Controlled release of nitrogen‐source fertilizers by natural‐oil‐based poly(urethane) coatings: The kinetic aspects of urea release

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.     

聚氨酯包膜尿素的制备

用异氰酸酯与聚氧化丙烯二醇(PPG)合成聚氨酯,再以其包裹尿素制成聚氨酯包膜尿素.采用比色法绘制聚氨酯包膜尿素的缓释曲线,讨论了异氰酸酯与羟基摩尔比(NCO/OH)、包膜率、反应方式、异氰酸酯、PPG分子量对包膜尿素缓释性能的影响.结果发现,以丙酮为溶剂,NCO/OH为1.1,在50～60℃的水浴温度下,PPG-300...     

聚氨酯缓/控释肥制备与膜层表征

利用多亚甲基多苯基异氰酸酯与蓖麻油在尿素表面反应成膜,制备了聚氨酯包覆的尿素缓/控释肥,通过红外光谱和扫描电镜研究了聚氨酯包覆量对膜层结构的影响,采用凯氏定氮法测定了尿素的溶出曲线。结果表明,不同包膜量聚氨酯膜层的反应程度存在差异;随着包膜量的增加,膜层的厚度增加;当聚氨酯的包覆质量分数为3.3%时,25℃下尿素的缓释期达到40～50 d;根据尿素的溶出曲线推测该缓/控释肥的释放为扩散机制。     

Preparation and characterization of modified castor oil via photo-click chemistry for UV-curable waterborne polyurethane with enhanced water resistance and low conductive percolation threshold

A castor oil (CO) was modified via thiol-ene click chemistry reaction between CO and 3-mercaptopropyl trimethoxysilane, with the conversion of CC bonds of CO over 99% based on ¹HNMR spectra. The obtained modified castor oil (MCO) was used as a biobased polyol to prepare waterborne polyurethane (WPU) dispersions. The modification of CO exhibited a great effect on the properties of WPU dispersions and coatings, and an obvious change is the improvement of the water resistance of WPU coatings. WPU dispersions with MCO had good storage stability. A WPU coating with 7% MCO had high surface hydrophobicity, and its water absorption was as low as 3.2%. Conductive carbon black filled WPU coatings with MCO were cured by efficient UV radiation, and their conductive percolation threshold could decrease to 0.76%, which could be attributed to the well filler dispersion and strong filler-polymer interaction. The WPU dispersions are ecofriendly, and can be used to produce biobased WPU coatings with a great application potential in antistatic coating fields.     

A Review on Waterborne Thermosetting Polyurethane Coatings Based on Castor Oil: Synthesis,Characterization, and Application

Waterborne polyurethane coatings made from castor oil as polyol resource, replacing oil from fossil fuels are attracting lot of recognition during recent decades. In this review, castor oil and its modifications to synthesize various biobased waterborne polyurethane and their nanocomposite systems have been addressed. Various synthesis procedures for waterborne polyurethane dispersions and their applications as a coating material have been described. This review will be helpful to the green research community for selection of monomer and further development of biobased waterborne polyurethane utilizing advanced technology.     

Improvement of polyurethane adhesion to glass using novolac primer

The adhesion of polyurethane (PU) coatings based on toluene diisocyanate, poly(propylene glycol) (PPG) 2000, polyethylene adipate (PEA) 2000 and castor oil (CO) was studied. The coatings were applied to glass slides with and without novolac primer (due to the high functionality of castor oil, the resultant PU coatings have limited shelf life). Our studies showed that satisfactory adhesion strengths were achievable for immediate bonding. Furthermore, our study also found that the adhesion of polyurethane to glass surfaces was increased by using a thin layer of novolac primer.     

蓖麻油改性的水性聚氨酯涂料的制备及其防蚀性能

以可再生的蓖麻油和环氧树脂改性水性聚氨酯,研究了涂膜的耐水性能等,改性后的水性聚氨酯吸水率下降仅为3%,耐水性好。对该树脂所制成的富锌防腐涂料进行了腐蚀电位和电化学阻抗谱(EIS)的测试分析,考察了富锌涂层在3%NaCl溶液中的电化学行为,结果表明耐水性的提高导致蓖麻油改性的水性聚氨酯富锌涂料耐蚀性的改进。     

Characterization of structure and corrosion resistivity of polyurethane/organoclay nanocomposite coatings prepared through an ultrasonication assisted process

In this study, a series of castor oil based polyurethane/organically modified montmorillonite (OMMT) clay nanocomposite coatings have been successfully prepared by effective dispersing of OMMT nano-layers in polyurethane matrix through an ultrasonication assisted process. Effectiveness of ultrasonication process in de-agglomeration of clay stacks in castor oil dispersions was evaluated by optical microscopy and sedimentation test. Structure of nanocomposite coatings was investigated by wide angle X-ray diffraction (WAXD) and Fourier-transform infrared spectroscopy (FT-IR). The anticorrosive properties of nanocomposite coatings were characterized by electrochemical impedance spectroscopy (EIS), Tafel polarization study, water absorption and pull-off adhesion tests. The experimental results showed that PU/OMMT nanocomposite coatings were superior to the neat PU in corrosion protection effects. Also, it was observed that the corrosion protection of polyurethane organoclay nanocomposite coatings is improved as the clay loading is increased up to 3 wt.%.     

Effect of Filler Treatment on the Release Properties of Coating on Urea Granules

Polyurethane composite coatings on urea granules were prepared by SBA-15 mesoporous silica (in as-synthesized and calcined forms) as a pseudo-crosslinker without any other chain extenders. The calcination of mesoporous silica leaded to reduction of hydroxyl groups and increase of mesopores. The composite coating containing calcined SBA-15 showed enhanced controlled release properties compared with the other two coatings. At the loading content of 1 wt%, the initial release rate and release duration of urea coated by polyurethane/calcined SBA-15 composite were 0.08% and 83 d, respectively. It is shown that the calcination played an important role in controlling the properties of composite coating.     

Synthesis and characterization of novel renewable castor oil-based UV-curable polyfunctional polyurethane acrylate

In recent years, a lot of interest has been given to renewable resources for their environmental friendliness and potential biodegradability in the synthesis of urethane-derived polymers. In this work, UV-curable castor oil-based polyfunctional polyurethane acrylate (COPUA) was prepared by the reaction of isophorone diisocyanate (IPDI) with castor oil and pentaerythritol triacrylate (PETA). The structures and molecular weights of the targeted IPDI–PETA and COPUA were characterized by FTIR, ¹H NMR, and GPC, respectively. In addition, the effect of reactive diluent content on damping properties, thermal stabilities, and mechanical properties of COPUA was characterized by dynamic mechanical analysis (DMA), thermogravimetric analysis (TGA), and universal test machine. DMA revealed the copolymers had a glass transition temperature (T _g) from 31.81 to 48.09°C. TGA showed that thermal initial decomposition temperatures were above 344.5°C, indicating the copolymers had certain thermal stability. Finally, some physical properties of curing films were studied by the contact angle and water absorption, and the results showed that the coatings exhibited good hydrophobicity. The COPUA obtained from castor oil can be used as eco-friendly materials and other applications alternative to the use of other petrochemicals in coatings.     

蓖麻油改性环氧聚氨酯防腐蚀涂料的研制

介绍了一种蓖麻油改性的环氧聚氨酯防腐蚀涂料.以蓖麻油改性异氰酸酯预聚物和环氧树脂为基料,以价格较为低廉的滑石粉、钛白粉、沉淀硫酸钡为颜填料制备了成本较低,性能较为优异的防腐蚀涂料.检测了优化条件下制备的涂料的性能.以蓖麻油改性环氧聚氨酯防腐蚀涂料和未经蓖麻油改性的环氧聚氨酯防腐蚀涂料进行防腐蚀性能对比,蓖麻油改性环氧聚氨酯防腐蚀涂料的耐酸、碱、盐水等防腐蚀性能更好.     

Physical Properties of Polyurethanes Produced from Polyols from Seed Oils: II. Foams

Rigid polyurethane (PU) foams were prepared using three North American seed oil starting materials. Polyol with terminal primary hydroxyl groups synthesized from canola oil by ozonolysis and hydrogenation based technology, commercially available soybean based polyol and crude castor oil were reacted with aromatic diphenylmethane diisocyanate to prepare the foams. Their physical and thermal properties were studied and compared using dynamic mechanical analysis and thermogravimetric analysis techniques, and their cellular structures were investigated by scanning electron microscope. The chemical diversity of the starting materials allowed the evaluation of the effect of dangling chain on the properties of the foams. The reactivity of soybean oil-derived polyols and of unrefined crude castor oil were found to be lower than that of the canola based polyol as shown by their processing parameters (cream, rising and gel times) and FTIR. Canola-PU foam demonstrated better compressive properties than Soybean-PU foam but less than Castor-PU foam. The differences in performance were found to be related to the differences in the number and position of OH-groups and dangling chains in the starting materials, and to the differences in cellular structure.     

Biobased polyisocyanates from plant oil triglycerides: Synthesis,polymerization, and characterization

In this study, an easy and efficient synthesis of unsaturated plant oil triglycerides having isocyanate groups is reported. In the first step of the synthesis, the triglyceride was brominated at the allylic positions by a reaction with N‐bromosuccinimide, and in the second step, these brominated species were reacted with AgNCO to convert them to isocyanate‐containing triglycerides. At the end of the reaction, approximately 60–70% of the bromine was replaced by NCO groups, and the double bonds of the triglyceride were not consumed. When the amount of AgNCO was increased, the yield also increased. The final products were characterized with IR and ¹H‐NMR, and polyurethanes and polyureas were obtained from these fatty isocyanates with alcohols and amines, respectively. The polymers were characterized by differential scanning calorimetry and thermogravimetric analysis. Differential scanning calorimetry curves showed that glycerin polyurethane showed a glass‐transition temperature at 19°C, castor oil polyurethane showed two glass‐transition temperatures at ?43 and 36°C, and triethylene tetraamine polyurea showed a glass‐transition temperature at 31°C. Some properties of the polymers, such as the tensile strength and swelling ratios, were also determined. The swelling rate of glycerin polyurethane was higher than that of castor oil polyurethane in dichloromethane. The equilibrium swelling ratio was highest for the castor oil polyurethane. The polyurethanes synthesized in this study had a Young's modulus around 50 kPa and a tensile strength around 0.01 N/mm² (100 kPa). The tensile strength of glycerin polyurethane was higher than that of castor oil polyurethane. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

聚氨酯包膜控释尿素制备工艺与养分释放特性研究

4,4'-二苯基甲烷二异氰酸酯(MDI)与植物油多元醇均匀喷涂在流化状态的尿素颗粒表面并发生化学反应,形成聚氨酯膜层。以侧喷流化床包膜工艺为基础,通过研究包膜量、反应温度、反应物比例等不同工艺条件下包膜尿素的养分释放性能,获得的生产聚氨酯包膜尿素的最佳工艺条件为反应温度75℃、MDI与植物油质量比1.0:1.0、反应时间20 min、催化剂用量0.40%(质量分数)、包膜比率为4.0%(质量分数),此包膜控释尿素的养分释放周期可达70 d。     

Natural castor oil based 2-package waterborne polyurethane wood coatings

The effects of four kinds of hardener on the properties of castor oil (CO) based 2-package waterborne polyurethane (2K-WPU) wood coatings were examined. Modified castor oil (MCO) was prepared by transesterification of glycerol and CO at the molar ratio of 2.0. The waterborne polyurethane-dispersed polyol (PUDp), one component of the 2K-WPU, was synthesized from MCO, dimethylol propionic acid (DMPA) and isophorone diisocyanate (IPDI) by the acetone process to provide a prepolymer with a carboxyl and hydroxyl groups. Then the prepolymer was neutralized by triethylamine (TEA) and dispersed into water. After vacuum distillation to remove acetone, the PUDp was obtained and then mixed with four different hardeners: IPDI, hexamethylene diisocyanate (HDI), polyethylene glycol (PEG) modified PIPDI (polymeric IPDI) and PEG-modified PHDI (polymeric HDI). The NCO/OH molar ratio of 1.5 was used and a 2K-WPU coating was obtained. The results showed that the film of the 2K-WPU coatings obtained from IPDI hardener had excellent gloss and hardness. On the contrary, the film containing PEG-modified PIPDI hardener (PEG-PIPDI) had lower hardness and gloss but higher tensile strength. The film containing PEG-modified PHDI hardener (PEG-PHDI) showed the best elongation at break, abrasion resistance and impact resistance, though it had the worst hardness. The film with HDI hardener had the best hardness and highest tensile strength and superior water resistance among all the films with different hardeners, and it was suitable for wood coatings.     

紫外光固蓖麻油改性聚氨酯水分散体的研究

制备了蓖麻油封端的聚氨酯水分散体,成膜于四氟乙烯板上,在紫外光照射下,通过水性光引发剂引发,制备得到聚氨酯涂层。通过FT-IR,DSC,凝胶量,耐水,耐溶剂性以及硬度测试对水分散体的物化性能,光固化前后涂膜的结构和性能进行了研究。结果表明,蓖麻油改性聚氨酯在紫外光照下发生了交联反应:固化后涂层的凝胶量较固化前有所增加,涂层的吸水率大幅度下降,铅笔硬度由3H提高至6H,耐甲乙酮拭擦次数增加了158次。     

Structure and properties of semiinterpenetrating polymer networks based on polyurethane and nitrochitosan

Two semiinterpenetrating polymer networks (semi‐IPNs) based on trihydroxyl methylpropane–polyurethane (T‐PU) or castor oil–polyurethane (C‐PU) were prepared by curing the mixed solution of the polyurethane prepolymer and nitrochitosan (NCH). During the curing process, crosslinking and grafting reaction between the molecules of the PU prepolymer and NCH occurred, because of the high reactivity of remaining hydroxyl groups in the NCH with ? NCO groups of PU. The structure of the original semi‐IPN sheets and the sheets treated with acetone were studied by infrared, ¹³C‐NMR, scanning electron microscopy, and dynamic mechanical analysis, showing interpenetration of NCH molecules into the PU networks. When nitrochitosan content (C_NCH) was lower than 10 wt %, the semi‐IPN sheets T‐PU and C‐PU had higher density and tensile strength (σ_b) than the systems with C_NCH more than 20%. The trihydroxymethyl propane‐based PU reacted more readily with nitrochitosan to form the semi‐IPNs than castor oil‐based PU. The semi‐IPN coatings T‐PU and C‐PU were used to coat cellophane, resulting in intimate interfacial bonding. The mechanical strength and water resistivity of the cellophane coated with T‐PU coating were improved remarkably. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 3109–3117, 2001     

Synthesis of polymeric dyes based on self-colored network of castor oil-based waterborne polyurethane

The development of vegetable oil-based polymers was particularly suitable for the era of increasingly scarce petroleum. Self-colored castor oil-based waterborne polyurethanes (PUs) were successfully synthesized based on castor oil and 1-amino-4-hydroxy-2-(6-hydroxyhexyl) anthraquinone (DR) as polyols. The UV–Vis spectrum showed that the addition of carboxylic acid groups make the spectrum of the PU produce the hyperchromic effect under alkaline conditions. Castor oil-based waterborne colored PUs possessed excellent stability under weak alkaline conditions. The connection of castor oil caused the PU to constitute soft polymer networks. PU coatings on cotton fabrics possessed excellent color properties. The urethane groups in the PUs formed hydrogen bonds with the hydroxyl groups on the cotton fibers and the polymer network structure formed by the PU coating itself made the color fastness of the cotton coatings reached grade 5. With the increase of castor oil content, the degradation rate of castor oil-based waterborne colored PU increased from 3.45% to 3.65%. This work provides a way to impart excellent color properties and fastness to PU coatings by inserting dye molecules and vegetable oils into the PU macromolecular chain.     

蓖麻油改性聚氨酯与醇酸树脂的共混改性

介绍邻苯二甲酸醇酸树脂与醇解的蓖麻油改性聚氨酯冷拼共混改性。用反射ＦＴ－ＩＲ、ＴＥＭ及热分析（ＤＴＡ,ＴＧ）等对共混物的表面结构、聚集状态及热失重进行了考察。结果表明,共混物呈现团状结构,相界面处模糊产生了ＩＰＮ相,而且在涂层表面处为聚氨酯的择优聚集。由于在共混物中引入了芳香族氨酯键,增加了醇酸树脂漆膜的附着力、硬度、固化速度及表面能。     

Effects of nanoparticulate silver on the corrosion protection performance of polyurethane coatings on mild steel in sodium chloride solution

Waterborne polyurethane (WPU) and high solid polyurethane (HPU) coatings containing nanoparticulate silver were coated on mild steel and compared to the corresponding coatings without nanoparticulate silver in NaCl solution using electrochemical impedance spectroscopy (EIS). The EIS results showed WPU coating degradation in the presence of nanoparticulate silver, while inclusion of nanoparticulate silver in HPU coating revealed no significant effect on the coating resistance. The WPU and HPU coatings morphology was investigated by SEM cross-section, which showed loss of WPU coating integrity in the presence of nanoparticulate silver, while no significant effect was observed for the HPU coating. The dual behavior of nanoparticulate silver in WPU and HPU coatings was connected to their different chemical structures confirmed by FTIR spectroscopy.