Influence of thermal runaway in styrene–acrylonitrile bulk copolymerization revealed by computational fluid dynamics modeling

The computational fluid dynamics (CFD) and kinetic-based moment methods coupled approach is adopted to simulate the bulk copolymerization of styrene–acrylonitrile (SAN) in a stirred tank reactor. Numerical simulations are carried out to investigate the impacts of impeller speed, monomer ratio, initiator ratio, and initial reaction temperature on the copolymerization process and product properties. Particularly, the Chaos theory is selected as a criterion for evaluating the occurrence of the thermal runaway. The Flory's and Stockmayer's distributions are employed to calculate chain length distribution and copolymer composition distribution of copolymer. The simulation results highlight that the appearance of thermal runaway can be postponed by properly increasing the rotation speed, decreasing the initiator loadings, initial acrylonitrile contents and initial reactor temperature. Furthermore, significant differences exist in the product properties that predicted by the ideal and non-ideal models, which demonstrates that the temperature heterogeneity plays a crucial role in SAN copolymerization. This study could offer references for the safe operation and design of polymerization processes.     

Experimental campaign and assessment of a complete 240-kW Proton Exchange Membrane Fuel Cell power system for maritime applications

This work shows the results of the experimental assessment of the HI-SEA joint laboratory between Fincantieri, the main Italian shipbuilder, and the University of Genova. The HI-SEA system is a 240 kW real-scale test rig complete of auxiliaries, made up of 8 Proton Exchange Membrane Fuel Cell stacks installed on two parallel branches, which can operate independently or in parallel by means of two dedicated DC/DC converters. The experimental assessment is performed by considering: (i) Stationary performance; (ii) dynamic performance; (iii) a maritime operative profile defined together with Fincantieri. The experimental results obtained in this work demonstrated that the system can successfully respond to static, dynamic, and typical maritime operative load profiles. It was also assessed the ability of the system to work simultaneously with two parallel branches, by means of two DC/DC converters, which represents a clear advantage in terms of load sharing and redundance onboard for security issues. Furthermore, the present study gives important advice and criteria for the design, construction, and control of similar Fuel Cell complete systems for maritime applications, which is particularly relevant considering that experimental studies on complete Fuel Cell systems is still limited.     

活性磷酸钙微观形貌对SAN悬浮聚合的影响

活性磷酸钙作为悬浮聚合的分散剂,在苯乙烯-丙烯腈共聚物(SAN)聚合体系中对聚合产物形貌粒径有重要影响。对活性磷酸钙(HAP)进行扫描电镜观察,发现不同来源的HAP表面形貌有较大差异。将这几种活性磷酸钙作为分散剂用于苯乙烯-丙烯腈共聚物(SAN)的悬浮聚合。对比聚合产物的粒子形貌及粒径分布,发现当HAP微观形貌为均匀竹叶形或棒状,且堆积松散时得到的聚合物粒子外观规整,粒径分布均匀。     

适用于涂装工艺的喷涂级ABS产品研制

分析了涂装件喷涂漆膜与ABS产品之间的相互结合性能,并针对喷涂级ABS产品研制开展了系列改良实验,通过对高丙烯腈含量SAN牌号的开发和极性助剂包的改善,开发了喷涂级ABS产品。通过对喷涂级ABS产品的性能分析,证实了开发的喷涂级产品更适用于涂装件市场的生产需求。     

不同粒径SiO_2对PMMA/SAN共混物相行为的影响

采用溶液浇铸法制备了不同组分比的聚甲基丙烯酸甲酯(PMMA)/苯乙烯–丙烯腈无规共聚物(SAN)共混物。通过光学显微镜,考察了不同粒径的SiO2粒子对PMMA/SAN非临界组成共混物相行为的影响。结果表明,SiO2粒子的加入会抑制PMMA/SAN共混物相形态的发展,这种抑制作用在填料粒径越小时表现越明显。此外,SiO2粒子对PMMA/SAN共混物相分离动力学的影响具有组分依赖性,当PMMA为少数相时,粒子对PMMA/SAN共混物相分离动力学的抑制作用更为明显。该现象可能是由于SiO2粒子的选择性吸附限制了PMMA分子链的运动,从而导致PMMA为少数相的PMMA/SAN体系的黏弹性增加更大。     

Effect of heat treatment on foaming properties of ostrich (Struthio camelus) egg white proteins

The effect of heat-treatment on foaming properties of ostrich albumen was investigated. At pH 7.5, coagulation of ovotransferrin (OT) resulted in minimum foaming capacity (FC) and maximum foam density (FD). While both exposure of sulfhydryl groups of ovalbumin (OV) and OT-OV interactions improved FC at lower pH, neither of them had beneficial effect on FC at pH 9. At pH 9, FC and FD were mildly affected by heat-treatment because of less aggregation of OT, then FC decreased due to covalent aggregates composed of ovomucin and OV, but at higher temperatures, higher level of OV unfolding resulted in enhanced FC.     

浅析IP—SAN和FC—SAN解决方案

存储技术发展日新月异，SAN可说是DAS网络化发展趋势下的产物。本文简单介绍IPSAN和FCSAN，对IPSAN和FCSAN的架构以及构建成本、可扩展性、易用性、兼容性、稳定性和速度等的比较，认为各有千秋，两者之间应取长补短，互相共存。     

FC200现场总线模块在转炉炼钢厂的应用

介绍现场总线模块原理及FC200现场总线模块产品的特点,结合转炉工艺特点配置系统硬件及设置参数;根据转炉工艺要求介绍编程要点。FC200现场总线模块是成熟的产品,经现场应用结果表明它能出色应用在冶金等行业,相比传统集中式系统节约大量有色金属,减少自动化系统的整体投资,提高可靠性,方便维护。     

国内常见ABS产品对比剖析

收集了国内市场上常见的几种ABS产品,通过力学分析以及组成、结构分析,总结出各种产品特点及适用领域。考察组成ABS的接枝物含量以及SAN分子质量、氮含量对ABS性能的影响。发现苯乙烯组分对ABS产品的流动性影响较大,丙烯腈组分对拉伸强度、冲击强度影响较大。     

视频监控云存储的发展趋势

本文介绍了视频监控系统DAS、NAS和IPSAN三种典型的存储架构，以及云存储的优势和发展趋势。