Controlled release of insecticide carbaryl from sodium alginate,sodium alginate/gelatin,and sodium alginate/sodium carboxymethyl cellulose blend beads crosslinked with glutaraldehyde

Interpenetrating network polymeric beads of sodium alginate (NaAlg) and its blend with gelatin (gels) or sodium carboxymethyl cellulose (NaCMC) have been prepared by crosslinking with a common crosslinking agent, glutaraldehyde (GA), for the release of insecticide carbaryl (Carb). The prepared beads were characterized by Fourier transform infrared spectroscopy and scanning electron microscopy. Scanning electron microscopy confirmed the spherical nature and surface morphology of the particles. Bead characteristics, such as carbaryl entrapment efficiency, particle size, equilibrium swelling degree, and carbaryl release kinetics, were determined. The effects of the preparation conditions, such as Carb/NaAlg ratio, time of exposure to GA, blend ratio, and temperature of release medium on the carbaryl release, were investigated for 25 days at 25°C. It was observed that the carbaryl release decreased with increase in crosslinking of network, while it increased with increase in Carb/NaAlg ratio and temperature. The release of carbaryl also increased with increase in Gel or NaCMC content in the blend beads. The highest carbaryl release was found to be 100%, for the beads that were prepared with 1 : 1 NaAlg/Gel at 16 days. The diffusion coefficients have been calculated for the transport of insecticide through the polymeric beads, using initial time approximation method. These values were also consistent with the carbaryl release data. The carbaryl release from most of the bead formulations followed the Fickian trend. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 1310–1319, 2006     

Preparation and characterization of a novel positively charged nanofiltration membrane based on polysulfone

The goal of this study was to prepare positively charged nanofiltration (NF) membranes to remove cations from aqueous solutions. A composite NF membrane was fabricated by the modification of a polysulfone ultrafiltration support. The active top layer was formed by the interfacial crosslinking polymerization of poly(ethylene imine) (PEI) with p‐xylene dichloride (XDC). Then, it was quaternized by methyl iodide (MI) to form a perpetually positively charged layer. The chemical and morphological changes of the membrane surfaces were studied by Fourier transform infrared spectroscopy, scanning electron microscopy (SEM), and atomic force microscopy. To optimize the membrane operation, the PEI solution concentration, PEI coating time, XDC concentration, crosslinking time, and MI concentration were optimized. Consequently, high water flux (5.4 L m^?2 h^?1 bar^?1) and CaCl₂ rejection (94%) values were obtained for the composite membranes at 4 bars and 30°C. The rejections of the NF membrane for different salt solutions, obtained from pH testing, followed the order Na₂SO₄ < MgSO₄ < NaCl < CaCl₂. The molecular weight cutoff was calculated by the retention of poly(ethylene glycol) solutions with different molecular weights, and finally, the stoke radius was calculated as 1.47 nm. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41988.     

Preparation of alginate flame retardant containing P and Si and its flame retardancy in epoxy resin

In the present paper, a novel biomass flame retardant based on alginic acid was synthesized through chemical combination with a reactive P–Si compound. Compared with alginates, the modified alginate showed obviously increased thermal stability and water resisting property, as well as better compatibility with epoxy resin, which can satisfy the requirements of a flame‐retardant additive in the polymer. The flame‐retardant properties were evaluated by vertical burning tests, limiting oxygen index, and microscale combustion calorimetry. Due to the self‐charring capacity of alginate combined with the charring catalyst from P and the charring reinforcer from Si, the modified alginate exhibited much better flame retardancy, taking advantage of the formation of a more continuous, denser, and strengthened char layer than either individual alginate or P–Si flame retardant. The corresponding flame‐retardant mechanisms were investigated and discussed. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45552.     

Thermal conductivity and stability of a three‐phase blend of carbon nanotubes,conductive polymer,and silver nanoparticles incorporated into polycarbonate nanocomposites

Metallic and non‐metallic nanofillers can be used together in the design of polycarbonate (PC) nanocomposites with improved electrical properties. Here, the preparation of three‐phase blend (carbon nanotubes (CNT), silver nanoparticles, and conductive polymer) in a two‐step process before incorporation in the PC is reported. First, ethylene diamine functionalized multiwall carbon nanotubes (MWCNT‐EDA) were decorated with Ag nanoparticles. Next, the Ag‐decorated CNTs were coated with poly(3,4‐ethylenedioxythiophene) polystyrene sulfonate (PEDOT : PSS). Due to the high thermal conductivity instrinsic to both metallic and non‐metallic phases, it is expected that the thermal properties of the resulting nanocomposite would largely differ from those of pristine PC. We thus investigated in detail how this hybrid conductive blend affected properties such as the glass transition temperature, the thermal stability, and the thermal conductivity of the nanocomposite. It was found that this strategy results in improved thermal conductivity and thermal stability of the material. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42281.     

Preparation and property investigation of crosslinked alginate/silicon dioxide nanocomposite films

Crosslinked nanocomposite films of sodium alginate (SA) and silicon dioxide (SiO₂) with different SiO₂ loading values were prepared by in situ synthesis. Biocomposite films were produced by solution casting and solvent evaporation with glycerol as the plasticizer and calcium chloride as the crosslinking agent. The effects of the addition of nano silicon dioxide (nano‐SiO₂) in SA on the microstructural, physical, mechanical, and optical properties of the nanocomposite films were characterized. The results show that nano‐SiO₂ was dispersed homogeneously in the SA matrix; it thereby formed a strong interfacial interaction between the nano‐SiO₂ particles and the matrix. The transparency of the bionanocomposite films was enhanced. Thermogravimetric analysis also revealed that nano‐SiO₂ improved the thermal stability of the SA films. The incorporation of SiO₂ further reduced the water vapor permeability and swelling degree and significantly increased the tensile strength and elongation, which are parameters important for packaging industries. Finally, the lower light transmission of UV light from 200 to 250 nm indicated that SA/SiO₂ nanocomposite films could potentially be used to prevent lipid damage by UV light in food conservation. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43489.     

Synthesis and swelling properties of a pH‐ and temperature‐dual responsive hydrogel by inverse microemulsion polymerization

A novel pH‐ and temperature‐dual responsive hydrogel was synthesized by inverse microemulsion polymerization, using itonic acid (IA) as pH‐responsive monomer, N‐isopropylacrylamide (NPAM) as thermo‐responsive monomer and acrylamide (AM) as the nonionic hydrophilic monomer. Factors affecting water and salt absorption, as well as swellability of the dual responsive hydrogels, such as IA/NPAM mass ratio and crosslinker amount, were investigated. pH‐ and temperature‐sensitivity and dynamic viscoelasticity behaviors of the dual responsive hydrogels were also studied. The dual responsive responsive hydrogels showed suitable water and salt absorbency, remarkable pH‐, and temperature‐sensitivity, adjustable swellability and enhanced viscoelastic behaviors under high stress. Water absorbency and pH‐sensitivity increased while salt absorbency and temperature‐ sensitivity decreased with increasing IA/NIPAM mass ratio. Both water absorbency and salt absorbency increased first with crosslinker amount increased to 0.2 wt %, and then decreased with increasing crosslinker amount. Temperature‐induced shrinkage range of the dual responsive hydrogels was higher and broader than that of the conventional poly(N‐isopropylacrylamide) hydrogel. TEM indicated that the as‐synthesized hydrogel particles were regular and spherical‐like in shape and had the mean particle size of 49nm in the range of 30–78 nm. FTIR indicated the structure of the dual responsive hydrogels. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42139.     

Thin film composite sodium alginate membranes for dehydration of acetic acid and isobutanol

Dehydration of widely used organic solvents such as acetic acid (AA) and isobutanol (IB) is challenging tasks, which form close boiling mixtures with water. Sodium alginate (SA) thin film composite membranes were prepared and crosslinked with 2,4‐toluene diisocyanate (TDI) and glutaraldehyde for dehydration of IB and AA/water mixtures through pervaporation (PV). The crosslinked and uncrosslinked SA composite membranes were characterized by Fourier transform infrared spectroscopy (FTIR), X‐ray diffraction, thermogravimetric analysis, scanning electron microscopy, and universal testing machine for intermolecular interactions, crystalline nature, thermal stability, surface morphology, and tensile strength, respectively. At a feed composition of 98 wt % IB and 95 wt % AA aqueous solutions, the TDI crosslinked SA composite membrane exhibited separation factors of 3229 and 708 with reasonable fluxes of 0.021 and 0.012 kg m^?2 h^?1, respectively. The results obtained in the study for IB and AA systems were compared with other SA membranes reported in the literature. The membranes appeared to have potential for commercial PV ability to dehydrate the solvents up to desirable purity levels (>99%) and feasibility of preparing them in a composite form which would enable scale‐up into modular configurations. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2014 , 131, 40018.     

Preparation and characterization of composite hydrogels based on crosslinked hyaluronic acid and sodium alginate

In this study, a novel composite hydrogel with improved cellular structure and mechanical properties was prepared by the crosslinking of hyaluronic acid (HA) and sodium alginate (SAL). The amide linkages (covalent bonds) in the hydrogel that we expected to form were confirmed by Fourier transform infrared spectroscopy. The hydrogels had a pore size larger than 100 μm and were observed by scanning electron microscopy. Texture profile analysis indicated that the hardness of the hydrogels was enhanced by an increase in the polymer's concentration, but it declined with an increase in the HA/SAL molar ratio. The swelling capacity was reduced with increases in the polymer's concentration and the 1‐ethyl‐3‐(3‐dimethyl aminopropyl)‐1‐carbodiimide hydrochloride (EDC)/HA molar ratio, and it was enhanced by an increase in the HA/SAL molar ratio. The resistance against hyaluronidase was negatively correlated with the proportion of HA in the hydrogels and positively correlated with the EDC/HA molar ratio. Given the improved physicochemical properties that we produced, these novel hydrogels may have the potential to be applied in tissue engineering scaffolding. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41898.     

Study of crosslinked copolymer nanospheres with temperature resistance,salinity resistance,and deep profile control

Three crosslinked copolymer nanospheres were prepared by inverse microemulsion polymerization. Resistance temperature and resistance salinity of the copolymer CP(AM‐AA‐AMPS) [crosslinked poly(acrylamide‐acrylic acid‐2‐acrylamide‐2‐methylacrylic sulfonic acid)] nano‐spheres were superior to the CPAM (crosslinked polyacrylamide) nano‐spheres and CP(AM‐AA) [crosslinked poly(acrylamide‐acrylic acid)] nano‐spheres. The nanospheres had a tendency to plug the high‐permeability layer and drive crude oil from the low‐permeability layer. Meanwhile, these nanospheres displaced crude oil that existed in the pores or throats when they were conveyed in porous media. Consequently, deep profile control and oil displacement could be entirely actualized, and the ultimate goal of enhanced oil recovery could be achieved for high‐temperature and high‐salinity reservoirs. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45131.     

Effect of Ca2+ induced crosslinking on the mechanical and barrier properties of cast alginate films

The use of alginate as a coating material for packaging applications is currently limited due to its difficult processability and high moisture sensitivity. Therefore, this study addresses the crosslinking and scale‐up to a continuous application. Three different crosslinking agents were applied: CaCl₂ with ethylene diamine tetraacetic acid and two low soluble salts (CaHPO₄ and CaCO₃). Those were incorporated by internal setting in an alginate matrix with varying Ca²⁺ concentration ( ) and ratio. With the addition of Ca²⁺, the tensile strength and elongation at break of the cast alginate films increased. This was optimal for a of 0.010–0.015 g (g alginate)^?1 dependent on the crosslinking agent. The decrease in water vapor and oxygen permeability due to crosslinking was independent of the crosslinking agent. However, the optimal aiming to decrease permeability was different for the crosslinking agents: CaHPO₄ showed best results at a of 0.010 g (g alginate)^?1, CaCl₂ at 0.012 g (g alginate)^?1, and CaCO₃ at 0.027 g (g alginate)^?1. Upon all analyzed properties CaHPO₄ was the most promising crosslinking agent for alginate. Moreover, selected alginate formulations were successfully processed in a continuous lacquering plant. The produced two‐layer systems have very low oxygen permeabilities which can be further reduced by crosslinking. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45754.     

Comparison of the initial reactant structure and crosslinked network of poly(dimethyl siloxane) membranes from different macromonomers

Some of the best entities for the removal of volatile organic pollutants from water, poly(dimethyl siloxane) (PDMS) membranes from two types of initial PDMS precursors, were thoroughly investigated. In both the cases, the sizes of the initial macromonomers increased because of the crosslinking in the liquid state, and they exhibited Gaussian chain statistics, which were condensed by further crosslinking to the formation of the membranes. The structures of both the membrane types exhibited large interchain spacing on swelling; this implied a high degree of chain mobility. Their structural properties were corroborated by their separation performances. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41461.     

Synthesis and characterization of PLA nanocomposites containing nanosilica modified with different organosilanes II: Effect of the organosilanes on the properties of nanocomposites: Thermal characterization

Thermal behavior of polylactic acid (PLA)/nanosilica nanocomposites prepared via bulk ring opening polymerization from lactide was investigated by differential scanning calorimetry and thermogravimetric analysis (TGA). Both unmodified nanosilica and modified by surface treatments with different amounts of two distinct silanes were used. Samples containing pure silica show enhanced crystallization processes; with silane‐modified silica this effect is magnified, especially in the case of materials with high loadings of epoxy silane. Nonisothermal crystallization temperatures become higher and isothermal crystallization kinetics show a marked increase of Kinetic constant (K_c). TGA analyses show that, when pure nanosilica is present, nanocomposites have a thermal stability far greater than the one of standard PLA, starting their degradation at temperatures up to 70°C higher than the ones of pure PLA. When silanes are present, thermal stability lowers as silane content increases, but it is anyway higher than the one of the pure polymer. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Flame retardancy and thermal properties of organoclay and phosphorous compound synergistically modified epoxy resin

Phosphorous flame retardants (PFRs) are common halogen‐free flame retardants. However, the flame retardancy of PFRs has not been fully exploited. Herein, the synergistic flame retardant effect of a typical phosphorous compound, 9,10‐dihydro‐9‐oxa‐10‐phosphaphenanthrene‐10‐oxide (DOPO), and organoclay on epoxy is studied. Results show that the peak of heat release rate (pHRR) and smoke production rate of modified epoxy resin (EP) with both 2.0 wt % phosphorus and 4.0 wt % organoclay are only 40% and 46% of that of neat EP resin, respectively, while the sole use of 2.0 wt % phosphorus only decrease the pHRR to 59% of that of neat EP resin. The structure and thermal decomposition behavior of as‐prepared nanocomposites are analyzed, and a synergistic flame retardant mechanism is proposed. This investigation opens a new approach to obtain halogen‐free EPs with higher flame retardancy and better overall properties than the EPs loaded with DOPO only. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43367.     

Phase distribution changes of neat unsaturated polyester resin and their effects on both thermal stability and dynamic-mechanical properties

A relationship between phase distribution of a commercial unsaturated polyester resin (UPR) and both thermal stability and dynamical mechanical properties, measured by thermogravimetric analysis and dynamic-mechanical analysis respectively, is observed. Changes in phase distributions are achieved varying UPR components miscibility by means of temperature. Morphologies of the internal surfaces are analyzed by atomic force microscopy showing that more homogeneous nanostructures with smaller nodules result in the increase of the storage modulus and glass transition temperature of the thermosetting UPR. Tan δ peaks show that the phase rich in UP and the phase rich in polystyrene tend to decrease their differences at higher curing temperatures. Changes in the curing mechanism and kinetics with curing temperature are verified by differential scanning calorimetry. A theoretical explanation of archived morphology is proposed using interaction parameter between UP and styrene showing that higher temperatures increased their miscibility.     

Mechanical and thermal properties of modified kaolin clay/unsaturated polyester nanocomposites

The improvement in thermal and mechanical properties of Nanocomposites prepared with unsaturated polyester (UP) as polymer matrix and various loadings of amino‐modified nano kaolinite clay as filler has been studied. Mechanical stirring and ultrasonication resulted in better dispersion of the clay. For curing polyester resin, cobalt naphthenate was used as accelerator and MEKP as initiator. Dynamic Mechanical Analysis (DMA) was carried out to find storage and loss modulus. Thermal stability was found through thermogravimetric analysis and the evaluation of structure and morphology of the nanocomposites were done through XRD, SEM, and TEM. Nanocomposite with 3 phr of amino modified clay has shown higher storage modulus and an improved thermal stability of UP/clay nanocomposites has been established. Tensile strength and toughness of the composite have been found to achieve maximum values at 1 phr of clay and the storage modulus has had an improvement of 38% compared to neat UPR. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43245.     

Preparation and characterization of alginate hydrogel membranes crosslinked using a water‐soluble carbodiimide

The preparation of alginate hydrogel membranes by the film immersion method was optimized for maximum crosslinking using swelling measurements as an indicator of the degree of crosslinking. The variables investigated were the concentration of the nonsolvent (ethanol) for sodium alginate, water‐soluble carbodiimide (WSC) concentration, and pH of the crosslinking medium. Optimum conditions resulted when the crosslinking medium contained 60 vol % ethanol and 100 mM WSC at pH 4. Membranes prepared using different ethanol concentrations (100 mM WSC, pH 4) and different WSC concentrations (60 vol % ethanol, pH 4) were investigated using infrared spectroscopy. The spectra showed the characteristic ester linkage (crosslinking) band at 1698 cm^?1 in cases where swelling measurements indicated that crosslinking had occurred. Differential scanning calorimetry of noncrosslinked and crosslinked membranes indicated that crosslinking increased the crystallinity of the membrane. Durability trials showed that membranes crosslinked using the optimum conditions determined in this work retained all weight when immersed in water for 32 days. Membranes prepared using these conditions possessed the characteristics required for use in the pervaporation separation of ethanol–water mixtures. These membranes also have potential as protective coatings for hydrophobic, microporous membranes in the membrane distillation and osmotic distillation concentration of feeds containing surface active components. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 747–753, 2003     

Preparation of superhydrophobic surfaces by cauliflower‐like polyaniline

Cauliflower‐like polyaniline (PANI) was successfully prepared using an interfacial polymerization method. By modification with polydimethylsiloxane (PDMS) using chemical vapor deposition method, the surface wettability of cauliflower‐like PANI can be tailored to be superhydrophobic with a water contact angle of 160.4°. The deposition of the low‐surface‐energy silicon coating originated from PDMS pyrolysis on the cauliflower‐like PANI was confirmed by X‐ray photoelectron spectroscopy and Fourier Transform Infrared Spectroscopy. The changes in thermal stability and conductivity of the as‐prepared PANI before and after PDMS treatment were also investigated by thermogravimetric analysis and using a four‐probe method. Compared with nanofiber‐shaped PANI by electrodepositing polymerization, the PDMS‐treated cauliflower‐like PANI has superior surface wettability. Our study may open a new way for fabrication of superhydrophobic surfaces by developing novel nanostructured PANI. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39767.     

Sustained‐release properties of cotton fabrics impregnated with nanotuberose fragrance

Tuberose‐fragrance (TF) loaded polybutylcyanoacrylate nanoparticles were successfully prepared via emulsion polymerization. The nanotuberose fragrance (Nano‐TF) was directly impregnated into the cotton fabrics as an aromatic reagent. Dynamic light scattering and transmission electron microscopy showed that the average size of the spherical Nano‐TF was 202.4 nm. Fourier transform infrared spectroscopy demonstrated that TF was encapsulated into the BCA nanoparticles and that the Nano‐TF was in existence in the cotton fabrics. Thermogravimetric analysis showed that the loading TF content of the Nano‐TF was 50.9% and that 10.02% Nano‐TF had been impregnated into the fabrics. A lot of Nano‐TF was adhered onto the surface of the cotton fabrics after 50 washings, as shown by scanning electron microscopy and gas chromatography/hydrogen flame ionization detection (GC–FID). In addition, GC–FID demonstrated that most aroma compounds of the cotton fabrics impregnated with Nano‐TF only lost less than 20% of their aroma after 60 days of deposition and around 75% of their aroma after 6 h of deposition at 120°C, so they showed better sustained‐release properties than those with TF. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41678.     

Zein-based microcapsule for vanillin sustained release

Currently, microcapsules are attracting great attention and becoming more and more widely used in sustained release system. In this research, zein-based microcapsules were prepared by anti-solvent precipitation technology and spray drying. The properties of as-prepared microcapsules were optimized by adjusting the reaction conditions and parameters such as the mass ratio of zein to vanillin, the drying temperature and whether polyethylene glycol was added or not. Meanwhile, the morphologies, chemical structures, and application performances of microcapsules were characterized and determined by SEM, FT-IR, TG, and so on. The results showed that the morphology of as-obtained microcapsules was a regular spherical shape with no cracks when the mass ratio of zein to vanillin was 1:1, the inlet temperature was 120 C and the polyethylene glycol was introduced. Meanwhile, it was also proved that the polyethylene glycol has a positive effect on the encapsulation efficiency in microcapsules. Moreover, zein microcapsules can effectively improve the thermal stability and release behavior of vanillin, meanwhile the exist of polyethylene glycol can further improve the properties of zein microcapsules. This research provided guidelines for the study of microcapsules.     

Multilayer photoactive nanocolloidal PPy:PSS as a novel substitute for Pt free counter electrode in DSSC

Water dispersible and highly processable, Polypyrrole (PPy) nanocolloidal particles were synthesized by chemical oxidation polymerization with 15 wt % of anionic polyelectrolyte poly(styrene sulfonate) (PSS) at 5°C has been reported in this work. This polymer composite (PPy:PSS) was competent with conventional Pt counter electrode (CE) when compared for dye sensitized solar cells (DSSCs). Morphological analysis revealed smooth and spherical shaped nanoparticles of PPy. Interaction between the SO₃H groups and Py units in PPy improved the thermal stability of PPy with higher doping levels of PSS. The nanocolloidal solution was spin coated at 4000 rpm. The layer by layer, self‐assembled multilayer thin films were used as CE in DSSCs. There was a linear dependence of DSSCs performance with film roughness for the self‐assembled multilayer PPy:PSS films. Single layer films showed better electrocatalytic behavior than multilayer films. All the PPy:PSS films had good electrochemical stability. The DSSC efficiency of 3.40% was observed for chemically oxidized PPy with 15 wt % PSS for single layer film, with a highest FF of 0.7154. The low cost, good performance, rapid and simple fabrication method of PPy:PSS composite modified CE could be a potential alternative for Pt in the DSSCs. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43114.