Polymerization of liquid propylene with a fourth‐generation Ziegler–Natta catalyst: Influence of temperature,hydrogen, monomer concentration,and prepolymerization method on powder morphology

Liquid propylene was polymerized in a 5‐L autoclave batch reactor using a commercially available TiCl₄/MgCl₂/Al(ethyl)₃/DCPDMS Ziegler–Natta catalyst, with a phthalate ester as internal electron donor. The powders from these polymerizations were characterized using laser diffraction particle size distribution (PSD) analysis, scanning electron microscopy (SEM), and bulk density measurements. These characteristics were analyzed as a function of the process conditions, including hydrogen and monomer concentration, polymerization temperature, and the prepolymerization method. It was shown that polymerization temperature influences the powder morphology to a large extent. At low temperatures, high‐density particles were obtained, showing regular shaped particle surfaces and low porosities. With increasing temperature, the morphology gradually was transferred into a more open structure, with irregular surfaces and poor replication of the shape of the catalyst particle. When using a prepolymerization step at a relatively low temperature, the morphology obtained was determined by this prepolymerization step and was independent from conditions in main polymerization. The morphology obtained was the same as that observed after a full polymerization at temperature. Even when using a short polymerization at an increasing temperature, the morphology was strongly influenced by the initial conditions. The effect of variation in hydrogen concentration supported the conclusion that the initial polymerization rate determines the powder morphology. In the absence of hydrogen, high bulk densities, and regularly shaped particles were obtained, even at high temperatures. With increasing hydrogen concentration, the reaction rates increased rapidly, and with that changed the morphology. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 1421–1435, 2003     

多交联体系PU/分子筛复合材料的制备及表征

以聚酯多元醇(PEA)、2,4-甲苯二异氰酸酯(TDI-100)和13X分子筛为原料,采用预聚法制备PU/13X分子筛预聚体,再将预聚体分成两部分,分别与不同比例的扩链剂(MOCA)混合反应,然后将两种体系混合后浇铸成型,制备出多交联体系PU/13X分子筛复合材料.对其力学性能、耐溶剂性能进行了测试并与聚氨酯材料的性能进行了比较.结果表明,多交联体系PU/13X复合材料的耐撕裂性能明显提高,拉伸性能稍有下降;通过DMA、DSC测定,表明多交联体系PU/13X复合材料的玻璃化转变温度降低,微相分离更好,阻尼性能下降;分子筛可以改善多交联体系PU/13X复合材料的耐溶剂性能.     

一种高温固化环氧基体树脂的研制

采用预聚合、B阶树脂合成及机械共混工艺制备了一种高温固化环氧基体树脂,探讨了增韧剂-端羧基液体橡胶(CTBN)用量对基体树脂韧性和耐热性的影响.试验结果表明:当CTBN的用量为5phr,且与环氧树脂采用预聚合方式制得的基体树脂获得了较高的耐热性和韧性,玻璃化转变温度为189℃,冲击强度达到了26.12k J/m2;制得...     

A new route for the preparation of cyano‐containing poly(N‐isopropylacrylamide) microgel latex for specific immobilization of antibodies

A prepolymerization process was used to prepare functionalized poly(N‐isopropylacrylamide) latexes with surface cyano groups. The functionalized latexes prepared were characterized by FTIR, ¹H NMR, scanning electron microscopy and quasi‐elastic light scattering. In addition, the polymerization conversion and the water‐soluble polymer amounts were quantified. The polymerization conversions were found to be above 80% with 5–14 wt% of water soluble polymer formation. The immobilization of antibody (immunoglobulin) onto such cyano‐containing thermally sensitive particles, suggests the feasibility of specific dipole–dipole interactions between the cyano and hydroxyl functional groups from particle and antibody, respectively. Copyright © 2004 Society of Chemical Industry     

TiCl4-Mg(OC2H5)2催化乙烯聚合和形态学研究Ⅱ.预聚合对聚合物颗粒形态的修正

在较低的温度和乙烯分压下进行预聚合 ,然后提高温度和压力进行后续的聚合实验 ,考察了预聚合条件对催化剂聚合动力学和聚合物颗粒形态的影响。发现预聚合可以提高催化剂的活性 ,预聚合时间越长 ,催化剂活性提高越多。通过SEM分析发现 ,预聚合显著改善了聚合物的颗粒形态。由于聚合物颗粒中的线团状形态结构消失 ,聚合物粉体的堆密度显著上升。证明预聚合可以成功解决聚合速率提高与聚合物堆密度下降的矛盾     

超声波本体聚合在甲基丙烯酸甲酯-Al2O3陶瓷膜注凝成型中的应用研究

通过探讨水浴加热预聚合、微波恒温预聚合、微波预聚合及超声预聚合反应方式对甲基丙烯酸甲酯(MMA)进行预聚合反应,来确定适合作为Al2O3陶瓷膜注凝成型工艺中的预混液制备方式。结果表明:超声的空化作用能够有效地加快预聚合的反应速率,且在预聚合反应过程中,超声波的机械振动作用使MMA反应均匀,且不会发生局部爆聚现象。适合作为MMA预聚合的引发剂为偶氮二异丁腈(AIBN),其最佳用量为0.08%。发现微波的"致热效应"是MMA聚合速率加快的原因。     

The Solid State Postcondensation of PET, 3

Summary: It was demonstrated that it is possible to produce prepolymers with a number‐average degree of polymerisation on the order of 5–40 directly in a liquid‐liquid dispersion in less than three hours. It was also shown that prepolymers made via this route and rapidly crystallised by the addition of a dispersant at ambient temperature are more porous than prepolymers made in an industrial liquid melt process.

SEM micrograph of prepolymers pLL‐PTA with \overline {DP} _{\rm n} = 28, d_p ∈ 63–125 μm.     

40t/d PA6前聚合反应器设计简析

从设备与工艺两方面剖析了PA6生产前聚合反应器的设计。将反应器长径比例从原来的3:1改为10:1,并改进加热方式,优化结构设计,前聚合反应器设计为4段,各段间采用法兰连接,设计出生产能力40 t／d的前聚合反应器。     

降低TDI-TMP预聚物中游离-NCO含量的方法

研究用己内酰胺封闭TDI-TMP预聚物来降低游离-NCO含量的方法。试验确定了催化剂的种类及用量、温度、反应时间和封闭剂的用量等对封闭率的影响。选用了SD-101为催化剂,封闭温度80℃,使用理论用量的封闭剂反应3h后,游离-NCO含量降到0．5％(质量分数)以下,符合国际标准要求。     

Influence of the synthesis conditions on the properties of thermoplastic polyurethane elastomers

Thermoplastic polyurethane elastomers (TPUs) of constant composition were prepared by using the prepolymer method and by changing the reaction conditions (prepolymerization and chain‐extension time) to study the influence of these conditions on the final TPU properties. The TPUs were characterized by gel permeation chromatography, differential scanning calorimetry, strain–stress measurements, and contact‐angle measurements. To test the adhesion properties of the TPUs, poly(vinyl chloride) strips were bonded to each other by using TPU solutions and the T‐peel strength of the adhesive joints was measured. It was found that provided a threshold is crossed, the prepolymerization time markedly influences the final properties of the TPUs (viscosity of solutions, molecular weight, mechanical and adhesive behavior), whereas the chain extension time does not. Therefore, it is possible to prepare TPUs with specific properties by playing with the prepolymerization conditions. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 1590–1595, 2000