Preparation of a self‐compatibility alloy via a seed‐graft concentrated‐emulsion pathway

A novel polymerization procedure, the concentrated‐emulsion graft polymerization of styrene monomer with poly(butyl acrylate) seed, was proposed for the production of a self‐compatibility macromolecule alloy. The effects of the butyl acrylate content, sodium dodecyl sulfate concentration, and polymerization temperature on the graft ratio were investigated. Scanning electron microscopy, transmission electron microscopy, and impact strength were used to characterize the microstructure and mechanical performance of the self‐compatibility macromolecule alloy. The results showed that increasing the butyl acrylate content, reducing the sodium dodecyl sulfate concentration, and improving the polymerization temperature all favored an increased graft ratio, which resulted in increased impact strength of the self‐compatibility macromolecule alloy. Therefore, the concentrated‐emulsion polymerization method is particularly suitable for seed‐graft polymerization. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 2915–2920, 2002; DOI 10.1002/app.10288     

CO2‐assisted polymer processing: A new alternative for intractable polymers

CO₂‐assisted polymer processing is proposed as an alternative route for intractable and high molecular weight polymers based on the plasticization effects of CO₂ and its direct effect on the melting behavior of semicrystalline polymers. A modified processing system was used to process a variety of polymers in the presence of high‐pressure CO₂. The system includes an extruder that was modified to allow for high pressures created by the injection of CO₂. The new design includes a modified feed section that allows a given mass of polymer to interact with CO₂ before and during the extrusion process. The inherent shear mixing and the presence of CO₂ allow for a specific control over the extrudate morphology. Results suggest that this alternative design provides a new and easy route to melt process high melt viscosity polymers of commercial importance, such as polytetrafluoroethylene (PTFE), fluorinated ethylene propylene copolymer (FEP), and syndiotactic polystyrene (s‐PS). The increased processability of these systems in CO₂ is related to the plasticization effect of CO₂ that was quantified through a depression in the glass‐transition temperature according to the Chow model. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 1501–1511, 2004     

On‐line determination of the conversion in a styrene bulk polymerization batch reactor using near‐infrared spectroscopy

A fast on‐line method for measuring the monomer conversion of a styrene batch polymerization reaction with near‐infrared spectroscopy (NIR) has been developed. Multivariate calibration was performed, using polymer samples having temperatures around the set point of the batch reactor (75–85°C) and monomer conversions up to 35%. The calibration model was built in such a way that the effect of the temperature on the predicted conversion of the sample was minimized. The method was validated in a number of batch runs. In these runs, the batch temperature and molar mass distributions of the polymer were varied. At‐line size‐exclusion chromatography was used as a reference method for measuring the monomer conversion. Results show that on‐line conversion monitoring with NIR offered overall an excellent accuracy (～ 0.32% conversion). For high and low monomer conversions a small bias in the predicted conversion is present. The method proved to be insensitive to both relative large changes (10°C) of the batch temperature and to considerable changes of the molar mass distribution of the polymer. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 90–98, 2002; DOI 10.1002/app.10241     

Synthesis and dielectric properties of polystyrene‐clay nanocomposite materials

Polystyrene‐clay nanocomposite (PsCN) materials were synthesized and their properties of crystallinity, thermal behavior, and dielectric characteristics were investigated. A polymerizable cationic surfactant, [2‐(dimethylamino)ethyl]triphenylphonium bromide, was used for the intercalation of montmorillonite (MMT). The organophilic MMT was prepared by Na⁺‐exchanged MMT and ammonium cations of a cationic surfactant in an aqueous medium. Organophilic styrene monomers were intercalated into the interlayer regions of organophilic clay hosts followed by a free‐radical polymerization. Exfoliation to 2 wt % MMT in the polystyrene (PS) matrix was achieved as revealed by X‐ray diffraction (XRD) and transmission electron microscopy (TEM). Thermal properties by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) were also studied. The dielectric properties of PsCNs in the form of film with clay loading from 1.0 to 5.0 wt % were measured under frequencies of 100 Hz–1 MHz at 25–70°C. A decreased dielectric constant and low dielectric loss were observed for PsCN materials. The dielectric response at low frequency that originated from dipole orientation was suppressed due to the intercalation of clay materials. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 1368–1373, 2004     

微波合成SiO2气凝胶核/聚苯乙烯壳微球研究

将水玻璃为硅源所制备的纳米孔硅气凝胶与苯乙烯单体用微波加热合成法制备出SiO2气凝胶核/聚苯乙烯壳复合微球.用顺序间隔取样测试方法试验复合微球的密度、转化率和包覆率与微波合成温度、时间和聚合体系各组分变化情况,分析讨论了影响变化因素和原因.通过TEM和FE-SEM对复合微球进行结构与形貌表征.结果表明,优选体系组分配比为SiO2气凝胶3g、苯乙烯21g、乙醇水溶剂配比为380g∶20g、引发剂4.2g及稳定剂2g,微波合成工艺参数为加热功率500W,加热时间40min、加热温度60℃.在此工艺条件下合成,复合微球合成转化率是67.1%、包覆率为32.7%,制备出的核壳结构复合微球的粒径约为100~200nm、震实密度为0.353g/cm3,且表面凹凸不平状似"草莓"的微粒.     

夏热冬冷地区双面保温体系传热系数研究

本文通过改变挤塑式聚苯乙烯保温板的位置和厚度,测定了普通砖墙双面保温体系的传热系数.研究结果表明：设置双面保温体系的普通砖墙受热桥影响很小,能够较好地满足夏热冬冷地区的建筑节能标准和要求.     

两亲嵌段共聚物(聚苯乙烯-b-聚己内酯)的合成与表征

采用原子转移自由基聚合法合成聚苯乙烯,经过四氢铝锂还原,制得单羟基封端的聚苯乙烯.与己内酯进行开环反应制备AB型两亲性嵌段共聚物(聚苯乙烯-b-聚己内酯),并通过凝胶渗透色谱和红外光谱对聚合物进行了结构表征.研究表明,将此两亲性嵌段聚合物加入到环氧树脂/甲基四氢苯酐固化剂混合体系中,经过反应诱导相分离发现,该嵌段在环氧基体中发生微观相分离,相分离尺寸控制在纳米尺度,可以作为环氧改性剂使用.     

聚苯乙烯注塑成型制品双折射行为模拟分析

建立了模拟聚合物注塑成型过程中流动应力的数学模型.利用Leonov黏弹性模型对聚苯乙烯熔体在非等温幂率稳态剪切流下的流动行为进行模拟分析.并研究了聚苯乙烯在注塑成型填充过程中,由于流动而产生的剪切和拉伸作用以及模腔内聚合物熔体的温度变化对制品双折射行为的影响,得到了与实验相符的结果,证明了本研究中模拟方法的可行性.     

高抗冲聚苯乙烯粒子发灰原因分析及对策

针对高抗冲聚苯乙烯（HIPS）生产过程中出现的粒子发灰现象,从原料、聚合和脱挥单元分析了原因,并采取了相应对策。结果表明:原料苯乙烯的含氧储存环境、聚丁二烯橡胶（BR）中挥发分及氯离子含量高是导致产品粒子发灰的主要原因;将苯乙烯存储由有氧环境改为氮气环境,严格控制 BR 中挥发分质量分数小于 0.5%,且优选线型低顺式BR,可有效降低 HIPS 产品粒子发灰的几率。     

Hybrid anion exchange membranes with adjustable ion transport channels designed by compounding SEBS and homo-polystyrene

Hybrid anion exchange membranes (AEMs) were prepared via chemically functionalizing and crosslinking poly(styrene-b-[ethylene-co-butylene]-b-styrene) (SEBS) copolymers and low molecular weight homo-polystyrene (hPS). Via sequential chloromethylation, crosslinking, quaternization, and alkalization, a series of hPS/SEBS AEMs were obtained with varying content of hPS. Systematic structural, morphological, mechanical, absorption, and transport measurements reveal that these properties depend on the total PS content in the membranes. Particularly, increasing total PS content causes (a) PS domains in the AEMs transition the cylindrical morphology to lamella-like morphology with comparable correlation length; (b) Young's modulus, water uptake, swelling ratio, ionic exchange capacity and ionic conductivity of the AEMs, and T_g of PS phase increase. In addition, the alkaline stability of the hPS/SEBS AEMs is also improved by addition of hPS. These findings suggest that the proposed method can develop high performance SEBS AEMs that are suitable for fuel cell applications.