聚氨酯制品发展概况

聚氨酯是世界六大合成材料之一，具有许多优异特性。介绍了国内外聚氨酯工业的历史与现状，简述了聚氨酯制品的原料与助剂及其主要品种的发展概况。     

Field Validation of DNDC Model for Methane and Nitrous Oxide Emissions from Rice-based Production Systems of India

The DNDC (DeNitrification and DeComposition) model was tested against experimental data on CH₄ and N₂O emissions from rice fields at different geographical locations in India. There was a good agreement between the simulated and observed values of CH₄ and N₂O emissions. The difference between observed and simulated CH₄ emissions in all sites ranged from −11.6 to 62.5 kg C ha⁻¹ season⁻¹. Most discrepancies between simulated and observed seasonal fluxes were less than 20% of the field estimate of the seasonal flux. The relative deviation between observed and simulated cumulative N₂O emissions ranged from −237.8 to 28.6%. However, some discrepancies existed between observed and simulated seasonal patterns of CH₄ and N₂O emissions. The model simulated zero N₂O emissions from continuously flooded rice fields and poorly simulated CH₄ emissions from Allahabad site. For all other simulated cases, the model satisfactorily simulated the seasonal variations in greenhouse gas emission from paddy fields with different land management. The model also simulated the C and N balances in all the sites, including other gas fluxes, viz. CO₂, NO, NO₂, N₂ and NH₃ emissions. Sensitivity tests for CH₄ indicate that soil texture and pH significantly influenced the CH₄ emission. Changes in organic C content had a moderate influence on CH₄ emission on these sites. Introducing the mid-season drainage reduced CH₄ emissions significantly. Process-based biogeochemical modeling, as with DNDC, can help in identifying strategies for optimizing resource use, increasing productivity, closing yield gaps and reducing adverse environmental impacts.     

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     

热敏微胶囊热响应特性研究

将热敏微胶囊作为基本显影单元,影像稳定性和分辨率得到了提高,影像形成速度也更符合数字化成像的要求。本文结合热敏技术、微胶囊技术,将染料前体微胶囊化,制备出粒径在1μm以下的热敏微胶囊。测量了囊壁的玻璃化温度,对显影后的影像进行了对比,测量了不同显影温度下的影像密度,分析了影像密度随显影温度变化的关系。     

光敏变色纤维材料

简单介绍了光敏变色纤维材料的发展情况，集中介绍了目前应用于纤维材料领域的光致变色有机化合物的光致变色机理、化合物类型，以及应用于纤维材料中的方法及这方面的发展趋势。     

Liquid-phase stereoselective thymol hydrogenation over supported nickel catalysts

The stereoselective hydrogenation of thymol was studied in liquid phase over several nickel catalysts, modified by coimpregnation of inorganic compounds containing chlorine. The total activity of all catalysts studied was decreased and was on the same order of magnitude, indicating that chlorine even after reduction remains on the surface and is responsible for the poisoning effects. Such blocking of accessible sites results in similar reaction rates for the catalysts studied. Selectivity and stereoselectivity to menthols and menthones changed significantly. The modifiers could influence the rate of keto-enol transformations, which is thought to be the key selectivity and stereoselectivity governing step.     

硅橡胶在电气绝缘方面的应用进展

简述了国内外硅橡胶(高温硫化型硅橡胶、室温硫化型硅橡胶、液体硅橡胶等)在电气绝缘方面的应用情况。     

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     

SiC质耐火材料的氧化机理

SiC材料是一种性能优良的耐火材料，具有高导热性，高抗热震性，良好的高温强度等优点，但是由于碳化硅在氧化性气体，如O2，CO2，水蒸汽中发生膨胀劣化，严重影响SiC耐火材料的使用湿度和应用范围，本文主要讨论不同结合剂类型的SiC耐火材料的氧化特征，并提出抗氧化的可能途径。