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41.
将水溶性纳米Zn0.2Fe2.8O4(ZFO)粒子、用氢氧化钠(NaOH)中和的丙烯酸(PAAS)加入一定量的聚乙烯醇(PVA)水溶液中分散均匀,再加入引发剂过硫酸钾、交联剂N,N’-亚甲基双丙烯酰胺引发聚合,制备了PVA/PAAS/ZFO水凝胶。采用傅里叶红外光谱仪(FTIR)、透射电子显微镜(TEM)对其组成和结构进行表征,并系统研究了复合水凝胶在不同溶剂中的溶胀性能。结果表明,纳米ZFO粒子均匀分散在PVA/PAAS凝胶网络中,纳米ZFO粒子的加入使水凝胶的溶胀速率和平衡溶胀度先增加后减小,在纳米ZFO含量为1%时达到最大;在不同浓度的电解质溶液和不同pH值的溶液中进行溶胀时,水凝胶表现出良好的离子浓度和p H刺激响应性。 相似文献
42.
Dipti Biswal 《Polymer》2011,52(26):5985-5992
A novel one-step method for the preparation of poly(β-amino ester) hydrogels has been developed. The one-step method utilizes a Michael type addition reaction between a difunctional diacrylate and a tetrafunctional primary diamine to create a crosslinked biodegradable hydrogel. It was shown that the molar ratio of the reactive acrylate to amine controlled the extent of polymerization and crosslinking density of the hydrogel system, which enabled for the end properties of the network (e.g., swelling, degradation, and mechanical) to be tuned. 相似文献
43.
介绍了一效蒸发器的主要制作工艺,将设备的整体热处理改为局部热处理和胀紧率的确定,为强度胀接大口径管子积累了经验。 相似文献
44.
Bryan D. Vogt Christopher L. Soles Hae-Jeong Lee Eric K. Lin Wen-li Wu 《Polymer》2005,46(5):1635-1642
Moisture absorption into ultrathin poly(vinyl pyrrolidone) (PVP) films with varying thickness was examined using X-ray reflectivity (XR) and quartz crystal microbalance (QCM) measurements. Two different surfaces were used for the substrate: a hydrophilic silicon oxide (SiOx) and a hydrophobic hexamethyldisilazane (HMDS) treated silicon oxide surface. The total equilibrium moisture absorption (solubility) was insensitive to the surface treatment in the thickest films (≈150 nm). However, strong reductions in the equilibrium uptake with decreasing PVP film thickness were observed on the HMDS surfaces, while the SiOx surface exhibited thickness independent equilibrium absorption. The decreased absorption with decreasing film thickness is attributed a depletion layer of water near the polymer/HMDS interface, arising from hydrophobic interactions between the surface and water. The diffusivity of water decreased when the film thickness was less than 60 nm, independent of the surface treatment. Changes in the properties of ultrathin polymer films occur even in plasticized films containing nearly 50% water. 相似文献
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47.
《Soils and Foundations》2022,62(1):101099
With the interests to see specimen thickness (hsp) effect on apparent swelling pressure (ps) of compacted bentonite and capture characteristics of ps development during wetting bentonite specimens (ps evolution, hereafter), a series of tests to measure ps of compacted bentonite specimens with a dry density (ρd) range of 0.99–1.76 Mg/m3 and a specimen thickness (hsp) range of 2–10 mm were conducted. Test results suggest: (1) ps evolution generally has common characteristics with four feature points chronologically: peak (tp, pp), valley (tv, pv), initial equilibrium (tei, pei) and an equilibrium (teq, peq), where, tp, tv, tei and teq represent time (t) and pp, pv, pei, and peq denote ps of the four feature points, respectively; (2) within the tested range, hsp effect is generally minor on ps at feature points, and pp, pv, pei, and peq have well correlations with specimen final dry density (ρdf); (3) time scale for specimens with different hsp can be well unified by a time coefficient χsp (=hsp/√t). 相似文献
48.
A method to prepare submicron-sized porous titanium oxide (TiO2) particles is studied in this work. Polystyrene (PS) template particles were prepared by emulsifier-free emulsion polymerization. The polymer templates dispersed in the aqueous solution have been used for entrapping titanium(IV) isopropoxide (TTIP), by the swelling process in a suitable solvent mixture containing a swelling solvent (good solvent or poor solvent), a TiO2 precursor (TTIP), and a chelating agent (AcAc), within the polymer templates, followed by hydrolysis/condensation reaction of TTIP confined in PS template particles by the addition of the chelating agent. The influence of various reaction parameters, such as mixtures of different weight ratios between the PS particles and desiccative TTIP, AcAc amounts, and the swelling solvent amounts and type, on the size, bulk, and composition of the particles was investigated. Porous TiO2 particles have been prepared by thermal decomposition of the PS templates at 500 °C. 相似文献
49.
Nanotubes were coated on the surface of active LiCoO2 particles using electrostatic heterocoagulation to enhance the electrochemical properties of a Li-ion battery. Only 0.5 wt% of multiwalled carbon nanotubes (MWCNTs) was added as a conducting agent into the LiCoO2 cathode, which had a density of 4.0 g cm−3. We found that our electrode that was prepared using heterocoagulation with 0.5 wt% of thin MWCNTs maintained a volumetric capacitance of 403 mAh cm−1 after 40 cycles from the initial 624 mAh cm−1, compared with previous result of 310 mAh cm−1 obtained from simple mixing with 3 wt% MWCNTs. The high volumetric capacity with smaller swelling using less amount of MWCNTs was attributed to the self-assembled nanotube network formed between active particles during coagulation, which was maintained with volume expansion during cycle testing. 相似文献
50.
Amino acid based superabsorbent polymer (SAP) organogel library has been synthesized from Boc-glycine/alanine/valine/leucine/isoleucine/phenylalanine methacryloyl-oxyethyl ester (Boc-Gly/Ala/Val/Leu/Ilu/Phe-HEMA), which can switch over to corresponding hydrogels by simple one step Boc deprotection method. Swelling behaviour of organogels is investigated in various organic solvents (dielectric constant (ε) between 2.25 and 46.7), shows superabsorbent property in nonpolar organic solvents (2.25 ≤ ε ≤ 10.26) and moderate degree of swelling in polar aprotic solvents like acetone, N,N-dimethylformamide (DMF), acetonitrile, dimethyl sulfoxide (DMSO), etc. Swelling property of organogels is greatly influenced by the –R group of pendant amino acids and increases as bulkiness and hydrophobicity of –R increased. Organogels release absorbed volatile organic compounds (VOCs) very rapidly at room temperature and bulkiness of –R group accelerate the deswelling kinetic. Deprotection of Boc groups in the organogel network converts them to superabsorbent cationic polyelectrolyte hydrogels with high degree of swelling (∼518 for hydrogel from leucine) due to the presence of –NH3+ ion functionality, and the swelling ratio of hydrogels is drastically affected by the –R group of amino acids moiety, pH of aqueous medium and ionic strength of the solutions. 相似文献