Synthetic hydrogels 3. Solvent effects on poly(2-hydroxyethyl methacrylate) networks

Poly(2-hydroxyethyl methacrylate) networks were synthesized in aqueous solutions of propylene glycol, ethylene glycol, ethylene glycol monomethyl ether, or ethylene glycol dimethyl ether and the influences of solvent on phase separation during the polymerization process studied. Results from conversion-phase diagrams, turbidity measurements, swelling studies, and viscosity measurements show that the phase separation process is dependent upon the solubility parameter of the organic solvent, the instantaneous monomer concentration at each stage of the gel formation process, and the crosslinker content of the reaction mixture.     

基于RecurDyn的旋转弹发射出筒过程动力学仿真

针对某旋转弹筒弹分离试验时出现尾翼座与筒壁刮擦的问题,用Recur Dyn对弹体出筒过程进行动力学仿真.对筒弹分离试验进行故障复现,分析故障原因;根据故障分析结论对筒弹设计方案提出更改建议并再次仿真;第二次试验结果表明该分析结论和仿真结果正确.此外,还给出设计方案更改后正常发动机推力状况下的弹体出筒过程的重要总体仿真结果.该研究缩短产品设计周期、降低研制成本.     

活性端基聚氨酯橡胶改性不饱和聚酯树脂的研究(Ⅱ)

通过在不饱和聚酯树脂中加入活性端基聚氨酯橡胶来降低树脂的体积收缩.树脂固化前,橡胶与不饱和聚酯树脂相溶性好;树脂固化时橡胶中的不饱和双键反应可参与反应,并呈一定粒径的胶粒析出.本文研究了几种活性端基聚氨酯橡胶对不饱和聚酯树脂收缩控制的影响.     

Specially elaborated thermally induced phase separation to fabricate poly(L‐lactic acid) scaffolds with ultra large pores and good interconnectivity

Poly(L ‐lactic acid) (PLLA) scaffolds with pore diameters from several micrometers to ～300 μm were fabricated by a specially elaborated thermally induced phase separation technique. Two different coarsening protocols, i.e., normal coarsening and multi‐step coarsening were compared in consideration of phase separation and domain growth. A normal coarsening route produced scaffolds with pore size from several micrometers to 150 μm depending on the coarsening time after phase separation, accompanying with the emergence of isolated pores at long time coarsening. Scaffolds with large pores with size up to ～300 μm were fabricated by the two‐step coarsening technique, e.g., the PLLA‐solvent (dioxane/water) system was coarsened at a temperature after phase separation for a period, followed by coarsening at a lower temperature for another period. In parallel with formation of the large pores, the interconnectivity between pores was also improved, which was evidenced by scanning electron microscopy, gelatin solution pervasion, and collagen entrapment. The present technique provides the ability to produce scaffolds with high purity, controllable microstructures, and ease of modification, and hence can be widely used in tissue engineering field. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 3336–3342, 2006     

Preparations and properties of thermosensitive terpolymers of N‐isopropylacrylamide,sodium 2‐acrylamido‐2‐methyl‐propanesuphonate,and N‐tert‐butylacrylamide

Terpolymers based on N‐isopropylacrylamide, sodium 2‐acrylamido‐2‐methyl‐propanesulfonate, and N‐tert‐butylacrylamide were synthesized by free‐radical copolymerization with 2,2′‐azobisisobutyronitrile as an initiator. The lower critical solution temperatures (LCSTs) of the linear polymer aqueous solutions were determined by the measurement of the transmittance on UV at different temperatures. The influence of the polymer concentration, polymer composition, and ionic strength on the LCSTs of the linear polymers was investigated. The LCST decreased with increases in the hydrophobic monomer N‐tert‐butylacrylamide, polymer concentration, and ionic strength. The phase transition became sharp when the polymer concentration and ionic strength increased. Meanwhile, the crosslinked hydrogels were prepared with the same recipe used for the linear terpolymers, but a crosslinker was added to the reaction system. The swelling ratios of the hydrogels at various temperatures and salt solutions were determined. The hydrogels possessed both high swelling ratios and thermosensitivity. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

石油亚砜树脂分离稀土的性能研究

应用石油亚砜萃取树脂与ＮＨ＿４ＣＮＳ体系，测定了稀土元素的分配比（Ｋｄ）、分离因素（β）和分离度Ｒｓ），讨论了ＮＨ＿４ＣＮＳ的浓度、稀土进样量和温度等对稀土分离的影响。应用于混合稀土的分离和测定，分析了６０．３２％的氧化钇，相对标准偏差为±１．４７％。     

Surface modification of macroporous Al2O3 tubes with carbon-doped TiO2 intermediate layer and preparation of highly permeable palladium composite membranes for hydrogen separation

ABSTRACT

To prepare H₂-permeable palladium composite membranes, a novel carbon-doped microporous TiO₂ intermediate layer was introduced to modify the surface of macroporous Al₂O₃ substrates. The Pd/TiO₂–C/Al₂O₃ membrane was prepared via electroless plating, and thereafter, carbon residue in the intermediate layer was removed by calcination in air, yielding a Pd/TiO₂/Al₂O₃ membrane. Experimental results indicate that the carbon residue shrinks the pore size of the intermediate layer and facilitates a decrease of membrane defects. Additionally, carbon removal induces a higher effective membrane area at the permeate side, which enhances hydrogen permeability. Furthermore, the apparent activation energy (E_A) and stability of the as-prepared Pd/TiO₂/Al₂O₃ membrane were investigated.     

异丙醇一步法生产甲基异丁基酮分离过程的研究

本文对异丙醇一步法合成MIBK工艺的分离过程进行了基础测定，包括气液平衡和液液平衡测定。在此基础上。对原有的MIBK分离工艺进行了研究，提出了改进的工艺流程，使MIBK的回收率由32％提高到91．7％．能耗由11,42t水蒸汽／t产品降为8．27t水蒸汽／t产品。     

分离式反应器在精细化工中的应用

对分离式反应器原理进行了分析 ,将分离式反应器用于汽液反应 ,可使反应的选择性大大提高     

连续式双膜分离塔的数学模型

本文建立了适用于连续式双膜分离塔的数学模型。用实验数据验证了数学模型的可行性和合理性。将本模型与已发表的模型进行了比较,结果表明本模型具有形式简单、计算方便和适用范围更宽广等优点。