高分子材料老化机理初探

本文分析了各种环境因素对高分子材料的影响 ,介绍了常用的几种加速老化试验的方法及老化材料防护措施。     

高分子材料的环境行为与老化机理研究进展探讨

现如今,高分子材料在日常生活中应用十分广泛,而影响高分子材料的环境因素较多,如光、电、氧、水等。如何延缓高分子材料的老化,延长高分子材料的使用寿命备受科学界的关注和重视。本探讨主要围绕影响高分子材料的环境行为,高分子材料老化的表现,如何降低高分子材料的老化机理及现阶段高分子研究发展动态上,使人们对高分子材料有进一步的了解。     

在化学介质作用下高分子材料的老化

6高分子材料在应力──介质环境中使用性能耐久性的探讨6．1塑料的应力腐蚀试验在高分子材料用作制造化工设备的耐腐蚀材质的场合，充分了解这种荷载的结构材料在化学介质中使用性能的耐久性是十分重要的。大量的事例表明，单纯采用材料的静态浸泡试验结果来作为化工设备设计工作中材质选择的依据，往往会酿成装置灾难性破坏的事故。化工设备的材料问题，同运转条件（工作介质、温度。压力）和结构设计割裂开来是不可想象的，因此，高分子材料的动态条件下的耐化学介质之稳定性能和试验方法的研究倍受重视，人们努力开发一些力求接近实际的…     

部分高分子材料老化研究进展

分析了部分高分子材料在贮存过程中因不同的温、湿度环境造成性能老化的相关资料,总结了用于表征高分子材料老化性能的方法,举例说明了其应用,并对其老化模拟情况进行了汇总。     

在化学介质作用下高分子材料的老化（续前）

3高分子材料在化学介质中的化学降解当大多数聚合物曝露在氧化性介质环境之中，或那些主链或支链含有双键或杂原子基团之聚合物与水、酸或碱溶液接触时，都会有化学降解反应发生。前已指出，由于化学介质的多样性，难以把它们与高分子材料发生的具体反应—一讨论。本节仅把在高分子材料的重要应用领域里常碰到的、属于本章讨论范围的那些主要的化学降解反应予以概述。3．至二氧化氛对聚乙烯的反应获原等【到发现，进行二氧化氛曝露试验的聚乙烯薄膜，它的大分子链有硝基、亚硝酯基、谈基和羟基出现。以不同曝露温度下的硝基增加速率作Arrhe…     

在化学介质作用下高分子材料的老化（续前）

4高分子材料在化学介质中的物理变化除上节述及的微量的活性介质（又称化学腐蚀介质）攻击聚合物的共价键，导致聚合物的化学组成发生转化的化学反应外，化学介质对高分子材料的老化过程还存在另一种作用，即高分子材料吸收了大量的非活性介质（如被称为物理腐蚀介质的有机液体，一定场合下的水等），导致聚合物分子链间互相作用的破坏，代之渗透物质的中介作用力，例如：这样的分子间次价键的改组过程，原则上是一个可逆的变化。当介质的解吸，聚合物分子间的次价键重新形成后，材料可望恢复原来的性能。但这种可逆性有时是很难完全的，特…     

高分子材料的老化及防老化研究

介绍了环境因素如温度、湿度、氧气、光、化学介质、微生物等对高分子材料老化的影响机理,在此基础上,提出了高分子材料的防老化方法。     

高分子材料在生物体内的老化

高子分材料,作为主要的人工内脏器官材料及生物体机能再建材料在生物体内使用,预计今后还要增加。随着使用时间的延长,材料的稳定性与老化问题日益变得更重要了。但是目前关于生物体内高分     

高分子材料的老化表征方法

高分子材料的老化会使其性能降低,从而部分或完全丧失其使用价值,因此对高分子材料的老化与防老化研究已成为高分子科学的重要研究领域。本文从高分子材料老化过程中外观变化、力学性能变化、电性能变化、波普性能变化4个方面综述了高分子材料的老化表征方法,展望了表征高分子材料老化的研究方向。     

热空气老化粘弹性丁基橡胶阻尼材料的性能及其老化机理研究

采用热空气加速老化试验方法对粘弹性丁基橡胶阻尼材料的老化性能及其老化机理进行了研究,获得了老化前后丁基橡胶阻尼材料力学性能、阻尼性能及其变化规律。研究结果表明：在所选定的热空气老化65℃×310天试验条件下,阻尼材料的拉伸强度提高了1MPa,阻尼性能曲线整体向高温区域平移了10℃,而有效阻尼温域基本保持不变,与模拟计算结果一致,可以满足等效25℃×10年储存条件下的使用要求。同时,采用FTIR和SEM技术分析了阻尼材料在热氧老化条件下分子链结构和微观结构的变化,得到了粘弹性丁基橡胶阻尼材料的热空气老化机理。     

Longitudinal polymer gradient materials based on crosslinked polymers

Polymer gradient materials (PGMs) are known to reduce stress concentrations and to increase fracture toughness. The first system we reported for the preparation of longitudinal PGMs was based on poly(dimethyl siloxanes), covering a relatively low Young's modulus range. In this study, we used two photochemically and one thermally curing polyaddition systems, enabling us to cover a much larger modulus range up to 1300 MPa. Three different gradient structures, hard-soft, hard-soft-hard, and soft-hard-soft, were realized and confirmed by position-dependent UV/Vis absorbance measurements. Tensile testing in dependency on the gradient structure was performed. A comparison with non-gradient samples with discrete composition revealed a significant improvement, specifically in the case of hard-soft-hard gradients. Hence, PGMs are a promising approach for the development of materials with a special mechanical property profile particularly at different temperatures, leading to novel thermoresponsive materials.     

橡胶材料老化试验的研究现状及发展趋势

橡胶材料的老化已经是一个历来已久的问题,国内外学者都通过不同的方法研究橡胶材料的老化性能和机理。本文综述了橡胶材料老化试验研究方法的国内外研究现状和发展趋势。橡胶材料的老化试验研究方法正朝着多因子、同步循环、复杂承载以及计算机模拟材料老化过程的方向发展。     

聚合物/无机杂化纳米复合材料制备方法的研究进展

聚合物/无机杂化纳米复合材料是纳米材料发展的一个重要方向。简述了纳米粒子对聚合物纳米复合材料的力学性能和功能特性的影响,介绍了聚合物/无机杂化纳米复合材料的制备方法及应用,并对其研究进行了展望。     

高分子材料微观形态结构的扫描电镜研究

利用扫描电镜对聚乙烯(PE)、丙烯腈-丁二烯-苯乙烯共聚物(ABS)等高分子材料填料的分散性及表面与断裂界面进行了研究。结果表明,扫描电镜能够详细观察研究高分子材料的表面结构、微观相分离等,便于表征高分子材料微观结构形态,是分析高分子材料微观结构形态的有效手段。     

Grain-size effect on the properties of materials under dynamic deformation

Some deformation features in fine-grained copper under gradient dynamic stresses are studied which provide a better understanding of the mechanism of the processes involved. The experimentally observed abrupt change in the properties of materials with grain sizes smaller than a certain critical value is shown to be related to intergranular slip during deformation. Materials with a grain size of 5–50 μm are found to exhibit properties characteristic of nanomaterials with a strain rate varying from 10⁴ to 3 · 10⁶ sec⁻¹. __________ Translated from Fizika Goreniya i Vzryva, Vol. 44, No. 3, pp. 133–138, May–June, 2008.     

Physical aging in the mechanical properties of miscible polymer blends

Changes in mechanical properties during isothermal physical aging were investigated for three miscible blends: polystyrene (PS)/poly(2,6-dimethyl 1,4-phenylene oxide) (PPO), PS/poly(vinylmethylether) (PVME), and poly(methylmethacrylate) (PMMA)/poly(ethyleneoxide) (PEO). The kinetics of stress relaxation was investigated for the blend, dilute in one component, and compared with that of the neat major component at equal temperature distances, Tg-T, from the midpoint glass transition temperature. It is demonstrated that for all three blends, the mean stress relaxation time (τ) does not scale with Tg-T. For PS/PPO and PS/PVME blends, the stress relaxation rates are faster compared to neat PS; for PMMA/PEO, they are slower than for neat PMMA. Two effects appear to be important in contributing to this discrepancy. First, addition of the second component produces a change in the packing density of the blend: less dense for PS/PPO and PS/PVME; more dense for PMMA/PEO. Comparison of average free volume hole sizes and fractional free volumes measured via orthopositronium annihilation lifetime measurements for all three blends versus the pure constituents are qualitatively consistent with this interpretation. Second, because of the presence of concentration fluctuations in the blend, it is expected that the initial stress decay is dominated by regions enriched in the more mobile component. From observations of the change in width of the stress relaxation time distribution, this effect appears to be particularly significant in the PS/PVME blend. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 63: 483–496, 1997     

Recently emerging trends in polymer nanocomposites packaging materials

As a result of excellent nanoparticle dispersion tendencies, polymer based nanocomposites exhibit a significantly enhanced packaging characteristics. Moreover, the feasibility of inclusion of biologically-active additives has shown great potentials of rendering enhanced functional properties to the end product. Hence, polymer nanocomposites exhibiting bio-functional propensities have revealed a broad potential for application as packaging materials in the functional food packaging industry. This is due to accruable improvements in properties such as enhancements in strength and modulus, reduced gas permeability, and increment in resistance to water. Thus, the incumbent paper discusses state of the act recently emerging trends in the preparation and characterization of polymer nanocomposites as eco-benign and biodegradable packaging materials, inaddition to their future market prospects.Emerging novelties in polymer nanocomposites packaging films.     

轮胎材料在典型环境下老化性能研究进展

对实验室轮胎的老化方法及轮胎橡胶材料在典型环境下的失效进行了总结,并综述了轮胎橡胶在热氧、湿热和臭氧环境下的老化行为、老化机理及防老化措施,展望了轮胎抗老化性能研究的发展趋势。