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141.
玻璃纤维增强聚氨酯泡沫塑料的压缩力学性能研究 总被引:12,自引:0,他引:12
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。 相似文献
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144.
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。 相似文献
145.
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. 相似文献
146.
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. 相似文献
147.
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. 相似文献
148.
Investigation on a new electrospun gel polymer electrolyte consisting of thermoplastic polyurethane (TPU) and poly(vinylidene fluoride) (PVdF) has been made. Its characteristics were investigated by scanning electron microscopy, FT-IR, Differential Scanning Calorimeter (DSC) analysis. This kind of gel polymer electrolyte had a high ionic conductivity about 3.2 × 10− 3 S cm− 1 at room temperature, and exhibited a high electrochemical stability up to 5.0 V versus Li+/Li, good mechanical strength and stability to allow safe operation in rechargeable lithium-ion polymer batteries. A Li/GPE/LiFePO4 cell delivered a high discharge capacity when it was evaluated at 0.1 °C—rate at 25 °C (167.8 mAh g− 1). And a very stable cycle performance also existed under this low current density. 相似文献
149.
Melinda VargováGustav Plesch Ulrich F. Vogt Miroslav ZahoranMichal Gorbár Karol Jesenák 《Applied Surface Science》2011,257(10):4678-4684
TiO2 thick films deposited on macroporous reticulated Al2O3 foams with pore size of 10 ppi and 15 ppi were prepared using dip coating from slurries of Aeroxide® P25 nanopowder and precipitated titania. All prepared films have sufficiently good adhesion to the surface of the substrate also in case of strongly cracked films. No measurable release of deposited TiO2 after repeated photocatalytic cycles was observed. The photocatalytic activity was characterized as the rate of mineralization of aqueous phenol solution under irradiation of UVA light by TOC technique. The best activity was obtained with Aeroxide® P25 coated Al2O3 foam with the pore size of 10 ppi, annealed at 600 °C. The optimal annealing temperature for preparation of films from precipitated titania could be determined at 700 °C. Films prepared by sol-gel deposition technique were considerably thinner compared to coatings made of suspensions and their photocatalytic activity was significantly smaller. 相似文献
150.
Veara Loha Aleš Prokop Liping Du Robert D. Tanner 《Applied biochemistry and biotechnology》1999,79(1-3):701-712
Foam fractionation isone of the low operating-cost techniques for removing proteins from a dilute solution. The initial bulk
solution pH and air superficial velocity play an importantrole in the foam-fractionation process. Denaturation of proteins
(enzymes) can occur, however, during the foamfractionation process from the shear forces resulting from bursting air bubbles.
At the extreme bulk solution pHs (lower than 3.0 and higher than 10.0), the en zymatic activity of cellulase in the foamate
phase drops significantly. Within these two pH boundsan increase in the air superficial velocity, Vo, and a decrease in the bulk solution pH leads to a decrease in the separation ratio (SR), defined as theratio of the protein
concentration in the foamate to the protein concentration in the residue. On the other hand, an increase in Vo provides a higher foamate-protein recovery. The process efficiency is defined as the product of foamate-protein recovery
times the SR times the cellulase activity. The optimal operating condition of the cellulase foamfractionation process is taken
into account at the maximum value of the processefficiency. In this study, that optimal condition is atan air superficial
velocity of 32 cm/min and a bulk-solution pH of 10.0. At this condition, the recovered foamate is about 80% of the original
protein mass, the SR is about 12, and the en zymatic activity is about 60% of the original cellulase activity. 相似文献