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H. Yamamoto N. Heyamoto T. Matsui N. Murayama J. Shibata 《International Journal of Thermophysics》2003,24(5):1385-1394
Polyvinylalcohol (PVA) polymer gel is a temperature sensitive polymeric gel, with a critical transition temperature (with H2O) of 310 K. At higher than 310 K, this temperature sensitive polymer gel shrinks because of discharging water, whereas at lower temperatures, the gel swelled because of absorbing water. The reversibility of the gel's volume change was confirmed by temperature swing. The adsorption behavior of an organic compound onto the PVA polymer gel in water was tested at various temperatures. The amount of adsorbed organic compound increased remarkably at temperatures higher than about 310 K. Then, it was confirmed that the organic compound in PVA polymer gel could be reversibly adsorbed and desorbed by a temperature change between 293 and 323 K. The mechanism of adsorption of the organic compound onto the PVA polymer gel could be explained by hydration and dehydration of polymer gel. 相似文献
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采用聚乙烯醇(PVA)对碳酸钙、淤泥进行改性并将其作为不饱和聚酯树脂填料。研究了PVA掺量对碳酸钙/不饱和聚酯树脂和淤泥/不饱和聚酯树脂体系力学性能的影响。采用IR、DSC和SEM探讨了PVA对这2类体系的改性机理。实验结果表明:加入5%PVA后,碳酸钙/树脂体系,淤泥/树脂体系弯曲强度分别提高了55.3%和58.4%。PVA对2种体系的改性增强效应均源于PVA与填料和树脂之间氢键的桥梁作用,氢键改善了无机填料与树脂的相容性,这与以往改性剂与碳酸钙反应生成酯酸钙固化物的机理是不同的。 相似文献
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Polyvinylalcohol (PVA) of different molecular weights was cross-linked with succinyl, adipoyl, or sebacoyl chloride to obtain hydrogel-forming polymers and to determine their suitability as colon-specific drug delivery systems. Diclofenac sodium, propranolol hydrochloride, and vitamin B6 hydrochloride were used as hydrophilic model drugs with colon-specific release that should yield high concentrations in the large intestine, minimizing release in the upper part of the gastrointestinal tract. Spray-dried mixtures of the drugs and the polymer (at a 1 : 2 w/w ratio) were prepared, and the release of the drugs from the mixtures was evaluated in vitro at pH 2.0, 5.5, and 7.4. The results indicated the ability of the cross-linked polymers to slow the release of the drugs analyzed with respect to the pure drug dissolution at each pH. The lengthening of the cross-linker acyl chain was noted to decrease drug release further. 相似文献
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Frank Schulze Anke Dienelt Sven Geissler Paul Zaslansky Janosch Schoon Katja Henzler Peter Guttmann Azza Gramoun Lindsey A. Crowe Lionel Maurizi Jean‐Paul Vallée Heinrich Hofmann Georg N. Duda Andrea Ode 《Small (Weinheim an der Bergstrasse, Germany)》2014,10(21):4340-4351
Mesenchymal stromal cells (MSCs) are promising candidates in regenerative cell‐therapies. However, optimizing their number and route of delivery remains a critical issue, which can be addressed by monitoring the MSCs’ bio‐distribution in vivo using super‐paramagnetic iron‐oxide nanoparticles (SPIONs). In this study, amino‐polyvinyl alcohol coated (A‐PVA) SPIONs are introduced for cell‐labeling and visualization by magnetic resonance imaging (MRI) of human MSCs. Size and surface charge of A‐PVA‐SPIONs differ depending on their solvent. Under MSC‐labeling conditions, A‐PVA‐SPIONs have a hydrodynamic diameter of 42 ± 2 nm and a negative Zeta potential of 25 ± 5 mV, which enable efficient internalization by MSCs without the need to use transfection agents. Transmission X‐ray microscopy localizes A‐PVA‐SPIONs in intracellular vesicles and as cytosolic single particles. After identifying non‐interfering cell‐assays and determining the delivered and cellular dose, in addition to the administered dose, A‐PVA‐SPIONs are found to be non‐toxic to MSCs and non‐destructive towards their multi‐lineage differentiation potential. Surprisingly, MSC migration is increased. In MRI, A‐PVA‐SPION‐labeled MSCs are successfully visualized in vitro and in vivo. In conclusion, A‐PVA‐SPIONs have no unfavorable influences on MSCs, although it becomes evident how sensitive their functional behavior is towards SPION‐labeling. And A‐PVA‐SPIONs allow MSC‐monitoring in vivo. 相似文献
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The effect of moisture on the fibre/matrix interaction in epoxy/anhydride composites is investigated and explained through the characterisation of the matrix cure in the interphase. The fibre/matrix interaction is inferred from ILSS measurements on the composite, which are compared with a recently-introduced DSC interaction parameter. The matrix cure in the bulk as well as in the interphase is characterised through FT-IR microspectroscopy. Complementary information is gained by measuring the overall Tg value. Moisture is shown to lower the fibre/matrix interaction if the prepreg (= composite precursor) is stored at room temperature or lower prior to final cure. This is due to the reduced crosslink density of the matrix. For PE prepreg stored in ordinary atmospheric conditions, moisture from the surroundings lowers the fibre/matrix interaction sharply. If the prepreg is stored in a dry environment, nearly no effect of the storage is detected on the fibre matrix interaction in PE (polyethylene) fibre composites, while for PVAL (polyvinylalcohol) fibre composites a strong decrease is still found, caused by water adsorbed at the more hydrophilic fibre surface. 相似文献
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高强高模聚乙烯醇纤维研究进展 总被引:2,自引:0,他引:2
本文主要介绍近年来高强高模聚乙烯醇纤维研究在聚合度选择、纺丝方式、拉伸方式、溶剂选择、凝固条件以及萃取等方面的新进展及其在产业上的应用。 相似文献
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讨论了用聚乙烯醇纤维制备活性炭纤维的碳化过程中,纤维成分、结晶形态及物理织构的变化,并指出了中空结构的形成过程和影响因素。获得较高得率的均匀活性炭纤维,应采用7℃/m in 较慢的升温速率。 相似文献
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Masako Sato Kenichi Yoshikawa Motoi Minagawa 《Journal of the American Oil Chemists' Society》1990,67(11):711-716
The effect of builders on the stability of protease enzyme activity was studied in an effort to identify superior builders
which are soluble in water and compatible with enzymes formulated into heavy duty laundry powders. Various poly(styrenesulfonate-methacrylate)
copolymers, polyacrylate and tripolyphosphate anionic builders, as well as various poly(vinylalcohol-vinylacetate) nonionic
copolymers, namely PVAs, were used. Zeolite 4A was also used as a typical nonphosphate particulate builder in the detergents.
The protease used is frombacillus stearothermophilus. The calcium content was determined to be 16.7 mole/mole of protease by atomic spectrophotometry.
In binary systems composed of a fixed concentration of 10 U/mL protease and varied concentrations of compound, builder or
surfacant, it was found that compounds having the larger calcium ion binding capacity (C.B.C.) lowered the relative activity
of protease enzyme. The activity of protease enzyme alone was lowered about 20% by addition of 0.02% sodium dodecylbenzene
sulfonate (DBS).
The anionic builders added to the binary system of fixed 10 U/mL protease and 0.02% DBS reduce the protease enzyme activity
in proportion to the magnitude of their C.B.C. Addition of anionic builders further lowered the protease enzyme activity.
The nonionic builders and the nonionic surfactant can enhance the protease enzyme activity by protection of protease against
the inhibitor, DBS.
It is certain that calcium atoms contained in the protease must play an important role for the protease enzyme activity and
its stability. Calcium atoms must have a great influence on the formation of protease-substrate complex, protease-compound
complex and substrate-compound complex, because the protease, protein substrate and anionic compound would all be negatively
charged in alkaline solutions. Builders for enzyme-containing detergents should be constructed to be insensitive to calcium
ion. 相似文献