碳纳米管/聚乙烯复合材料薄膜紫外线透过性能的研究

阳光中的紫外线是引起高分子材料老化的最主要因素,高分子材料被紫外线照射后发生一系列的光化学反应,导致材料变色、变脆、透明度下降和力学性能降低,缩短了其使用寿命,长期以来,围绕紫外光对高分子材料老化作用的问题,科学工作者进行了广泛的观测和研究。结果表明,在高     

《高分子物理实验》教学中耐候性材料老化综合性实验的设计与探究

《高分子物理实验》是高分子科学体系的重要组成部分,从事高分子研究必须掌握的基础技能。"高分子材料力学性能测定"是《高分子物理实验》中一个重要的实验项目。本文结合新疆的气候特点和新疆大学高分子材料专业的实际情况,把教师的科研成果与本科教学相结合,设计出独具特色的耐候性材料老化综合性实验。学生在实验中,不仅了解了高分子材料温差老化的作用及其对力学性能的影响,还拓宽了学生对专业的综合认识,提高学生的实际操作和分析解决问题的能力。     

复杂条件下高分子材料老化规律、寿命预测与防治研究新进展

复杂条件下有机高分子材料的老化、寿命预测和防治研究对满足相关行业发展的迫切需求,实现节能减排、环境保护及可持续发展等战略目标具有重大意义。本文重点综述了近年来针对聚烯烃、工程塑料、橡胶、涂料等大宗高分子材料在我国复杂大气环境中的自然老化及人工模拟加速老化研究的新进展,对材料老化失效基本规律和分子机理、老化数据库的建立及老化分级图谱的绘制进行了介绍,探讨了户外自然环境和人工模拟环境下材料老化失效规律的对应关系、服役寿命理论的预测模型及失效防治延寿新方法,并对其中存在的问题及下一步发展方向进行了展望。     

有机高分子材料使用寿命预测方法

有机高分子材料在使用过程中,因受各种环境因素的作用,材料的性能会出现衰变、劣化,及至完全丧失使用性能的老化现象,老化伴随了材料的整个生产和使用过程。为保证材料的使用安全,人们对有机高分子材料在自然环境中的使用寿命展开了大量的研究工作。本文整理和归纳了近几十年来有机高分子材料使用寿命的预测方法,对由于新检测技术的出现而发...     

高分子的表面化学组成与生物相容性

生物相容性是高分子材料在临床上用作医用装置的基本要求，改变高分子材料的表面化学组成是提高其生物相容性的重要途径。综述了构建表面化学组成改性高分子材料生物相容性的最新研究进展，并对改善高分子材料生物相容性的研究方法提出了一些看法。     

同步辐射小角和广角X射线散射在高分子材料研究中的应用

同步辐射X射线散射是研究高分子材料不可替代的重要工具。第三代同步辐射光源—上海光源的成功建设,标志着我国进入国际先进光源俱乐部,为我国高分子材料研究大发展提供了一个契机。本文结合作者和国内外同行的工作,以具体案例的形式介绍了同步辐射小角和广角X射线散射在高分子材料研究中的一些应用,阐述了同步辐射高亮度原位在线研究高分子材料结构形成和演化动力学以及结构与性能关系的独特优势。同时介绍几种自主研制的原位装置和常用的X射线散射数据处理方法。希望本文能起到抛砖引玉的作用,吸引更多的高分子研究同行利用同步辐射开展研究。     

荧光探针在灵敏表征高分子材料老化中的研究进展

目前高分子材料早期老化或轻微老化的检测和监测面临诸多难题,最迫切的需要是发展灵敏且高效的表征方法。荧光探针技术作为一种成功应用于生物医学、环境科学和材料科学等多个领域非常灵敏的分析技术,其低检出限、强直观性的优点预示出它表征早期老化的潜力。高分子材料老化过程中往往会产生自由基物种以及羟基、羧基等基团,环境应力、湿度和基体极性等性质也会发生改变,这为荧光探针的刺激响应行为提供了用武之地。本综述简述了多种荧光探针的发展历史,讨论了靶向前述材料变化的荧光探针的本质机理,结合材料老化阐述了化学响应荧光探针和微环境响应荧光探针的典型应用以及部分探针的合成方法,最后对荧光探针技术存在的科学问题与应用挑战等方面进行了系统梳理,希望对广大同行的研究工作有所裨益。     

阻燃剂与阻燃机理

由于石油化工和有机合成技术的进步,推动了合成高分子材料工业的发展。塑料、合成纤维和合成橡胶等形形色色的高分子材料得到广泛应用。合成或天然高分子材料通常都是易燃物,因其燃烧引起的火灾每年都给世界各国带来巨大的经济损失和人身伤亡。为了减少火灾的发生,各国开始大力研究和应用阻燃剂和阻燃材料。许多国家以法律形式规定要求使用高分子阻燃材料。我国也已做出对飞机、轮船、矿井设备等使用阻燃材料的规定;一些省市对建筑用高分子材料的阻燃性能也提出了要求。近些年来在我国阻燃剂的研究与应用已日益受到重视。     

Pickering乳液在功能高分子材料研究中的应用

功能高分子材料制备的瓶颈问题是如何解决多重材料的相容性问题,传统的物理共混技术和聚合添加技术无法保证材料的稳定性及均一性。 Pickering乳液具有成本低、毒性小、环境友好、稳定性好、制备的多重材料结构稳定等优点,在制备功能高分子材料的应用中越来越受到人们的重视。 本文详细介绍了Pickering乳液在功能性高分子材料制备中的应用研究进展,提出了Pickering乳液聚合制备功能高分子材料面临的一些问题,并结合本课题组的研究方向,对其发展前景进行了展望。     

CO2/生物基环氢化合物共聚制备绿色聚碳酸酯材料

以CO_2为原料合成脂肪族聚碳酸酯材料不仅利用了廉价、可再生的CO_2资源,而且可以实现全生物降解高分子材料的制备,是一条绿色可持续的高分子材料合成路线。但长期以来,该领域研究多集中在利用CO_2与一些石油来源的环氧烷烃(如环氧丙烷、环氧环己烷等)共聚方面,未能完全摆脱对石油资源的依赖。因此,发展基于生物基的环氧单体制备全生物基高分子材料逐渐成为CO_2基高分子材料研究的热点。生物基来源化合物的引入有助于丰富CO_2基高分子材料的结构和性能,拓展其应用领域。本文综述了近年来利用生物基环氧化合物与CO_2共聚合成全生物基高分子材料的研究进展,并对未来该领域发展的趋势进行了展望。     

Comparative Study of PHA Degradation in Natural Reservoirs Having Various Types of Ecosystems

The kinetics of polyhydroxyalkanoate (PHA) degradation in natural environment in two water reservoirs having various ecological characteristics was studied. It was shown that biodegradation of polymer essentially depends on the environment temperature and inorganic composition of water. The processes of polymer degradation under aerobic and anaerobic conditions were compared. The polymer degradation was slower under anaerobic conditions.     

Mass spectrometry in bioresorbable polymer development,degradation and drug‐release tracking

A detailed characterization of polymeric matrices and appropriate degradation monitoring techniques are required to sustain the development of new materials as well as to enlarge the applications of the old ones. In fact, polymer analysis is essential for the clarification of the intrinsic relationship between structure and properties that ascertains the industrial applications in diverse fields. In bioresorbable and biodegradable polymers, the role of analytical methods is dual since it is pointed both at the polymeric matrices and at degradation tracking. The structural architectures, the mechanical and morphological properties, and the degradation rate, are of outstanding importance for a specific application. In some cases, the complexity of the polymer structure, the processes of decomposition or the low concentration of the degradation products need the concurrent use of different complementary analytical techniques to give detailed information of the reactions taking place. Several analytical methods are used in bioresorbable polymer development and degradation tracking. Among them, mass spectrometry (MS) plays an essential role and it is used to refine polymer syntheses, for its high sensitivity, to highlight degradation mechanism by detecting compounds present in trace amounts, or to track the degradation product profile and to study drug release. In fact, elucidation of reaction mechanisms and polymer structure, attesting to the purity and detecting defects as well as residual catalysts, in biodegradable and bioresorbable polymers, requires sensitive analytical characterization methods that are essential in providing an assurance of safety, efficacy and quality. This review aims to provide an overview of the MS strategies used to support research and development of resorbable polymers as well as to investigate their degradation mechanisms. It is focused on the most significant studies concerning synthetic bioresorbable matrices (polylactide, polyglycolide and their copolymers, polyhydroxybutyrate, etc.), published in the last ten years.     

Initiation of polymer degradation via transfer of infectious species

A novel dual stage chemiluminescence detection system incorporating individually controlled hot stages has been developed and applied to probe for material interaction effects during polymer degradation. Utilization of this system has resulted in experimental confirmation for the first time that in an oxidizing environment a degrading polymer A (in this case polypropylene, PP) is capable of infecting a different polymer B (in this case polybutadiene, HTPB) over a relatively large distance. In the presence of the infectious degrading polymer A, the thermal degradation of polymer B is observed over a significantly shorter time period. Consistent with infectious volatiles from material A initiating the degradation process in material B it was demonstrated that traces (micrograms) of a thermally sensitive peroxide in the vicinity of PP could induce degradation remotely. This observation documents cross-infectious phenomena between different polymers and has major consequences for polymer interactions, understanding fundamental degradation processes and long-term aging effects under combined material exposures.     

Degradation of Polymer Materials in Low Earth Orbits

The results of study on two batches of polyimide film materials exposed to the space environment for 28 and 42 months at the Mir space station are discussed. The resistance of polymer films to space environment factors depends on the chemical structure and composition of a polymer material, the polyimide films, especially fluorinated and metalized, undergo considerably stronger changes than fluoropolymers. It was found that the rate of degradation of polymer materials is nonlinearly related to the time of exposure to the space environment. The circular brightness plots and contact angles of outer polyimide films are anisotropic in character, the directions of brightness plot axes and the contact angle are determined by the orientation of the film on the panel with respect to the direction of spacecraft motion. Irradiation by solar light at 200 nm did not lead to noticeable degradation of the polymers. It was assumed that the degradation of polymer materials was initiated by bombardment with heavy particles (molecules, atoms, and ions of oxygen, nitrogen, etc.) due to a spacecraft residual atmosphere.     

Thermal Analysis of Some Environmentally Degradable Polymers

The thermal characteristics of a series of degradable polymers have been investigated using thermogravimetry and differential scanning calorimetry. While the results of the thermogravimetry experiments suggest that the thermal stability of the polymers should not pose any problems at the temperatures that can be expected in a commercial composting process (60°C), phase changes associated with some of the polymers investigated may cause problems in the interpretation of data from composting degradation studies. Several biodegradable polymers were observed to have melt transitions at temperatures similar to those found in a composting environment. Consequently, under the controlled composting conditions used to evaluate biodegradable polymers, degradation of a polymer may be inferred, while actually the polymer has merely undergone a phase change. This revised version was published online in July 2006 with corrections to the Cover Date.     

Degradation issues of polymer materials used in railway field

Polymer materials used in railway field are degraded by environmental factors such as thermal, oxidative, photolytic, hydrolytic, and mechanical. The expected service life of the polymer materials used in railway field is approximately 20 years that is relatively long period for the polymer material; therefore, respective degradation factors should be well considered. Some of the degradation conditions indicate similar mechanism. The oxidative reaction was seen in every degradation conditions under air atmosphere. The hydrolytic reaction was mainly observed in chemical and biological degradations. The degradation behavior of the polymer material was analyzed by various methods. FTIR, thermal analysis (TG, DSC), and molecular weight determination were mainly applied for its purpose. However, the degradation mechanism of practical products made of polymer material was insufficiently studied and the exchange criteria of the products depended on the visual inspection without the suitable degradation analysis not only in the railway field but also in other commercial and industrial fields. In addition, most of the methods to analyze degradation of polymer material are performed on the standard specimen forms. For the installed product, some kinds of damage are generated through the sample collection process; therefore, the damaged products have to be exchanged for brand new ones or repaired totally to be used for more period. Moreover, it is hard to suspend the railway service for the degradation analysis of polymer products. From these backgrounds, the prospect of degradation analysis related to polymer materials used in railway field was proposed.     

The evolution of poly(lactic acid) degradability by dielectric spectroscopy measurements

Dielectric spectroscopy is a powerful method that allows the study of the dynamics of polymers in a wide frequency range. The different regimes of the dielectric spectra can be observed and the dynamics of the primary and secondary relaxations can be found.In this work, the systems investigated included industrial and purified poly(lactic acid), PLA. This is an aliphatic polyester, one of the most important biocompatible and biodegradable material that has received increasing attention in the last 10 years.Thermal analyses indicated that the glass transition temperature of the polymer was about 320 K.The β relaxation was observed between −150 °C and −30 °C, depending on the measurement frequency (1 Hz-100 kHz), and was assigned to the secondary relaxation in the glassy state. We studied the changes that are connected with the water penetration in the polymer, and directly affect that relaxation process. Water molecules confined by polymer chains and in the polymer networks play an important role in the degradation of the matrix, and then we can observe the evolution of that degradation during some weeks, in a controlled humidity environment. It is accepted that water preferentially enters in the amorphous zones, but also affects the crystalline regions. It is observed a clear evolution of the relaxation activation energy during the degradation of the polymer.The dielectric relaxation results are complemented with molar mass measurements during the degradation process with time.     

Polymer combustion

Experimental conditions have been defined for the steady-state combustion of vertically positioned polymer rods burning at the top surface. Temperature and composition profiles through solid and gas phases of the system, polymer consumption rate, and flame height were measured, and the response of these parameters to changes of the oxygen concentration in the environment were determined. Measurements showed that unreacted oxygen diffused from the environment to the burning surface and was absorbed into the polymer, forming a well defined oxygen-rich layer. Concentration of chemically bound oxygen at the surface of this layer were high, e.g., with polypropylene ca. 26 wt-%, and identical with the stoichiometry of the gases leaving the surface and serving as fuel for the flame. The composition of the gas phase at the surface indicated the conversion of 11.4% of the hydrocarbon fuel to CO, CO₂, and H₂O. An energy balance for the system confirmed that fuel production in this surface layer takes place via simultaneous oxidative and pyrolytic degradation of the polymer, with exothermic processes supplying the energy for endothermic processes. Conductive and radiative contributions from the gas phase were found to play a minor role in maintaining fuel formation. The rate of degradation of a polymer to fuel, normalized to the area of the burning surface, was found to be independent of polymer supply rate and to increase with the oxygen concentration in the environment. The degradation process was successfully modeled in TGA experiments at temperatures and oxygen concentrations representative of the burning surface. The existence of an oxidative surface layer was confirmed and the TGA degradation rate related to the surface-to-volume ratio of the polymer sample. Compositional analysis of a methane diffusion flame of a geometry identical to that of the polymer flame, revealed the presence of unreacted oxygen throughout the preheating zone and at the surface of the burner. Conversion of fuel to final combustion products at the surface was 6.3%. Temperature and composition changes as a function of oxygen concentration in the environment were determined and compared with the polymer diffusion flame. It was concluded that a polymer flame, because of its autogenerative fuel production, possesses only one degree of freedom, viz., the oxygen concentration in the environment, in contrast to the conventionally fueled diffusion flame for which fuel supply rate is an additional independent parameter. Due to this single degree of freedom, the sensitivity of the polymer flame to environmental influences is increased. Effects caused by these extrinsic factors will be the subject of a separate report.     

Thermal stability of polyurethanes

Summary The combined application of thermogravimetry reactiongas chromatography and gel-permeation chromatography permits to follow the heat degradation of polyurethane polymers in inert gas, air and water-saturated environment. The examinations give information on the rate of thermal degradation, the individual volatile degradation components, the critical points of the polymer chains and on the change of their molecular-weight distribution. Gas chromatographic examinations also permit the identification of the chain-extending components of different types of polyurethanes.     

高分子材料生物降解性能的分析研究进展

本文介绍了近年来生物降解材料降解方法的研究现状,主要从不同的降解环境,包括在堆肥环境、水性环境、惰性固体介质环境等进行的材料生物降解性能研究进行了比较、评述与展望。