最新刊期
卷 32 ， 期 4 ， 2019
- 摘要：The technology of stable isotope labeling has a wide range of applications in chemical analysis. As polymer materials have become more and more widely used in various fields, more and more research has been conducted on the serviceability, environmental degradation performance,metabolism in vivo,and functionalization of polymer materials of polymer materials. The demand for molecular materials is increasing. However, there are few varieties of stable isotope-labeled macromolecules, few studies, and applications are difficult to meet. In this paper, the status quo of label synthesis and application of stable isotope-labeled macromolecules at home and abroad is reviewed from the aspects of (selection, synthesis method and application research of macromolecule materials),and the future research directions and application prospects in this field are prospected.关键词：Stable isotopes;Polymers;Applications;Advances
- 9
- |
- 12
- |
- 1
发布时间：2022-09-02 - 摘要：The technical difficulties in preparing high solid content waterborne polyurethane (WPU) with low viscosity have been discussed in this article. The phase inversion principle of WPU prepolymers was expounded, and the influence of material characteristics and process conditions of prepolymer on phase inversion and phase inversion point were analyzed. From the perspective of hydration layer, the influence of the hydration layer thickness on the solid content of WPU was discussed. In addition, the influence of the size and space density of latex particles on high solid content WPU with low viscosity was discussed. Finally,the future research work of high solid content WPU with low viscosity was prospected.关键词：Waterborne polyurethane;High solid content;Low viscosity;Prospect
- 7
- |
- 11
- |
- 1
发布时间：2022-09-02 - 摘要：Molecular weight and molecular weight distribution are the most important and basic parameters that affect the processing and service properties of polymer materials. Therefore, Characterization of molecular weight and molecular weight distribution of polymer materials are the key to the analysis of their properties,and gel permeation chromatography is the most effective tool for the determination of molecular weight and molecular weight distribution of polymers. In this paper, the separation mechanism and molecular weight calibration of gel permeation chromatography are introduced. The application of gel permeation chromatography in characterization of polymer materials in recent years are reviewed, including the composition of copolymer,the degree of branched polymer,the low molecular content of polymer and the degradation of polymer. The future trend of gel permeation chromatography is also prospected.关键词：Gel permeation chromatography;Molecular weight;Molecular weight distribution;Application
- 7
- |
- 13
- |
- 3
发布时间：2022-09-02 - 摘要：High energy consumption and serious environmental pollution are the two main disadvantages for traditional synthetic fibers. Therefore, it is of great application prospect to develop new kinds of biodegradable fibers to prepare composite materials. Hemp fiber is a kind of natural cellulose fiber with high specific strength and modulus which is applied in polymer matrix composites have attracted a wide spread attention owing to its excellent advantages such as light weight, low price, environmental protection and renewability. The reinforced composites can be obtained via the addition of surface modified hemp fiber into polymer matrix. Thus,it is promising for hemp fiber to become a new reinforcement and replace the traditional synthetic fibers. In this paper, the structure and properties of hemp fiber and its surface modification methods were introduced. The latest research trends on the properties of hemp fiber composites are reviewed,and the further research prospects of hemp fiber composites are also discussed.关键词：Hemp fiber;Fiber modification;Polymer composites
- 8
- |
- 12
- |
- 3
发布时间：2022-09-02 - 摘要：In order to promote the application and rapid development of flame retardant viscose fiber, the production technology and application field of flame retardant viscose fiber and fire-retardant mechanism of flame retardant are introduced. The development of flame retardants is described in detail and their advantages and disadvantages are evaluated objectively. On this basis, the technical characteristics of the different flame retardant technology are emphatically analyzed, and the existing problems of the three flame-retardant processes are put forward. In view of the existing problems, it is suggested that the idea of multi-technology collaborative innovation should be adopted to design the flame-retardant processes. Finally,the development prospect of flame retardant viscose fiber and the important contents on preparation of flame retardant are summarized.关键词：Flame-retardant viscose fibers;Flame retardant;Flame retardant mechanism;Flame retardant technology;Development prospect
- 10
- |
- 13
- |
- 1
发布时间：2022-09-02 - 摘要：Poly (L-lactide acid)/polyvinylpyrrolid three-dimensional nanofibers porous scaffold was prepared by low-temperature quenching, extraction, washing and drying from tetrahydrofuran/water co-solvent without the assistance of other additives. The effects of THF/H2O ratio, concentration, PLLA/PVP ratio and quenching temperature etc. on the morphology of fibrous scaffold were investigated by SEM. The influence of addition of PVP in water absorption and bioactivity were also investigated through water absorption test and in vitro bioactivity test. The results showed that fibrous scaffold was produced by crystallization of PLLA. The addition of PVP impeded the crystallization of PLLA and increased hydrophilia of fibrous scaffold. The optimum test conditions were as followed: THF/H2O=90 : 10,concentration 9%(wt),PLLA/PVP=90 : 10 and quenching temperature -10℃, the uniform three-dimensional nanofibers porous scaffold with diameter of 270±73 nm were obtained. The water absorption, porosity and specific surface areas of fibrous scaffold were 17.29%,96.36% and 13.45m2/g, respectively. High porosity and specific surface areas will offer good condition of cell adhesion, cell differentiation, cell prolifer and nutrients transport.关键词：Poly(L-lactide acid);Polyvinylpyrrolid;Porous scaffold;Thermally induced phase separation;Cellular biocompatibility
- 8
- |
- 11
- |
- 0
发布时间：2022-09-02 - 摘要：silica sol hybrid was synthesized by the hydrolysis reaction of ethyl silicate(TEOS) at 25℃ under alkaline conditions.Then a series of modified epoxy resins were successfully prepared by using the silica sol hybrid. IR spectrum, epoxy value indicated that the silica sol hybrid is incorporated into epoxy resin. The modified epoxy resin was cured with isophorone diamine (IPDA), Then investigated the cured materials via measuring the flame retardancy, glass transition temperature (Tg),thermal stability, tensile strength and elongation, microstructure of the cured materials, The effects of chemical modification, physical mixing and the content of the TOES on the properties of the composites were discussed. The results show that the modified epoxy resin obtained by chemical reaction has better performance. The limiting oxygen index and thermal stability of the cured product are obviously higher than that of pure epoxy resin, and the tensile strength and other mechanical properties have been greatly improved, which achieved that the flame retardant, heat resistance and mechanical properties of the epoxy materials were increased at the same time.关键词：Epoxy resin;Flame retardant;Thermal properties;Silicate-sol
- 6
- |
- 12
- |
- 0
发布时间：2022-09-02 - 摘要：Macromolecule migration subjected to thermal gradient exists widely in biological and medical engineering problems. Exploring the thermo-hydrodynamic mechanism is of great significance both for biochemical engineering and micro/nanotechnology. In this paper, the energy-conserving dissipative particle dynamics (eDPD) is extended to investigate the flow of macromolecular solutions and macromolecule behaviors in a micro-channel subjected to thermal gradient. The accuracy and reliability of the codes are verified by comparative studies. Then, the velocity of macromolecular solutions under different temperature gradients and lengths, as well as their coupling effects are comparatively analyzed,and the macromolecular centroids distribution and behaviors including stretching, winding and folding are investigated systemically. The results show the macromolecular solution flow, probability distribution of centroids and the behaviors of macromolecules are obviously affected by thermal gradient, and some new features are revealed. The theoretical basis provides a potential way for the precise control of macromolecules (ex. drugs or DNA),and a new approach is proposed to investigate the complex dynamic behaviors of macromolecule under thermal condition.关键词：Energy-conserving dissipative particle dynamics (eDPD);Macromolecule;Microflow;Temperature gradient;Finite-extensive nonlinear elastic(FENE) model
- 6
- |
- 12
- |
- 0
发布时间：2022-09-02 - 摘要：As a green self-reinforcing polymer material,natural rubber has the advantage that synthetic rubber can't match. There have been a lot of literature reports on strain-induced crystallization of natural rubber, but there are few reports on the research of low-temperature crystallization of natural rubber. The research on low-temperature crystallization of natural rubber has theoretical guiding significance for the production of low-temperature resistant natural rubber products. In this paper, the low temperature crystallinity and grain size of natural rubber were studied by differential scanning calorimetry (DSC) and wide-angle X-ray diffraction (WAXD). The results show that there are two kinds of crystals when natural rubber is crystallized at low temperature. The crystallinity increases with the crystallization time,and it crystallizes completely at about 5 h. The crystallinity and grain size of natural rubber do not change. It indicates that the increase in the crystallinity of low-temperature crystallinity of natural rubber is derived from the increase in grain size rather than the increase in the number of grains.关键词：Natural rubber;Low temperature crystallization;DSC;WAXD
- 5
- |
- 11
- |
- 0
发布时间：2022-09-02 - 摘要：Chain polymerization is an important reaction to prepare polymer compounds, and is also an important knowledge in the course of polymer chemistry. In the course of teaching chain polymerization, the selectivity of vinyl monomers on polymerisation types has always been a key and difficult problem in process of polymer chemistry teaching. In this paper, the direction and intensity of the substituent electron effect are discussed qualitatively and quantitatively from three aspects: the induction effect,the conjugation effect and the substituent radical constant, then the reasons for the difference in polymerization types between the two groups of monomers were analyzed by using vinylidene chloride and vinylidene fluoride, methyl acrylate and vinyl acetate as examples,in order to help students understand the selectivity of the vinyl monomers on the type of polymerization.关键词：Monomer structure;Types of polymerization;Electronic effects;Substituent constant
- 7
- |
- 12
- |
- 0
发布时间：2022-09-02 - 摘要：Structure and Properties of Polymers is one of the most important basic courses of polymer materials. Its task is to explore the structure and properties of polymers and to reveal the internal relation and its basic law between structure and performance. It is expected to provide the theoretical basis for the synthesis, processing, testing, materials selection and development of polymer materials. Based on characteristics of the course and basic task, this paper studies and discusses the teaching reform of the course from two aspects: teaching contents and teaching methods.关键词：Structure and properties of polymers;Key course construction;Teaching reform
- 6
- |
- 15
- |
- 0
发布时间：2022-09-02
- 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