomer was prepared by melt-polycondensation of glycolic acid (GA) at 190℃, and then it was subjected to solid-state polycondensation at the same temperature to increase the molecular weight. PGA product was characterized by IR, DSC and X-ray diffractometry. By examining the effect of different catalysts, catalyst amount, melting or not, reaction temperature and time on the polymerization, optimum conditions of the PGA synthesis was obtained as follows:reaction temperature 190℃,0.4% zinc acetate dihydrate and p-toluene sulfonic acid of same Molar as catalyst, melting one time after 40 hours solid polycondensation, then continuous 60 hours solid polycondensation after being crashed into pieces.关键词：Biodegradable materials;Ploy(glycolic) acid;Solid polycondensation;Melt polycondensation
- 5
- |
- 11
- |
- 1
发布时间：2022-09-18 - 摘要：In situ X-Ray measurements can record the structure change of samples at any time, which is helpful to clarify the relationship between structure and property, so they are the most widely used techniques and provide better insights into designing processing parameters and material structure. It introduces the common equipments combined with X-Ray to study the microstructure evolution, enumerating some important achievements and prospecting new applications in that aspect.关键词：X-ray;In-situ measurements;Microstructure evolution
- 3
- |
- 10
- |
- 0
发布时间：2022-09-18 - 摘要：Polylactide(PLA) is the completely biodegradable materials, widely used in packaging, textile, biomedical fields, etc. But it has some shortcomings,such as brittleness, the higher price, hydrophobicity, development of PLA is limited. Polylactide blending modification has become a hotspot. According to the biodegradable properties of the other composition in the blends, polylactide blends are divided into two varieties of completely biodegradable blends and partially biodegradable blends.This paper described the research of completely biodegradable polylactide blend system in recent years, mainly introduced PLA/starch, PLA/natural fiber , and briefly introduced the other PLA blending composite materials with natural polymer(PLA/chitin, PLA/protein) and PLA blending composite materials with synthetic polymer(PCL, PEO, etc).关键词：Polylactide;Blend;Biodegradation
- 6
- |
- 19
- |
- 7
发布时间：2022-09-18 - 摘要：The course of Polymer Physics is an important basic course of Polymer Materials and related major. It is an extremely abstract and theoretical course with abundant contents which undergoes unceasing development and improvement. Besides that, the lack of excellent quality of graduate students and teaching resources make the course teaching of Polymer Physics facing up with great challenge. Based on the characteristics of course content and requirement of higher education reform, the teaching reform and practice are explored in the aspects such as teaching contents, teaching methods and teaching means to obtain better teaching effect. The results show that condensing the main clue of teaching and arranging the contents for each chapter of Polymer Physics according to it are very significant to highlight the core contents, avoid the repetition of the same contents and reduce the time for class. The introduction of analysis of practical cases and seminar teaching model to the class is very helpful for the students to not only understand the core contents well by applying polymer phycics theory to the practices but also be able to follow the advances in Polymer Science. Moreover, the application of various teaching means such as multimedia courseware, video and flash, and so on, can greatly improve the teaching effect during the limited time for class.关键词：Polymer physics;Graduate student teaching;Teaching reform;Practice
- 3
- |
- 14
- |
- 0
发布时间：2022-09-18 - 摘要：Polymer chemistry teaching is a fundamental work for establishing macromolecular concepts. In the process of polymer chemistry teaching carried out for engineering professionals, by reversely dissecting the formation of scientific laws and theories, abstract concepts, important phenomena and difficult theories were destructed and analyzed in different levels of visualization into imaging representations, appropriate metaphors and vivid instances, with which a set of design ideas and concrete methods for visualized teaching were established. Starting form this idea, with figurative language as an adjunct and appropriate multimedia tools as carriers, the effects of classroom teaching and the teaching qualities are expected to be promoted by combining with the unique logical polymer chemistry theories.关键词：Visualized teaching;Polymer chemistry;Design and practice
- 2
- |
- 9
- |
- 0
发布时间：2022-09-18
- Technical support is provided by Beijing Founder electronics co., LTD 京ICP备09064830号-19
京公网安备11010802024621 - It is recommended to read the content of this site in Chrome&IE9+. Please switch to extreme mode in browser 360.
- Cookies We use cookies to help provide and enhance our service and tailor content. By continuing, you agree to the use of cookies.
0