Carbonaceous microsphere-based superabsorbent polymer as filler for coating of NPK fertilizer: Fabrication,properties, swelling,and nitrogen release characteristics

Recently, the use of controlled release fertilizers in agriculture has resulted in huge benefits in plant growth and cultivation. Superabsorbent polymer (SAP)-coated fertilizers have the added advantage in retaining water in soil after irrigation and also reduce the nutrient release rate from soil in a controlled manner. This study aimed to produce a nitrogen–phosphorus–potassium (NPK) fertilizer coated with superabsorbent carbonaceous microspheres polymer (SPC) by inverse suspension polymerization method with water-retention and controlled release properties. Two sets of experiments were conducted: (1) three different weight percentages and (2) different materials. NPK coated with SPC showed increasing water-retention ability with respect to carbon microsphere percentages and retains >80% water at the 30th day of experiment compared with pure NPK and NPK coated with SAP. The slow release behavior of all samples was investigated by induced coupled plasma mass spectrometry spectrometry and results showed that NPK coated with SAP and SPC has a low release rate with <50% nutrient release compared with uncoated NPK at the 30th day. The release mechanism kinetics of NPK coated with SAP and SPC were studied based on the Kosmeyer–Peppas model. The mechanisms approached Fickian diffusion-controlled release as the n value for both samples was less than 0.5. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48396.     

Enzyme-based green approach for the synthesis of gum tragacanth and acrylic acid cross-linked hydrogel: its utilization in controlled fertilizer release and enhancement of water-holding capacity of soil

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.     

Synthesis of a cellulose‐based hydrogel network: Characterization and study of urea fertilizer slow release

In the present study, we synthesized a low‐cost biodegradable hydrogel based on cellulose in order to perform controlled release of fertilizer. For this purpose, the cellulose was modified and crosslinked with urea. Then the prepared hydrogel underwent loading with the fertilizer in order to study the controlled release. Characterization of the samples was carried out by Fourier Transform Infrared (FT‐IR) spectroscopy, elemental analysis, thermal gravimetric analysis (TGA), and scanning electron microscopy (SEM). The hydrogel showed a good swelling behavior in distilled water, tap water, and 0.9% NaCl solution. Besides, water holding and water retention behavior of the hydrogel was investigated. Finally, the release of fertilizer from the loaded hydrogel was studied and showed excellent controlled release. According to the results, this hydrogel can be employed as a suitable moisture‐holding additive in the soil for agricultural purposes. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 42935.     

Preparation and characterization of triple polymer‐coated controlled‐release urea with water‐retention property and enhanced durability

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     

Intramolecular and intermolecular crosslinked poly(vinyl alcohol)–borate complexes for the sustained release of fertilizers and enzymes

Therapeutic agents or agricultural fertilizers captured in polymer colloids (PCs) give rise to interesting applications, which are typically related to sustained release. We synthesized crosslinked polymer structures with poly(vinyl alcohol) (PVA) and borax precursors. Fourier transform infrared spectroscopy showed that a polymer–boron ion complex was formed with the crosslinking reaction at the O H site of PVA; thereby, PCs were formed. Field‐emission scanning electron microscopy showed that a uniform mesoporous two‐dimensional structure formed via intermolecular and intramolecular crosslinking. Trypsin enzyme and phosphate fertilizer were trapped in these PCs independently to study sustained release. Fertilizer‐incorporated PCs were mixed with soil samples, in which seeds of fenugreek were sown, and the plant growth was monitored a duration of 15 days. The fertilizer release, studied with UV–visible spectroscopy, showed a sustained signature of the fertilizer (at 690 nm) in the water extracts of soil, with much healthier plant growth compared to the control. For the trypsin‐incorporated PC samples, the released enzyme was made to interact with bovine serum albumin protein to monitor the released percentage with UV absorption spectroscopy. A systematic increase in the enzyme signature (at 280 nm) was observed for a duration of 60 min; this indicated the potential of PC for sustained drug release. The swelling calculations predicted that the mechanism involved was composed of pseudo‐swelling behavior. We envisaged that the hydroxyl groups of the PC broke in water and formed a complex with water. This complex slowly dissolved in water to release the entrapped molecules. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

缓／控释BB肥是我国缓／控释肥料的发展方向

分析了树脂和硫磺包裹尿素缓释肥料发展缓慢的原因和弊端,提出以水溶性聚合物作为尿素和复混肥料的包膜、胶结和内质缓释剂,具有降解快、对作物无害、改善土壤结构、成本低等特点,将促进缓释肥料的发展。采用生产不同时间段释放养分的缓释肥,按作物不同生育期对养分的需求比例掺混在一起,生产作物专用的缓／控释BB肥料简单易行,应是我国缓／控释肥料的发展方向。     

HPMC layered tablets modified with chitosan and xanthan as matrices for controlled‐release fertilizers

Polymeric matrices based on hydroxypropyl methylcellulose (HPMC) with xanthan (X) or chitosan (Q) and using KNO₃ as a model fertilizer were prepared as three‐layered tablets and assayed as controlled release fertilizers (CRFs). The dynamic swelling behavior was analyzed in order to interpret the water uptake mechanism, which in general proved to be non‐Fickian. The presence of HPMC allows a substantially constant rate of fertilizer release. The release mechanism of KNO₃ was analyzed and can be described as non‐Fickian diffusion, with release exponents ranging from 0.85 to 1.01, suggesting polymer relaxation as the major process controlling fertilizer release. Durability in soil indicates the blend Q‐HPMC as the more long‐lasting matrix of those tested, remaining at least 34 weeks. Both blends improve HPMC properties for agronomical applications, with X‐HPMC increasing the swelling rate and Q‐HPMC extending the permanence in the soil. Therefore, layered X‐HPMC and Q‐HPMC matrices can be proposed as suitable materials for the development of CRFs. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40839.     

Synthesis and characterization of bio‐based PA/EP interpenetrating network polymer as coating material for controlled release fertilizers

A novel controlled release fertilizer was developed using interpenetrating polymer network (IPN) as the coating material. The IPN was successfully sprayed on the surface of the urea particles to form IPN‐coated fertilizers (IPNCU) for controlled nitrogen release. The IPN was synthesized by bio‐based polyamide (PA) from d ‐glucaric acid and epoxy (EP) through network interpenetrating. The chemical structure and microscopic morphology characteristics of IPN were examined by Fourier transform infrared spectroscopy, ¹H‐nuclear magnetic resonance, and scanning electron microscopy. The property of IPN with the different PA/EP mass ratios were investigated and compared with that of EP‐coated fertilizers (EPCU). The nutrient release behaviors of IPNCU in water and soil were detected. The results showed that the IPNCU with 5% PA content increased the nitrogen release longevity by 41 days, raised the water contact angle of surface by 23.9°, and then significantly slowed the nitrogen release rate of the IPNCU. The nutrient release mechanism of IPNCU was discussed in detail. This work indicated that the environment‐friendly IPN with superior controlled release properties could be especially useful in horticultural and agricultural applications. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46052.     

含氮磷高分子肥料的制备和结构研究

水溶性合成高分子聚合物能被微生物分解,是一种优良的土壤改良剂,并对土壤营养元素有良好的吸附作用,可减少元素流失,提高肥效。合成了一种营养元素高分子缓释化肥,将含氮磷的降解水溶性高分子材料引入到化肥领域,并通过实验研究不同的反应工艺条件对高分子肥料结构和含氮磷肥效的影响。     

Structure–property behavior of gamma‐irradiated poly(styrene) and poly(methyl methacrylate) miscible blends

Polymer blends based on various ratios of polystyrene (PS) and polymethyl methacrylate (PMMA) were exposed to different doses of gamma radiation up to 25 Mrad. The structure–property behavior of the polymer blends before and after they had been irradiated was investigated by DSC, TGA, and FTIR spectroscopy. The DSC scans of the glass transition temperature (T_g) of the different polymer blends showed that the T_g was greatly decreased by increasing the ratio of the PMMA component in the polymer blends. Moreover, the T_g of PS/PMMA blends was found to decrease with increasing irradiation dose. The depression in T_g was noticeable in the case of blends rich in PMMA component. The TGA thermograms showed that the thermal stability of the unirradiated polymer blends decreases with increasing the ratios of PMMA component. Also, it was found that the presence of PS polymer in the blends affords protection against gamma radiation degradation and improves their thermal stability. However, exposing the polymer blends to high doses of gamma radiation caused oxidative degradation to PMMA components and decreased the thermal stability. The investigation of the kinetic parameters of the thermal decomposition reaction confirm the results of thermal stability. The FTIR analysis of the gamma‐irradiated polymer blend films gives further support to the TGA data. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 72: 509–520, 1999     

Preparation of superabsorbent slow release nitrogen fertilizer by inverse suspension polymerization

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 (M_c) 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     

Characterization of slow-release collagen-g-poly(acrylic acid-co-2-acrylamido-2-methyl-1-propane sulfonic acid)–iron(III) superabsorbent polymer containing fertilizer

A novel, slow-release polymer containing phosphorous fertilizer was synthesized by the rapid coordination of iron ions with polymers after the microwave radiation polymerization of collagen, 2-acrylamido-2-methyl-1-propanesulfonic acid, and acrylic acid. We obtained an optimized collagen-g-poly(acrylic acid-co-2-acrylamido-2-methyl-1-propane sulfonic acid) collagen-g-p(AA-co-AMPS)–Fe(III) polymer with great equilibrium swelling capacities of 2595 g/g in distilled water and 121 g/g in 0.9 wt % NaCl solution and an excellent sustained fertilizer release of about 30 days. In addition, for the collagen-g-p(AA-co-AMPS)–Fe(III) polymer, the effect of cations on its swelling followed the order K⁺ > Na⁺ > Mg²⁺ > Ca²⁺. The structure and morphology were characterized by Fourier transform infrared spectroscopy, thermogravimetric analysis, and scanning electron microscopy. Moreover, the collagen-g-p(AA-co-AMPS)–Fe(III) polymers emancipated the nutrients in a more controlled manner than collagen-g-p(AA-co-AMPS). The thermal stability, water absorbency, and good slow-release of fertilizer provide the collagen-g-p(AA-co-AMPS)–Fe(III) polymer with great potential as a fertilizer-carrying vehicle and an aquasorb to be applied in agriculture and horticulture. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47178.     

Experimental assessment of the utilization of a novel interpenetrating polymer network in different processes in the agricultural sector

We synthesized a biodegradable, controlled release formulation via the impregnation of methyl methacrylic acid onto the natural polysaccharide, gum tragacanth, and a polyacrlyic-based hydrogel with glutaraldehyde as crosslinker. The biodegradation behavior of the prepared interpenetrating polymer network (IPN) was investigated with soil burial and composting methods, and the biodegradability stages were studied with Fourier transform infrared spectroscopy and scanning electron microscopy analyses. The controlled release data of the calcium nitrate was analyzed in accordance with Fick's power law, and the kinetics parameters of the release process were calculated. The values of the initial and lateral diffusion coefficients indicated a fast initial release rate of the fertilizers in comparison to the lateral release. The synthesized IPN was degraded 91.62% within 11 weeks under composting methods, whereas it degraded 78.83% under the soil burial method. The results show that the synthesized IPN was ecofriendly and could be used for the controlled release of agrochemicals. The impact of the degraded IPN on the fertility of the soil was also studied. We concluded from the results obtained that the biodegraded IPN did not have any adverse effects on the soil fertility. Hence, this biodegradable IPN could be of great significance from a green revolution point of view. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47739.     

Radiation polymerization and controlled drug release of polymer hydrogels with NIPA and NVP

P(NIPA–NVP) and P(NIPA)/PVP interpenetrating polymer network hydrogels were synthesized by radiation polymerization in this article. Acetylsalicylic acid proved a model drug of salt resistance. Drug‐controlled release of these hydrogels containing acetylsalicylic acid was investigated. Influences of radiation dose, feed composition on the lower critical solution temperature (LCST), swelling behavior, salt dissolubility, and controlled release effect were discussed. The preferable preparation conditions for the titled aim were dose rate of 1 KGy/h, total dose of 30 KGy, feed monomer ratio of NIPA:NVP between 1:1 and 4:1, and total monomer concentration of 10%. As NVP content of the hydrogel increased, LCST rose, swelling ratios increased, salt resistance improved, and both swelling and deswelling rates slowed. Due to the ability of forming association complex, these hydrogels had the function of solubilization that made the drug release of difficult dissoluble medicine effective. These hydrogels had a higher drug release at physiological environment. The experimental results showed that these hydrogels were promising materials for causing solubilization and developing a long‐term controlled release system. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 724–729, 2003     

土壤培养条件下控释肥高分子残膜降解特性研究

研究了控释肥高分子残膜在模拟土壤培养条件下的降解特性.采用傅里叶变换红外光谱(FT-IR)、示差扫描量热(DSC)、粘度法等方法,对添加质量分数为0%、15%的淀粉的控释肥高分子残膜的降解性能进行了分析.结果表明,控释肥高分子残膜具有降解性,在土壤培养条件下,含淀粉控释肥聚乙烯残膜较不含淀粉控释肥聚乙烯残膜更易降解.随...     

控释肥提高烟叶钾含量的机理研究

通过控释肥养分释放试验和烤烟盆栽试验,研究了控释肥料对植烟土壤供肥特性、烟株伤流液和烤烟根系活力的影响.结果表明:施用控释肥提高了土壤养分含量及其空间有效性;提高了土壤真溶液的钾含量,烟株旺长期土壤真溶液的养分含量最高;大幅度提高了成熟期伤流液中钾的累积量.控释肥能够降低K+与Ca2+、Mg2+拮抗作用,提高钾的有效性...     

聚合物在缓/控释肥料中的应用研究

用一种聚合物为主要包膜原料给肥料包膜,并将包膜肥料与未包膜肥料进行对比试验。结果表明,包膜肥料达到了作物所要求的缓／控释效果,说明这种聚合物在包膜肥料中的应用是可行的。     

聚乙烯溶液构成对控释肥料释放性能的影响

以聚乙烯为主要膜材料,采用喷雾相转化法和流化床设备制备控释肥料。系统研究聚合物溶液质量分数、低密聚乙烯(LDPE)与线性低密聚乙烯(LLDPE)配比、溶剂对制备包膜尿素释放期的影响。结果表明,包膜液质量分数从5%增加到8%,包膜尿素释放期由20 d增加到173 d,说明包膜液质量分数增加对释放期延长有显著影响;LDPE/LLDPE质量比从1增加到3,控释尿素释放期从98 d减少到32 d,说明聚乙烯分子的线性结构对释放期影响显著;质量分数控制在7%时,使用四氯乙烯、正辛烷、十氢化萘和环己烷4种溶剂处理的包膜肥养分释放期在87—108 d之间,4种不同溶剂对释放性能没有显著影响。为了制备释放期适宜的包膜肥料,包膜液质量分数宜控制为7%,不同线性聚乙烯混用能改变包膜控释肥料的控释性能,上述4种溶剂均可以用来配制包膜液。     

聚合物乳液包膜控释肥料技术研究进展

综述了包膜控释肥料聚合物乳液包膜剂的研究现状和基本特性,分析了流化床和转鼓流化床包膜过程中的主要影响因素,对目前聚合物乳液包膜控释肥料的释放性能进行了评述,分析了乳液包膜控释肥料研发中的关键问题,并对其发展前景进行了展望。     

Preparation of poly(acrylic acid)–chitosan hydrogels by gamma irradiation and in vitro drug release

Biocompatible and biodegradable pH‐responsive hydrogels based on poly(acrylic acid) (AAc) and chitosan were prepared for controlled drug delivery. These interpolymeric hydrogels were synthesized by a gamma irradiation polymerization technique. The degree of gelation was over 96% and increased as the chitosan or acrylic acid content increased. The equilibrium swelling studies of hydrogels prepared in various conditions were carried out in an aqueous solution, and the pH sensitivity in the range of pH 1–12 was investigated. The AAc/chitosan hydrogels showed the highest water content when the 30 vol % AAc and 0.1 wt % chitosan were irradiated with a 30‐kGy radiation dose. Also, an increase of swelling degree with an increase in the pH was noticed and showed the highest value at pH 12. The drug, 5‐fluorouracil, was loaded into these hydrogels and the release studies were carried out in simulated gastric and intestinal fluids. The in vitro release profiles of the drugs showed that more than 90% of the loaded drugs were released in the first 1 h at the intestinal pH and the rest of the drug had been released slowly. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 3660–3667, 2003