Search

Fertilizers and water play critical roles in supporting plant growth, and enhancing the efficiency of their application is essential, especially in drought-affected regions, to maximize the utilization of these vital resources. In this study, our objective was to examine the impact of water deficit stress and a superabsorbent slow-release fertilizer (SSRF) on the growth, yield, and oil production of Thymus daenensis Čelak.. The experiments were conducted using a total of 27 drainage lysimeters to ensure accurate measurements and observations. The experiment was designed as a completely randomized factorial design, specifically investigating the effects of three fertilizer rates (0, 10, and 50 Mg/ha) and three irrigation regimes (50%, 70%, and 100% of water requirement). The synthesis of the SSRF involved the graft-copolymerization of acrylic acid and acrylamide onto sodium alginate and rapeseed meal biochar. The preparation of the biochar was carried out at a temperature of 300 ºC. The surface morphology analysis of the SSRF provided evidence for the successful occurrence of graft polymerization. Additionally, the graft copolymers exhibited a significant nitrogen content, which greatly contributed to their high free-absorbency capacity of 40%. as determined by the tea bag method. The results of the study indicate that water stress had a negative impact on growth, herbage production, and herbage content. Conversely, water stress had a positive influence on the essential oil content of the plants. Based on the findings, it can be concluded that the application of 50 Mg/ha fertilizer resulted in a significant increase in biomass production compared to the other treatments. [ABSTRACT FROM AUTHOR]

The improvement of water consumption efficiency is very significant, especially in arid and semi-arid regions. In this research, the effects of three hydrogel rates (0, 10, and 50 Mg ha-1) and three irrigation regimes (50%, 70%, and 100% of water requirement) on growth, yield, and oil production of Thymus daenensis were studied in a lysimetric experiment. The process of hydrogel synthesis was performed with sodium alginate as the main bone of the polymer and acrylic acid and acrylamide as monomers with the rapeseed meal biochar was made at 300 ºC. The results showed that the essential oil content produced by the plant was impressed by the hydrogel application. The essential oil content increased with an increase in water deficit, but the essential oil yield decreased in the lysimeters with water deficit compared to the ones without water stress. Besides, the application of 50 Mg ha-1 hydrogel caused a 17% increase in the dry matter and a 12% increase in the plant's height. According to the results of this experiment, the application of hydrogel caused the improvement in most characteristics of the Thymus daenensis in water stress conditions.

The improvement of water consumption efficiency is very significant, especially in arid and semi-arid regions. In this research, the effects of three hydrogel rates (0, 10, and 50 Mg ha-1 ) and three irrigation regimes (50%, 70%, and 100% of water requirement) on growth, yield, and oil production of Thymus daenensis were studied in a lysimetric experiment. The process of hydrogel synthesis was performed with sodium alginate as the main bone of the polymer and acrylic acid and acrylamide as monomers with the rapeseed meal biochar was made at 300 ºC. The results showed that the essential oil content produced by the plant was impressed by the hydrogel application. The essential oil content increased with an increase in water deficit, but the essential oil yield decreased in the lysimeters with water deficit compared to the ones without water stress. Besides, the application of 50 Mg ha-1 hydrogel caused a 17% increase in the dry matter and a 12% increase in the plant's height. According to the results of this experiment, the application of hydrogel caused the improvement in most characteristics of the Thymus daenensis in water stress conditions. [ABSTRACT FROM AUTHOR]

This article deals with the exploration of the design of network crosslinked structure by covalent bonding for use as wound dressing materials keeping in view inherent therapeutic role of neem gum in wound healing. These copolymeric hydrogels were prepared by graft-copolymerization reaction of carbopol and poly (N-vinylpyrrolidone) (poly (NVP). Antibiotic drug levofloxacin was encapsulated in dressings for better wound healing. The scanning electron microscopy (SEM), atomic force microscopy (AFM), Fourier transform infrared (FTIR) spectroscopy, 13C nuclear magnetic resonance (NMR) spectroscopy, X-ray diffraction (XRD), thermogravimetric analysis (TGA), differential thermal gravimetry (DTG), and differential scanning calorimetry (DSC) techniques were applied for characterization. NMR and FTIR demonstrated incorporation of carbapol and poly (NVP) in dressings. XRD indicated amorphous state in copolymeric dressings. Interactions of copolymers with drug, blood and bio membrane were studied to evaluate biomedical properties which revealed controlled release of drug from hydrogel dressings which were possessing blood-compatible (haemolytic value ​= ​2.45 ​± ​0.82) and mucoadhesive (detachment force ​= ​124 ​± ​41 ​mN) properties. Dressings were permeable to O2 and H2O vapour and absorbed 6.68 ​± ​0.62 ​g/g wound fluid which is ideal dressing characteristic. Diffusion mechanism type of drug levofloxacin was Fickian with kinetic model First order. These properties suggested use of hydrogel material for wound dressing and drug delivery applications for better wound care management.

Keeping in view the progressive future prospectus of carbohydrate research, herein, the potential of bioactive polysaccharides aloe vera (AV) and sterculia gum (SG) was explored to develop network hydrogel wound dressings. Both polysaccharides, acemannan of AV gel and glucuronic-galacturonic acid of SG accelerate wound healing process. The antibiotic drug cefuroxime encapsulated dressings were designed by graft-copolymerization with carbopol. The copolymers were characterized by SEM, AFM, FTIR, C13 NMR, XRD, TGA-DTG, DSC and swelling studies. The slow diffusion of cefuroxime drug exhibited non-Fickian mechanism and release of drug was occurred with a first order kinetic model. Polymer-bio membrane interactions indicated mucoadhesion nature. The clot formation was reduced during polymer-blood interactions indicated bio-compatible nature of the dressings moreover dressings were found antioxidant in nature. The porous dressings were O2 permeable and microbial impermeable. The hydrogel dressings revealed antimicrobial activity against P. aeruginosa. Degree of antimicrobial activity enhanced in case of hydrogel wound dressings loaded with cefuroxime. Overall, the results of these biochemical assays, sustained release of antibiotic drug and inherent wound healing potential of AV-SG indicated the use of hydrogels as dressing materials for better wound healing.

Neem gum is a bioactive polysaccharide that has various therapeutic applications. Herein, it was explored in designing network structure in the form of hydrogel wound dressings (WD) by covalent and supramolecular interactions. These hydrogel dressings were encapsulated with the antibiotic drug cefuroxime for better wound healing. SEM and AFM showed surface heterogeneity with a rough surface of the hydrogel network. 13C-NMR and FTIR demonstrated incorporation of carbopol and poly (vinylsulphonic) (VSA) in dressings. XRD and TGA indicated the amorphous state of copolymers with improved thermal properties. Interactions of copolymers with drug, blood, and bio-membrane have revealed sustained drug release, blood-compatible and mucoadhesive nature of hydrogel dressings which have capacity to absorb 8.50 ± 0.18 g/g of simulated fluid. Dressings were O2 and H2O vapour permeable. The diffusion mechanism of the antibiotic drug cefuroxime was found Fickian-type with first- order kinetic model. Antibacterial character of polymeric hydrogels was found against microbes during the antimicrobial test. These properties advocated these hydrogels as materials for WD and drug delivery (DD).

In this work, the green material based on epoxidized natural rubber (ENR) and modified cellulose were prepared through a completely eco-friendly procedure. Cellulose was extracted from sugarcane bagasse through removal of hemicellulose and lignin by a simple method. Thereafter, purified cellulose was modified by graft-copolymerization of acrylonitrile in the presence of ammonium persulfate initiator in emulsion state. The obtained cellulose was blended with ENR in molten state. The structural characterization through FT-IR spectroscopy confirmed that polyacrylonitrile was successfully grafted on cellulose. The optimal condition for graft-copolymerization was found at 5 °C and ammonium persulfate concentration of 0.022 mol/kg cellulose, at which the highest nitrogen content of the resulting material was 2.82 wt%. The blend of ENR cellulose-graft-polyacrylonitrile of which the nitrogen content is 2.82 wt% (Cel-Pan-2.82) expressed the outstanding properties in term of tensile strength, hardness, thermal resistance, and self-cleaning. The tensile strength and hardness of the blend containing 10 wt% of Cel-Pan-2.82 was 6.5 MPa and 49.0, respectively; those of the blend containing 20 wt% of Cel-Pan-2.82 was 5.5 MPa and 59.5, respectively. The mechanical properties of the blends were better than those of ENR. The initial decomposition temperature of the blends was 150 °C higher than that of ENR. The contact angle of the blends containing Cel-Pan-2.82 was about 12–25° higher than that of ENR, which confirmed the waterproof of the blends. SEM observation confirmed the fine dispersion of Cel-Pan-2.82 in ENR. The improvement in the properties of the blends was attributed to the effect of polyacrylonitrile which enhanced the compatibility of ENR phase and cellulose phase. [ABSTRACT FROM AUTHOR]

An interpenetrating polymer network (IPN) containing gum acacia (GA), poly(methacrylic acid) (MAA), and poly(acrylic acid) (AA) was developed using a two-step aqueous polymerization method. Firstly, semi-IPNs were produced by radical polymerization of MAA chains onto GA in the presence of ammonium persulfate as a free radical initiator and N, N′-methylene-bisacrylamide (MBA) as a cross-linking agent using a microwave heating. To obtain a semi-IPN with a higher swelling percentage, several reaction parameters such as initiator, monomer, and crosslinker concentrations were varied. The percentage swelling (%S) was highly dependent upon the reaction conditions. The optimal reaction conditions for maximal %S were 2.55 × 10–2 mol/L initiator concentration, 12 mL solvent, 0.424 × 10–3 mol/L of monomer, and 2.16 × 10–2 mol/L cross-linker concentration, according to the findings. GA-g-poly(MAA) was the name to given to the semi-IPN. Second, IPN was created by grafting AA chains onto a GA-g-poly(MAA) matrix that had been optimized. The IPN was named as a GA-g-poly(MAA-IPN-AA). The reduction of silver ions to silver nanoparticles (AgNPs) was carried out by heating the mixture of flower extract of Koelreuteria apiculate under microwave radiation. Finally, the as-prepared semi-IPN and IPN samples were used as templates for the loading of AgNPs. XRD, FTIR, SEM, and TGA were used to characterize the synthesized semi-IPN, IPN, and their composites with AgNPs. GA, GA-g-poly(MAA), GA-g-poly(MAA-IPN-AA), and their composites with AgNPs are tested for antibacterial activity against five common bacteria strains: Escherichia coli, Micrococcus luteus, Pseudomonas aeruginosa, Rhizobium species, and Staphylococcus aureus. All of the bacteria strains were shown to have a noticeable zone of inhibition when IPN and their composite with AgNPs were used. When compared to other bacteria strains, Pseudomonas aeruginosa was observed to be more vulnerable to the tested samples. The obtained results demonstrate that the synthesized systems are suitable for application as antibacterial agents. [ABSTRACT FROM AUTHOR]

Hydrogenated deproteinized natural rubber (HDPNR) with nanomatrix structure was prepared through graft‐copolymerization of acrylonitrile and styrene onto HDPNR particle in latex stage. Structural characterization of the resulting materials through nuclear magnetic resonance and Fourier‐transform infrared spectroscopy confirmed that acrylonitrile and styrene were grafted onto HDPNR. The weather resistance, thermal properties, mechanical properties, storage modulus, and morphology of the resulting materials were investigated in comparison with those of HDPNR. The obtained result indicated that the graft‐copolymerization of HDPNR with hydrogenation conversion of 60 mol% attained the highest grafting efficiency. Thermal resistance and storage modulus of HDPNR‐graft‐poly (styrene‐co‐acrylonitrile) (HDPNR‐g‐SAN) were superior compared with those of HDPNR and deproteinized natural rubber. This was attributed to the nanomatrix formed in HDPNR‐g‐SAN, which was confirmed through a transmission electron microscope. Ribbed smoked sheet natural rubber exhibited the outstanding mechanical properties and weather resistance when it was mixed with HDPNR‐g‐SAN. [ABSTRACT FROM AUTHOR]

Chitosan shows selective antimicrobial activity as a bioactive polymer. In this work, a quaternary ammonium derivative of chitosan was synthesized by graft -copolymerization of chitosan with poly[2-(acryloyloxy)ethyltrimethylammonium chloride] or pATC by the redox polymerization method to enhance chitosan's antimicrobial activity. The structural characterizations of the quaternized chitosan were confirmed by Fourier transform infrared spectroscopy, and also by 1 H and 13 C nuclear magnetic resonance spectroscopy. The produced chitosan was converted into films by solution casting. The physicomechanical properties of the modified chitosan were compared with the unmodified chitosan. Thermal stability of the films was characterized by thermogravimetric analysis. The pATC grafted chitosan films showed lower thermal stability, water absorption, swelling ratio, and tensile strength compared to the unmodified chitosan film. Antimicrobial activity of the quaternized chitosan was tested against three kinds of bacteria ( Staphylococcus aureus , Klebsiella pneumoniae , and Pseudomonas aeruginosa ) and two fungi ( Aspergillus brasiliensis and Aspergillus fumigatus ). The unmodified chitosan showed good antibacterial activity but no resistance against any fungus. However, the pATC grafted chitosan showed enhanced antibacterial activity against all bacteria investigated. The fungicidal test shows that the pATC-grafted-chitosan showed higher activity against the tested fungi ( Aspergillus fumigatus and Aspergillus brasiliensis ) compared to the unmodified chitosan, especially against Aspergillus fumigatus . [ABSTRACT FROM AUTHOR]

The two-stage method for poly(methyl acrylate) grafting starch using triethylborane and 1,4-benzoquinone has been developed. The first stage was borylation of alcohol groups of starch. The second stage was polymerization of methyl acrylate in the inhibitor - 1,4-benzoquinone - presence accompanied by the S2-substitution at the boron atom. The advantages of developed method were the homogeneity of the process, the high yield of graft-copolymer, the possibility to control of chain length of synthetic polymer, and the absence of homopolymer in the final product. The molecular weight characteristics of starch-graft-poly(methyl acrylate) copolymer was determined by gel-permeation chromatography. The evidence of the graft-copolymer formation was B nuclear magnetic resonance data and its glass-transition temperature. The resulting graft-copolymer has an amphiphilic nature and a high thermal stability compared to the corresponding homopolymers (starch and poly(methyl acrylate)). According to the calculated values of the surface Gibbs energy the surface of starch-graft-poly(methyl acrylate) films is characterized as a high-energy surface. [ABSTRACT FROM AUTHOR]

Cassava waste pulp (CWP) contains high carbohydrates that can be modified into super absorbent polymer (SAP) through grafting and cross-linking copolymerization. Acrylamide (AM) was grafted onto CWP with ammonium persulfate (APS) as the initiator and N,N'-methylene-bis-acrylamide (MBA) as the cross-linker under atmospheric nitrogen. The effect of APS and MBA concentrations on water absorption capacity of saponified SAP was studied, while the evaluation of grafting ratio (GR) and grafting efficiency (GRE) was conducted on unsaponified SAP. The grafting success was indicated by the occurrence of IR peaks at wave numbers of 573, 765, 858, and 1667 cm-1. In the saponified SAP, the very intense characteristic band at 1562 cm-1 is due to C=O asymmetric stretching in the carboxylate anion. Saponification increases significantly water absorption capacity compared to that of unsaponified SAP (from 39.79 g/g to 578.23 g/g). The highest water absorption capacity is reached at 0.74% APS and 0.09% MBA. The percentage of GRE and GR tends to increase with increasing APS concentration until reaching the highest value and then decreases. Effect of MBA concentration on water absorption capacity, GR, and on GRE is similar to the effect of initiator concentration on GR and GRE.

Gamma irradiation is a powerful tool for modifying the physicochemical properties of polymers. Gamma radiation has been widely used to carry out reactions such as crosslinking, depolymerization, and graft copolymerization, with a wide variety of synthetic and natural polymers. Although gamma irradiation proved to be useful to modify the chemical properties of several polysaccharides, this method has not been applied to mucilage. However, irradiation could bring beneficial changes to mucilage for its use in different applications. Thus, the aim of this work was to study the radiochemical transformation of mucilage extracted from Opuntia ficus-indica using gamma radiation. Results obtained from FTIR-ATR, pH and electrical conductivity in aqueous solution showed that decarboxylation of mucilage occurs applying a radiation dose from 2 to 12 kGy. Further, it was observed that thermal stability of mucilage was enhanced with a radiation dose of 2 and 6 kGy. The decarboxylation degree was proportional to the radiation dose in the interval of 0–12 kGy. Further, mucilage was irradiated in the presence of acrylic acid forming mucilage/PAA hydrogels with high swelling capacity. The best swelling capacity (734%) was observed for the hydrogel obtained applying 2 kGy of gamma radiation. Hydrogels prepared with higher radiation doses (4–20 kGy) showed lower swelling capacity and higher thermal stability, which suggest a higher crosslinking degree. The experiments performed in this work were performed using 100 mg of mucilage but gamma irradiation allows a high scalability of the process. The usefulness of gamma irradiation relays on the development of a method for preparing hydrogels by an easy and scalable method. [Display omitted] • Gamma irradiation decarboxylates mucilage yielding a polysaccharide with lower ionic character. • Mucilage-g-poly(acrylic acid) was prepared with a high degree of grafting. • Hydrogels were prepared from mucilage and acrylic acid under gamma irradiation. [ABSTRACT FROM AUTHOR]

In this paper, we report the effect of surface modification ofB. morisilk fibers on its physico-chemical properties. Modification of silk fibers was carried out through graft-copolymerization of acrylonitrile monomer onto it in the presence of ascorbic acid/ H2O2initiator. The effects of varying the time, temperature, initiator concentration, and monomer concentration on graft-copolymerization were studied in terms of grafting parameters, such as percent grafting and percent efficiency. The graft copolymers were characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), X-ray diffraction (XRD), and thermo gravimetric analysis (TGA) techniques. The grafted samples were further evaluated for their physical properties such as swelling behavior, moisture absorption, and chemical resistance properties. [ABSTRACT FROM PUBLISHER]

Graft copolymer of natural rubber (NR) and polystyrene was successfully prepared by electron beam irradiation for the first time. The experiments were designed based upon the Taguchi method, using Minitab software, in order to reduce the number of experiments. The radiation dose was varied from 25 to 100 kGy. The content of sensitizer (n-BA) was varied from 0 to 5 phr. Various NR/St ratios were used: 90:10, 80:20, 70:30, and 60:40. Characterization of graft copolymer was confirmed by Fourier transform infrared spectroscopy (FTIR)and transmission electron microscopy (TEM) techniques. The core–shell structure of graft copolymer was obtained and the monomer conversion, grafting efficiency, grafting yield, and crosslink density were studied. Optimum conditions were determined by the experimental design: radiation dose of 75 kGy, content of n-BA of 5 phr, and NR/St ratio of 80:20. Finally, the tensile strength of latex films was found to be significantly related to the studied factors. [ABSTRACT FROM AUTHOR]

The mechanism of proton transport of a polymer electrolyte membrane (PEM) with nanomatrix channel was investigated with respect to the activation energy of proton conductivity. The PEM with nanomatrix channel was prepared by graft-copolymerization of styrene onto deproteinized natural rubber (DPNR) followed by sulfonation with chlorosulfonic acid. The resulting sulfonated graft-copolymer (SDPNR- graft -PS) was characterized by FT-IR spectroscopy, solid-state 13 C CP/MAS NMR spectroscopy, elemental analysis, transmission electron microscopy (TEM) and impedance analysis. The PEM was found to form completely continuous nanomatrix channel consisting of natural rubber particle of about 1 μm in average diameter as a dispersoid and sulfonated polystyrene of about 60 nm in thickness as a matrix. The value of the activation energy of proton conductivity estimated from the slope of Arrhenius plot was 12 kJ/mol for SDPNR- graft -PS, suggesting that the proton transport occurred in a manner of Grotthuss mechanism. [ABSTRACT FROM AUTHOR]

Highlights: [•] Visible light-induced surfactant-free emulsion polymerization (SFEP) was developed. [•] 3°-Amine containing polymer/CQ can be used as photo-induced initiating system. [•] The amine-functionalized nanoparticles can be fabricated in one step. [ABSTRACT FROM AUTHOR]

Abstract: Methoxy poly (ethylene glycol) grafted carboxymethyl chitosan (mPEG-g-CMC) and alginate were chosen as the constituents of hydrogel beads for the construction of an interpenetrating polymeric network matrix. A contrast study between the mPEG-g-CMC hydrogel and mPEG physically mixed with CMC hydrogel was carried out. Bovine serum albumin (BSA) as a model for a protein drug was encapsulated in the hydrogel network, and the drug release properties were studied. The hydrogels prepared by these two methods maintained good pH sensitivity; the loading capacity of the mPEG-g-CMC/alginate hydrogel was enhanced in comparison with that of the hydrogel prepared by physically mixing mPEG. The burst release of the protein was slightly decreased at pH 1.2, while the release at pH 7.4 was improved, suggesting that the mPEG-g-CMC/alginate pH-sensitive hydrogel will be promising for site-specific protein drug delivery in the intestine. [Copyright &y& Elsevier]

Preparation of natural rubber (NR) with a soft nanomatrix structure was made by graft-copolymerization of butyl acrylate (BA) onto deproteinized natural rubber with tert-butyl hydroperoxide/tetraetylenepentamine in latex stage. The resulting graft-copolymer of deproteinized natural rubber and poly (butyl acrylate) (DPNR- graft-PBA) was characterized by Fourier-transform infrared spectroscopy. Conversion and grafting efficiency of BA were dependent upon BA concentration, which were more than 90 mol% under a suitable condition of the graft-copolymerization. Morphology of DPNR- graft-PBA was observed by transmission electron microscopy after staining film specimens with I vapor for 5 min. The NR particles of about 0.5 μm in diameter were dispersed in PBA matrix of about 15 nm in thickness. Storage modulus and loss tangent of DPNR- graft-PBA were measured, and they were related with the soft nanomatrix structure. The tensile strength and elongation at break decreased as monomer concentration increased. [ABSTRACT FROM AUTHOR]

Hibiscus sabdariffa (Roselle) stem fiber has 73.9% cellulose and is present in abundance though-out the world. It has a low therapeutic potential but lesser weight and high tensile strength promotes it to serve as an effective backbone for graft copolymerization. This renewable biomass was graft copolymerized with efficient acrylate as principal monomer while incorporating the secondary monomers in addition, to enhance the graft yield. The increase in graft yield affected the properties and behavior of the fiber. The morphological transformations in the graft co-polymers were characterized by FTIR, SEM, TG-DTA and XRD. The modified fiber were found to be physico-chemico-thermally resistant, hydrophobic whereas, percentage crystallinity, crystallinity index decreased with increase in percentage grafting. The use of raw fiber and graft copolymers as reinforcement in phenol-formaldehyde polymer matrix based bio-composites improved the physico-chemico-thermal properties and the mechanical strengths like the flexural strength/modulus of rupture, young's modulus/modulus of elasticity, stress at the limit of proportionality and hardness. These advanced materials could be useful in various scientific and industrial applications and serve as pioneer for the development of technology. [ABSTRACT FROM AUTHOR]

Abstract: Photo-reactive particle was prepared by graft-copolymerization of 3-acryloyloxy-2-hydroxypropyl methacrylate (AHM) as a bi-functional monomer onto natural rubber (NR) in latex stage with potassium persulfate (KPS) as an initiator, after deproteinization with urea in the presence of surfactant. A terminal vinyl group of AHM was used for the graft-copolymerization, while the other remained in the resulting graft-copolymer, due to different reactivities of vinyl groups in the end of the bi-functional monomer. After graft-copolymerization, the resulting latex was UV-crosslinked to make chemical linkages between the residual pendant vinyl groups of grafted polymers linking up to the rubber particle. The resulting products were characterized by 1H NMR and 13C NMR measurements. Effects of amount of rubber, monomer concentration and reaction time on conversion, grafting efficiency and amount of residual carbon–carbon double bond after graft-copolymerization were investigated. Under the optimum condition, high conversion of monomer and high amount of residual carbon–carbon double bond after graft-copolymerization were achieved without side reaction. A dramatic increase in modulus after UV-irradiation was associated with the connection of the functional polymer linking up to NR particle. [Copyright &y& Elsevier]

Abstract: This paper presented a new approach for preparing a new type of slow-release membrane-encapsulated urea fertilizer with starch-g-PLLA as biodegradable carrier materials. By solution-casting and washing rapidly with water the urea was individually encapsulated within the starch matrix modified by l-lactide through in situ graft-copolymerization. The release behavior of urea encapsulated in the films was studied, and following conclusions were achieved: (1) the introduction of hydrophobic PLLA reduced the swellability of starch matrix and decreased the release rate of urea; (2) the urea release rate could be controlled from several hours to 1 day by adjusting the graft efficiency; (3) scanning electron microscopy revealed that the urea encapsulated within the starch matrix was uniformly dispersed in the form of tiny cell and the urea encapsulated in the modified starch film released through a diffusion mechanism. Therefore, the modified starch products for controlled release could be expected to have widely potential application in agriculture industry as fertilizer carrier. [Copyright &y& Elsevier]

Abstract: Nano-matrix structure was formed by graft-copolymerization of styrene onto urea-deproteinized natural rubber (U-DPNR) latex. The grafted U-DPNR was characterized by FT-IR spectroscopy, 1H NMR spectroscopy and transmission electron microscopy. Conversion and grafting efficiency of styrene were more than 90% under the best condition of the graft-copolymerization. In transmission electron micrograph of film specimen stained by OsO4, it was found that natural rubber particle of about 0.5μm in diameter was dispersed in polystyrene matrix of about 15nm in thickness. The conversion and grafting efficiency for the grafted U-DPNR were compared with those for a control sample prepared from enzymatic deproteinized natural rubber (E-DPNR) with styrene. [Copyright &y& Elsevier]

Graft-copolymerization of acrylonitrile onto natural rubber in latex stage was investigated in order to cover the natural rubber particles with polyacrylonitrile, after the proteins present in natural rubber were removed with urea. Each rubber particle of about 1 pm in diameter was covered with polyacrylonitrile of about 15 nm in thickness, as confirmed by transmission electron microscopy. Penetration of linoleic acid was suppressed by covering NR particles with polyacrylonitrile. [ABSTRACT FROM AUTHOR]

The graft copolymerization of acrylonitrile (AN) onto butadiene rubber (BR) was carried out in toluene at 80°C, using dibenzoyl-peroxide (BPO) as initiator. The synthesized poly acrylonitrile-grafted-butadiene rubber (AN-g-BR) was characterized by N% elemental analysis and Fourier-transform infrared (FT-IR) spectroscopy. Styrene butadiene rubber/acrylonitrile butadiene rubber (SBR/NBR) blends were prepared with different blend ratios in presence and absence of AN-g-BR, where the homogeneity of such blends were examined with intrinsic viscosity (?) measurements, differential scanning calorimetry (DSC), and scanning electron microscopy (SEM). The scanning electron micrographs illustrate disappearance of the macro-scale phase separation of SBR/NBR rubber blend as a result of the incorporation of AN-g-BR into that blend. Viscosity measurements confirm homogeneity of that blend. Differential Scanning Calorimetry traces exhibit shifts in glass transition temperatures ( T g 's) of SBR and NBR in their blend, indicating some degree of homogeneity. Physico-mechanical properties of the rubber blend vulcanizates with different blend ratios, in presence and absence of AN-g-BR, were investigated before and after accelerated thermal aging. The SBR/NBR (25/75) homogeneous blend possessed the best physico-mechanical properties after thermal aging, together with the best swelling behavior in motor oil. The physico-mechanical properties of SBR/NBR (25/75) filled blend with different types of inorganic fillers during thermal aging were studied. [ABSTRACT FROM AUTHOR]

Abstract: Central Glass produces a diverse range of fluorocompounds for pharmaceuticals, agrochemicals as well as for semiconductor industries. Some of its products and chemistry developed at Central Glass in the field of industrial fluorine compounds are described. [Copyright &y& Elsevier]

A novel starch-graft-acrylamide/mineral powder superabsorbent composite with water absorbency about 4000 times is synthesized by graft-copolymerization reaction among acrylamide, potato starch and mineral ultrafinepowder, followed by hydrolysis with sodium hydroxide. It is found that the composite doped with kaolinite powder possess higher water absorbency than those doped with bentonite or sercite powder, since the kaolinite powder can moderately disperse in the water and cross-link with acrylamide and starch. By controlling the amount of NaOH and reaction time during saponification process, the hydrophilic groups on the composite can be adjusted, it is found that the collaborative absorbent effect of −CONH2, −COONa and −COOH groups is superior to that of single −CONH2, −COONa or −COOH group. By the IR characterization, the polymerization reaction mechanism and structure of the composite is supposed, the mineral ultrafinepowder as a cross-linking point play an important role in the formation of network structure of the superabsorbent composite. [Copyright &y& Elsevier]

Preparation of a model nano-matrix-dispersed polymer was investigated in terms of graft-copolymerization of deproteinized natural rubber latex with styrene, using tert-butyl hydroperoxide/tetraethylenepentamine as an initiator. The products were characterized by 1H-NMR spectroscopy and size-exclusion-chromatography after ozonolysis. The grafting efficiency of styrene was found to be more than 90% under the best condition of the graft-copolymerization. The morphology of the film specimens, prepared from graft-copolymers, was observed by transmission electron microscopy after staining the films with OsO4. Natural rubber particle of about 0.5 μm in diameter was dispersed in polystyrene matrix of about 15 nm in thickness. [Copyright &y& Elsevier]