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以烯丙基硫脲改性魔芋葡甘聚糖为包膜剂制备包膜缓释尿素。对包膜缓释材料进行扫描电子显微镜(SEM)表征,并分析其吸水性能;评价温度及土壤水含量对包膜缓释尿素氮素溶出率的影响,利用土柱淋溶法检测包膜缓释尿素的缓释效果,并分析缓释尿素对白菜的生长影响。结果表明,烯丙基硫脲接枝魔芋葡甘聚糖在接枝率为35%~45%时,吸水性能最好,吸水量高达794 g/g;随着温度和土壤水含量的升高,包膜缓释尿素氮素溶出率逐渐增加;氮素溶出具有典型的缓释肥溶出特征,表现出良好的缓释效果;白菜对缓释尿素中氮素的利用率提高。 相似文献
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如何高效利用湿法磷酸生产工业级磷酸一铵副产的缓释磷铵是一个急需解决的课题。以缓释磷铵为包膜原料,三聚氰胺甲醛树脂为包膜黏结剂,包膜氮磷钾复混肥,得到缓释磷铵包膜的复混肥。研究了不同包膜黏结剂和包膜材料比例对肥料颗粒强度和养分初期释放率的影响,通过对肥料颗粒水中溶出前后进行电镜扫描,分析了其缓释机制。缓释磷铵包膜复混肥在25℃水中氮的初期溶出率为63%,磷的初期溶出率为71%,钾的初期溶出率为74%,具有很好的缓释性能,实现了缓释磷铵的高值化利用,具有很高的经济和环境效益。 相似文献
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《塑料》2019,(6)
以废弃聚苯乙烯为原材料制备抗凝剂,既降低了冬季路面的养护成本,又扩大了废弃聚苯乙烯的应用范围,减少环境污染。废弃聚苯乙烯作为原材料,使用3种混合溶剂,并掺加改性剂、增塑剂、增强剂等添加剂制备了具有缓释效果的抗凝冰剂。在实验条件下,混合溶剂中乙酸乙酯、二氯甲烷与甲苯比例为3:2:1,包膜溶液的浓度为0. 5 g/m L,改性剂松香掺量为12%,增塑剂邻苯二甲酸二丁酯掺量为9%,增强剂SBS树脂掺量为2%时,选用粒径为4. 75~9. 5 mm的大粒盐进行2层包膜,并且第一层包裹载体、第二层未包裹载体制备出的抗凝冰剂具有良好的缓释性能,其高温稳定性、低温抗裂性及水稳定性等路用性能均满足规范要求,且融冰雪性能良好。 相似文献
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介绍了脲醛树脂包膜尿素的制备方法,研究了脲醛树脂及植物油用量对脲醛树脂包膜尿素氮初期溶出率的影响。结果表明,包膜量越多,包膜尿素氮的溶出率越低,但使用脲醛树脂直接包膜尿素的方法并不理想;先使用植物油在尿素颗粒的表面包一层油膜,再使用脲醛树脂包膜,可大幅度降低包膜尿素氮的溶出率,在使用1.0%的植物油后,树脂包膜量为15%时,氮的初期溶出率即可低于40%,大大降低包膜材料的使用量。 相似文献
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用聚合物乳液为包膜剂制备缓释尿素 总被引:6,自引:0,他引:6
介绍了采用聚合物乳液作为包膜剂制备包膜缓释尿素,具有工艺简洁和包膜过程绿色的特点,能够根本解决现有包膜过程中毒性有机溶剂的污染和回收问题。实验考察了聚合物乳液包膜剂平板成膜时的渗透系数,表明聚合物乳液是良好的缓释包膜剂。实验采用转鼓流化床工艺制备包膜尿素,测定了包膜尿素在水中的释放特性。通过扫描电镜检测包膜尿素和膜层的形貌特征。结果表明,采用聚合物乳液直接对尿素颗粒包膜时,在颗粒表面形成的高湿性环境容易导致尿素表面溶解,水分蒸发后形成针状尿素结晶,复合在聚合物膜层中,包膜尿素进入水中时,针状尿素快速溶出,造成膜层多孔性渗漏,降低了包膜尿素的缓释性能。在聚合物乳液包膜前,先在尿素颗粒表面包覆一层硫磺阻隔层或石蜡疏水层,能有效抑制尿素在包膜时的溶出过程。 相似文献
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About 40–70% of the applied urea fertilizer is lost to the environment, causing serious pollution. Controlled-release technology is useful in increasing the efficiency of fertilizer urea as well as in checking environment pollution. Four laboratory-level controlled-release urea fertilizers were formulated based on polymers which are soil conditioners and then evaluated for their slow-release property. Urea was coated with the copolymer of acrylamide and divinylbenzene/N,N′-methylenebisacrylamide /tetraethyleneglycol diacrylate or pentaerythritol triacrylate and sealant materials (wax and polystyrene). Urea coated with co-polymer of acrylamide-tetraethyleneglycol diacrylate was found to be having a better slow-release property among the systems prepared. © 1996 John Wiley & Sons, Inc. 相似文献
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Determining permeability of coatings of polymer-coated urea 总被引:10,自引:0,他引:10
Permeability of polymer coatings on urea varies greatly with the type of polymer. A conventional test of measuring the effectiveness of coating involves a 7d static dissolution rate of coated urea into concentrated urea solution, but the results are only qualitative. Our approach was, instead, to make quantitative measurements of permeability, and so make more accurate predictions of release rate of urea across a membrane. A simple device, consisting of a container attached to vertical pipes at the bottom, was constructed to determine permeability of coats on urea granules. A turbulent flow of water ran over a 2 cm pack of coated-urea granules so urea did not accumulate at the outer surface of the coated granules. Separate determinations with two thicknesses of coats (8.8 and 14.7µm) were conducted with water at 12 or 31°C. Permeability and activation energy of permeability were calculated. A comparison was also made between release rate of urea calculated from permeability and that determined by 7d dissolution rate method at 23°C. Nearly 100 h were required for 100% release with the thick coating, but only 20% urea was released after 168 h with the 7d dissolution rate method. 相似文献
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To improve the water vapor permeability of coating materials, aqueous sodium alginate (SA) solution was blended with waterborne polyurethane‐urea (WBPU) dispersions synthesized by prepolymer mixing process. The content of SA for stable WBPU/SA dispersions was found to be below 30 wt %. As the SA content increased, the number and density of total micropores (tunnel‐like micropores/isolated micropores) formed after dissolution of SA in water increased, and the water vapor permeability of coated Nylon fabric also increased remarkably. These results clearly demonstrate that utilizing WBPU/water soluble polymer SA blends as coating materials and then dissolving SA in water surely facilitate obtaining prominent breathable fabrics. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007 相似文献
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The elastic and viscous properties of polymer melts may be affected by the shear history of the polymer. The extrudate swell of a polymer melt is primarily a manifestation of the elasticity of the polymer melt. In this study, a single screw extruder was used to impose different shear histories on a polystyrene polymer which was processed with and without added plasticizer. The extrudate swell and apparent viscosity of these melts were measured with a capillary rheometer. These characteristics of unplasticized polystyrene are almost not affected by the various preshearing processes. However, the extrudate swell and viscosity of polystyrene containing plasticizer are affected by plasticizer level, shear history and thermal history. After most of the plasticizer in the presheared plasticized polystyrene was extracted, the extrudate swell was still lower than that of the parent sheared polystyrene with the same shear history and the same plasticizer content. These results were obtained without significant changes in molecular weight. Shear modification by conventional process equipment may become impractical if the shear field intensity or dwell time of the material in the apparatus is limited. In such cases, shear refinability by standard process equipment may be observed if the coupling density in the polymer is reduced by some additional means, such as blending with a plasticizer. 相似文献