Unusual Phase Separation Kinetics in Poly(Methyl Methacrylate)/Poly(Styrene-co-Acrylonitrile) (PMMA/SAN) Blends with PMMA of Different Molecular Weights

The influence of molecular weight of poly (methyl methacrylate) (PMMA) on the thermodynamics and dynamics of phase separation in PMMA/poly (styrene-co-acrylonitrile) (SAN) blends was investigated via optical microscopy, time-resolved small-angle light scattering (SALS), and dynamic rheological measurements. It was found that the cloud point temperature of the blends decreased with an increase in the molecular weight of the PMMA. The phase separation rates of PMMA 48K/SAN and PMMA 85K/SAN blends with the near-critical composition were almost the same at small quench depths due to the limited mobility of molecular chains at low temperatures. However, an unexpected phase separation dynamics was observed at larger quench depths. Not only the morphology evolution but also the apparent diffusion coefficient D_app calculated from SALS revealed that the phase separation rate was faster in the PMMA 85K/SAN blend than in the PMMA 48K/SAN blend. The possible reasons for this unusual rapid kinetics of phase separation observed in the higher molecular weight blend were discussed in terms of molecular mobility and viscoelasticity.     

存储区域网络的安全性分析与对策研究

论述了对存储区域网络(SAN)进行安全性研究的意义,阐述了存储区域网络的概念和结构体系,系统分析了SAN技术中存在的安全威胁,并针对其不安全因素提出了相应的策略,对利用SAN进行安全存储起到了指导作用。     

A Study of the Synthesis of EPDM-g-MAN and Toughness of its Blend with SAN (AEMS)

Ethylene–propylene–diene–methyl methacrylate/acrylonitrile terpolymers (EPDM-g-MAN) were synthesized by comonomers methyl methacrylate and acrylonitrile (MMA-AN) grafted on EPDM macromolecules with solution graft copolymerization. The engineering plastics of the blend of EPDM-g-MAN with SAN (AEMS) were prepared by blending EPDM-g-MAN with SAN resin. The effect of AN/MMA-AN weight percentage (f _AN) on monomer conversion ratio, grafting ratio, and grafting efficiency of the graft copolymerization and the notched Izod impact strength of AEMS were investigated. The notched Izod impact strength of AEMS, prepared by blending SAN with EPDM-g-MAN, was synthesized under our optimum S2 reaction conditions, with EPDM/MMA-AN weight proportion of 50/50 and f _AN of 10 wt%, presenting a peak with the maximum value of 61.0 kJ/m². The microstructure of AEMS prepared with S2 reaction conditions showed that when the polarity of EPDM-g-MAN was appropriate, the EPDM phase formed a pseudocontinuous phase in the SAN matrix and the interfacial adhesion was strong, which could induce shear yielding of the SAN matrix. Differential scanning calorimetry analysis showed that there was good compatibility between SAN resin and EPDM-g-MAN synthesized with f _AN of 10 wt% and a EPDM/MMA-AN weight ratio of 50/50.     

统一存储网的研究和设计

NAS为用户提供件I／O服务,SAN为用户提供数据块I／O服务,计算机应用的发展要求存储网络同时提供2种服务．统一存储网(USN)利用TCP／IP协议,将NAS和IP-SAN整合成单一的存储空间,同时为用户提供件I／O和数据块I／O2种服务．理论分析和实验证明这种方案是可行的。     

高校数字图书馆中网络存储系统的选择方案

针对高校图书馆数据流量大 ,共享并发用户多的特点 ,叙述了目前应用于数字图书馆中的网络存储系统 ,并对DAS、NAS和SAN三类网络存储系统性能进行比较 ,提出了适合我国高校数字图书馆建设中的网络存储解决方案     

SAN技术及其在远程网络教学中的应用

随着越来越多的学校开展网络教学，对网络教学的要求也越来越高，但教学资源的配置并没有因网络的存在而最大程度地趋向合理。这里通过提出把SAN存储网络技术引入教学系统，将存储能力从服务器中分离出来，以便使远程教学系统更加能够满足大量远程访问端同时学习，以及使大量流媒体课件的传输和访问得以快速无阻碍的实现。从而使远程网络教学系统得以更加迅速的发展。     

网络存储的发展与研究

网络存储提高了数据的共享性、可用性和可扩展性、管理性，但以存储网络为中心的存储解决不了全部的数据存储问题，如存储共享、数据的共享与融合等。因此，网络存储将不断地向前发展。首先论述NAS、SAN和IP—SAN的结构、特点以及目前正在研究的网络存储新技术NASD和OBS，然后分析网络存储未来发展的趋势。     

主流存储技术的研究与应用

介绍了传统存储结构的优点和不足，分析了主流存储技术IPSAN技术和FCSAN技术。介绍了齐齐哈尔大学网络信息中心在网络存储上选用了基于iSCSI协议的IPSAN产品。     

SAN存储技术在高校数字图书馆中的应用

随着计算机和网络技术的发展,高校数字图书馆如何应对急剧膨胀的数字资源和激增的访问量成为图书馆建设中的一个重要问题。本文介绍了当前较为先进的数据集中管理新技术SAN,及其在高校数字图书馆中的应用。     

Morphology of PC/SAN blends: effect of reactive compatibilization,SAN concentration,processing, and viscosity ratio

This article examines the effects of dispersed phase concentration, processing apparatus, viscosity ratio, and interfacial compatibilization using an SAN–amine compatibilizer on the morphology of blends of bisphenol A–polycarbonate (PC) with styrene–acrylonitrile (SAN) copolymers. For uncompatibilized blends, the dispersed phase particle size increased significantly with SAN concentration, and was found to exhibit a minimum at a viscosity ratio of approximately 0.35 for a fixed concentration of 30% SAN in the blend. Although the morphology of uncompatibilized PC/SAN blends mixed in a Brabender mixer, single‐ and twin‐screw extruders were quite similar, the twin‐screw extruder produced significantly finer morphologies in blends containing SAN–amine. The average particle size for blends compatibilized with the SAN–amine polymer was approximately half that of uncompatibilized blends and was relatively independent of viscosity ratio and dispersed phase composition. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 71–82, 1999