高分子聚合物力学阻尼材料的研究进展

1　前言阻尼材料是近年来发展起来的一种减振降噪材料 ,是能够把振动能和声能转变为热能耗散掉的新型功能材料。高分子材料由于结构的特殊性而广泛地应用于阻尼材料。高分子聚合物在玻璃化转变温度Ｔｇ区域时 ,大分子链段松驰运动的能力很强 ,能产生很强的分子内摩擦力 ,吸收一部分振动能 ,再以“热”的形式而损失 ,从而产生振动的阻尼。2　高分子聚合物的阻尼机理众所周知 ,阻尼材料就是使振动衰减的高分子材料。用来衡量材料阻尼特性的参数是材料的损耗因子 ( β)。其定义为 β =Ｇ″/Ｇ′ =ｔｇα[1 ] 。式中 ,α是材料受激励后 ,应变滞…     

高分子聚合物复合材料的自愈合研究进展

从自愈合机理出发,综述了高分子聚合物复合材料自愈合的研究进展,展望了其应用前景。     

高分子聚合物包覆无机纳米粒子的研究进展

简单介绍了非液滴内成核法、液滴内成核法包覆无机纳米粒子的原理,重点讨论了乳液聚合法、无皂乳液聚合法、分散聚合法、悬浮聚合法、细乳液聚合法包覆无机纳米粒子的优缺点。针对包覆过程中产生的独立聚合物粒子、独立无机粒子,提出采用引发剂吸附在无机颗粒表面、采用反应性乳化剂和偶联剂处理无机粒子并控制单体用量;针对包覆多个无机粒子,提出采用聚合前超声空化技术。     

多成分系高分子的动态接触角及润湿张力的松弛现象

多成分系高分子的动态接触角及润湿张力的松弛现象村知之，高绅矢（日本歧阜大学工学部）１前言接触角的测定，历来都是在固体表面放上液滴后在一分钟内进行的，测出的值接近于前近接触角。然而，对共聚合体或高分子共混物这类多成份系高分子表面，接触角是随时间而变化的...     

高分子聚合物在太阳能电池中的应用探析

介绍了高分子聚合物作为电解质在染料敏化纳米晶TiO2太阳能电池中的应用研究进展,按电解质的物理状态不同,分别对高分子聚合物凝胶准固态电解质和导电高分子聚合物固态电解质进行了综述,并对存在的问题和未来的研究方向进行了探讨。     

高分子聚合物在洗涤剂中的应用

从高分子聚合物的特点出发 ,综述了不同分子结构、不同分子量的高分子聚合物在洗涤剂中各个方面的应用。这些应用方面包括 :高分子表面活性剂 ;高分子对洗涤剂在制造和使用中的流变行为改性 ;高分子在洗涤过程中的抗再沉积作用、防色转移作用和对织物纤维的抗污处理作用(又称污垢释放剂作用)。最后 ,就高分子在洗涤剂中应用研究的现状及趋势作了简要概述。     

聚合物流变学中的高分子物理问题

聚合物流变学作为一门交叉学科,是建立在高分子物理等相关学科基础之上的,因此,在聚合物流变学的研究与教学过程中,必然涉及到对高分子物理问题的深入理解与探讨.在本文中,作者通过部分实例说明了在聚合物流变学教学过程中体现出的具体的高分子物理问题,分析了流变学现象之下的高分子物理基本理论,指出了聚合物流变学与高分子物理课程之间...     

Experimental and constitutive analyses of the stress relaxation behavior of glassy polymers

The physical mechanism underlying the mechanical behavior of glassy polymers has been studied over decades but remains a long-standing issue. A consensus view achieved is that the yield, flow, and stress relaxation behaviors are due to structural relaxation in the polymer mainly caused by chain conformation transitions. This is the key physical idea behind the many existing elastic–plastic constitutive models for glassy polymers. In this paper, such a constitutive model was employed for predicting and analyzing the stress relaxation of a glassy polymer. It is found that the model works well in predicting the pre-yield stress relaxation but significantly underestimates the post-yield stress relaxation. As considering the chain conformation transition alone leads to a dilemma for the model to concurrently represent the yield/flow and stress relaxation behaviors, the model was extended to incorporate an additional structural relaxation mechanism assumed to originate from the dissociation of weak linkages in the chain network. The extended model succeeds in concurrently representing the yield/flow, and stress relaxation behaviors in the whole deformation region, of which the reasons were analyzed. The knowledge revealed in this paper is instructive and may shed new light on understanding the structural relaxation and mechanical behavior of glassy polymers.     

Aliphatic polyesters as models for relaxation processes in crystalline polymers: 3. Mechanical relaxation in copolymers of adipic acid with 1,6 and 2,5-hexanediols

The shear moduli of a series of the title polyesters spanning a crystallinity range of 0–60% have been measured as a function of temperature at ≈1 Hz using a torsion pendulum. The experimental isochronal temperature scans of G′ and G″ are fitted to phenomenological equations. With only minor adjustments, the same relaxation spectrum parameters as found dielectrically for these polymers (relaxation shape, central relaxation times) fit the mechanical data. Thus, for the β (glass—rubber) relaxation in the amorphous fraction the broadness is very sensitive to the presence of the crystal fraction and becomes increasingly broad as the degree of crystallinity increases. In contrast, the γ process dynamic behaviour is insensitive to the presence of and degree of crystallinity. Unrelaxed and relaxed moduli values are determined for the γ and β processes. A composite model approach is used to determine bounds on the amorphous-phase unrelaxed and relaxed γ and β moduli from the bulk specimen values. As was the case dielectrically, the γ process, in addition to being assigned to the amorphous fraction, has a strength that depends on the diol composition also. The relaxed (γ + β) amorphous-phase rubbery shear modulus is bound reasonably well from application of the composite model to the bulk specimen values and is assigned the value 100 ± 20 MPa at 250 K. It decreases relatively strongly with increasing temperature.     

1H magnetic relaxation times in isotactic polypropylene crystallized at high temperature. Effect of molecular weight

The temperature dependence of ¹H spin-lattice, T₁(H), and spin-spin, T₂(H), relaxation times of isotactic polypropylene with relatively low molecular weight, M?_w = 1.95 × 10⁵, and ultra-high molecular weight, M?_w = 1.78 × 10⁶, crystallized at high temperature (155° C) for a long time (200 h), was measured with a broad line pulse spectrometer. T₁(H) for the ultra-high molecular weight sample is shorter than that for the low molecular weight sample, while T₂(H) for the ultra-high molecular weight sample is longer than that for the low molecular weight sample. From the analysis of free induction decay (FID), three components of T₂(H), i.e. T_2c(H), T_2m(H) and T_2a(H), were obtained. These relaxation times are associated with the crystalline, intermediate and amorphous regions, respectively. Here the intermediate regions are the regions in which chain molecules have intermediate mobility between that of crystalline and amorphous regions. A decrease in signal intensity of methylene, methine and methyl carbons was measured as a function of delay time following a 90° pulse before cross-polarization. From the slope of a log (intensity) versus t² plot a relaxation time associated with rigid regions of proton nuclei, T_2r(H), was obtained, where the rigid regions are the regions in which cross-polarization occurs easily. The value of T_2r(H) lies between that of T_2c(H) and T_2m(H), indicating that the intermediate regions act as the rigid regions so far as cross-polarization is concerned.     

Morphology and stress relaxation in oriented polyolefin shrink films

Morphology and stress relaxation of oriented polyolefin films has been studied. The influence of orientation on morphology of the films has been investigated using X‐ray, DSC, and TEM. The relaxation time spectrum of oriented films has been investigated. It was shown that relaxation time spectrum of composite film can be predicted if one knows the relaxation time spectrum of each component in the film. An influence of irradiation on relaxation behavior of polyethylene film was shown as well. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 3424–3429, 2003     

Experimental correlation for pipe flow drag reduction using relaxation time of linear flexible polymers in a dilute solution

In this study, we investigate the drag reduction property of a linear flexible polymer, PEO (polyethylene oxide) in a fully turbulent pipe flow. The aim of this study is to develop a correlation to predict the drag reduction using the Weissenberg number, a dimensionless number related to the relaxation time of the polymer and the polymer concentration in dilute solutions. The physical meaning of the relaxation time of polymers and overlap concentration between the dilute and semi-dilute polymer solution are clarified. A higher polymer concentration, Reynolds number, and Weissenberg number lead to an increasing drag reduction. A semi-empirical correlation to predict the drag reduction with two dimensionless variables mentioned above is established and can predict the experimental data in this work and other previous works well. Previous correlations that use Reynolds number often require high flow velocity or large pipes in the experimental setup to predict drag reduction in large-scale industrial applications, which involves extra cost and potential safety issues. The current new correlation method uses relatively low velocities to avoid the problems mentioned above.     

超分子聚合物研究进展

介绍了超分子聚合物领域的研究进展及其应用,阐述了其主要类别（如氢键超分子聚合物、配合物型超分子聚合物、π-π堆积超分子聚合物及离子效应超分子聚合物）,最后讨论了超分子化合物研究过程中的表征方法。超分子聚合物的研究前景将朝着更大产率、更简便制备步骤及更新颖结构的方向发展。     

Aliphatic polyesters as models for relaxation processes in crystalline polymers: 4. Dielectric relaxation in oriented specimens

To investigate further the effect of the crystal phase on amorphous-phase relaxation, samples of 6-6, 5–7, and 6–10 polyesters have been oriented by extrusion in the solid-state through a tapered die and the dielectric constant and loss measured both parallel and perpendicular to the extrusion direction. The data have been analysed quantitatively in terms of the Cole—Cole phenomenological equation and relaxation times, width parameters and relaxation strengths determined. For the β (glass—rubber relaxation) the relaxation times are shifted 2–3 orders of magnitude to longer times and the relaxation is broadened slightly compared to the unoriented polymers. There also tends to be reduction of overall parallel and perpendicular relaxation strength for the β process on orientation. The γ processes show little effect of orientation on relaxation time and width and do not show reduction of overall relaxation strength. These observations are consistent with crystal displacement further restricting amorphous-phase longer-range segmental motion (β process) but having little effect on the locallized motions associated with the γ process. Both the γ and β processes show anisotropy in relaxation strength. The anisotropy is analysed with a newly developed theory to separate inherent phase anisotropy from apparent anisotropy due to composite or form effects. The average angle made by the lamellar surface normal to the extrusion direction enters as a parameter in the theory. Measurements of relaxed specimen $\text{ε}{}_{\mathrm{}}$ and ε_⊥ values for both the γ and β processes serve to determine both f_a the amorphous-phase orientation function and the average tilt angle for the specimens here. This is possible because for the γ process relaxation strength is small and specimen anisotropy is dominated by inherent phase anisotropy but for the γ + β processes larger relaxation strength leads to specimen anisotropy being strongly influenced by crystal—amorphous phase composite effects. Values of f_a are in the range of 0.05–0.20 for specimens with f_c in the range 0.5–0.9. Indicated lamellar tilt angles are in the range of 24°–80°.     

超导高分子聚合物的研究进展

简要介绍了超导和导电高分子材料的发展,对超导和高分子材料两个学科的交叉前景作了展望,并对实现有机高分子超导聚合物的可能性作了一个初步的展望。     

Effect of fillers on the relaxation behavior of chlorobutyl vulcanizates

The effect of addition of fillers (carbon black (CB), carbon silica dual phase filler (CSDPF), and nanoclays) on the relaxation behavior of chlorobutyl vulcanizates has been studied. The primary relaxation (α‐transition, the glass transition) was studied by dynamic mechanical analysis as a function of temperature (?60 to +100°C) and positron annihilation life time spectroscopy (?70 to +110°C). Irrespective of the filler and its loading, all the composites showed the glass transition temperature in the range of –29 to –33°C, which was explained on the basis of relaxation chain dynamics of polyisobutylene in the vicinity of fillers. The secondary relaxation (α* or β relaxation) was studied using dielectric relaxation spectra in the frequency range of 100–10⁶ Hz. Nanoclays had a profound influence on the secondary relaxation, whereas CSDPF and CB had a marginal effect. The nonlinear strain dependent dynamical parameters were also evaluated at double strain amplitudes of 0.07–5%. The nonlinearity in tan δ and storage modulus has been explained on the concept of filler–polymer interactions and the interaggregate attraction (filler networking). The “percolation limit” of the fillers in the composites has been studied by DC conductivity measurements. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 3161–3173, 2006