Iranian polymer journal
Volume:21 Issue: 6, 2012

The silica sol/fluoroacrylate core–shell nanocomposite emulsion was successfully synthesized via traditional emulsion polymerization through grafting of KH-570 onto silica particles. Comparing the performance of the polyacrylate copolymer, the fluorinated polyacrylate copolymer and the silica sol/fluoroacrylate core–shell nanocomposite emulsion, we can come to a conclusion that the silica sol/fluoroacrylate core–shell nanocomposite emulsion presents significantly excellent performance in all aspects. The products were characterized by Fourier transform infrared (FTIR), photon correlation spectroscopy (PCS), transmission electron microscopy (TEM), thermogravimetry (TGA), Contact angle and UV–vis analyses techniques. The chemical structure of polyacrylate copolymer, fluorinated polyacrylate copolymer and silica sol/fluoroacrylate nanocomposite were detected by FTIR. The size and stability of emulsion latex particles were determined by PCS technique. TEM analysis confirmed that the resultant latex particle has the core–shell structure, obviously. The water absorption and contact angle data also showed that the silica sol/fluoroacrylate nanocomposite film has good hydrophobic performance. TGA analysis indicated the weight loss of the silica sol/fluoroacrylate nanocomposite film begins at around 350 °C which testifies its good thermal stability. The UV–vis spectroscopy analysis showed that the silica sol/fluoroacrylate nanocomposite film possess UV–vis shielding effect when the added volume amount of KH570 modified silica sol is up to 5 mL. Therefore, the excellent properties of hydrophobicity, thermodynamics and resistance to ultraviolet provide the silica sol/fluoroacrylate nanocomposite film with potential applications in variety fields. In addition, the formation mechanism of core–shell structure silica sol/fluoroacrylate nanocomposite latex particles was speculated.

In this paper, we aim to report the effects of catalyst (types and concentrations) on the fracture mechanics of epoxidized soybean oil (ESO) based thermosets. ESO resin was thermally cured using methylhexahydrophthalic anhydride curing agent in the presence of two types of catalysts, i.e., tetraethylammonium bromide and 2-ethyl-4-methylimidazole (EMI). The loading of the catalysts varied from 0.3 to 0.8 phr. The fracture behaviour of ESO thermoset was examined on the basis of the principle of linear elastic fracture mechanics (LEFM) and essential work of fracture (EWF). LEFM measurements were performed using single-edge notched tensile and double-edge notched tensile (DENT) tests, while, EWF measurements were carried out using DENT tests. The fracture morphologies of the ESO thermosets were characterized via field emission scanning electron microscopy. It was determined that the plane-strain fracture toughness (K IC), the specific EWF (w e), and the specific plastic fracture work (βw p) of ESO thermosets were significantly influenced by the types and loading of catalysts. In addition, the fracture toughness properties were associated with the crosslink density of the ESO thermosets. In addition, it was found that the brittle–ductile transition of EMI-catalyzed ESO thermosets can be assessed by the combination of LEFM and EWF in the fracture toughness measurement.

The thermosensitive micelles based on the two series of cholesteryl-modified hydroxypropyl cellulose (series 1 and 2, respectively) were used as a promising drug carrier. The polymers 1a and 2a with side chain substitution degrees D Chol = 0.7 and 2.1 mol% were selected for micelle preparation, respectively. Polymeric micelles were prepared by the co-solvent evaporation method. The aqueous self-assembly of the polymers was studied using fluorescence analysis and transmission electron microscopy (TEM). The critical micelle concentrations (CMCs) values of the various D Chol of polymers were evaluated in the range of ca. 0.13–0.29 g/L which decreased with the increase of D Chol in both series. Furthermore, the CMC values displayed a downtrend profile, with increasing the temperature. The polymer 1a with less D Chol had lower CMC than that of polymer 2a. By using the naproxen as a hydrophobic model drug, the drug-loaded micelles were prepared. The TEM image of naproxen-loaded micelles of polymer 1a with 40 % drug-loading efficiency and 8 % loading capacity showed that micelles were regularly spherical in shape with a mean diameter of 70 nm. The unmodified HPC exhibited a lower critical solution temperature (LCST) of more than 41 °C in water, while polymeric micelles in aqueous solution presented an LCST of 38.7 °C. A drug release study was performed by dialysis method in phosphate-buffered solution at 25, 37 and 40 °C, respectively. The release kinetics of naproxen from the polymeric micelles revealed a thermosensitivity, since its release rate was higher at 40 °C than at 25 °C.

In this study, thin film composite PVA/PES nanofiltration membranes were fabricated for the treatment of pulp and paper industrial wastewater. Phase separation induced by immersion precipitation was used to prepare the PES support membrane. PVA/PES composite nanofiltration membranes were prepared by dipping the support PES membrane in the PVA and cross-linking solutions at different conditions. Maleic acid (MA) was used as cross-linking agent. PVA and MA have concentrations of 0.5–2 and 0.05–1 wt%, respectively. Morphological studies were carried out by means of scanning electron microscopy (SEM) as well as atomic force microscopy (AFM) techniques. In addition, the hydrophilicity of membranes was examined by contact angle measurements. Permeability and ability of PVA/PES composite nanofiltration membranes to reduce COD of the wastewater were evaluated by a cross flow filtration system. SEM images indicated that the PVA layer was uniformly formed on the PES support membrane. AFM images showed that the surface roughness, porosity and pore sizes of PES support membrane were reduced after formation of PVA layer on the support surface. Moreover, the hydrophilicity of the membranes was significantly increased. Experimental results demonstrated that the PVA/PES composite nanofiltration membranes were able to reduce the COD of wastewater. Optimum conditions for preparation of PVA/PES composite membrane are consisted of PVA concentration: 1 wt%, MA concentration: 0.5 wt%, cross-linking time: 3 min and curing time: 3 min.

The effects of polystyrene-co-maleic anhydride (SMA) compatibilizer on mechanical, thermal and morphological properties of polystyrene (PS)/zinc oxide (ZnO) composites were investigated for the first time in this study. PS/ZnO composites were prepared using a twin screw extruder and were then molded by compression method. In order to improve adhesion between filler and matrix, SMA compatibilizer is used in the composites. Tensile strength and Young’s modulus were increased with increasing ZnO and SMA at low concentration, but they were decreased with increasing high concentrations of ZnO and SMA content. Thus, mechanical properties can be enhanced in the composites with SMA compatibilizer. Moreover due to the effect of particle size, 250 nm ZnO particles (ZnO250) improved the mechanical properties of PS more than 71 nm ZnO particles (ZnO71) due to the increased aggregation of latter particles. Glass transition temperatures were not significantly changed when both ZnO and SMA were incorporated. Degradation temperatures of the composites increased with the addition of ZnO particles compared with neat PS and slightly decreased with the incorporation of SMA compared with the nascent composite. Scanning electron microscopy (SEM) analysis showed the better dispersion and compatibility of ZnO particles in PS/ZnO composites with the addition of SMA especially at the content of 3 wt%.

The main goal of this study was to develop a full range multi-scale modeling technique to extract Young’s modulus and Poisson’s ratio of carbon nanotube reinforced polymer (CNTRP) composites covering all nano, micro, meso and macro scales. The developed model consists of two different phases as top-down scanning and bottom-up modeling. At the first stage, the material region will be scanned from the macro level downward to the nano-scale. Effective parameters associated with each scale will be identified through this scanning procedure. Taking into account identified effective parameters of each specific scale, the suitable representative volume elements (RVE) will be defined for all nano, micro, meso and macro scales, separately. In the second stage of the modeling procedure, a hierarchical multi-scale modeling approach is developed. This modeling strategy would analyze the material at each scale and obtained results that were fed to the upper scale as input information. Due to involved random parameters, the developed modeling technique is implemented stochastically. It has been shown that the developed modeling procedure provides a clear insight to the properties of CNTRP and it is a very efficient tool for simulation of mechanical behavior of CNTRP composites. A sensitivity analysis was conducted to quantify the influence of the identified random parameters on the overall behavior of CNTRP.

The aim of this study was to predict broad molecular weight distribution (MWD) of commercial high-density polyethylene (HDPE) samples from their linear viscoelastic (LVE) responses using a tube-based model. In the first step, a forward model based on time-dependent reptation mechanism was applied to predict LVE properties from MWD. Material parameters of the considered tube-based model were adjusted by comparing experimental and theoretical dynamic storage and loss moduli values. Adjusted parameters were compared with previously reported values and the effects of important parameters on the LVE properties were studied. It was found that higher polydispersity may lead to more relaxation which will be reflected in model by increase of mixing exponent. In the second step, the adjusted material parameters of one of the samples were used for prediction of MWD of all samples from their dynamic storage and loss moduli values. Two standard distribution functions were used for prediction of MWDs and the results were compared. It was shown that the Gaussian distribution function is suitable for prediction of broad unimodal MWD specimens, as they regularly appear in Ziegler–Natta catalyzed polyolefins, but the GEX function brings about optimal combination of flexibility and generality and is more appropriate for samples with asymmetric MWD curves. Considered combination of modeling elements including a Gaussian distribution function, a time-dependent diffusion relaxation function, a double-reptation mixing rule and the Nelder–Mead simplex optimization algorithm offers a practical tool for prediction of broad MWD of the commercial HDPE samples which can be used for online measurements.