Evaluation of the water sorption and controlled‐release potential of binary polymeric beads of starch and alginate loaded with potassium nitrate as an agrochemical

Binary polymeric beads of sodium alginate and starch were prepared and characterized by IR spectral and scanning electron microscopy (SEM) techniques. The beads were examined for water uptake potential, and he influence of various factors, including chemical composition of the macromolecular matrix, pH, ionic strength, and temperature of the swelling medium, were investigated on the degree of water sorption. The prepared beads were loaded with KNO₃, as a model agrochemical, and the release kinetics of KNO₃ were studied under varying experimental conditions, as mentioned previously. The release data were analyzed by Fick's equation, and the mechanism of KNO₃ release was worked out at different experimental conditions. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 1815–1826, 2004     

Controlled release on sand bed columns and biodegradability in soil of chitosan: Hydroxypropyl methylcellulose films

The main purpose of this work is to prepare and characterize films based on chitosan (Q) and hydroxypropyl methylcellulose (HPMC) blends to achieve adequate properties to be used as coating of conventional fertilizers to prolong their availability for crops. The films loaded with KNO₃ as model fertilizer were prepared by casting. Release of fertilizer was studied using sand bed columns. To quantify films durability in soil, their areas were measured in function of time. Results showed that chitosan substantially improved the durability of HPMC, lengthening its permanence in soil 900‰. Relative humidity had influence in mechanical properties. Comparing KNO₃ powder and that loaded in the film, the time of residence in the column was much lower for the powder than the second one: 4 and 56 days, respectively. Chitosan–HPMC film would be promising as polymeric coating for controlled release fertilizers taking into account field conditions. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47532.     

Prediction of microbial growth rate in biofilters by using the nutrient diffusion coefficient

In this study, an optimal process for preparing a synthetic filter material with nitrogen nutrient (PVA/peat/KNO₃ composite beads) was developed for biofiltration and the optimal initial nitrogen concentration of the boric acid and phosphate aqueous solutions was found to be 3.94 and 1.52 g nitrogen L^?1, respectively. The water‐soluble nitrogen content in the prepared composite beads was higher than that of the compost. The mass transport process for the water‐soluble nitrogen dissolving out of the composite beads occurred in two stages: external mass transport occurred in the early stage and an intraparticle diffusion process occurred in the long‐term stage. The rate of water‐soluble nitrogen dissolving out during the external mass transport process increased with increasing the concentration of KNO₃ aqueous solution and that during the intraparticle diffusion process had a maximum value for the composite beads that had been immersed in 0.384 M KNO₃. The path of water‐soluble nitrogen dissolving out from the composite beads was that the water‐soluble nitrogen dispersed in the peat phase firstly diffused into the outer poly(vinyl alcohol) (PVA) phase and then it diffused out of the bead surface. The percentage of volatile organic compounds (VOCs) removed by the biofilter from an air stream remained above 99% for 230 days for the composite beads that had been immersed in KNO₃ before packing. The microbial growth rate had a maximum value for the composite beads that had been immersed in 0.384 M KNO₃ and was higher than that of the compost by a factor of 1.49. The rate of nitrogen dissolving out during the intraparticle diffusion process could be used as an index to predict the microbial growth rate in the biofilter. Copyright © 2005 Society of Chemical Industry     

Preparation,characterization and preliminary calcium release study of floating sodium alginate/dextran‐based hydrogel beads: part I

Ionically crosslinked calcium alginate/dextran‐based floating beads were prepared using NaHCO₃ as porogen. Various micrometric properties such as tapped density, apparent density, compressibility index, etc., were determined for beads with different compositions. The beads were also evaluated for their mechanical strength. The percent buoyancy of the beads was measured as a function of time in simulated gastric fluid (pH = 1.2 at 37 °C). The beads prepared with higher concentrations of NaHCO₃ porogen and CaCl₂ crosslinker possessed 100% buoyancy and remained buoyant for nearly 20 h, or even more. Finally, the release of calcium from the beads was observed to follow diffusion‐controlled Higuchi kinetics. Copyright © 2007 Society of Chemical Industry     

Glutaraldehyde‐crosslinked chitosan beads for controlled release of diclofenac sodium

An inexpensive and simple method was adopted for the preparation of chitosan beads, crosslinked with glutaraldehyde (GA), for the controlled release of diclofenac sodium (DS). The beads were prepared by varying the experimental conditions such as pH, temperature, and extent of crosslinking. The absence of any chemical interaction among drug, polymer, and the crosslinking agent was confirmed by FTIR and thermal analysis. The beads were characterized by microscopy, which indicated that the particles were in the size range of 500–700 μm and SEM studies revealed smooth surface and spherical shape of beads. The beads produced at higher temperature and extended exposure to GA exhibited lower drug content, whereas increased drug loading resulted in enhanced drug release. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 211–217, 2007     

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.     

Controlled release of chlorpheniramine maleate through IPN beads of sodium alginate‐g‐methylmethacrylate

Controlled release of chlorpheniramine maleate drug, through sodium alginate‐g‐methylmethacrylate (NaAlg‐g‐MMA) interpenetrating polymeric network beads, has been investigated. Beads were prepared by precipitating the viscous solution of NaAlg‐g‐MMA in acetone followed by cross‐linking with glutaraldehyde. The beads were characterized by Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), and scanning electron microscopy (SEM). Different formulations of beads were developed by varying amounts of MMA, cross‐linking agent, and drug concentration. DSC thermograms of chlorpheniramine maleate drug‐loaded NaAlg‐g‐MMA beads confirmed the molecular level distribution of drug in the polymer matrix. FTIR of beads confirm the grafting and cross‐linking, SEM of the beads suggested the formation of spherical particles. Swelling experiments on the beads provided an important information on drug diffusion properties. Release data have been analyzed using an empirical equation to understand the nature of transport of drug containing solution through the polymeric matrices. The controlled release characteristics of the matrices for chlorpheniramine maleate was investigated in pH 7.4 media. Drug was released in a controlled manner upto 12 h. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Polymeric sodium alginate interpenetrating network beads for the controlled release of chlorpyrifos

Novel polymeric sodium alginate (Na‐Alg) interpenetrating network (IPN) beads have been prepared by crosslinking Na‐Alg blend with gelatin (GE) or egg albumin (EA) using glutaraldehyde (GA) as the crosslinking agent. These beads were used for the controlled release of chlorpyrifos. The swelling experiments were performed in water at different temperatures, and these data were used to calculate the molecular mass (M_C) between crosslinks as well as diffusion coefficients. Diffusion coefficients calculated from desorption data were lower by about two orders of magnitude than those calculated from sorption results. Higher values of M_C were obtained for the gelatin‐based IPNs than the neat Na‐Alg and egg albumin‐based matrices. Size of the beads did not vary significantly either by the network or by increasing the exposure time to the crosslinking agent. The scanning electron microscopy (SEM) was used to understand the surface characteristics of the beads. Differential scanning calorimetry (DSC) indicated a molecular level dispersion of chlorpyrifos in the polymer matrix. The percentage entrapment efficiency showed a dependence on the type of network polymer as well as time of exposure to the crosslinking agent. The encapsulation efficiency decreased with an increase in time of exposure to the crosslinking agent. In vitro release experiments have been performed to follow the release kinetics of chlorpyrifos from the matrices. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 911–918, 2002     

Calcium‐carboxymethyl chitosan hydrogel beads for protein drug delivery system

In this study, carboxymethyl chitosan (CMC) hydrogel beads were prepared by crosslinking with Ca²⁺. The pH‐sensitive characteristics of the beads were investigated by simulating gastrointestinal pH conditions. As a potential protein drug delivery system, the beads were loaded with a model protein (bovine serum albumin, BSA). To improve the entrapment efficiency of BSA, the beads were further coated with a chitosan/CMC polyelectrolyte complex (PEC) membrane by extruding a CMC/BSA solution into a CaCl₂/chitosan gelation medium. Finally, the release studies of BSA‐loaded beads were conducted. We found that, the maximum swelling ratios of the beads at pH 7.4 (17–21) were much higher than those at pH 1.2 (2–2.5). Higher entrapment efficiency (73.2%) was achieved in the chitosan‐coated calcium‐CMC beads, compared with that (44.4%) in the bare calcium‐CMC beads. The PEC membrane limited the BSA release, while the final disintegration of beads at pH 7.4 still leaded to a full BSA release. Therefore, the chitosan‐coated calcium‐CMC hydrogel beads with higher entrapment efficiency and proper protein release properties were a promising protein drug carrier for the site‐specific release in the intestine. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 3164–3168, 2007     

Study and modeling of the liquid–solid equilibrium of the KCl–KNO3–HCl–H2O system at 283.15 K

In this work, the liquid–solid equilibrium of the KCl–KNO₃–HCl–H₂O system at 283.15 K was investigated. To calculate the solubility product constants of KCl and KNO₃ in HCl solution, the Pitzer equation was used to calculate the activity coefficient of the ionic species in aqueous solution. In addition, the thermodynamic model with the Pitzer equation was constructed to regress the temperature coefficient parameters for HCl and HNO₃. The calculation and prediction of the KCl–KNO₃–HCl–H₂O system using the results of the regression confirmed that the regression was successful and the Pitzer equation was suitable. For the reaction KCl(s) + HNO₃ → KNO₃(s) + HCl , the equilibrium constant K can be obtained from the solubility product constants of KCl and KNO₃. Eutectic points for the KCl–KNO₃–HCl–H₂O system were also predicted. These equilibrium data could be expressed by the triangular phase diagram. The process of the reaction to produce KNO₃ could be explained through this triangular phase.     

Synthesis and characterization of poly(N‐vinyl‐2‐pyrrolidone) grafted sodium alginate hydrogel beads for the controlled release of indomethacin

Graft copolymers of sodium alginate (NaAlg) with N‐vinyl‐2‐pyrrolidone were prepared using azobisisobutyronitrile as initiator. The graft copolymers (NaAlg‐g‐PVP) were characterized with Fourier transform infrared spectroscopy, elemental analysis, and differential scanning calorimetry. Polymeric hydrogel beads of NaAlg and NaAlg‐g‐PVP were prepared by crosslinking method using glutaraldehyde (GA) as a crosslinker in the hydrochloric acid catalyst (HCl) and these beads were used to deliver anti‐inflammatory drug, indomethacin (IM). Chemical stability of the IM after encapsulation into beads was confirmed by FTIR. Preparation conditions of the NaAlg‐g‐PVP beads were optimized by considering the percentage entrapment efficiency, particle size, swelling capacity and their release data. In vitro release studies were performed in simulated gastric fluid (pH 1.2) for the initial 2 h, followed by simulated intestinal fluid (pH 7.4) for 4 h. Effects of GA concentration, exposure time to GA, drug/polymer (d/p) ratio, and concentration of HCl on the release of IM were discussed. It was observed that IM release from the beads decreased with increasing GA concentration and exposure time. IM release also decreases with increasing d/p ratio and HCl concentration. The highest IM release was obtained to be 77% for beads crosslinked with 0.027M GA. Swelling experiments were also performed to compute molecular mass between crosslinks of the beads. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Adsorption of trypsin onto magnetic ion‐exchange beads of poly(glycidylmethacrylate‐co‐ethyleneglycoldimethacrylate)

Magnetic beads were prepared from glycidyl methacrylate (GMA), and ethyleneglycol dimethylmethacrylate (EGDMA) in the presence of Fe₃O₄ nano‐powder via suspension polymerization. The magnetic beads were characterized by surface area measurement, electron spin resonance (ESR), and scanning electron microscopy (SEM). ESR data revealed that the beads were highly super‐paramagnetic. The effects of contact time, pH, ionic strength, and temperature on the adsorption process have been studied. Adsorption equilibrium was established in about 120 min. The maximum adsorption of trypsin on the magnetic beads was obtained as 84.96 mg g^?1 at around pH 7.0. At increased ionic strength, the contribution of the electrostatic component to the overall binding decreased, and so the adsorption capacity. The experimental equilibrium data obtained trypsin adsorption onto magnetic beads fitted well to the Langmuir isotherm model. The result of kinetic analyzed for trypsin adsorption onto magnetic ion‐exchange beads showed that the second order rate equation was favorable. It was observed that after six adsorption–elution cycle, magnetic beads can be used without significant loss in trypsin adsorption capacity. Finally, the magnetic beads were used for separation of bovine serum albumin (BSA) and trypsin from binary solution in a batch system. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Binary biopolymeric beads of alginate and gelatin as potential adsorbent for removal of toxic Ni2+ ions: A dynamic and equilibrium study

Binary biopolymeric beads of alginate and gelatin were prepared and characterized by IR spectral and scanning electron micrograph techniques. On to the surfaces of the prepared beads were performed static and dynamic adsorption studies of Ni²⁺ ions at fixed pH and ionic strength of the aqueous metal ion solutions. The adsorption data were applied to Langmuir and Freundlich isotherm equations and various static parameters were calculated. The dynamic nature of adsorption was quantified in terms of several kinetic constants such as rate constants for adsorption (k₁), Lagergreen rate constant (k_ad), interparticle diffusion rate constant (k_p), and pore diffusion coefficient (D ). The influence of various experimental parameters such as solid to liquid ratio, pH, temperature, presence of salts, and chemical composition of biopolymeric beads on the adsorption of nickel ions was investigated. Various thermodynamic parameters were also calculated. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 2581–2590, 2007     

Preparation and evaluation of cellulose acetate butyrate and poly(ethylene oxide) blend microspheres for gastroretentive floating delivery of repaglinide

In this study, hollow microspheres of cellulose acetate butyrate (CAB) and poly(ethylene oxide) (PEO) were prepared by emulsion–solvent evaporation method. Repaglinide was successfully encapsulated into floating microspheres. Various formulations were prepared by varying the ratio of CAB and PEO, drug loading and concentration of poly(vinyl alcohol) (PVA) solution. Encapsulation of the drug up to 95% was achieved. The microspheres tend to float over the simulated gastric media for more than 10 h. The micromeritic properties of microspheres reveal the excellent flow and good packing properties. The % buoyancy of microspheres was found to be up to 87. SEM showed that microspheres have many pores on their surfaces. Particle size ranges from 159 to 601 μm. DSC and X‐RD revealed the amorphous dispersion in the polymer matrix. In vitro release experiments were performed in simulated gastric fluid. In vitro release studies indicated the dependence of release rate on the extent of drug loading and the amount of PEO in the microspheres; slow release was extended up to 12 h. The release data were fitted to an empirical equation to compute the diffusional exponent (n), which indicated that the release mechanism followed the non‐Fickian trend. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Semiinterpenetrating polymer networks of chitosan and L‐alanine for monitoring the release of chlorpheniramine maleate

In vitro studies have been carried on semiinterpenetrating polymer network (IPN) beads of chitosan–alanine as carrier for the controlled release of chlorpheniramine maleate (CPM) drug. A viscous solution of chitosan–alanine was prepared in 2% acetic acid solution, extruded as droplets by a syringe to NaOH–methanol solution and crosslinked using glutaraldehyde as a crosslinker. The swelling behavior of crosslinked beads in different pH solutions was measured at different time intervals. The swelling behavior was observed to be dependent on pH and degree of crosslinking. The structural and morphological studies of beads were carried out by using a scanning electron microscope. The drug release experiments of different drug loading capacity beads were performed in solutions of pH 2 and pH 7.4 using CPM as a model drug. The concentration of the released drug was evaluated using UV spectrophotometer. The results suggest that chitosan–alanine crosslinked beads are suitable for controlled release of drug. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 3751–3757, 2007     

Microheterogeneous polymer systems prepared by suspension polymerization of methyl methacrylate in the presence of poly(ε‐caprolactone)

Poly(methyl methacrylate) – polycaprolactone (PMMA/PCL) microheterogeneous beads were synthesized by suspension polymerization starting from methyl methacrylate (MMA) monomer and PCL, which was synthesized by ring‐opening polymerization of ε‐caprolactone using ZnCl₂ as initiator. The resulting polymer was fully characterized by ¹H and ¹³C NMR, differential scanning calorimetry (DSC), gel permeation chromatography (GPC) and dynamic mechanical thermal analysis (DMTA). The size distribution and morphology of the resulting beads were investigated by optical microscopy and scanning electron microscopy (SEM). Moreover, blends of PMMA beads and PCL in different proportions were prepared and the morphology of the films was examined by optical microscopy. The low compatibility between PMMA and PCL was clearly evidenced through these experiments.     

Preparation and characterization of interpenetrating network beads of poly(vinyl alcohol)‐grafted‐poly(acrylamide) with sodium alginate and their controlled release characteristics for cypermethrin pesticide

Interpenetrating network polymeric beads of poly(vinyl alcohol)‐grafted‐acrylamide with sodium alginate have been prepared by crosslinking with glutaraldehyde. Cypermethrin, a widely used pesticide, was loaded with 80% efficiency in these hydrogel beads. The beads were characterized by Fourier transform infrared spectroscopy to confirm the grafting. Scanning electron microscopy was used to know the morphology of the beads. Equilibrium swelling experiments indicated that swelling of the beads decreased with an increase in crosslinking. The in vitro release studies were performed under static conditions and the release data have been fitted to an empirical relation to estimate the transport parameters. The diffusion coefficients have been calculated for the transport of pesticide through the polymeric beads using the initial time approximation method. These values showed decrease with increasing crosslinking as well as increasing pesticide loading. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 552–560, 2002; DOI 10.1002/app.10306     

Morphology,dynamic mechanical,and electrical properties of bio‐based poly(trimethylene terephthalate) blends,part 2: Poly(trimethylene terephthalate)/poly(ether esteramide)/polycarbonate blends

Bio‐based poly(trimethylene terephthalate) (PTT) and poly(ether esteramide) (PEEA) blends were prepared by melt processing with varying weight ratios (0–20 wt %) of polycarbonate (PC). The blends were characterized by differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), polarized light microscopy (PLM), and transmission electron microscopy (TEM). Electrostatic performance was also investigated for those PTT blends since PEEA is known as an ion conductive polymer. DMA suggests that PC is miscible with PEEA and selectively goes into PEEA phase in case of ternary blends of PTT/PEEA/PC. The glass transition temperature (T_g) for PC/PEEA is well predicted by Gordon Taylor equation. Addition of PC retards the electrostatic decay performance of PTT/PEEA blends by restricting the motion of ions in PEEA through increasing the T_g of PEEA. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Complex formation in molten salts - IV: Association constants of silver-bromo complexes in molten KNO3Ba(NO3)2 eutectic as solvent

Potentiometric measurements on the molten salt concentration cell: Ag/AgNO₃, KNO₃Ba(NO₃)₂//AgNO₃, KBr, KNO₃Ba(NO₃)₂/Ag were carried out over a wide range of solute concentration and at temperatures in the range 350–410°C to study the association equilibria in dilute solutions of Ag⁺ and Br^? in molten KNO₃Ba(NO₃)₂(89:11 mole %). The results indicated formation of the species AgBr, AgBr^?₂; Ag₂Br⁺ was not formed under the experimental conditions employed. The temperature-dependence of the association constants were, within limits of experimental precision, predictable from the quasi-lattice model.     

Combustion of Ti and Zr Particles with KNO3

This paper describes the thermochemical properties and combustion characteristics of pyrolants consisting of Ti/KNO₃ and Zr/KNO₃ mixtures. Differential thermal analysis (DTA) and thermogravimetry (TG) were conducted in order to elucidate the reaction processes of these pyrolants. The results of the experiments suggest that Ti particles react exothermically at 970 K with the decomposed gases of KNO₃, and Zr particles react also exothermically at 700 K with liquified product of KNO₃. Burning rates of the pyrolants were measured with a chimney type strand burner which was pressurized with argon gas. The burning rate of Ti/KNO₃ is more sensitive to pressure than that of Zr/KNO₃. The results indicate that a major exothermic reaction on the combustion wave of Zr/KNO₃ pyrolants is in the condensed phase. The burning rates of both pyrolants are dependent on the oxidizer/fuel ratio and initial temperature of the pyrolants.