Rheological study of poly(ethylene glycol)/poly(N‐isopropylacrylamide‐co‐2‐acrylamido‐2‐methylpropanesulphonic acid) semiinterpenetrating network formation

The formation of a series of semiinterpenetrating network (SIPN) hydrogels made by free‐radical copolymerization of N‐isopropylacrylamide (NIPA) and 2‐acrylamido‐2‐methylpropanesulphonic acid (AMPS) with varying comonomer mole ratios, crosslinked with N,N′‐methylene‐bisacrylamide (MBAA) in the presence of poly(ethylene glycol) (PEG) with average molecular weight 6,000 g mol^?1 was studied via determination of complex viscosity, η*, using plate–plate rheometry. The isothermal time dependence of η* at various temperatures or the variation of η* with temperature of pregel solutions was utilized to detect the onset of gelation. The SIPN systems were compared with the corresponding gels made under the same conditions in the absence of PEG. The copolymer mainchain composition has a major effect on the time or temperature for onset of gelation and in particular gelation appears to be inhibited to some extent by MBAA when the AMPS/NIPA mole ratio in the pregel solution exceeds 0.5. The presence or absence of PEG in pregel solutions has a lesser effect on gelation. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 2083–2087, 2004     

The compatibility of the blends of PUs with PVC and the adhesion behavior of PU to PVC

Three series of polyurethane adhesives—polyethyleneadipateurethane (PEAU), polybuthyleneadipateurethane (PBAU), and polyhexyleneadipateurethane (PHAU)—with the same MW and hard/soft segment ratio, based on the three polyesters polyethyleneadipate (PEA), polybuthyleneadipate (PBA), polyhexyleneadipate (PHA), with 4,4′-diphnylmethane diisocyanate (MDI), and butendiol were synthesized by solution polymerization. The crystallinity of these polyesters and polyurethanes (PUs) and the compatibility of blends of PUs with PVC were studied by means of wide-angle x-ray diffraction (WAXD), differential scanning calorimetry (DSC), dynamic thermomechanical analysis (DMA), testing of solubility, and phase contrast microscopy. The results indicated that PBAU/PVC and PHAU/PVC were compatible systems, but PEAU/PVC was incompatible. The adhesive strengths of the three adhesives were quite different from one another, in the order of PBAU ≥ PHAU ? PEAU. The influences of crystallinity and compatibility on adhesion were discussed, and the Diffusion Theory for PU-PVC systems was recommended. © 1995 John Wiley & Sons, Inc.     

塑料激光成型新技术

研究和探讨了塑料激光塑性成型的成型机理、变形方向控制。阐述了该成型方法的特点、影响因素及材料特性。并介绍了成型实例。     

一种适用于降压DC-DC的改进型电流检测电路

基于电流模式控制能够较好地改善DC-DC的性能,设计一种适用于降压DC-DC的改进型电流检测电路,所提出的电流检测电路提高了电流感应的速度和精度。通过对电路的理论分析与设计,采用SMIC 0.18μm CMOS工艺模型,利用Cadence工具对电路进行仿真验证,所提出的电流检测电路在负载电流为50 mA~500 mA时都能够达到96%的效率以及小于40 ns的建立时间。在开关频率为2 MHz时,输入电压范围为2.5 V~4.2 V,所需电感值为4.7μH,电容值为10μF,输出电压纹波小于18 mV。     

Entanglement Loss in Fast-Flowing Entangled Polymer: Numerical Simulation of The Short-Chain Behavior and Interpretation of Phenomenology

Although some of the important consequences of flow-induced entanglement loss in entangled polymer rheology have recently been recognized, this specific molecular mechanism has rarely been investigated quantitatively based on experiments or molecular theories. For the first time, the amount of entanglement loss of a short entangled linear polymer (i.e., seven entanglements per chain at equilibrium) during fast-flow deformation is directly tracked in the stochastic simulation of an existing reptation model. The primary finding is that significant entanglement loss is observed in both fast elongation and fast shearing, and, contrary to some earlier conjectures, is particularly pronounced in elongational flow when polymer chain stretching formally commences. Furthermore, according to the current simulation in which three different CCR (Convective Constraint Release) schemes are considered, entanglement loss appears to have very prominent effects on the elongational rheology of an entangled linear polymer – an observation that had rarely been recognized or considered before. On the other hand, the currently explored features of flow-induced entanglement loss are tentatively linked to a wide variety of peculiar empirical properties of temporarily entangled polymer liquids. In particular, we are thus able to provide a consistent molecular explanation of the fairly well-known phenomenological effects of polydispersity and long-chain branching leading to a pronounced strain-hardening phenomenon, in view of two newly proposed effects of heterogeneous relaxations in preventing, directly or indirectly, fast entanglement loss during flows.     

Preparation and properties of (BATB–ODPA) polyimide–clay nanocomposite materials

A series of polymer–clay nanocomposite (PCN) materials consisting of 1,4‐bis(4‐aminophenoxy)‐2‐tert‐butylbenzene–4,4′‐oxydiphthalic anhydride (BATB–ODPA) polyimide (PI) and layered montmorillonite (MMT) clay were successfully prepared by an in situ polymerization reaction through thermal imidization up to 300°C. The synthesized PCN materials were subsequently characterized by Fourier‐Transform infrared (FTIR) spectroscopy, wide‐angle powder X‐ray diffraction (XRD) and transmission electron microscopy (TEM). The effects of material composition on thermal stability, mechanical strength, molecular permeability and optical clarity of bulk PI and PCN materials in the form of membranes were studied by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), dynamic mechanical analysis (DMA), molecular permeability analysis (GPA) and ultraviolet‐visible (UV/VIS) transmission spectra, respectively. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 1072–1079, 2004     

压力流化床燃烧煤水混合燃料泵送给料技术在国外的研究进展

压力流化床燃烧技术近二十年来在世界上得到很大发展。煤的湿法给料系统具有比干法输送系统更简单，运行调节更可靠等优点。煤水混合物可泵送的水分在２５％左右，煤的粒度一般为０～６ｍｍ，表现为非牛顿的假塑性流体特性，通过级配来达到一定的稳定性和良好输送性能，且流动阻力低，不用添加剂即可实现泵送，它的应用使压力流化床的燃烧制备和输送系统成本大大降低。     

Experimental analysis of particle deposition on single collectors

Experimental studies of particle deposition from liquid suspensions of monodispersed particles flowing past single spherical collectors were carried out and compared with theoretical results based on trajectory calculations. The experimental observations indicate the significant effect of particle flocculation and thus suggest the importance of sedimentation as a collection mechanism. The agreement between the theoretical results and the experimental data is good when the surface force interactions are favorable for collection. However, when the electrokinetic repulsion dominates in the neighborhood of the collector, the rate of collection drops rapidly, although not to zero as predicted by theory.     

影响裂解汽油二段加氢催化剂长周期运转因素及解决措施

从裂解汽油二段加氢催化剂性能、裂解汽油和操作条件等方面论述了影响该催化剂长周期运转的因素,并针对这些因素提出相应的措施,以达到延长催化剂运转周期的目的。