Effects of nanoclay and coupling agent on the physico‐mechanical,morphological, and thermal properties of wood flour/polypropylene composites

This article presents the effects of coupling agent and nanoclay (NC) on some properties of wood flour/polypropylene composites. The composites with different NC and maleic anhydride grafted polypropylene (MAPP) contents were fabricated by melt compounding in a twin‐screw extruder and then by injection molding. The mass ratio of the wood flour to polymer was 40/60 (w/w). Results showed that applying MAPP on the surface of the wood flour can promote filler polymer interaction, which, in turn, would improve mechanical properties of the composite as well as its water uptake and thermal stability. Composite voids and the lumens of the fibers were filled with NC, which prevented the penetration of water by the capillary action into the deeper parts of composite. Therefore, the water absorption in composites fabricated using NC was significantly reduced. Scanning electron microscopy has shown that the treatment of composites with 5 wt% MAPP, promotes better fiber–matrix interaction, resulting in a few numbers of pull‐out traces. In all cases, the degradation temperatures shifted to higher values after using MAPP. The largest improvement on the thermal stability of composites was achieved when NC was added. POLYM. ENG. SCI., 2011. © 2010 Society of Plastics Engineers     

Study on the structure and properties of nanocomposites based on high-density polyethylene/starch blends

The effects of nanoclay on the structure and final properties of high density polyethylene (HDPE)/thermoplastic starch (TPS) blends were investigated. Neat blends as well as nanoclay containing samples were prepared by melt blending in an internal mixer. Also, a poly (ethylene-g-maleic anhydride) (PE-g-MA) copolymer was used as compatibilizer in some of the formulations. Nanocomposites with intercalated structures were obtained in the samples lacking the compatibilizer, based on the rheological, X-ray diffraction (XRD) and transmission electron microscopy (TEM) results. However, some of the silicate layers were nearly exfoliated in the presence of the compatibilizer. The nanoclay was located preferably in the HDPE matrix as well as at the interface of the HDPE matrix and TPS dispersed phase. The ability of the nanoclays in decreasing the average size of TPS phase in the HDPE matrix was confirmed by scanning electron microscopy (SEM) observations. Furthermore, thermo-gravimetric analysis (TGA) showed that the nanoclays could enhance the thermal stability of the samples. It seems that nanoclays performed as an insulator and mass transport barrier to the small molecules generated during decomposition, and assisted in the formation of char after thermal decomposition of the polymer matrix. All the samples containing the compatibilizer possessed higher tensile strength and elongation at break, but lower modulus, compared to the corresponding un-compatibilized samples. Finally, incorporation of the nanoclays was found to be in favor of developing nanocomposites with higher biodegradability as evidenced through a biodegradation test by fungi as well as water uptake experiments.     

Investigation on the correlation between rheology and morphology of PA6/ABS blends using ethylene acrylate terpolymer as compatibilizer

Phase morphology and rheological behavior of polyamide 6 (PA6)/acrylonitrile butadiene styrene (ABS) polymers blends was studied using scanning electron microscopy and rheometry. The results showed that the phase morphology and rheological properties depends on blend composition. We evaluated the effect of addition of ABS as dispersed phase and EnBACO‐MAH (ethylene n‐butyl acrylate carbon monoxide maleic anhydride) as a compatibilizer on the morphological and rheological behaviors of PA6/ABS blends. It was concluded that there is a good agreement between the results obtained from rheological and morphological studies. As a consequence, addition of the ABS and compatibilizer weight percent led to a significant change in morphological structure and a great mounting in the viscosity as well as the elasticity. The rheological properties results demonstrate that adding compatibilizer to polymer blends led to increasing the crossover point, which shows a transition from a high viscous to a considerably more elastic behavior. Also, the slow transition of relaxation time peak from the peak of the PA6 to the peak of the ABS implies increasing the miscibility of the PA6/ABS blend components by increasing compatibilizer content. In addition, the Carreau–Yasuda model was used to extract information on rheological properties (zero shear viscosity and relaxation time) for PA6/ABS/EnBACO‐MAH blends by fitting the experimental data with this model. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Relationship between droplet size and fluid flow characteristics in miniemulsion polymerization of methyl methacrylate

Static mixer (SM) can be applied for emulsification, but the fundamental understanding of the nature of fluid flow and mixing in static mixers, is however poor. Droplet size is a very important parameter in miniemulsion systems and affects strongly the mechanism of particle formation in polymerization reactions. In this study, static mixer was used as homogenization device for emulsification of methyl methacrylate (MMA). Re number (Re) was obtained for SM inserted tube in different flow rates. It was demonstrated the nature of fluid flow was turbulent under our experimental conditions. The relationship between droplet size—the most important variable in our study—and Weber number (We) was investigated. The results showed that the ratio of the droplet size to the pipe diameter was fit as an exponential function with an order of −0.35. The polymerization of created droplets under certain We values by SM showed that it is possible to obtain a reasonable 1 : 1 copy of droplets to the particles. All these, indicate that using relationship between We and droplet size allow one to obtain acceptable condition of droplet nucleation in miniemulsion polymerization. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Application of artificial neural network for vapor liquid equilibrium calculation of ternary system including ionic liquid: Water, ethanol and 1-butyl-3-methylimidazolium acetate

A feed forward three-layer artificial neural network (ANN) model was developed for VLE prediction of ternary systems including ionic liquid (IL) (water+ethanol+1-butyl-3- methyl-imidazolium acetate), in a relatively wide range of IL mass fractions up to 0.8, with the mole fractions of ethanol on IL-free basis fixed separately at 0.1, 0.2, 0.4, 0.6, 0.8, and 0.98. The output results of the ANN were the mole fraction of ethanol in vapor phase and the equilibrium temperature. The validity of the model was evaluated through a test data set, which were not employed in the training case of the network. The performance of the ANN model for estimating the mole fraction and temperature in the ternary system including IL was compared with the non-random-two-liquid (NRTL) and electrolyte non-random-two-liquid (eNRTL) models. The results of this comparison show that the ANN model has a superior performance in predicting the VLE of ternary systems including ionic liquid.     

Antimicrobial properties of treated cotton fabrics with non-toxic biopolymers and their dyeing with safflower and walnut hulls

Novel results were obtained by selection of chitosan treatment parameters on cotton fabrics to obtain antimicrobial properties against E. coli, gram-negative bacteria. Taguchi experimental design was used in this study and microbial reduction rate was considered as the response. The signal-to-noise and the analysis of variance (ANOVA) were used to find the optimum levels to indicate the impact of treatment parameters on antimicrobial properties. The antimicrobial behavior of the fabric against bacterium as a function of each parameter was plotted. A verification test was also performed to prove the validity of Taguchi technique for this study after the determination of parameters’ optimum levels. Also the effect of chitosan and the mordanting on the dyeing properties of cotton fabrics with natural dyes such as walnut hull and safflower was investigated by measuring the color strength (K/S values) of the treated and untreated substrates at various concentrations. The results revealed that the K/S of dyed chitosan-treated cottons increased compared to untreated samples. In addition, antimicrobial properties of natural-dyed treated and untreated fabrics were determined. Walnut hull and safflower have shown antimicrobial properties. Although dyeing the chitosan-treated fabric reduced its antimicrobial effects but the results showed that chitosan-treated cotton fabrics had excellent antimicrobial properties against E. coli. Applying Taguchi experimental design for treating cotton fabrics with chitosan and utilizing these native natural dyes have never been used elsewhere.     

Modeling industrial thickener using computational fluid dynamics (CFD), a case study: Tailing thickener in the Sarcheshmeh copper mine

Separation of particles from liquid in the large gravitational tanks is widely used in mining and industrial wastewater treatment process. Thickener is key unit in the operational processes of hydrometallurgy and is used to separate solid from liquid. In this study, population balance models were combined with computational fluid dynamics (CFD) for modeling the tailing thickener. Parameters such as feed flow rate, flocculant dosage, inlet solid percent and feedwell were investigated. CFD was used to simulate the industrial tailing thickener with settled bed of 120 m diameter which is located in the Sarcheshmeh copper mine. Important factor of drag force that defines the rake torque of rotating paddles on the bed was also determined. Two phases turbulence model of Eulerian/Eulerian in accordance with turbulence model of k-ε was used in the steady-state. Also population balance model consists of 15 groups of particle sizes with Luo and Lehr kernel was used for aggregation/breakage kernel. The simulation results showed good agreement with the operational data.     

Surface modification of multiwalled carbon nanotubes via surface RAFT copolymerization method and capecitabine-loaded anticancer hydrogel for controlled drug delivery in stomach

ABSTRACT

In our work, reversible addition-fragmentation chain transfer (RAFT)/carbon nanotube (CNT)/acrylic acid (AA)/acrylamide (AAm) nanocomposite was synthesized by living radical polymerization. The structure and surface morphology of the synthesized RAFT-CNT-Hydrogel nanocomposites were analyzed by FTIR, ¹HNMR, SEM, TEM, XRD, and TGA/DTG techniques. The results indicated that PAA/AAm chains grafted with CNT by RAFT polymerization. RAFT-CNT-Hydrogel nanocomposites for drug release investigated in different buffers resulted in a strong pH-sensitive behavior. In total, the obtained hydrogel drug-delivery systems are presented a proper effect versus stomach cancer in vitro and in vivo, and it can be used as candidates for controlled release of anticancer drugs in stomach with exalted remedial agents.     

CFD study of non-premixed swirling burners: Effect of turbulence models

This research investigates a numerical simulation of swirling turbulent non-premixed combustion. The effects on the combustion characteristics are examined with three turbulence models: namely as the Reynolds stress model, spectral turbulence analysis and Re-Normalization Group. In addition, the P-1 and discrete ordinate (DO) models are used to simulate the radiative heat transfer in this model. The governing equations associated with the required boundary conditions are solved using the numerical model. The accuracy of this model is validated with the published experimental data and the comparison elucidates that there is a reasonable agreement between the obtained values from this model and the corresponding experimental quantities. Among different models proposed in this research, the Reynolds stress model with the Probability Density Function (PDF) approach is more accurate (nearly up to 50%) than other turbulent models for a swirling flow field. Regarding the effect of radiative heat transfer model, it is observed that the discrete ordinate model is more precise than the P-1 model in anticipating the experimental behavior. This model is able to simulate the subcritical nature of the isothermal flow as well as the size and shape of the internal recirculation induced by the swirl due to combustion.     

Silica aerogel/epoxy nanocomposites: Mechanical,vibrational, and morphological properties

The present study was an attempt to examine the effects that adding silica aerogel (SA) nanoparticles to epoxy would exert on its mechanical, vibrational, and morphological properties. Neat epoxy was consecutively combined with 1, 2, and 4 wt% of SA nanoparticles. A number of tests of mechanical properties were then performed on the samples, including tests of tensile, bending, compressive, dynamic mechanical thermal, hardness, and Izod impact. Vibration and water uptake tests were also conducted on the samples. The highest modulus and strength values were found in the nanocomposite sample with 4 wt% of SA, and the highest toughness and elongation values were detected in the sample with 1 wt% of SA. Furthermore, adding the SA nanoparticles to the epoxy improved the energy absorption and hardness of the epoxy matrix. The findings from the tests of dynamic mechanical thermal and vibration properties demonstrated that, with an increase in the nanoparticles content in the samples, the values of storage modulus and natural frequency increased while the values of tan δ and damping ratios decreased. A comparison between the values of natural frequency from the vibration test and the values from the Euler–Bernoulli beam theory showed a good agreement between the theoretical and experimental results.