Synthesis of alginate beads filled with nanohydroxyapatite: An efficient approach for fluoride sorption

Nanohydroxyapatite (n‐HAp) powder is a promising adsorbent material with high defluoridation capacity (DC); however, it causes pressure drop during field applications. To overcome such problems and utilize the advantages of n‐HAp, it is aimed to prepare n‐HAp in a usable bead form with the support of alginate (Alg) biopolymer. n‐HApAlgLa composite beads were synthesized by introducing n‐HAp powder in Alg polymeric gel, and the resulting solution was dropped into La³⁺ ions for crosslinking. Defluoridation experiments were carried out in batch mode to optimize various influencing parameters like contact time, pH, challenger anions, initial fluoride concentrations, and temperature. The beads were characterized using Fourier transform infrared spectroscopy, X‐ray diffraction, and scanning electron microscopy with energy‐dispersive X‐ray analyzer analysis. The sorption process was explained using diverse isotherms and kinetic models. The values of thermodynamic parameters indicate that the nature of fluoride is spontaneous and endothermic in nature. In field studies, n‐HApAlgLa beads reduce the fluoride concentration below the tolerance limit. The regeneration and reusability studies were proposed to effectively use the sorbent. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41937.     

Porous chitosan/graphene oxide biocomposites for tissue engineering

Porous chitosan/graphene oxide (CHT/GO) biocomposites with 0.5, 1, 2, and 3 wt% GO were prepared by freeze‐drying method. The biocomposites were characterized regarding structural, morphological, and thermal properties, degradation, and swelling responses. Raman spectroscopy and scanning electron microscopy (SEM) results indicated good GO dispersion within the polymer host and highly porous structure for the obtained biocomposites. The GO presence has a profound effect on the structural features of the biocomposites generating decrease of swelling degree and enzymatic biodegradation rate. Conversely, the thermal stability of the biocomposites was significantly improved, and the decomposition temperature at which the mass loss is 3% (T _d,3%) was increased with 64°C by adding 3 wt% GO within the CHT. The ability of the biocomposites to form apatite‐like crystals was also investigated. X‐ray diffraction and SEM analyses indicated the formation of apatite deposits on the CHT/GO biocomposites. POLYM. COMPOS., 38:363–370, 2017. © 2015 Society of Plastics Engineers     

Rheological and thermal behaviour of poly(N‐isopropylacrylamide)/alginate smart polymeric networks

Interpenetrating polymeric networks based on sodium alginate and poly(N‐isopropylacrylamide) (PNIPAAm) covalently crosslinked with N,N′‐methylenebisacrylamide have been investigated using rheology, thermogravimetry, differential scanning calorimetry, X‐ray diffraction measurements and scanning electron microscopy (SEM). An improved elastic response of the samples with a higher PNIPAAm content and increased amount of crosslinking agent was found. The temperature‐responsive behaviour of the hydrogel samples was evidenced by viscoelastic measurements performed at various temperatures. It is shown that the properties of these gels can be tuned according to composition, amount of crosslinking agent and temperature changes. X‐ray scattering analysis revealed that the hydrophobic groups are locally segregated even in the swollen state whilst cryo‐SEM showed the highly heterogeneous nature of the gels. Copyright © 2011 Society of Chemical Industry     

Mesua ferrea L. seed oil based highly branched polyester/epoxy blends and their nanocomposites

Mesua ferrea L. seed oil based highly branched polyester and epoxy resins blends were prepared by mechanical mixing at different weight ratios. The best performing blend was used as the matrix for the preparation of nanocomposites with different dose levels of organophilic montmorillonite (OMMT) nanoclay. The prepared nanocomposites were characterized by X‐ray diffraction, scanning electron microscopy, Fourier transform infrared spectroscopy, and transmission electron microscopy. Data resulting from the mechanical and thermal studies of the blends and nanocomposites indicated improvements in the tensile strength and thermal stability to appreciable extents for the nanocomposites with OMMT loading. The nanocomposites were characterized as well‐dispersed, partially exfoliated structures with good interfacial interactions. From the X‐ray diffraction analysis, the absence of d₀₀₁ reflections of the OMMT clay in the cured nanocomposites indicated the development of an exfoliated clay structure, which was confirmed by transmission electron microscopy. The homogeneous morphologies of the pure polyester/epoxy blend and clay hybrid systems were ascertained with scanning electron microscopy. The tensile strength of the 5 wt % clay‐filled blend nanocomposite system was increased by 2.4 times compared to that of the pure blend resin system. The results suggest that the prepared nanocomposites have the potential to be used as active thin films for different applications. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Semiconductor‐assisted self‐cleaning polymeric fibers based on zinc oxide nanoparticles

Self‐cleaning polymeric fibers have been successfully prepared by depositing ZnO nanoparticle onto wool and polyacrylonitrile (PAN) fibers with good compatibility and significant photocatalytic self‐cleaning activity using the sol‐gel process at ambient temperature. scanning electron microscopy, energy dispersive spectroscopy, transmission electron microscopy, diffuse reflectance spectroscopy, X‐ray diffraction, Brunauer‐Emmett‐Teller surface area analysis, and thermogravimetric analysis have been adopted as the characterization techniques. Transmission electron microscopy studies revealed presence of zinc oxide nanoparticles with 10–15 nm in size. Brunauer‐Emmett‐Teller measurement showed surface area of 48 m²/g for the ZnO nanoparticles. Photocatalytic activity of the self‐cleaning materials were tested by measuring the photo‐assisted degradation of methylene blue (MB) and eosin yellowish (EY) under ultraviolet‐visible illumination. The results indicate that both of the ZnO‐coated polyacrylonitrile and ZnO‐coated wool fibers acquire photocatalytic activity toward dyes degradation. The photocatalytic activity of the treated fibers is maintained upon several numbers of photodegradation cycles. This facile and cheap preparation technique can be also applied to new polymeric fabrics to produce self‐cleaning materials for industrial application. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Processing and properties of nano‐ and macro‐hydroxyapatite/poly(ethylene‐co‐acrylic acid) composites

Hydroxyapatite (HAp)/poly(ethylene‐co‐acrylic acid) composites have been synthesized by a solution‐based method, using nanosized (n‐HAp) and coarse hydroxyapatite (c‐HAp) particles, respectively. X‐ray diffraction study has indicated the development of compressive and tensile stresses in composites because of the thermal expansion mismatch between the particles and polymer matrix. Fourier transform infrared absorption spectra and thermal analysis have showed the presence of strong interfacial bonding between the particles and polymer. The surface roughness and the homogeneous dispersion of HAp particles in the polymer matrix have been observed by scanning electron microscopy. A comparison in mechanical properties between composites prepared with n‐HAp and c‐HAp particles, respectively, has been studied. Nanosized particles contribute excellent improvement of mechanical properties of the composites rather than the coarse particles. The uniform dispersion of HAp particles, followed by the improvement in mechanical properties of the composite, provides a means of preparing HAp/polymer composites for low load‐bearing implant applications. POLYM. COMPOS., 27:633–641, 2006. © 2006 Society of Plastics Engineers     

Nano‐hydroxyapatite (HAp) and hydroxyapatite/platinum (HAp/Pt) core shell nanorods: Development,structural study,and their catalytic activity

The development of a new kind of material that is a nanostructured catalytic material with an environmentally benign nature that can be used for alternative energy has acquired significance in recent years. In this context, the use of heterogeneous catalysts for the transesterification of vegetable oils has gained prominence due to their eco‐friendly and reusable nature. Hence in the present study, pure hydroxyapatite (HAp) and hydroxyapatite/platinum (HAp/Pt) nanostructured particles have been prepared successfully through a facile chemical method without templates and surfactants and their catalytic activity investigated for transesterification of natural vegetable oil to bioenergy (biodiesel). The textural and structural features of pure HAp and HAp/Pt were investigated using various characterization techniques such as x‐ray diffraction, Fourier transform infrared (FTIR) and Raman spectroscopy, field emission scanning electron microscopy (FESEM), and transmission electron microscopy (TEM). The elements present in the prepared nanostructures were confirmed through energy dispersive spectroscopy (EDS) and x‐ray photoelectron spectroscopy (XPS) techniques. The XPS analysis also confirms the metallic nature of the platinum in HAp/Pt. The specific surface area and porous nature of the prepared nanostructured catalysts were studied using the N₂ physisorption Brunauer‐Emmett‐Teller‐Barrett‐Joyner‐Halenda (BET‐BJH) method. The catalytic activity of the pure HAp nanoparticles and HAp/Pt core shell nanorods with the Simarouba glauca plant seed oil was investigated. The obtained results indicate that the pristine HAp nanoparticles and HAp/Pt core shell nanorods (NRs) show 91.4% and 87.1% fatty acid methyl ester (FAME) conversion, respectively, potentially offering environmental benign biocatalysts for biofuel production from natural feed stock.     

Effect of nanoclay on physical,mechanical, and microbial degradation of jute‐reinforced,soy milk‐based nano‐biocomposites

Jute‐reinforced, soy milk‐based nano‐biocomposites were fabricated using both natural and organically modified nanoclay to study their effect on physical, mechanical, and degradation properties. Different weight percentages of nanoclays were used to modify soy milk by solution casting process. The jute fibers were then impregnated in modified soy resin and compressed to fabricate nano‐biocomposites. About 5 wt% of organically modified nanoclay‐loaded jute composite showed maximum tensile and flexural strength. X‐ray diffraction and transmission electron microscopy (TEM) analysis of fabricated composites confirmed about the formation of nanostructure. Impact, microhardness, dynamic mechanical analysis results of nano‐biocomposites revealed that nanoclay has influenced to improve such physical and mechanical properties. Microbial degradation study of nano‐biocomposites was carried out in cultured fungal bed. Weight loss, tensile loss, and field emission scanning electron microscopy photographs of composites revealed that composites are biodegradable in nature. The prime advantages of these composite are their eco‐compatibility as jute and soy resin, the basic constituents of composites are biodegradable in nature. These composites can be utilized in automobile, packaging, furniture sectors by replacing nondegradable plastic‐based composite. POLYM. ENG. SCI., 54:345–354, 2014. © 2013 Society of Plastics Engineers     

Synthesis route to regioselectively functionalized bifunctional polyarene

We report the regioselective oxidative synthesis of polyaminonaphthol sulfonic acid (PANSA) particles and firstly obtained nanoparticles with molecular weight of ca 23 200 g mol^?1 using a template‐free polymerization process in which NaOCl was used as an oxidant in aqueous basic medium. Nanoparticles were characterized using NMR, Fourier transform infrared and UV‐visible spectroscopies, gel permeation chromatography, thermogravimetry (TG), differential scanning calorimetry (DSC), cyclic voltammetry, photoluminescence (PL), dynamic light scattering, X‐ray diffraction, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and conductivity techniques. SEM and TEM analyses showed that the nanoparticles had a self‐stabilizing structure interconnecting with micro‐channels. PANSA also exhibited reversible redox behaviour due to its electroactive nature. Nanoparticles display a slight hypsochromic shift and hyperchromic effect with higher intensity in PL spectra and also emitted an intense white light in dimethylsulfoxide. In addition, the thermal stability of PANSA was investigated using TG and DSC techniques. Finally, the kinetic parameters related to the solid‐state thermal decomposition of PANSA were calculated from non‐isothermal methods based on multiple heating rates. © 2015 Society of Chemical Industry     

Preparation and characterization of PET/clay nanocomposites by melt compounding

Poly(ethylene terephthalate) (PET) nanocomposites were prepared via melt compounding using a twin‐screw extruder at 265°C. Three different types of organomodified clay were melt compounded with PET: a commercial ammonium‐modified silicate clay (Cloisite 30B) and specially prepared thermally stable phosphonium‐ and imidazolium‐modified montmorillonites. X‐ray diffraction, scanning electron microscopy, transmission electron microscopy (TEM), and thermogravimetric analysis were used to characterize and evaluate the quality of the nanocomposites. To obtain quantitative evaluation of the dispersion level in nanocomposites, statistical analysis of TEM micrographs was performed using a dispersion parameter, D_0.1, based on free‐path spacing measurements. The results showed that the ammonium surfactant yielded the best intercalation results in nanocomposites. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers     

Thermoforming starch‐graft‐polycaprolactone biocomposites via one‐pot microwave assisted ring opening polymerization

A thermoformable starch‐graft‐polycaprolactone biocomposite was prepared by initiating ring‐open polymerization of caprolactone monomer onto starch under microwave irradiation. In this case, the thermoplastic and hydrophobic modification of starch could be realized by one‐pot grafting PCL, where the grafted PCL chains acted as the “plasticizing” tails of thermoforming and as the hydrophobic species of water‐resistance. The resultant biocomposites were injection‐molded as the sheets and their structure and properties were investigated by Fourier transform infrared spectroscopy, X‐ray diffraction, scanning electron microscopy, differential scanning calorimetry, dynamic mechanical analysis, contact angle measurement, and tensile testing. In this case, the grafted PCL chains entangled each other, and hence contributed to the strength and elongation of biocomposites. This work provided a simple strategy of one‐pot thermoplastic and hydrophobic modification of starch, and may be applied in a continuous process of modification, compounding, and molding. Meanwhile, the resultant biocomposites containing starch are believed to have a great potential application as an environment‐friendly and/or biomedical material. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Processing of natural resourced hydroxyapatite from eggshell waste by wet precipitation method

Abstract

Abstract

In the present paper, synthesis of hydroxyapatite (HAp) powder from eggshell waste is produced through wet precipitation process at 50–55°C. The thoroughly washed and dried eggshell powder is treated with dilute nitric acid followed by diammonium hydrogen phosphate under controlled reaction conditions such as pH, temperature, stirring time, etc. to obtain white HAp precipitate. The formation of the HAp phase and its thermal stability were identified through thermogravimetric/differential thermal analysis, Fourier transform infrared spectroscopy and X‐ray diffraction studies at different calcined temperatures. The dried powder at 90–100°C was wet ball milled for several hours and compacted to cylindrical shapes at a lower pressure of 850?kg?cm^?2. The green compacts were sintered at different temperatures for 2?h in dry atmosphere. Average grain sizes of sintered samples are mostly in submicrometre range. The morphologies of the green as well as sintered compacts were observed by field emission scanning electron microscopy.     

Development of poly(acrylamide)‐hydroxyapatite composites as bone substitutes: Study of mechanical and blood compatible behavior

The Hydroxyapatite (HAp) serves as potential biomaterial in various biomedical applications. This study is a continuing attempt to design the biomimetic bone‐like composite materials. The authors have tried to develop HAp/Polyacrylamide (PAm) composites with different weight ratios through a suspension polymerization method. The prepared composite materials were characterized by Fourier transform infrared spectroscopy, X‐ray diffraction analysis, thermogravimetric analysis, scanning electron microscopy, optical microscopy techniques, and compressive strength tests. The composites were also studied for water sorption capacity and the water sorption data were used to evaluate network parameters revealing the internal chemical architecture of the composite. In vitro tests were carried out to study water uptake and dissolution profiles of HAp/PAm composites. Furthermore, in vitro blood compatibility of the composites was also judged using protein adsorption, percentage haemolysis, blood clot formation, and platelet adhesion tests. The results obtained fairly support the objectives of the study to meet physiochemical and biological concerns for a bone‐like material. POLYM. COMPOS., 2009. © 2009 Society of Plastics Engineers     

Optical Characterizations of Hot‐Pressed Erbium‐Doped Calcium Fluoride Transparent Ceramic

Nanoparticles of erbium‐doped calcium fluoride were synthesised by the coprecipitation method. Micromorphology of the obtained nanoparticles was observed by transmission electron microscopy. The nanoparticles were hot‐pressed in a vacuum environment to achieve Er:CaF₂ transparent ceramic. X‐ray diffraction analysis confirmed the crystallization of a single fluorite phase after sintered. Transmittance spectrum of Er:CaF₂ ceramic sample was measured, and the transmittance at 1200 nm reached about 87%. Microstructures were characterized using field‐emission scanning electron microscopy. The luminescence spectrum of Er:CaF₂ transparent ceramics under 488‐ and 978‐nm excitation was measured and discussed. It was evidenced that strong cross‐relaxation processes between Er³⁺ ions occur at high dopant concentration, and favoring the red emission at the expense of the green one.     

The Role of MgAl2O4 Powder Packing on Phase Stability of Hydroxyapatite During Sintering

MgAl₂O₄ (spinel) was utilized as a packing powder in the sintering of hydroxyapatite (HAp) and the composite of HAp/3 mol% Y₂O₃‐stabilized tetragonal zirconia (3Y‐TZP). The influence of spinel on phase stability of HAp was investigated using X‐ray diffraction (XRD), scanning electron microscopy (SEM), Raman spectroscopy, and electron probe microanalysis (EPMA) to reveal the reaction in the vicinity of the interface between HAp and spinel. When covered with spinel powder, decomposition temperatures for both HAp monolith and HAp in the composite were raised from 1360°C to 1470°C and from 930°C to 1280°C, respectively. SEM images supported the role of spinel on retardation of the decomposition, showing a dense cross section of the monolith after sintering for 2 h at 1400°C with the spinel as opposed to a porous feature without the covering. XRD results indicated that the increase in the decomposition temperatures was accompanied by a decrease in the a‐axis dimension of the hexagonal structure of HAp, probably as a result of the substitution of F^? for OH^?. EPMA revealed that negligible reaction occurred between HAp and spinel even at 1500°C, but the Ca²⁺ in HAp diffused about 20 μm into 3Y‐TZP to form a cubic zirconia solid solution at 1275°C, resulting in the decomposition. The involvement of F^? ion in the contraction of a‐axis parameter and the consequent phase stability were manifested by an increase in the Raman band of the symmetric stretching of the P–O bonds at 962.3 cm^?1 and the appearance of a band for fluoroapatite at 3538 cm^?1.     

Synthesis of hydroxyapatite/poly(vinyl alcohol phosphate) nanocomposite and its characterization

Hydroxyapatite (HAp)/poly(vinyl alcohol phosphate) (PVAP) nanocomposite has been prepared using a solution‐based method varying HAp from 10 to 60% (w/w). X‐ray diffraction, Fourier transform infrared absorption spectra (FTIR), and thermal analysis have indicated the presence of bonding between HAp particles and PVAP matrix. Transmission electron microscope analysis shows the needle‐like crystals of HAp powder having a diameter of 6–10 nm and a length of 26–38 nm. The surface roughness and the homogeneous dispersion of HAp particles in the polymer matrix have been observed by scanning electron microscopy. Particle size distribution analysis shows the narrow distribution of hydrodynamic particles in the polymer matrix. The tensile stress–strain curves show the improvement in mechanical properties of the composites with increase in amount of HAp particles loading. The composites along with polymer are highly hemocompatible. The use of PVAP promotes the homogeneous distribution of particles on the polymer matrix along with strong particle–polymer interfacial bonding, which has supported the improvement in mechanical properties of the composites. The prepared HAp/PVAP composite with uniform microstructure would be effective to act as a potential biomaterial. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers     

Mechanical properties of layered silicate/starch polycaprolactone blend nanocomposites

The mechanical behavior of layered silicate/starch polycaprolactone blend nanocomposites was evaluated. Three different clays (Cloisite Na⁺, Cloisite 30B and Cloisite 10A) were used as reinforcement. Nanocomposites were prepared by melt intercalation followed by compression molding. These nanocomposites were characterized using X‐ray diffraction, scanning electron microscopy, dynamic mechanical analysis and tensile testing. X‐ray diffraction results showed that most of the clays were intercalated within the polymeric chains. In all cases, mechanical properties were improved with clay incorporation and the improvement was better as the clay content was increased. The best properties were achieved with Cloisite 10A due to their greatest compatibility with the matrix. A mechanical model, which takes into account the effective parameters of the clay, was used in order to estimate the dispersion of clay within the polymer. The highest dispersion was obtained for Cloisite 10A, which is in accordance with the experimental mechanical properties. Although dynamical‐mechanical properties improved with clay incorporation, the glass transition temperature was not affected. Copyright © 2006 Society of Chemical Industry     

Synthesis of intercalated lamellar hydroxyapatite/gelatin nanocomposite for bone substitute application

Hydroxyapatite (HAp)/polymer composites have been widely investigated for bone substitute applications in recent years. Inspired by the arrangement of ordered organic and inorganic layers in natural bones and seashells, for the first time a novel intercalated nanocomposite of gelatin and lamellar HAp was prepared via solution intercalation process. X‐ray diffraction (XRD) results showed that the basal spacing of HAp lamellas enlarged by 3.0 nm from 3.1 nm to 6.1 nm, indicating that the gelatin molecules had been intercalated into the gallery of lamellar HAp. The microstructures of pure lamellar HAp and intercalated gelatin/HAp nanocomposite were observed by transmission electron microscopy (TEM) analysis. Fourier transform infrared spectroscopy (FT‐IR) analysis revealed that there were chemical interactions between gelatin molecules and HAp. Thermogravimetric analysis (TGA) results confirmed that thermal stability of the composites was enhanced. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Light‐curable composite of siloxane/hydroxyapatite prepared by the sol–gel process for bone defect treatment

The light‐curable composite of siloxane/hydroxyapatite (HA) had been successfully achieved by photopolymerization of a kind of gel combined tetraethoxyorthosilicate (TEOS) and 3‐methacryloxypropyltrimethoxysilane (MAPS) with siloxane‐modified nano‐HA (HA‐g‐Si). HA‐g‐Si was prepared by grafting reaction of 3‐isocyanatopropyltrimethoxysilane (IPS) onto the surface of HA. Then, TEOS and MAPS were mixed as precursor, and photoinitiator 2‐hydroxy‐4′‐(2‐hydroxyethoxy)‐2‐methylpropiophenone (Irgacure 2959) and as‐prepared HA‐g‐Si were added into the precursor to form a homogenous and sticky gel. The movable gel that could be cured with UV light resulted in various sharp immovable composites of siloxane/HA in different mold. The HA, HA‐g‐Si nanoparticles, and composites were analyzed by Fourier transformed infrared spectroscopy, X‐ray photoelectron spectroscopy, X‐ray diffraction, thermogravimetric analysis, transmission electron microscopy, scanning electron microscopy, mechanical testing, and water contact angles. It could be a promising bone repairing material for orthopedic application. POLYM. COMPOS., © 2011 Society of Plastics Engineers.     

Electrospun poly(L‐lactic acid)/hydroxyapatite composite fibrous scaffolds for bone tissue engineering

Poly(L ‐lactic acid) (PLLA) is one of the most studied synthetic biodegradable polymeric materials as a bone graft substitute. Taking into account the osteoconductive property of hydroxyapatite (HAp), we prepared fibrous matrices of PLLA without and with HAp particles in amounts of 0.25 or 0.50% (w/v, based on the volume of the base 15% w/v PLLA solution in 70:30 v/v dichloromethane/tetrahydrofuran). These fibrous matrices were assessed for their potential as substrates for bone cell culture. The presence of HAp in the composite fibre mats was confirmed using energy dispersive X‐ray spectroscopy mapping. The average diameters of both neat PLLA and PLLA/HAp fibres, as determined using scanning electron microscopy, ranged between 2.3 and 3.5 µm, with the average spacing between adjacent fibres ranging between 5.7 and 8.5 µm. The porosity of these fibrous membranes was high (ca 97–98%). A direct cytotoxicity evaluation with L929 mouse fibroblasts indicated that the neat PLLA fibre mats released no substance at a level that was toxic to the cells. The presence of HAp particles at 0.50% w/v in the PLLA fibrous scaffolds not only promoted the attachment and the proliferation of MC3T3‐E1 mouse pre‐osteoblastic cells, but also increased the expression of osteocalcin mRNA and the extent of mineralization after the cells had been cultured on the scaffolds for 14 and 21 days, respectively. The results obtained suggested that the PLLA/HAp fibre mats could be materials of choice for bone tissue engineering. Copyright © 2009 Society of Chemical Industry