Band 34, Heft 8

The aim of this study was to evaluate the ability of almond gum, as a novel polymer, to encapsulate β-carotene by spray drying, in comparison with gum arabic. Encapsulation efficiency (EE) was around 66% and 70% using almond gum and gum arabic, respectively, and the reconstituted emulsions had relatively higher particle sizes than the fresh emulsions. A 60-day storage period at 25°C was carried out to investigate the effect of relative humidity (RH) on the kinetic degradation and on the decrease of the color of β-carotene powders. Results showed that β-carotene and color degradations were found to fit well with a first-order kinetic model. Degradation rates increased as RH increased, until a value at which the samples become sticky and collapsed (80% RH) when the degradation rate decreased. These results could prove that collapse phenomena were responsible for the decrease of the degradation rate by decreasing the diffusion of oxygen throughout the wall materials.

The ionic conductivity of poly(glycidyl methacrylate-co-ethyl methacrylate) [P(GMA-co-EMA)]-lithium perchlorate (LiClO 4 )-ethylene carbonate (EC) electrolyte and photovoltaic performances of dye-sensitized solar cells (DSSC) utilizing the electrolyte were investigated. P(GMA-co-EMA) as a host material of the electrolyte was synthesized by UV-curing and characterized by nuclear magnetic resonance (NMR). P(GMA-co-EMA) based solid polymer electrolyte containing 80 wt% EC exhibited the highest room temperature ionic conductivity. The crystallinity degree of the electrolyte decreases with the EC content, as confirmed by X-ray diffraction (XRD) studies. The electrochemical stability investigated by cyclic voltammetry (CV) reveals that the electrolyte is stable up to 4.8 V. A dye-sensitized solar cell of fluorine tin oxide (FTO)/TiO 2 -dye/P(GMA-co-EMA)-LiClO 4 -EC/Pt possessed the photovoltaic effect with a short-circuit current density ( J sc ) of 4.85×10 -3 mA cm -2 and open circuit voltage ( V oc ) of 0.4 V, respectively, under light intensity of 100 mW cm -2 .

A series of novel hydroxyl-terminated hyperbranched polyurethanes (HBPUs) were synthesized via stepwise polymerization by diethanolamine (DEOA), isophorone diisocyanate (IPDI) and trimethylolpropane (TMP). It is interesting to note that the HBPUs can be purified by water. The HBPUs were characterized with 1 H nuclear magnetic resonance (NMR), 13 C NMR, Fourier transform infrared spectroscopy (FT-IR) and elemental analysis. The average degree of branching (DB) of HBPUs was calculated from the first generation to the fourth generation to be 1.00, 0.74, 0.59 and 0.57 by quantitative 13 C NMR, respectively. The branching model and molecular structure of HBPUs were deduced by the 13 C NMR and the value of DB. To investigate the changes of hydrogen bonding interaction in HBPUs with a variation in structure of different generations, the deconvolution of FT-IR spectra was carried out using Origin 7.0 software through the Gaussian curve-fitting method. The ratio of hydrogen-bonded -NH and -OH groups of HBPUs was calculated to be 80.8%, 85.1%, 84.8% and 85.4% from the first generation to the fourth generation by deconvoluted -NH and -OH zone, respectively. The interaction of hydrogen bonding and glass transition temperature (Tg) of HBPUs increased with the increase of generation. The trend of thermal stability and Tg coincide with the change of hydrogen-bonded interactions.

A series of nylon 6-clay nanocomposites were prepared by melt mixing, followed by electron beam (EB) crosslinking at various doses. Effects of crosslinking on clay dispersion, gel content, crystallinity and water absorption properties (hygrothermal) were studied. No change of the dispersion pattern of clay in nanocomposites was observed after crosslinking [from X-ray diffraction (XRD) and transmission electron microscopy (TEM)]. Gel content, i.e., degree of crosslinking is seen to keep on increasing with irradiation dose, although clays hinder crosslinking of polymers to some extent. Crystallinity of polymers is reduced after incorporation of clay as well as crosslinks. However, water absorption rate and maximum water content of nanocomposites are found to increase and saturation time to decrease with clay content. However, these changes become opposite after crosslinking of polymers. The water absorption for all samples is noticed to increase with temperature. Thus, EB crosslinking, without affecting the nanocomposite morphology, i.e., properties derived from nano interface generation, decreases the water absorption properties of nanocomposites.

High density polyethylene (HDPE) has recently been established as the material of choice for the distribution and transport of drinking water on economic and public health levels. Because of this, a simulation study was conducted to investigate the effect of aging by two factors on HDPE, in order to check the mechanical robustness of this material with regards to climate change. First, specimens of the material (HDPE80) underwent treatment with irradiation by ultraviolet (UV) radiation for different periods up to 120 h. The accelerated aging process by UV irradiation gave a negative correlation between resilience and the irradiation time in hours. Second, we tested the HDPE80 resilience to different temperatures, at various notch depths (0.4, 0.8, 1, 1.25 and 1.5 mm), to external shocks.

Polyaminoamide dendrimers (PAMAM) surface-modified with anionic terminal groups (PIY) for use as scale inhibitors were prepared with the fourth-generation PAMAM and sodium acrylate (SAA), via the Michael addition reaction. The chemical structures of PIY were determined using Fourier transform infrared (FT-IR) spectrometry and 1 H nuclear magnetic resonance (NMR) spectra. The influence of scale inhibitor concentration, Ca 2+ concentration and bath temperature on the scale inhibition efficiency was researched. The study results signified that PIY can resist calcium carbonate scale as high as 92.8%. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) patterns showed that amorphous calcium carbonate had generated in the presence of PIY dendrimers.

Electromagnetic interference (EMI) is a disturbance that affects an electrical circuit due to electromagnetic radiation emitted from an external source. EMI may induce malfunction of equipment, interference with telecommunications and degradation up to total loss of data. EMI shielding refers to the reflection and/or adsorption of electromagnetic radiation by a highly electrically conductive material, usually metal, or polymer composites filled with conductive fillers. However, metal coatings tend to corrode and acceptable EMI shielding levels are difficult to achieve using conductive fillers in a thermoplastic matrix. This study presents a new approach to EMI shielding of plastic parts using in-mold coated (IMC) nanoparticle thin films or nanopapers to create a highly conductive top layer. EMI shielding effectiveness (SE) and electrical conductivity were measured.

Polyethylene terephthalate (PET) is a kind of high performance engineering plastic. However, the application of pure PET is subject to limitation because of its slow crystallization rate. In order to overcome this difficulty, thermoplastic resins are often added into PET matrix by a compounding technique. Polybutylene terephthalate (PBT) possesses many advantages such as a high degree of crystallinity and rapid molding, thus, is very suitable to adjust the crystallization behaviors of PET. In this work, the crystallization behaviors of PET/PBT alloys were studied by a differential scanning calorimeter (DSC) and thermal platform polarizing microscope. The obtained results indicate that the content of PBT could tune the melting and crystallization behaviors of the alloy. The parameters of non-isothermal crystallization of the alloys for blends were analyzed by the Jeziorny and Kissinger methods. The non-isothermal crystallization process for PET, PBT and PET/PBT alloys fit the Jeziorny model well at the early stage, but there is a certain small deviation at the later stage, indicating that the nucleation mechanism of PET/PBT alloy is complicated. In addition, the crystallization rate accelerates with an increase in cooling rate. The alloys show the best crystallization performance when the content of PBT is 10 wt%, and their crystallization activation energy reaches up to -201.78 kJ/mol.

This numerical paper presents the effects of viscous dissipation on both hydrodynamic flow behavior and thermal flow characteristics of fluid included in rheological polymer flow analysis. The shear rate dependence of the viscosity is modeled using a modified form of the Cross constitutive equation, while the density changes are modeled using the modified Tait state of equation. The Navier-Stokes equations are solved in a sequential, decoupled manner with energy conservation equations using a finite volume method based fluid flow solver. Hydrodynamic and thermal boundary layer developments in an asymmetric sudden expansion for different velocity and melt flow injection temperature boundary and geometry conditions are determined under the influence of viscous dissipation effects and the results are compared with each other to measure the relative effects of viscous dissipation on the interactions of these layers for a commercial polymer melt flow, namely polypropylene (PP). The numerical results demonstrate that proposed mathematical and numerical formulations for viscosity and density variations including viscous heating terms lead to more accurate representation of the polymer melt flow and heat transfer phenomena in plane channels or mold cavity associated with a sudden expansion.

Observations are reported in impact tests, uniaxial tensile tests with various strain rates, relaxation tests with various strains and cyclic tests with a mixed deformation program and various maximum strains per cycle on neat polypropylene (PP) and a blend of PP with styrene-(ethylene-butylene)-styrene copolymer (SEBS). Experimental data demonstrate a pronounced enhancement of impact resistance of PP due to the presence of an impact modifier, accompanied by improvement of its properties under low-speed loading, observed as a decrease in relaxation rate and residual strain under cyclic deformation. Material constants in constitutive equations are determined by matching the experimental data. Correlations are established between changes in the viscoelastoplastic response of PP and evolution of its microstructure induced by the presence of an impact modifier.

A new type of polymeric composite material spur gear was developed and fabricated using low cost Portland pozzolana cement (PPC) particles as filler into the polypropylene (PP) matrix. PP granules were mixed with PPC particles and an injection-molding process was followed to manufacture the thermoplastic composite gear. Several experiments were conducted with different percentages of PPC particles with the PP to optimize the gear material (cement filled poly-propylene composite) for fabrication. Tensile tests were conducted and the morphological studies of the fractured surface of the gear materials were investigated using scanning electron microscopy (SEM) and field emission SEM (FE-SEM). Dynamic mechanical analysis (DMA) was carried out and viscoelastic properties of the gear materials were studied with varying temperature. Further, extensive experimental studies were carried out to evaluate the performance of the gear tooth under loading conditions. The experimental results validate the suitability of the proposed non-metallic spur gear for low cost industrial applications.