Kinetics Of Nanocomposites Research Articles

Development of an antibacterial and antioxidative nanofibrous membrane using curcumin-loaded halloysite nanotubes for smart wound healing: In vitro and in vivo studies

Endowing wound dressings with drug delivery capability is a suitable strategy to transfer medicinal compounds locally to damaged skin layers. These dressings are especially useful for accelerating the healing rate in the cases of long-term treatment, and adding more functionalities to the platform. In this study, a wound dressing composed of polyamide 6, hyaluronic acid, and curcumin-loaded halloysite nanotubes (PA6/HA/HNT@Cur) was designed and fabricated for wound healing applications. The physicochemical properties of this platform were investigated through Fourier-transform infrared spectroscopy and field-emission scanning electron microscopy. Moreover, wettability, tensile strength, swelling, and in vitro degradation were assessed. The HNT@Cur was incorporated in the fibers in three concentrations and 1 wt% was found as the optimum concentration yielding desirable structural and mechanical properties. The loading efficiency of Cur on HNT was calculated to be 43 ± 1.8%, and the release profiles and kinetics of nanocomposite were investigated at physiological and acidic pH. In vitro antibacterial and antioxidation studies showed that the PA6/HA/HNT@Cur mat had strong antibacterial and antioxidation activities against gram-positive and -negative pathogens and reactive oxygen species, respectively. Desirable cell compatibility of the mat was found through MTT assay against L292 cells up to 72 h. Finally, the efficacy of the designed wound dressing was evaluated in vivo; after 14 days, the results indicated that the wound size treated with the nanocomposite mat significantly decreased compared to the control sample. This study proposed a swift and straightforward method for developing materials that might be utilized as wound dressings in clinical settings.

Silicone quaternary ammonium salt based nanocomposite: a long-acting antibacterial cotton fabric finishing agent with good softness and air permeability

A silicone quaternary ammonium salt based nanocomposite was synthesized and the chemical structure and stability of the nanocomposite were investigated. The results showed that the OQAS/(Ag/ZnO) nanocomposite had prepared successfully. The cotton fabrics were treated with different concentration of OQAS/(Ag/ZnO) nanocomposite and its antibacterial, durability, softness, hydrophilicity, and air permeability were also be examined using diverse characterization techniques. The antibacterial rate of treated cotton can reach to over 90%. After 10 cycles washing, antibacterial rate retain over 85% for both E. coli and S. aureus, because the chemical bond had formed between nanocomposite and cotton from the FT-IR result. In addition, a model bacterium, E. coli was used to evaluate the antibacterial mechanism and kinetics of nanocomposite. The hydrophilicity, air permeability and softness of the treated cotton fabrics were also had an improvement to some extent.

Thermal decomposition behavior and kinetics of nanocomposites at low-modified ZnO content.

In this study, a titanate coupling agent (TCA) was used to modify the surface of nano ZnO. The thermal properties of room temperature vulcanized silicone rubber (RTV) nanocomposites with modified nano ZnO were compared at nano-filler weight fractions ranging from 0% to 2%. The results indicated that the titanate coupling agent was successfully grafted on the surface of nano ZnO. The size and shape of the nanoparticles were not changed after modification and all particles were about 36 nm. With increasing amounts of nanoparticles, the initial thermal decomposition temperature increased from 344.6 °C to 420 °C and reached maximum at 1.5% ZnO addition. The thermal decomposition process of RTV can be divided into three different stages. In the first stage, the temperatures at maximum decomposition rate (T1max) for the five samples were similar. In the second and third stages, T2max and T3max increased 79.1 °C and 88.9 °C, respectively, upon addition of the modified nano ZnO. The thermal decomposition kinetics results showed that the activation energy (Eα) of RTV was lower than that of 1% ZnO/RTV at the low thermal conversion rate (α). The average Eα values of the two samples were similar, at 144.29 kJ mol−1 and 146.78 kJ mol−1, respectively. The kinetic energy index (n) of RTV was 3.84. Compared to pure RTV, 1% ZnO/RTV showed a more complex thermal decomposition process, as its n value was 0.66 higher than that of RTV. Comparing Eα and n values, it was found that the nanocomposites were less likely to transform into an activated complex due to their higher potential energy barrier.

Effect of surface property of halloysite on the crystallization behavior of PBAT

Abstract Halloysite (Hal), calcined Hal, and organosilane-modified Hal were used as filler for the preparation of Hal/PBAT nanocomposite. XRD, SEM, XPS, FTIR, DSC, POM, and Avrami, Jeziorny, Kissinger models were used to characterize the surface property of Hal and its effect on the crystallization morphology, structure and kinetics of nanocomposites. Hydrogen bonding, generated between NH2 or –OH groups on surface of organosilane-modified calcined Hal or calcined Hal and C (C O) O in ester of PBAT, efficiently enhanced the nucleation ability of Hal nanofiller, resulting in increment of crystallization temperature, decrease of half time, but retard the transport of PBAT molecules chains. The stronger the hydrogen bond was, the more remarkable such influence was. This study provides a promising approach of tailoring the surface characteristic of Hal to manipulate the crystallization of biodegradable aliphatic-aromatic polyesters, especially with extreme low loading of Hal nanofiller.

Effect of Clay Dispersion on the Nonisothermal and Isothermal Crystallization Behaviors of Polyethylene Composites

ABSTRACTThe presence of nanosized clay fillers can greatly influence the crystallization behaviors and crystalline morphologies of polymer composites. In this study, the modified montmorillonite polyethylene nanocomposites have been prepared by melt mixing, followed by injection molding. The morphology and microstructure of the composites were characterized by scanning electron microscopy and Fourier transform infrared spectrometry. The nanosized clay particles act as a nucleating agent in the solidification process of the matrix. The relative crystallinity ratio decreases with the decrement of polymer loading. Nonisothermal and isothermal crystallizations were conducted to characterize the crystallization kinetics of nanocomposites. The effects of clay dispersion on the crystallization of polymer were quantified by Avrami and Hoffman models. The addition of 1 wt% clay into polymer matrix has significantly increased the activation energy. The crystallization rate constants (G) have been determined which are higher for the composites than that for the polymer matrix.

Preparation and Kinetics of Nanocomposites Using WO3 with Carbon Nanomaterials for Photocatalytic Degradation of Organic Dyes

Preparation and Kinetics of Nanocomposites Using WO3 with Carbon Nanomaterials for Photocatalytic Degradation of Organic Dyes

Thermal stability and kinetics of thermal degradation of PMVS/SiO2/GO-C12-hep composites

In this study, a series of the PMVS/SiO2/GO-C12-hep (polymethylvinyl siloxane, PMVS) nanocomposites of varying fillers concentration were fabricated employing blending technique. Retained tensile tests showed that tensile strength of PMVS/SiO2/GO-C12-hep nanocomposites improved with increasing of GO-C12-hep content from 0 to 0.5 wt %, but it decreased when the GO-C12-hep content was up to 0.8 wt %. SEM results showed that GO/C12-hep had been dispersed into PMVS matrix, and the interfacial consistency property was very well between GO-C12-hep and PMVS. The degradation mechanism was also analyzed. The thermal stability and the degradation kinetics of nanocomposites had been evaluated using thermo-gravimetric analysis (TGA) at different heating rates in flowing nitrogen. TGA curves revealed that PMVS/SiO2/GO-C12-hep exhibited relatively better thermal stability than PMVS/SiO2, and the degradation temperatures of PMVS/SiO2/GO-C12-hep increased with GO-C12-hep increase. The apparent activation energies (Ea) were estimated with the Flynn–Wall–Ozawa method (FWO method). The Ea of PMVS/SiO2/GO-C12-hep nanocomposites had relevance to their content of GO-C12-hep. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

In vitro degradation of poly(l-lactide)/poly(ε-caprolactone) blend reinforced with MWCNTs

The physical and mechanical properties of poly(l-lactide)/poly(e-caprolactone) (PLLA/PCL) blends reinforced with multiwalled carbon nanotubes (MWCNTs) before and after in vitro degradation were investigated. Because of brittleness, PLLA needs to be plasticized by PCL as a soft polymer. The MWCNTs are used to balance the stiffness and the flexibility of PLLA/PCL blends. The results showed that with incremental increase in concentration of MWCNTs in composites, the agglomerate points of MWCNTs were increased. The physical and mechanical properties of prepared PLLA/PCL blends and MWCNT/PLLA/PCL nanocomposites were characterized. The X-ray diffraction analysis of the prepared blends and composites showed that MWCNTs, as heterogeneous nucleation points, increased the lamella size and therefore the crystallinity of PLLA/PCL. The mechanical strength of blends was decreased with incremental increase in PCL weight ratio. The mechanical behavior of composites showed large strain after yielding and high elastic strain characteristics. The tensile tests results showed that the tensile modulus and tensile strength are significantly increased with increasing the concentration of MWCNTs in composites, while, the elongation-at-break was decreased. The in vitro degradation rate of polymer blends in phosphate buffer solution (PBS) increased with higher weight ratio of PCL in the blend. The in vitro degradation rate of nanocomposites in PBS increased about 65% when the concentration of MWCNTs increased up to 3% (by weight). The results showed that the degradation kinetics of nanocomposites for scaffolds can be engineered by varying the contents of MWCNTs.

Isoconversional kinetic analysis of resol-clay nanocomposites

The curing kinetics of nanocomposites based on phenolic resol cured with triethylamine (TEA) containing different amounts of organic montmorillonite was analyzed by differential scanning calorimetry. Kissinger-Akahira-Sunose (KAS) model-free kinetics has been applied to correlate the dynamic cure behaviour in the presence of modified montmorillonite. The effect in the curing of the use of different clay modifiers has also been studied. A commercial clay with hydroxyl groups (Cloisite 30B) and a customized montmorillonite (PheMMT) whose reactive groups induce condensation reactions with the resol matrix have been used. Strong dependency of activation energy on apparent conversion has been observed for all compounds.

Effect of Pore Size on Dehydrogenation Temperature of Carbon Cryogel-Ammoniaborane Nanocomposites

AbstractThis study reports the effects of pore size of porous carbon scaffold on the dehydrogenation of ammoniaborane in the coherent carbon- ammoniaborane nanocomposites. Porous carbon scaffold is obtained from resorcinol formaldehyde derived carbon cryogels. The nanocomposites are made by simple soaking porous carbon scaffold in ammonia borane solution. Nitrogen sorption analysis and differential scanning calorimetry are used to investigate the structure and dehydrogenation of the nanocomposites. The results reveal that dehydrogenation temperature decreases in nanocomposites as compared to neat ammonia borane, and is lower in nanocomoposites with smaller pore sizes. These findings can be used to tune the dehydrogenation temperature to meet specific hydrogen storage applications. Also, dehydrogenation kinetics of nanocomposites is enhanced as compared to neat ammonia borane.

Isothermal Curing Kinetics and Thermal Degradation of o-CFER/MeTHPA/O-MMT Nanocomposite

The isothermal curing kinetics of nanocomposite of o-cresol-formaldehyde epoxy resin (o-CFER), 3-methyl-tetrahydrophthalic anhydride (MeTHPA) with organic montmorillonite (O-MMT) were investigated by means of X-ray diffraction (XRD) and differential scanning calorimetry (DSC) using N,N-dimethyl-benzylamine as a curing accelerant. The XRD result indicates that an exfoliated O-MMT nanocomposite was obtained. The analysis of DSC data indicated that an autocatalytic behavior appeared in the first stages of the cure for the system, which could be well described by the Kamal model. In the later stages, the reaction is mainly controlled by diffusion and a diffusion factor, f(α), was introduced into Kamal's equation. In this way, the curing kinetics were predicted well over the entire range of conversion. The thermal degradation kinetics of this composite were investigated by thermogravimetric analysis (TGA), which revealed that with increasing O-MMT content, TG curves shift to higher temperature.

Modified Carbon Cryogel-Ammonia Borane Nanocomposites for Hydrogen Storage

AbstractThis paper reports the synthesis and characterization of coherent Boron/Nitrogen –doped –carbon cryogels- ammonia borane nanocomposites for hydrogen storage. Resorcinol formaldehyde derived doped carbon cryogels (CC) were obtained via chemical modification.CC- ammonia-borane nanocomposites were made by incorporation of ammonia borane (AB), in CCs. Nitrogen sorption analysis, scanning electron microscopy, and X-ray photoelectron spectroscopy, are used to investigate the structure and morphology of the modified CCs. Differential scanning calorimetry is used to study the dehydrogenation of coherent doped-CC-AB nanocomposites. Modified CCs show higher mesoporosity, and more homogeneous porous structure compared to undoped CCs. Also, dehydrogenation kinetics of nanocomposites is enhanced as compared to neat AB. Possible nanoscale and catalytic effects of nanocomposites in improved dehydrogenation kinetics are discussed.