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In vitro studies of controlled release from chitosan/gelatin hybrid membranes were carried out using drugs of different molecular weight. It was found that release of urea, 5-fluorouracil (5-Fu), sodium benzoate, sodium salicylate, sodium mandelate, and sulfacetamide sodium followed zero-order kinetics after a short time lag. Variation of the diffusion coefficient, permeation coefficient, and degree of hydration with crosslinking and varying weight percent of gelatin in membrane matrices were studied in detail by using 5-Fu as a model drug. The diffusion coefficient and permeation coefficient of 5-Fu are dependent on the degree of hydration of the swollen membrane. The transport process of drug molecules in the hydrogel membrane is presumed to be predominantly of the pore mechanism. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 68: 1751–1758, 1998 相似文献
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在湖北省中稻上开展了控释尿素不同施用量的田间试验。研究结果表明,施用控释尿素不仅可以提高中稻产量,而且可以提高氮肥的农学效率及表观利用率,控释尿素70%的用量与普通尿素100%的用量效果相当,并随着控释尿素施用年限的增加,控释尿素施用效果越显著,控释尿素至少可以减少氮肥用量30%。 相似文献
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Controlled release of nitrogen‐source fertilizers by natural‐oil‐based poly(urethane) coatings: The kinetic aspects of urea release
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Urea is the most common source of nitrogen fertilizer, but it has serious disadvantages with respect to volatilization and leaching; these can be controlled by polymeric coatings on the granules. However, the effectiveness of this strategy depends on the formed polymer presenting good adhesion, reactivity with the urea surface, uniformity, and efficient release kinetics control. Therefore, in this study, we evaluated the release kinetics of urea coated by polyurethane produced from two oils (soybean and castor) by analyzing the influence of the thickness, coating stability, deposition interface, and total release time. The results demonstrate that castor oil produced superior materials, which achieved a total release time in water immersion of over 40 days with a total coating mass of less than 4% of the total mass. The good interface suggested that this material may produce coatings of good quality and long release times with minimum thickness, and this will maximize the total nitrogen present in the granule. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43790. 相似文献
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Enzyme lipase catalyzed graft copolymerization of acrylic acid onto gum tragacanth was carried out in an aqueous medium using glutaraldehyde as a cross-linker, one more step towards green chemistry. Various reaction variables such as time, amount of solvent, temperature, pH, lipase concentration, and monomer and cross-linker concentrations were optimized to achieve a cross-linked candidate polymer with maximum fluid absorbance capacity. The structure and morphology were confirmed by Fourier transform infrared spectroscopy and scanning electron microscopy. The synthesized hydrogel held a large amount of water and was used as a device for controlled release of urea. A 10 % (w/w) of swelled hydrogel was found to enhance the water-holding capacity of the soil. The synthesized device could increase the moisture content up to 52 % in sandy loam soil and 72 % in clay soil and was found to enhance the water-holding capability of the soil. Further, the candidate polymer was studied for the controlled release of urea under eco-friendly conditions and showed case-II type urea release. The initial diffusion coefficient was found to be higher than the later diffusion coefficient indicating a higher urea release rate during the early stage. Thus, the synthesized polymer is important from technological point of view. 相似文献
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To improve the utilization of fertilizer and water resource at the same time, a new type of slow‐release fertilizer with superabsorbent and moisture preservation was developed, with the combination of slow‐release technique and superabsorbent polymers. The coatings were formed by the inverse phase polymerization technique. The element analysis results showed that the product contained 22.58% nitrogen element, and the water absorbency of the product was 94 times its own weight if it was allowed to swell in tap water at room temperature for 2 h. The results of the slow‐release behavior of N and the water absorbency and retention properties in soil showed that the product not only had good slow‐release property but also had excellent water absorbency and water retention capacity, which was a significant advantage over the normal slow‐release or controlled‐release fertilizers. The effects of the amount of initiator, crosslinker, reaction time, and the degree of neutralization of acrylic acid on water absorbency were investigated and optimized. At the same, a rather new and simple method was used to make homogeneous urea‐formaldehyde granules. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 99: 3230–3235, 2006 相似文献
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A superabsorbent, slow release nitrogen fertilizer (SSRNF) was prepared by inverse suspension polymerization of partially neutralized acrylic acid using N,N′‐methylene bisacrylamide as a crosslinker and ammonium persulfate as an initiator in the presence of urea. The polymer was characterized using infrared spectral analysis, and network structural parameters such as molecular weight between crosslinks (Mc) and crosslink density (q) were calculated. The effects of reaction conditions, such as reaction time, reaction temperature, initiator, crosslinker and the degree of neutralization of acrylic acid, on water absorbency were investigated. The nitrogen content of SSRNF synthesized under optimal conditions was 22.7%, and the water absorbencies were about 965 g g?1 in distilled water and 185 g g?1 in tap water. The nitrogen slow release behaviors of the SSRNF in water and water retention capacity of soil with the SSRNF were also investigated. A possible slow release mechanism was proposed and the release rate constant K and the diffusion coefficient D of urea in the hydrogel was calculated. The results showed that the product not only had good slow release properties but also excellent soil moisture preservation capacity, which could effectively improve the utilization of fertilizer and water resources simultaneously. Therefore, the SSRNF is a multifunctional water managing material, which would find application in agriculture and horticulture, especially in drought‐prone areas where the availability of water is limited. Copyright © 2006 Society of Chemical Industry 相似文献
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介绍复混肥料缓释与防结块处理的一种新技术。利用熔融尿素液代替机械油作为复合氮素缓释剂(由硝化抑制剂和尿酶抑制剂构成)与防结块剂(由石蜡和阴阳离子表面活性物质构成)的载体,其熔融液喷涂在复合肥颗粒表面可短时间在肥料颗粒表面固化,形成坚固的复合包膜层,经防结块测试,6个月的防结块率达94.6%,氮素利用率提高13%。 相似文献
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This paper deals with the evaluation of the sorption‐induced release of an antimicrobial component, i.e., isopropanol, from two ethylene‐vinyl alcohol (EVOH) copolymers as measured by ATR‐FTIR spectroscopy. Three different swelling agents were considered namely, water, methanol, and ethanol, whose kinetics of diffusion were also evaluated during sorption. From the transport behavior of the latter components, it was found that a pseudo‐Fickian diffusion process appeared to take place in all systems. The corresponding simultaneous polymer plasticization was easily followed by evaluation of the sorption‐induced thickness expansion and swelling rate. The data indicated that the swelling process appeared to lag the sorption of the penetrant during the first instances of the uptake most probably due to the existence of a Langmuir (antiplasticization) regime previously reported for these polymers. The crossed‐diffusion of entrapped antimicrobial isopropanol was related to a typical swelling‐induced release process, which was found to be strongly dependent on the nature of the penetrant and on the composition of the polymer matrix. The results demonstrated both the usefulness of the ATR‐FTIR technique to uniquely characterize the complex phenomena that take place during sorption‐induced release and the suitability of EVOH copolymers for controlled release in antimicrobial applications. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 3431–3437, 2007 相似文献
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K. G. Papadokostaki 《应用聚合物科学杂志》2004,92(4):2468-2479
The performance of a model monolithic controlled release device, consisting of a swellable polymeric matrix subject to structural relaxation (cellulose acetate), loaded with a simple osmotically active solute (NaCl) and activated by the ingress of solvent (water), was studied experimentally and by computer simulation. The former study involved detailed monitoring of the kinetics of both solute release and solvent absorption (followed in due course by desorption of osmotically imbibed excess solvent). The computer simulation study was based on extensive previous modeling work. Values of the relevant input model parameters were derived from independent experimental measurements of the sorption and diffusion properties of solvent (cf. Part I) and solute (reported in the present article). The resulting simulation was highly successful, considering that it proved possible to simulate closely and consistently the kinetics of both solute release (over practically the whole experimental range) and concurrent solvent absorption (including correct prediction of the magnitude of the osmotically induced excess swelling of the polymeric matrix). Simulation of the final desorption of osmotically imbibed water was facilitated by the realization that this process actually reflects the kinetics of a long‐term deswelling relaxation of the polymer structure back to the state of normal hydration, the rate of which could be measured to a good approximation on the pure deswelling polymer. The results presented here are of obvious practical significance in relation to progress toward computer‐assisted design of monolithic controlled release devices exhibiting relatively complex kinetic behavior. They should also prove useful by calling attention to an important caveat when desorption into water is used as a method for the straightforward determination of solute diffusivity in hydrated polymers, in cases of osmotically active solutes diffusing in nonhydrophilic polymers. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2468–2479, 2004 相似文献
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Shuming Tao Jun Liu Kemo Jin Xiaoyun Qiu Yuan Zhang Xueqin Ren Shuwen Hu 《应用聚合物科学杂志》2011,120(4):2103-2111
Triple polymer coated with controlled‐release water retention fertilizer (TCWF) and enhanced mechanical property was developed by coating polyethylene (first layer), poly (acrylic acid‐co‐acrylamide) superabsorbent (second layer), and poly (butyl methacrylate) (third layer) consecutively on the granule core urea in the fluidized‐bed coater. The inner layer possessed controlled‐release property, the middle layer had water absorbent characteristic, and the thin outer layer aimed to protect the fragile layer of the superabsorbent. The relationship between the thickness of coating layer and the nutrient releasing properties was established. The effects of polymerization parameters on the water absorbency of the superabsorbent were studied and optimized as well. The nutrients release behaviors of this triple‐coated urea in both water and soil were investigated and compared. The results showed that TCWF not only performed as a good controlled‐release fertilizer but also had excellent water retention capacity. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011 相似文献
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以机械活化60 min的木薯淀粉、氢氧化钾部分中和的丙烯酸和丙烯酰胺为原料,合成农用淀粉基离子/非离子型复合高吸水树脂(SCSA),采用FT-IR和SEM对样品的官能团和表面形貌进行表征。以SCSA在5.0 mol·L-1的尿素溶液中平衡溶胀后所得的水凝胶(SCH)为尿素在水溶液中的释放材料,考察合成工艺条件和释放环境对尿素释放过程的影响。结果表明,尿素从SCH中的释放过程符合Fickian扩散机理;SCH的溶胀率越大,尿素的释放速率越慢;释放温度越高,尿素的释放越快。在丙烯酸和丙烯酰胺质量比为3:3,交联剂N,N'-亚甲基双丙烯酰胺溶液用量为1.0 ml(浓度为0.02 mol·L-1)的条件下制备的SCH对尿素的释放活化能为17.28 kJ·mol-1。 相似文献
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Measurement of diffusion in gel is an essential task for pharmaceutic technology and biochemical engineering. In this work we investigate diffusion coefficients and release kinetics of colored substances loaded in polymeric thin strips, by extending a simple spectrophotometric technique from catalysis science to swellable polymer matrices. Absorbance can be a measure of the average solute concentration in the swollen gel so that the time decay of film absorbance can be a quantitative measure of the release kinetics and henceforth of the diffusion coefficient in the swollen gel. Thin film dissolution is carried out in a newly proposed microfluidic continuous flow-through device. Hydroxypropyl methylcellulose (HPMC) is used as filming polymer. Film thickness, uniformity of content and swelling time-scales are accounted for in the estimation of the effective diffusion coefficient. 相似文献
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高氮缓释防结块复混肥料生产技术 总被引:2,自引:2,他引:0
选用熔融尿液为载体,以石蜡及阴离子表面活性剂烷基苯磺酸盐和阳离子表面活性剂烷基胺盐等混合物为复混肥料防结块剂,添加对尿素水解有抑制作用的尿酶抑制剂氢醌和对土壤中铵离子氧化有抑制作用的硝化抑制剂双氰胺混合物,经特制喷涂设备喷涂包衣生产具有养分缓释、防结块性能好的高氮型、高浓度复混肥料[以总养分45%的30 6 9复混肥料为例,w(N)可达30%]。使用熔融尿液替代机械油为复混肥料防结块剂载体,解决了因使用机械油造成的二次污染;通过氮素缓释剂的使用,氮素利用率提高13%。 相似文献
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