Simultaneous measurement of viscoelastic changes and cell opening during processing of flexible polyurethane foam

A parallel-plate rheomete was constructed and used to study the development of dynamic shear modulus and cell opening under forced adiabatic conditions for a series of flexible slabstock polyurethane foams. Typical industrial formulations were used. The plates were heated to follow the adiabatic temperature profile of a real foam bun during foaming. The rheometer overcomes difficulties encountered in other methods such as heat loss and bubble damage caused by the probe.A four-stage modulus development profile was observed: initial bubble growth, bubble network, polymer stiffening and final curing. Chemical structure development was also studied under forced adiabatic conditions, using Fourier transform infrared spectroscopy. Polymer stiffening coincided with bidentate (hydrogen-bonded) urea formation.The normal force exerted by the expanding foam on the plates was found to be a function of the rate of foam expansion and the foam modulus. A sudden drop in the normal force typically coincides with the visually observed blow-off in the reacting foam bun, thus the normal force profile is a new and accurate indicator of cell opening. The normal force profile clearly shows that cell opening occurs just after the onset of polymer stiffening, thus illustrating the role of polymer rheology in the cell opening mechanism.Dedicated to the memory of Professor Tasos C. PapanastasiouPortions presented at the SPI Polyurethanes Technical/Marketing Conference, October 9–12, 1994, Boston, massachusetts, USA (Best paper award) and at the XIIth International Congress on Rheology, August 18–23, 1996, Québec City, Québec, Canada.     

玻璃纤维增强聚氨酯泡沫塑料的压缩力学性能研究

本文研究了两种不同密度的玻璃纤维增强聚氨酯泡沫塑料在准静态压缩下的力学性能。给出了与相应密度的普通泡沫塑料力学性能的比较，实验结果表明：两种增强泡沫塑料在压缩载荷作用下，具有不同于普通泡沫塑料的应力－应变特性，压缩模量和强度一般均有不同程度的提高，而且对相同纤维含量的增强泡沫塑料来说，密度较高的材料增强效果较好。     

含球形空腔或刚性夹杂的中厚圆板在弯曲变形时的弹性场

本文将空间轴对称问题的Папковиц-Neuber通解用复变量广义解析函数表示,推导出用复变函数法求解空间轴对称问题的基本公式,并以此为工具求得了含球形空腔或刚性夹杂的中厚圆板在轴对称弯曲变形时的完全解.     

泡沫流体的剪应力与法向应力差

本文在同时考虑表面张力与粘性力的情况下,以三维模型—长菱形十二面体及泡沫的应力张量表达式为基础,得出了泡沫的剪应力及法向应力差表达式,并通过计算机进行了求解,讨论了泡沫粘度、泡沫大小等因素对剪应力及法向应力差的影响。 实验使用了 RMS-605 大型流交仪、RV-2 流变仪及毛细管流变仪测定泡沫流变特性。消除了表面滑移影响后得到的剪应力与法向应力表数据与理论结果较接近,说明理论模型具有一定的实用价值。     

泡沫液膜的分子动力学模拟及泡沫析液机制的研究

采用分子动力学MD方法模拟表面活性剂稳定的泡沫液膜,通过分析表面活性剂头基与水分子的径向分布函数,分析泡沫液膜中水分子的状态,对结合水、捕获水进行定量;采用电导法测定不同表面活性剂稳定的泡沫的析液曲线,结合分子模拟结果,分析泡沫析液的微观机制,建立泡沫析液量随时间变化的物理模型,给出了模型参数的物理意义.     

单油酸三羟甲基丙烷酯改性水性聚氨酯

利用单油酸三羟甲基丙烷酯(TMPM)、异佛尔酮二异氰酸酯(IPDI)和聚氧化丙烯(PPG)等制备水性聚氨酯。采用透射电镜(TEM)、动态激光光散射(DLLS)、红外光谱(FT-IR)、热重分析(TGA)和表面张力仪表征了乳液胶束形态、产物结构及性能。结果表明:水性聚氨酯(PU)分子上引入脂肪侧链容易在水中形成规整的胶束,但TMPM改性的水性聚氨酯胶束粒径随TMPM含量的增加不断增大,当w(TMPM)=0.07时,乳液不稳定;脂肪侧链的引入降低了水性聚氨酯乳液的表面张力,表面张力随着反应体系中—NCO和—OH摩尔比的增大而降低,随交联度的增大先增加后减小;TMPM的引入可以提高胶膜的热稳定性。     

Simultaneous Determination of Cadmium,Lead, Copper and Mercury Ions Using Organofunctionalized SBA‐15 Nanostructured Silica Modified Graphite–Polyurethane Composite Electrode

A new sensor has been developed for the simultaneous detection of cadmium, lead, copper and mercury, using differential pulse and square wave anodic stripping voltammetry (DPASV and SWASV) at a graphite–polyurethane composite electrode with SBA‐15 silica organofunctionalized with 2‐benzothiazolethiol as bulk modifier. The heavy metal ions were preconcentrated on the surface of the modified electrode at ?1.1 V vs. SCE where they complex with 2‐benzothiazolethiol and are reduced to the metals, and are then reoxidized. Optimum SWASV conditions lead to nanomolar detection limits and simultaneous determination of Cd²⁺, Pb²⁺, Cu²⁺ and Hg²⁺ in natural waters was achieved.     

Preparation and properties of PU/MCMMT nanocomposites

The cetyltrimethyl ammonium bromide (CTAB) was used as a swelling agent to be intercalated into the galleries of the montmorillonite (MMT) platelets to get the organic MMT (CMMT). Then 4,4′‐diphenylmethane diisocyanate (MDI) were grafted on CMMT by the reaction between hydroxyls in organic MMT platelets and MDI to synthesize the MDI modified CMMT (MCMMT). Polyurethane (PU)/MCMMT composites were prepared by situ polymerization. The MCMMT platelets dispersed in a PU matrix in nanometer scale. The dispersion and intercalation degree of the MCMMT platelets decreased with increase in the content of MCMMT. Under the same content of fillers, the tensile strength and tear strength of PU/MCMMT nanocomposites were higher than those of PU/organic MMT nanocomposites. The reinforcing effect of the MCMMT platelets to the PU was better than that of the organic MMT platelets. With increase in the content of MCMMT, the tensile strength and tear strength of the PU/MCMMT nanocomposites were increased, while the extent of the increase slowed down. Compared with those of PU, the thermal stability of PU/MCMMT nanocomposites was increased. Copyright © 2009 John Wiley & Sons, Ltd.     

采用高分辨电镜分析Cu掺杂聚-4-甲基-1-戊烯泡沫材料采用高分辨电镜分析Cu掺杂聚-4-甲基-1-戊烯泡沫材料

利用物理掺杂的方法,制备了铜掺杂聚-4-甲基-1-戊烯(PMP)低密度泡沫材料,采用高分辨扫描电子显微镜和透射电子显微镜,分析了泡沫材料的微观结构、成分及微区成分分布。结果表明:与PMP泡沫相比,铜掺杂PMP泡沫的孔洞直径和网络骨架尺寸变大;铜颗粒镶嵌在PMP泡沫的有机骨架上且有团聚现象;泡沫材料中除碳、铜外,还残留有杂质元素氧;铜颗粒被PMP泡沫包裹,与碳网络骨架之间接触紧密。     

Efficient One-Step Passivation of Polyurethane Using Transurethanization

The uncontrolled accumulation of biological materials on the surface of medical devices through protein adsorption or cell adhesion causes adverse biological reactions in the living host system, leading to complications. In this study, poly(ethylene glycol) (PEG) is successfully grafted onto polyurethane (PU) surfaces by using a new strategy through a simple and efficient transurethanization reaction. The PEG hydroxyl group is deprotonated and then reacted with the PU surface to provide antiadhesive hydrophilic surfaces in a single step. Surface analysis techniques proved the grafting to be efficient and the formation of a hydrophilic polymeric layer at the surface of PU. Biological assays showed that the surface modification induced lower protein adsorption, cell, platelet, and bacterial adhesion than untreated surfaces, showing a potential for biomedical applications.