聚四氟乙烯废料作为填料的回收工艺

介绍聚四氟乙烯（PTFE）废料粉碎后作为填料填充纯PTFE的回收工艺．研究了PTFE废料粒径、各种填料用量及预成型压力对产品性能的影响,结果表明,PTFE废料粒径以76μm（200目）为最佳,纯PTFE、铜粉、PTFE废料和二硫化钼的最佳质量比为100：60：30：2,此时产品拉伸强度19MPa,断裂伸长率300％,能满足实际使用要求。预成型压力以50MPa最为适宜。填充石墨和聚苯酯进行实验,效果不佳。指出此工艺的关键问题是解决填料之间的界面相容性．     

含乙酸木素复合型聚氨酯材料的合成及其性能研究

对以乙酸木素(AL)为原料合成复合聚氨酯材料的方法及其特性进行了研究和探索。对乙酸法制浆废液的木素进行了提取和纯化,并采用红外光谱和GPC研究了乙酸木素的结构和分子质量。以乙酸木素代替部分聚乙二醇合成了AL-TDI-PEG复合聚氨酯,并对其进行了拉伸强度、最大伸长率、DSC和TGA热性能的测定和红外光谱分析,而且也对木素用量和这些物理性能之问的规律进行了研究和探索。实验结果表明,木素-TDI-PEG复合PU片具有较好的拉伸强度、伸长率和耐热性。当木素用量为20％时,强度达到最大,而超过20％时,强度有所降低,说明乙酸木素的加入对PU的强度有一定的影响。     

精铵扩产技术改造总结

我厂联碱生产的两大产品是纯碱和氯化铵 ,其中氯化铵又分为农业氯化铵和工业氯化铵两种。工业氯化铵 (以下称精铵 )的生产能力为 1 0 kt/a,经过 2 0 0 2年技术改造后 ,达到了 40 kt/a。由于农业氯化铵销售价格受政府调控影响较大 ,定价偏低 ,而精铵与农铵相比 ,成本虽略有提高 ,但市场销售价格较高 ,且销售情况良好。为适应国内外市场对精铵的需求 ,提高经济效益 ,我厂及时调整产品结构 ,加大精铵的经济投入 ,于 2 0 0 3年又投资约30 0万元对现有精铵系统进行了技术改造 ,将精铵生产能力扩大到了 60 kt/a。1　精铵工段生产原理及工艺流程1 .…     

Bridgman法晶体生长过程中界面形状的改变

对不同生长条件下,Bridgm an法晶体生长过程进行了计算,对界面形状的改变的规律加以总结,并讨论了不同生长条件对界面形状的改变的影响。换热系数、导热系数和晶体宽度是影响界面凸凹程度及其变化趋势的重要参数。     

防氡防辐射水泥砂浆的研究

介绍了环保型防氡防辐射水泥砂浆的研制,包括原材料的选择、配方确定和生产程序等.通过加入重金属元素原料如重晶石(BaSO4)、沸石、氧化铁粉、高铝水泥、石膏等能吸引放射线和屏蔽氡的原材料,提出研究能达到环保要求的民用防氡防辐射水泥砂浆.优选和试验了防氡防辐射材料对水泥防氡防辐射能力、性能的影响及其原理和机理.     

A block copolymer nanotemplate for mechanically tunable polarized emission from a conjugated polymer

A polymer blend system consisting of polystyrene grafted onto poly (p-phenylene ethynylene) (PS-g-PPE) and poly (styrene-block-isoprene-block-styrene) triblock copolymer (SIS) yields highly polarized emission due to the unidirectional alignment of the PPE molecules. During the roll casting, the triblock copolymer microphase separates and creates unidirectionally aligned PS cylindrical microdomains in the rubbery PI matrix. PPE, a fluorescent conjugated polymer, was grafted with polystyrene (PS) side chains that enabled sequestration and alignment of these rigid backbone emitter molecules into the PS microdomains of the SIS triblock copolymer. Deforming the thermoplastic elastomer in a direction perpendicular to the orientation direction of the cylinders causes rotation of the PS cylinders and the PPE emitter molecules and affords tunable polarized emission due to re-orientation of the PPE containing PS cylinders as well as film thinning from Poisson effect.     

Poly(vinyl acetate)/Silver Nanocomposite Microspheres Prepared by Suspension Polymerization at Low Temperature

Summary: High molecular weight (HMW) poly(vinyl acetate)/silver nanocomposite microspheres (PVAc/Ag), which are promising precursors of embolic materials with radiopacity, were prepared via a suspension polymerization approach in the presence of silver nanoparticles. It was found that a high yield and high molecular weight PVAc/Ag could be concurrently obtained even using a low‐temperature initiator 2,2′‐azobis(2,4‐dimethylvaleronitrile) (≈30 °C). In the case of presence of silver nanoparticles, the rate of polymerization was slightly slower than that without Ag. The suspension polymerization approach introduced could produce PVAc/Ag composite with conversion and viscosity‐average molecular weight ( ) up to 95% and 1 300 000, respectively, in spite of the low polymerization temperature (≈30 °C), in sharp contrast with an only ≈30% conversion of VAc under bulk polymerization. Morphology studies revealed that except normal suspension microspheres with a smooth surface, a golf ball‐like appearance of the microspheres was observed, due to the migration and aggregating of the hydrophilic Ag nanoparticles at the sublayer beneath the microsphere's surface.

     

Long Crack R-Curve of Aligned Porous Silicon Nitride

Long crack R -curve of a porous Si₃N₄ with aligned fibrous grains was investigated, using a chevron-notched beam technique. A crack was constrained to propagate normal to the grain alignment. The crack growth resistance of aligned porous Si₃N₄ was much larger compared with that of dense Si₃N₄ ceramics. Microstructure observations showed that pullouts of fibrous grains in aligned porous Si₃N₄ markedly increased during crack propagation relative to those of dense Si₃N₄, due to the existence of pores. The efficient grain pullouts in porous Si₃N₄ increased the bridging stress at the crack wake.     

Surface photografting polymerization of vinyl acetate,maleic anhydride,and their charge‐transfer complex. VI. Charge‐transfer complex (2)

The photografting copolymerization of a low‐density polyethylene/vinyl acetate (VAC)–maleic anhydride (MAH) binary monomer system was studied from the perspective of dynamics. The total conversion percentage (CP) and grafting conversion percentage (CG) were measured by gravimetry. On the basis of plots of CP and CG as functions of the polymerization time, the total polymerization rate (RP) and grafting polymerization rate (RG) were calculated. In addition, the apparent activation energy (E_a) and the reaction orders of the photografting polymerization under different reaction conditions, such as the total monomer concentration and the concentration of benzophenone (BP), were determined also. The results showed that, in comparison with the photografting polymerization of the two single monomers (VAC and MAH), RP and RG noticeably increased for the VAC–MAH binary monomer system. When the total monomer concentration was kept at 4M, the apparent E_a's of the three photografting polymerization systems were as follows: for VAC ([MAH]/[VAC] = 0/4), E_a's for the total polymerization and grafting polymerization were 41.00 and 43.90 kJ/mol, respectively; for MAH ([MAH]/[VAC] = 4/0, E_a's were 39.65 and 43.23 kJ/mol, respectively; and for the VAC–MAH binary monomer system, E_a's were 34.35 and 40.32 kJ/mol, respectively. These results suggested that the polymerization of the binary system occurred more readily than the other two. The reaction orders of RP with respect to the total monomer concentration of the monomers and the concentration of BP were 1.34 and 0.81, respectively. According to these investigations, it could be inferred that in the binary monomer system, both the free monomers and charge‐transfer complex took part in the polymerization; to the termination of the propagating chains, two possible pathways, unimolecular termination and bimolecular termination, coexisted in this binary monomer system. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 95: 910–915, 2005     

不同管径水平管气液两相流流动特性数值模拟

为更好了解不同管径水平管气液两相流的压降特性,选用空气和水在管径分别为38.1,50.8,101.6 mm,长为9.525 m的水平管内进行气液两相流数值模拟,并结合理论分析了不同管径下水平管气液两相流压降的变化规律.利用Fluent软件研究结果表明:在同一管径下,当液速一定时,压降随气速的增大而增大;气速恒定时,压降...