热塑性弹性体在包覆成型方面的应用

热塑性弹性体是一种兼具橡胶和热塑性塑料特性,在常温显示橡胶高弹性,高温下又能塑化成型的高分子材料。也是继天然橡胶、合成橡胶之后的所谓第三代橡胶。通过包覆成型技术,热塑性弹性体使得制品具有更好的手感和外观,增加了制品功能性和附加值。随着人们对生活质量提出越来越高的要求,热塑性弹性体在包覆成型方面的应用越来越广泛,概述了包覆成型工艺、粘接机理及目前应用情况。     

Facile Preparation of Polydimethylsiloxane Elastomer with Self‐Healing Property and Remoldability Based on Diels–Alder Chemistry

The polydimethylisioxane elastomer based on Diels–Alder (DA) chemistry is successfully prepared by directly crosslinking bis(3‐aminopropyl)‐terminated polydimethylsiloxane with the bisepoxide containing two DA bonds in one molecule via epoxy‐amine reaction. The elastomer prepared based on DA chemistry exhibits good mechanical property, high self‐healing, and remolded efficiencies. The as‐prepared elastomer can be stretched to over 400% and its tensile strength can reach 0.80 MPa. The self‐healing efficiency and remolded efficiency are up to 93% and 95%, respectively. This work provides a simple and efficient way to fabricate the self‐healing and remolded polydimethylsiloxane elastomer with good mechanical properties. The as‐prepared elastomer has a promising potential in artificial muscles, protective coatings, and intelligent flexible electronics.     

校园网建设和多出口带宽设计

本文介绍了华东理工大学校园网的现状,阐述了校园网多出口带宽的设计以及徐汇、奉贤和金山校区网络的建设规划。     

羟基聚硅氧烷一步合成的速率研究

以四甲基氢氧化铵为催化剂,八甲基环四硅氧烷为单体,水为封端剂,一步合成羟基聚硅氧烷。采用凝胶渗透色谱(GPC)测定上述一步合成法的转化率,并建立转化率一时间关系曲线的模型函数(Bolzman函数),获得聚合过程中的重要特征参数：最大转化速率rm,极限转化率x(∞)等。研究表明．温度升高,rm加快,x(∞)降低;催化剂浓度增加,rm加快,x(∞)也增加,而转化速率与催化剂浓度在一定的范围内呈l级动力学关系;水浓度增加,rm降低,同时x(∞)也降低。     

Effect of Carbon Black Deactivation on the Mechanical and Electrical Properties of Elastomers

The role of polymer/filler interactions on the mechanical and electrical properties of elastomer nanocomposites is analyzed using dielectric spectroscopy, cyclic stress/strain tests, and online dc‐conductivity measurements. Pristine and deactivated (graphitized) CBs are studied in different rubber matrices. Due to confinement effects, an interphase of strongly immobilized polymer is present between adjacent filler particles, representing stiff but flexible mechanical bonds of the filler network. Under deformation of the sample, these bonds bend and finally break. Cyclic stress/strain measurements are analyzed by fitting the data to a microstructure‐based material model that allows for the evaluation of microscopic parameters of the polymer and filler network.

     

Effect of peroxide crosslinking on the dynamic modulus of silicone rubber

The effect of peroxide crosslinking on the dynamic modulus of a silica‐reinforced silicone [poly(dimethylsiloxane)] elastomer was investigated. Three different peroxides (t‐butyl peroxide, t‐butyl perbenzoate, and benzoyl peroxide) were employed at various practical loadings and differences in the nonlinear behavior of the dynamic modulus were found. Results are discussed with respect to changes in crosslinking density and the identity of the peroxide. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 1504–1512, 2005     

Effect of temperature on dynamic rheological properties of uncured rubber materials in both the linear and the nonlinear viscoelastic domains

Investigating how rubber materials are affected by strain and strain rate (or frequency) in the room‐to‐curing temperature range allows to fully characterize them not only with respect to their processing behavior but also in view of their likely performances after vulcanization. Using a closed cavity dynamic rheometer, the adequate test protocols and data treatment, three gum elastomers, and three carbon black filled compounds were investigated in the 60–180°C range. The article describes the test protocol and the associated data treatment that were developed to document the effects of strain and temperature in both the linear and the nonlinear domains. Complex modulus G* and third relative torque harmonic variations with strain amplitude and temperature are reported and discussed in details. A set of relatively simple mathematical equations are demonstrated to offer the possibility to summarize large quantities of experimental data through a limited number of parameters whose physical meaning can be explained with respect to known aspects of polymer and rubber sciences. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

路基处治土回弹模量试验研究

对路基处治土水泥砂进行室内回弹模量试验,并对所得试验结果进行深入分析和探讨,为相关工程实践提供数据支持。试验结果表明,水泥含量和压实度等对水泥砂的回弹模量有较大的影响。     

Study on the Optical and Mesomorphic Properties of Cholesteric Side-Chain Liquid Crystalline Elastomers Containing a Nematic Cross-Linking Agent

To study the effect of the content of the nematic cross-linking units on the mesophase behaviors, the optical and mesomorphic properties of liquid crystalline elastomers (LCEs), aseries of LCEs have been synthesized by hydrosilylation reaction with poly(methylhydrogeno)siloxane, a cholesteric liquid crystalline monomer, and a nematic cross-linking agent. The chemical structures and properties of the synthesized LCEs have been investigated by use of various techniques. Homopolymer P₀ bearing only cholesteric component displays a smectic A phase, but elastomers P₁-P₅ containing different content of nematic cross-linking units show a cholesteric mesophase. The reflection wavelengths of theLCEs show a weak temperature dependence at lower temperatures but a strong temperature dependence at higher temperatures. Furthermore, the maximum reflection wavelengths of the LCEs can be stabilized over a wide temperature range when the LCEs are heated, suggesting that the helical structure and pitch of the cholesteric phase can be stabilized with a polymer network.     

The Effect of the Density and Nature of Spatial Network in Elastomers on Their Viscoelastic Characteristics

Abstract

We have studied the effect of the density of the networks formed by fluctuating entanglements and chemical crosslinking on the relationships between the circular frequency ω and the storage and loss moduli, G' and G”, for polybutadienes of narrow and wide molecular weight distributions (the ratio M_w/M_n varied from 1.1 to 3.35) and different microstructure. Polybutadienes were crosslinked by thermal, radiation, and sulphur vulcanization. With increasing density v of a network of chemical crosslinks, which is characterized by the average molecular weight of a chain length (M_e ), pseudo-equilibrium plateau extends to the side of low frequencies with a certain small increase of its level. This increase becomes noticeable when M_e is approximately equal to the average molecular weight M_e of the chain length between the fluctuating entanglements of an uncrosslinked elastomer. At the same time the maxima on the curves of G”(ω) are smoothed out and the losses reduce to negligibly small values with decreasing frequency.     

Effects of fullerene derivatives on the gas permeability of thermoplastic polyurethane elastomers

In an effort to improve the gas barrier properties of thermoplastic polyurethane (TPU) elastomers, fullerene derivatives were added as fillers, and the resulting O₂ and CO₂ permeabilities were analyzed. The addition of 5 wt % polyhydroxylated fullerene {fullerenol [C₆₀(OH)_n] mixture, where n = 6–12} decreased the gas permeability by approximately 10–20%. According to the hole volumes computed with the results from positron annihilation lifetime spectroscopy, the addition of fullerene derivatives did not produce any changes in the hole volumes of the TPUs. Thus, the reduction in the TPU gas permeability was not caused by changes in the hole volumes. Instead, an inhibited diffusion of gas molecules by fullerene particles was deduced as the cause of the decrease in gas permeability from changes in the diffusion coefficient with temperature. The addition of urethanized fullerene, prepared through the chemical modification of fullerenol, markedly affected the TPU gas barrier properties. As compared to fullerenol addition, the gas barrier properties improved approximately fourfold for O₂ and approximately fivefold for CO₂. These results suggest that the dispersability of urethanized fullerene in TPU was higher than that of fullerenol. We found that the gas barrier properties were independent of the structure of polyol. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2014 , 131, 39986.     

基于神经网络的工艺参数对翘曲变形和收缩的影响研究

以拉伸和冲击试样(无缺口和有缺口)三种塑料零件的注射成型为例,以翘曲变形和收缩为评价指标,采用Taguchi方法及极差和方差分析方法,优化了模具温度、熔体温度、注塑压力、注塑时间、保压压力、保压时间和冷却时间,获得了最优的工艺参数组合。建立了神经网络模型,利用神经网络的预测功能,预测出变动单个工艺参数下的翘曲变形量和收缩率,研究了单个工艺参数对翘曲变形和收缩的影响,以指导生产实践。     

网络教育对高等教育公平的影响

在实现高等教育大众化进程中,教育公平已成为亟待解决的社会问题。网络教育,对教育公平的实现有积极的影响,但同时由于其自身的局限、教育手段、人们的观念、社会某些不规范办学等因素的影响,网络教育在实现高等教育公平中还存在种种阻抗因素。本文对我国的高等教育不公平现状及网络教育实现教育公平的优劣势进行了分析,并提出了一些解决措施,以期淡化其消极影响,扬长避短,促进高等教育公平的实现。     

Effects of processing parameters on the properties of microwave‐devulcanized ground tire rubber/polyethylene dynamically revulcanized blends

This work aimed to evaluate the effects of processing parameters on properties of dynamically revulcanized blends based on 60 wt % of devulcanized ground tire rubber (GTR) and 40 wt % of high density polyethylene (HDPE). Devulcanization of the GTR was carried out in a system comprised of a conventional microwave oven adapted with a motorized stirring system with speed control. The resulting devulcanized GTR contained 26 wt % soluble in toluene. It was processed with HDPE in a twin screw extruder to produce a dynamically revulcanized blend. Processing parameters such as screw speed and feeding mode were varied. Their effects were evaluated based on tensile, dynamic mechanical, thermal and rheological properties, as well as on morphology. The results show the importance of the processing parameters involved in the production of blends with dynamically revulcanized rubber phase in the extruder, and good match between the residence time of the rubber and its revulcanization kinetics. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43503.     

基于神经网络的深部液流转向效果预测方法研究

深部液流转向技术能有效地改善高含水后期的水驱效果,但由于其影响因素复杂且相互关联,为此提出了基于Matlab下神经网络技术预测转向效果的方法。分别建立BP和RBF网络,通过两种网络方法对深部液流转向效果进行预测,结果表明,采用神经网络方法克服了传统方法的局限性,建立的RBF模型预测精度比BP模型更高,能有效满足现场应用。     

网络环境对传统会计的影响及分析

随着网络技术的广泛应用,网络经济的蓬勃发展,会计已经进入了商络时代。在网络环境下的传统会计将会受到由于环境和技术变革带来的影响。本文将对网络环境对传统会计的影响进行探讨和分析。     

The prediction of elastic modulus of the mullite fiber network based on the actual structure architecture

Accurately establishing the relationship between the network architecture characteristics and performance of fibrous porous ceramics is instructive for structural design and performance control. In the present work, fibrous, high porous (82.87–90.02%), low density (0.247–0.512 g/cm³) and low elastic modulus (50.62–188.56 MPa) mullite ceramics were fabricated by freeze casting. The three dimensional network architectures were characterized by X-ray tomography technique and quantitatively analyzed by 3D image analysis software (imorph, www.imorph.fr). The radius (5.04 µm), types, lengths (64.72–96.49 µm) and orientations (0.87–1.45, anisotropy parameter) of fiber segments in the network architecture were investigated. The extracted results were employed to predict the Young's modulus of the mullite fibrous porous ceramics according to a model based on the bending and axial compression of single fiber segment. The predicted Young's modulus agreed well with the experimental results. The differences of Young's modulus and Poisson ratio between the prediction and the model of Markaki and Clyne were compared. The comparison showed that the difference became larger when the aspect ratio of the fiber segment was less than 6 due to the effect of axial compression. The predicted Poisson ratio had a certain dependence on fiber segment aspect ratio and got close to the constant (1/π) reported by Markaki and Clyne with the increase of fiber segment aspect ratio.     

基于BP神经网络在储层预测中研究及应用

利用人工神经网络模式识别技术可以在现有油层下面寻找新的油气储层,也可以预测储层类型。将用于预测的网络提供的浅层地震反演参数集作为输入,经BP网络学习后,对深层或无井储层进行预测。最后利用垦71地区实际参数,对BP神经网络进行检验。     

聚氨酯弹性体摩擦系数影响因素探讨

介绍了弹性材料的摩擦机理，从文献值和实验数据介绍了硬度、软段种类及其相对分子质量、异氰酸酯指数，成型温度以及环境温度等因素对聚氨酯弹性体摩擦系数的数据。聚氨酯摩擦系数与测试条件有关。相同测试条件下，硬度低、极性基团多（如聚酯型聚氨酯）的聚氨酯弹性体摩擦系数较大。在60℃以下，随环境温度的提高，聚氨酯弹性体的摩擦 系数增加。