高分子材料的环境行为与老化机理研究进展

总结了有关高分子材料在环境因素作用下老化研究的历史与现状,阐述了环境场(如光、热和化学介质)对高分子老化的影响,提出了材料老化的一些主要机理。在探讨了一些新研究手段的发展和取得的成果的基础上,进而展望了高分子材料老化及防护措施的研究动向和发展趋势。     

离子色谱法测定高分子抗静电剂中的硫含量

聚丙烯材料具有极高的表面电阻率和体积电阻率(1012Ω·m以上),在摩擦时易聚集静电,引起静电灾害。制备能与聚丙烯很好相容的高分子抗静电剂是聚丙烯改性的一条有效的途径。齐齐哈尔大学研究了以聚丙烯与丙烯腈接枝制得的新的高分子材料(PP-g-AN),并利用这种共聚物上的氰基与铜离子(C u 及C u2 )配合及活性硫(S2-)反应,在其表面形成C uxSy导电覆盖层。实验发现,这种抗静电剂能很好地与聚丙烯相容,导电性好,且保持了聚丙烯的加工及使用特性。C uxSy具有P型半导体的性质,是高分子抗静电剂的导电成分。因此,明确其中C u和S的含量十分必要…     

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...     

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。     

《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。     

聚(N-异丙基丙烯酰胺)类材料的应用

聚(N-异丙基丙烯酰胺)(PNIPAAm)及其共聚物,在水溶液中表现出最低临界溶液温度(LCST),在LCST附近会发生可逆相转变。利用这种特性,可将热敏性高分子材料应用于生物医学工程、免疫分析、催化、分离提纯等领域。主要综述了热敏性PNIPAAm类高分子材料,在这些领域中的应用情况。     

小角X射线散射技术在高分子表征中的应用

小角X射线散射(SAXS)技术是表征高分子材料微观结构的一种重要手段.当X射线穿过材料时,在材料不均一的电子云密度分布作用下,发生散射并形成特定的散射图案,使得我们可以根据特定的模型来反推材料的微观结构,并计算相关结构参数. SAXS特有的对微观结构的统计平均及无损探测使其成为了一种不可或缺的高分子材料微观结构分析手段.本文首先简述了SAXS技术的基本理论,在此基础上根据测试中的实际问题给出了测试时可采取的实验技巧.最后,结合典型实例,概述了高分子材料中可用SAXS技术表征的微观结构及其相应的理论模型.希望本文能作为入门文献,帮助初学者更好地理解SAXS技术的原理,并结合实际需求迅速了解SAXS技术的适用范围及相关实验技巧,高效地完成相关实验.     

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。     

新型荧光双重敏感响应性壳聚糖衍生物的合成及其发光性能研究

为了开发新型多功能天然高分子荧光材料,合成出一种新型含有环氧丙氧基荧光素(EPF)基团的水溶性壳聚糖衍生物GCS-EPF, 并用IR,1H NMR,UV光谱和荧光光谱等手段进行结构和发光性能的研究. 结果表明, 修饰后水溶性壳聚糖(GCS)的水溶液、 固体粉末和薄膜在520 nm附近具有较强的荧光发射, 其荧光强度不仅在0-60 ℃时对度有较快敏感响应, 同时在pH=0-13.5时对pH也有较快敏感响应, 具有双重敏感响应, 因此可将其作为温度荧光探针和pH荧光探针的高分子材料.     

聚对苯二甲酰对苯二胺/尼龙6复合物

随着材料科学的发展，纤维增强塑料已由纤维与树脂的复合，扩展到以刚性链高分子与柔性链高聚物在分子水平上的微观复合．棒状、刚性的液晶高分子是一种超高强度和超高模量的高分子材料，同时还具有在某种条件下易于自发取向形成微纤的特性．基于这些性能，液晶高分子自然成为代替无机纤维作增强剂，与柔性链高聚物进行微观复合最理想的材料．在与柔性链高聚物复合时，如何使之在基体中形成有很高的长径比（Ｌ／Ｄ）的液晶纤维，并在基体中又能起到强的增强效果，来获得高强度、高模量的复合材料．多年来一直是国际上研究的热点，有关这方面…     

高性能光催化降解聚乙烯薄膜的研究

利用酸性蓝BGA染料敏化的纳米TiO2作为光催化剂, 与低密度聚乙烯(LDPE)树脂复合制备了具有可见光催化降解性能的复合塑料薄膜. 采用SEM、FTIR、VHX-100数码显微镜和高温凝胶渗透色谱(HTGPC)等分析技术系统地研究了该塑料薄膜在紫外光和太阳光照射下的降解性能. 探讨了塑料薄膜在光辐照前后的力学性能、质量和分子量变化规律. 研究结果表明, 该薄膜在经紫外线照射5 d后质量损失达到17.6％, 数均分子量由21800降低为5900; 经太阳光照射48 d后质量损失达到12.5％, 分子量降为8100. 辐照后薄膜拉伸强度和断裂伸长率显著降低, 羰基含量升高.     

Tear anisotropy in films blown from polyethylenes of different macromolecular architectures

Blown films of different types of polyethylenes, such as branched low‐density polyethylene (LDPE) and linear high‐density polyethylene (HDPE), are well known to tear easily along particular directions: along the film bubble's transverse direction for LDPE and along the machine direction (MD) for HDPE. Depending on the resin characteristics and processing conditions, different structures can form within the film; it is therefore difficult to separate the effects of the crystal structure and orientation on the film tear behavior from the effects of the macromolecular architecture, such as the molecular weight distribution and long‐chain branching. Here we examine LDPE, HDPE, and linear low‐density polyethylene (LLDPE) blown films with similar crystal orientations, as verified by through‐film X‐ray scattering measurements. With these common orientations, LDPE and HDPE films still follow the usual preferred tear directions, whereas LLDPE tears isotropically despite an oriented crystal structure. These differences are attributed to the number densities of the tie molecules, especially along MD, which are considerably greater for linear‐architecture polymers with a substantial fraction of long chains, capable of significant extension in flow. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 413–420, 2005     

Morphology and mechanical properties of blown films of a low‐density polyethylene/linear low‐density polyethylene blend

The morphologies of films blown from a low‐density polyethylene (LDPE), a linear low‐density polyethylene (LLDPE), and their blend have been characterized and compared using transmission electron microscopy, small‐angle X‐ray scattering, infrared dichroism, and thermal shrinkage techniques. The blending has a significant effect on film morphology. Under similar processing conditions, the LLDPE film has a relatively random crystal orientation. The film made from the LDPE/LLDPE blend possesses the highest degree of crystal orientation. However, the LDPE film has the greatest amorphous phase orientation. A mechanism is proposed to account for this unusual phenomenon. Cocrystallization between LDPE and LLDPE occurs in the blowing process of the LDPE and LLDPE blend. The structure–property relationship is also discussed. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 507–518, 2002; DOI 10.1002/polb.10115     

Effect of LDPE on the thermomechanical properties of LLDPE‐based films

The present study compares the properties of five films: one film of low‐density polyethylene (LDPE), two films of linear low density polyethylenes (1‐octene comonomer)—one made by metalllocene catalyst (mLLDPE) and the other by Ziegler–Natta (zLLDPE)—and two blend films, one of mLLDPE/LDPE (film A) and the other of zLLDPE/LDPE (film B). The effect of LDPE (22% by weight) on the thermomechanical properties of LLDPE‐based films is investigated by using differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), and stress‐strain in the yield region measurements. The mechanical, dynamic, and thermal properties of film A are quite similar to a single component system (mLLDPE). The addition of this amount of LDPE does not affect the melting temperature of mLLDPE but it enhances its crystallinity. Film B is a rather inhomogeneous material, as opposed to film A, and its properties seem to be dependent on stretching conditions. Furthermore, the thermally activated rate process (Eyring's theory) is applied to analyze the yielding behavior of the two blend films. Double yielding manifested by film B is described with two thermally activated processes, while film A is satisfactorily described by a single process. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 1712–1727, 2005     

含羧酸共生稀土光敏剂的低密度聚乙烯膜紫外光氧化降解

含羧酸共生稀土光敏剂的低密度聚乙烯膜紫外光氧化降解林宜超（福建省测试技术研究所福州３５０００３）近年来，许多作者先后研究并开发出含硬脂酸铈（ＣｅＳｔ３）光敏剂的可控光降解低密度聚乙烯（ＬＤＰＥ）［１，２］、高密度聚乙烯［３］、聚丙烯［４］、聚苯乙烯...     

Surface changes brought about by corona discharge treatment of polyethylene film and the effect on subsequent microbial colonisation

Microbial colonisation of synthetic plastic films is normally slow, which affects the total period of biodegradation. Correlation between the modified surface condition and the ability for microorganisms to colonise low-density polyethylene (LDPE) film was studied. Corona discharge treatment was applied to obtain enriched and activated surface condition of LDPE film. It was found from water contact angle and FTIR spectrum evaluations that surface energy was significantly increased due to production of free radicals. Stabilised oxidised LDPE surface was also obtained by further exposure to the corona which gave more suitable condition for subsequent colonisation. Results were compared with UV irradiated (photo-oxidised) LDPE films. Colonisation of corona discharged and UV treated LDPE films were tested in the laboratory environment using known fungal isolates and in a natural compost environment. More active microbial colonisation was observed in all cases for corona discharged and UV treated LDPE films. Far longer UV exposure was required to have the same physicochemical and biological effect as the corona discharge treatment.     

Digital optical memory devices based on polymer-dispersed liquid crystals films: appropriate polymer matrix morphology

ABSTRACT

Permanent memory effect (PME) in polymer dispersed liquid crystal (PDLC) allows a greater applicability range than traditional PDLCs. One of the most interesting application could be the possible storing of optical information, the so-called Digital Optical Memory (DOM) devices. To test this application it would be required a display structure having an array of pixels addresses. Each pixel was filled with PDLC film with PME and electric field can be independently applied to different PDLC elements to define on/off pixel states (transparent or scattering states).PDLC films were obtained from a mixture of E7 nematic liquid crystal and poly(ethylene glycol) dimethacrylate with 875 g mol^-1oligomer as precursor of the polymeric matrix. The effect of the curing temperature and the UV light intensity as well time exposure during the polymerisations on the electro-optical performance of PDLC films were investigated. In this way, a high transparency state (T_OFF=55%) for a long period of time at room temperature even after the applied voltage has been switched off were obtained, started from an opaque state (T₀=0%) and after reaching a transparent state (T_MAX=75%), which causes 73% PME. The application to an 8x8 passive matrix using PDLC with PME is also demonstrated as proof-of-principle.     

芴酮引发光接枝改性LDPE膜的研究

采用紫外光引发接枝表面改性的方法,以芴酮(FL)为引发剂,在低密度聚乙烯(LDPE)薄膜表面上接枝丙烯酸(AA)、甲基丙烯酸(MAA)、丙烯酸甲酯(MA)、甲基丙烯酸甲酯(MMA)、丙烯酰胺(AM)等单体,以赋予薄膜表面新的化学性质.考察了引发剂浓度、紫外光的辐照时间、辐照强度、单体种类对LDPE薄膜接枝程度的影响.结果表明,在一定范围内,增加芴酮浓度,可以提高单体的接枝率,但当芴酮浓度达到5%时,接枝率反而下降.延长辐照时间至4 min和提高紫外光的辐照强度达100 W/m2,均有利于接枝反应的进行.不同单体在LDPE膜上的接枝能力与单体的活性、单体与基材的相容性等因素有关.接枝后,LDPE与水的接触角下降程度不仅与单体在膜上的接枝量有关,还与接枝单体的亲水性能密切相关.     

Studies on the photo-oxidative degradation of LDPE films in the presence of oxidised polyethylene

This paper reports the results of photo-oxidative degradation studies of LDPE in the presence of varying amounts of oxidised polyethylene (OPE), which was prepared by heating LDPE films containing 0.1% cobalt stearate in oxygen atmosphere at 100 °C. OPE, with a CI of 12 was used as an additive for LDPE. Varying amounts of OPE (0.5-5%) were blended with polyethylene in an extruder and films of 70 μm thickness were prepared by film blowing process. The physico-chemical properties of the films were evaluated and these were found to be proportional to the amount of OPE. The films thus obtained were subjected to UV-B exposure at 30 °C for extended time periods. The chemical and physical changes induced by UV exposure were followed by monitoring the changes in mechanical properties (tensile strength and elongation at break), carbonyl index (CI), morphology, molecular weight, MFI and DSC crystallinity. Incorporation of OPE was found to be effective in initiating the photo-degradation of LDPE in relatively short span of time and the degradation was found to be proportional to the amount of OPE in the formulation.     

High photocatalytic degradation activity of polyethylene containing polyacrylamide grafted TiO2

A novel photocatalytic polyacrylamide grafted TiO₂ (PAM-g-TiO₂) nanocomposite was prepared and embedded into a low density polyethylene (LDPE) plastic. Photocatalytic degradation of the LDPE/PAM-g-TiO₂ composite film was carried out under ambient conditions under ultraviolet light irradiation. The properties of composite film were compared with those of the pure LDPE film by measuring the changes in weight loss, carbonyl index, molecular weight, tensile strength and elongation at break. PAM-g-TiO₂ embedded LDPE showed highly enhanced photocatalytic degradation. Irradiating the LDPE/PAM-g-TiO₂ composite film for 520 h under UV light reduced its weight by 39.85% and average molecular weight (M_w) by 94.60%, while that of pure LDPE film was only 1.03% and 69.59%, respectively. The addition of PAM-g-TiO₂ brought about the good dispersion of TiO₂ in LDPE matrix and improved the hydrophilicity of composite film, which were able to facilitate the degradation of LDPE. The photocatalytic degradation mechanism of the films is briefly discussed.