共查询到20条相似文献,搜索用时 390 毫秒
1.
聚乙烯醇缓释膜缓释性能的初步研究 总被引:1,自引:0,他引:1
采用部分醇解级和完全醇解级的聚乙烯醇(PVA)混合物制备了PVA缓释膜,研究了缓释膜的缓释机理。以I(1788)含量的增大,缓释膜的缓释速率逐渐增大;缓释膜的厚度越小,其缓释速率越大;当PVA BM-I(1788)蒸馏水为载体,初步测定了PVA缓释膜的透水速率。探讨了PVA缓释膜缓释速率的影响因素,测定了PVA缓释膜的溶胀率以及溶解失重率,并对其稳定性进行了初步研究。结果表明:随着部分醇解级PVA BM-含量为30%时,缓释膜的溶胀率达到最大;缓释膜的稳定性良好,能够较长时间保持其缓释性能。 相似文献
2.
3.
4.
5.
6.
7.
8.
以聚乙烯醇(PVA)和聚乙烯亚胺(PEI)为原料,采用静电纺丝技术、戊二醛交联方法制备了PVA/PEI_(70 000)(重均分子量70 000)和PVA/PEI_(10 000)(重均分子量10 000)耐水性纳米纤维,通过傅里叶变换红外光谱和扫描电镜对其进行了表征,研究其力学性能和对铬酸根离子的吸附作用。结果表明,PVA/PEI_(70 000)纳米纤维具有较大的拉伸强度,对铬酸根离子的吸附效果明显好于PVA/PEI_(10 000)。溶液pH值的增加减弱了PVA/PEI纳米纤维对铬酸根离子的吸附效果,随着PVA/PEI纳米纤维用量的增加,对铬酸根离子的吸附率升高,但吸附量呈现逐渐降低的趋势。PVA/PEI纳米纤维的吸附机理遵循Langmuir等温吸附模型和准二级动力学方程,吸附过程具有自发性。重复使用性实验证明PVA/PEI纳米纤维材料具有良好的脱附再生性能。 相似文献
9.
10.
以提纯钙基蒙脱石为原料,在一定条件下制备出5-氟尿嘧啶/蒙脱石复合物(5-fluorouracil/montmorillonite,5-FU/MMT),探讨了蒙脱石对5-FU的吸附作用。通过透析法研究了释放介质的pH值和释放时间等因素对5-FU/MMT复合物体外释放的影响规律。采用2种体外释放模型对其释放实验数据进行拟合,探讨了5-FU的释放机理以及蒙脱石作为5-FU缓释载体的可行性。结果表明:蒙脱石与5-FU之间的相互作用主要是物理吸附、化学吸附和插层作用。蒙脱石对5-FU具有较好的缓释作用,是一种性能优异的药物缓释载体;其体外释放能力受释放溶液的pH值影响,在pH=1.2的释放介质中,5-FU的释放浓度和累积释放量最大,分别为9.01mg/L和23.05%,其次为pH=7.4时的,pH=5.0时的最小。一级动力学模型比Korsmeyer–Peppas模型能更好地拟合和描述5-FU在不同pH值释放介质中的体外释放量随时间的变化。拟合结果表明:5-FU从5-FU/MMT复合物中释放的行为主要由物理扩散和药物溶解作用决定,同时5-FU与释放介质之间的离子交换作用对释放过程也有一定贡献。 相似文献
11.
PVA/MMT纳米复合材料的化学改性研究 总被引:1,自引:1,他引:0
通过溶液插层-流延成膜法制备了四硼酸钠和戊二醛化学交联改性的聚乙烯醇/蒙脱土纳米复合材料薄膜。用扫描电子显微镜(SEM)和力学性能测试对复合材料的结构和性能进行了表征。结果表明:蒙脱土含量为5.0%时,含有不同质量改性剂的复合薄膜的拉伸强度、湿拉强度和耐水性能都得到了提高。 相似文献
12.
Seyed Mohammad Mahdi Dadfar Gholamreza Kavoosi Seyed Mohammad Ali Dadfar 《Polymer Composites》2014,35(9):1736-1743
Polyvinyl alcohol (PVA) thin films were reinforced by glutaraldehyde and multiwalled carbon nanotubes (MWCNTs) and then mechanical, water solubility, water swelling, water uptake, water vapor permeability, and antibacterial properties of the films were examined. Cross‐linking by glutaraldehyde or incorporation of MWCNT caused a significant increase in tensile strength, decrease in elongation at break, and increase in Young's modulus of the PVA films, while MWCNTs were more effective rather than that of glutaraldehyde. Cross‐linking by glutaraldehyde or incorporation of MWCNT caused a significant decrease in water solubility, water swelling and water uptake, with a similar manner. Cross‐linking by glutaraldehyde or incorporation of MWCNT caused a significant increase in the light absorbance, while maximum absorbance was at 400 nm. Only PVA/MWCNT films but no PVA/glutaraldehyde showed significant antibacterial activities in a dose‐dependent manner against both Gram‐positive and Gram‐negative bacteria. Thus, noncovalent improvement by MWCNT was more effective on the PVA thin films rather than covalent cross‐linking by glutaraldehyde. Our results suggest that the PVA/MWCNT composites films could be used as a very attractive alternative to traditional materials for different biomedical and food applications. POLYM. COMPOS., 35:1736–1743, 2014. © 2013 Society of Plastics Engineers 相似文献
13.
A novel physicochemical crosslinked nanocomposite hydrogel based on polyvinyl alcohol (PVA) and natural Na‐montmorillonite (Na+‐MMT) was synthesized by chemical crosslinking of nanocomposite hydrogel followed by a freezing‐thawing process. The effects of physical crosslinking, as well as physicochemical crosslinking, on the structure, morphology, and properties (thermal, mechanical, swelling, and deswelling) of nanocomposite hydrogels were investigated and compared with each other. The structure and morphology of nanocomposites were studied by Fourier transform infrared, X‐ray diffraction, field emission scanning electron microscopy, and transmission electron microscopy techniques. The thermal and mechanical properties of nanocomposites that were affected by physical and physicochemical crosslinking were evaluated by thermogravimetric analysis, differential scanning calorimeter, dynamic mechanical analysis, hardness test, and Water vapor transmission rate (WVTR) experiments. The results showed that the physicochemical crosslinking of a PVA nanocomposite leads to a reduction in crystallinity and melting temperature, as well as an increase in the Hardness and WVTR compared to a physically crosslinked PVA nanocomposite hydrogel. The swelling and deswelling experiments were performed using a gravimetric method, and it was shown that controlled crosslinking of PVA nanocomposite hydrogel with glutaraldehyde causes the swelling ratio to increase and the cumulative amount of water loss to decrease. The swelling (sorption) and deswelling (desorption) kinetics data for physically and physicochemical crosslinking of nanocomposite hydrogels were fitted with a fickian model. It is concluded that through control crosslinking of PVA nanocomposite can lead to a hydrogel with higher swelling capacity than that is in conventional PVA nanocomposite hydrogel. POLYM. COMPOS., 37:897–906, 2016. © 2014 Society of Plastics Engineers 相似文献
14.
We aim to couple the electrospinning in‐line with solution chemistry to fabricate novel crosslinked polymer nanofibers. Poly(vinyl alcohol) (PVA) was used as a model polymer due to its high amount of hydroxyl groups. To obtain ideal parameters for electrospinning, pure PVA was explored primarily. To gain crosslinked fibers, PVA was first crosslinked partially with glutaraldehyde (GA) followed by transferring this precursor to a long hot tube which was used as reactor and then electrospun right before gelation. The preheating time and tube‐passing time were determined with viscometer and rheometer. The reactive as‐spun fibers could maintain their original morphology after water immersion due to their high crosslinking degree. The thermal stability and mechanical property of reactive as‐spun fibers were improved drastically compared with pure and GA vapor crosslinked PVA fibers. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012 相似文献
15.
A facile surface segregation method was utilized to fabricate poly(vinyl alcohol)-polyethersulfone (PVA-PES) composite membranes. PVA and PES were first dissolved in dimethyl sulfoxide (DMSO), then casted on a glass plate and immersed in a coagulation bath. During the phase inversion process in coagulation bath, PVA spontaneously segregated to the polymer solution/coagulation bath interface. The enriched PVA on the surface was further crosslinked by glutaraldehyde. Scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and energy dispersive spectrometer (EDS) confirmed the integral and asymmetric membrane structure with a dense PVA-enriched surface and a porous PES-enriched support, as well as the surface enrichment of PVA. The coverage fraction of the membrane surface by PVA reached up to 86.8% when the PVA content in the membrane recipe was 16.7% (by mass). The water contact angle decreased with the increase of PVA content. The effect of co-agulation bath type on membrane structure was analyzed. The membrane pervaporation performance was evaluated by varying the PVA content, the annealing temperature, feed concentration and operation temperature. The mem-brane exhibited a fairly good ethanol dehydration capacity and long-term operational stability. 相似文献
16.
采用熔融插层法制备了聚乙烯醇(PVA)/蒙脱土(MMT)复合材料。通过X射线衍射仪和透射电镜对复合材料的结构进行表征,结果表明所得复合材料为剥离型或部分剥离型结构。热重测试、电子拉力试验和水溶性试验结果显示聚乙烯醇/蒙脱土纳米复合材料与纯聚乙烯醇相比,其加工热稳定性、综合力学性能以及耐水性能都得到了明显提高。 相似文献
17.
Thermoplastic polyvinyl alcohol/multiwalled carbon nanotube composites: Preparation,mechanical properties,thermal properties,and electromagnetic shielding effectiveness 下载免费PDF全文
Jia‐Horng Lin Zheng‐Ian Lin Yi‐Jun Pan Chien‐Teng Hsieh Chien‐Lin Huang Ching‐Wen Lou 《应用聚合物科学杂志》2016,133(21)
This study uses the solution mixing method to combine plasticized polyvinyl alcohol (PVA) as a matrix, and multiwalled carbon nanotubes (MWCNTs) as reinforcement to form PVA/MWCNTs films. The films are then laminated and hot pressed to create PVA/MWCNTs composites. The control group of PVA/MWCNTs composites is made by incorporating the melt compounding method. Diverse properties of PVA/MWCNTs composites are then evaluated. For the experimental group, the incorporation of MWCNTs improves the glass transition temperature (Tg), crystallization temperature, Tc), and thermal stability of the composites. In addition, the test results indicate that composites containing 1.5 wt % of MWCNTs have the maximum tensile strength of 51.1 MPa, whereas composites containing 2 wt % MWCNTs have the optimal electrical conductivity of 2.4 S/cm, and electromagnetic shielding effectiveness (EMI SE) of ?31.41 dB. This study proves that the solution mixing method outperforms the melt compounding method in terms of mechanical properties, dispersion, melting and crystallization behaviors, thermal stability, and EMI SE. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43474. 相似文献
18.
The development of low cost alkaline anion solid exchange membranes requires high ionic conductivity, low liquid uptake, strong mechanical properties and chemical stability. PVA/PSSA blends cross‐linked with glutaraldehyde and decorated with titanium dioxide nanoparticles introduce advantages relative to the pristine membrane of PVA and PVA/PVP membranes due to their improved electrical response and low methanol uptake/ swelling ratio allowing their use in alkaline direct methanol fuel cells. 相似文献
19.
Prior to investigate the influences of degree of crosslinking on the hydrophilicity and mechanical strength of polyvinyl alcohol
(PVA) membrane, the kinetics of crosslinking of PVA membrane with glutaraldehyde was examined. The reaction variables were
temperature, hydroxyl group concentration of PVA membrane, and concentrations of glutaraldehyde and sulfuric acid in crosslinking
solution. The overall reaction rate of crosslinking was suggested, which agrees well with the experimental results. The crosslinking
reaction is approximately first order with respect to the concentration of hydroxyl group of PVA membrane, of glutaraldehyde,
and of sulfuric acid. The activiation energy was estimated to be about 5.77 kcal/mol. It was also found that the degree of
crosslinking of PVA membrane can be easily changed by controlling the reaction variables. 相似文献
20.
戊二醛交联碱木质素/聚乙烯醇膜的制备及其光学性能 总被引:3,自引:0,他引:3
以碱木质素和聚乙烯醇(PVA)为原料,以戊二醛为交联剂利用流延法制备了碱木质素/PVA交联反应膜。通过单因素实验考查了碱木质素加入量、戊二醛加入量对木质素/PVA反应膜光学性能的影响。采用SEM和FT-IR方法分析反应膜的表面形貌和化学结构,紫外可见光谱法分析了交联膜的光学性能。结果表明:当碱木质素和聚乙烯醇质量比为1∶10,戊二醛加入量 1.67 %,薄膜的透光率和吸光度都较好。碱木质素/PVA薄膜结构中有醚键生成,碱木质素和PVA发生了交联反应;碱木质素/PVA反应薄膜表面较光滑;加入碱木质素后,薄膜在紫外光区的吸光度提高了近 90 %,在可见光区的透过率降低了近 40 %,碱木质素对薄膜的吸光度和透过率影响较大;戊二醛的加入量增多可见光区透过率有所增大,但戊二醛对薄膜在紫外区吸光度变化不大,薄膜的紫外线吸收主要是受碱木质素的影响。碱木质素/PVA反应膜可作为良好的紫外吸收材料。 相似文献