Hydraulic resistance of rigid polyurethane foams. I. Effect of different surfactants on foam structure and properties

Foams used in buoyancy applications must resist penetration by water at significant depths of immersion. The behavior of water blown rigid polyurethane foam at different water pressures from 0 to 3 MPa are studied in this work. The effects of different surfactants on the cell structure and hydraulic resistance of the foams are examined. The foams have densities in the range of 145 to 160 kg/m³. With increasing applied hydraulic pressure, it is found that the foams have very small buoyancy losses at low pressures but beyond a threshold pressure, buoyancy losses increase rapidly. The threshold pressures of the foams increase with decrease in cell window area. A cell window is the lamella of the foam material that separates two adjacent cells. The cell sizes of the foam are found to correlate with the size of the air bubbles entrained during initial mixing. Surfactants, which reduce the surface tension of the polyol to the greatest extent, are found to give the finest initial bubbles, smaller cells, and foams with the highest hydraulic resistance. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 2821–2829, 2004     

硬质泡沫橡胶浮子的试制

针对泡沫浮子的使用要求，筛选出了用于制备泡沫橡胶浮子的配方体系，通过实验确定出了3种不同发泡剂的泡沫橡胶浮子的配方，比较了垂直自由发泡法、垂直加压发泡法和水平加压发泡法的优缺点。     

建筑工程机电安装施工技术

机电安装在建筑工程中涉及的专业面非常广泛,学科跨度较大。虽然机电安装有自身的固有特征,但它的通用性很强。分析了机电安装工程的概况、特点和相关技术,研究了机电安装中出现的问题,并提出相应的解决措施。     

商业综合体地下室底板疏水施工

阐述了商业综合体地下室的疏水工程,包括各个工艺环节的要点、要求和安全性。     

复合泡沫塑料的性能改进研究

为改善复合泡沫塑料的介电性能,采用金属氧化物粒子填充改性双马来酰亚胺空芯玻璃微球复合泡沫塑料得到了高介电常数、低介质损耗因数、低密度、力学性能良好的电介质材料。     

无患子表面活性物及其复配体系的性质研究

对天然植物原料无患子提取物中的表面活性物的性质（临界胶束浓度、表面张力和起泡性能）及其影响因素（温度、pH、水硬度和盐度等）进行了系统的研究，结果表明无患子表面活性物具有很低的cmc和γcmc，且在一定范围内受一些因素的影响也不大，是一种理想的香波原料；同时也研究了无患子活性物与其他温和型的阴离子表面活性剂的复配体系，表明具有明显的协同增效效果。     

塑料注射成型新技术——微孔发泡技术的应用

主要介绍微孔发泡技术的工艺过程、应用特性及加工条件、气体条件对微孔发泡过程的影响     

国外聚氨酯硬泡发泡剂最新进展

零ODP(臭氧消耗能)发泡剂是在聚氨酯硬泡中替代CFCs的新一代发泡剂,阐述了美国、日本、欧洲CFCs替代的现状,并详细介绍了国外零ODP发泡剂的最新进展。     

Polyimide foams with ultralow dielectric constants

To explore ultralow dielectric constant polyimide, the crosslinked polyimide foams (PIFs) were prepared from 3,3′,4,4′‐benzophenonetetracarboxylic dianhydride (BTDA), 4,4′‐oxydianiline (ODA), and 2,4,6‐triaminopyrimidine (TAP) via a poly(ester–amine salt) (PEAS) process. FTIR measurements indicated that TAP did not yield a negative effect on imidization of PEAS precursors. SEM measurement revealed the homogeneous cell structure. Through using TAP as a crosslinking monomer, the mechanical properties of PIFs could be improved in comparison with uncrosslinked BTDA/ODA based PIF. The crosslinked PIFs still exhibited excellent thermal stability with 5% weight loss temperatures higher than 520°C. In the field with frequency higher than 100 Hz, the dielectric constants of the obtained PIFs ranged from 1.77 to 2.4, and the dielectric losses were smaller than 3 × 10^?2 at 25–150°C. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 1734–1740, 2006     

低雾化低挥发性汽车用新型聚氨酯泡沫塑料助剂

康普顿公司开发了一系列适用于消除或减少汽车内饰件中胺扩散或雾化的添加剂，其中包括快速、有效的生产用零扩散催化剂和低雾化表面活性剂。该系列添加剂能大大降低泡沫制品中的胺扩散，与异氰酸酯和多元醇原料能组成最佳组合，以保持良好的泡沫物理性能。