Making vinyl ester resin greener: Succinic acid–glycerol-derived reactive diluent as an alternative to styrene

A bio-based reactive diluent (BRD) was synthesized from succinic acid and glycerol, and successfully copolymerized with epoxy acrylate (EA). Chemical structure of BRD was studied by nuclear magnetic resonance and Fourier transform infrared. The performance of vinyl ester resin compositions has been examined through differential scanning calorimetry, thermogravimetric analysis, and dynamic mechanical analysis, as well as tensile and flexural tests. Results demonstrated good compatibility between EA and the BRD. Compared to styrene, the BRD contribution of 50 wt% enhanced the elastic modulus (~40%). Samples copolymerized with BRD or styrene, have shown a similar thermal stability. Mechanical properties of cured blends, containing up to 25 wt% of BRD, found to be superior than styrene-diluted compartments. Viscosities of EA–BRD blends were in range of 3.25–0.43 Pa/s at 30°C. Inexpensive bio-based source, good thermomechanical and rheological properties, and great compatibility with EA are of advantages of these BRD-containing formulations.     

Nonlinear Buckling Analysis of Cones with Rectangular Cutouts,Numerical and Experimental Investigation

International Journal of Steel Structures - In this paper a new regression relation for nonlinear ultimate buckling resistance of the cones with rectangular cutouts is presented. For this purpose,...     

Mineral recovery from inland reverse osmosis concentrate using isothermal evaporation

Mineral recovery from reverse osmosis (RO) concentrate after concentration by a secondary sea water-type RO system with lime–soda pretreatment was the focus of this study. Lime–soda pretreatment removed Ca, Mg and Si allowing for the application of sea water-type RO resulting in a concentrate composed of sodium, potassium, sulfate and chloride. The overall objective was reduction in concentrate volume that will require disposal by evaporation while producing by-products with potential resale value. Thermodynamic phase equilibrium calculations using Pitzer’s correlations for 25 °C, accurately predicted the solubility and evaporation path of the sodium sulfate minerals as potential by-products. Bench-scale evaporation experiments verified the model predictions and indicated that 81–88% of the sodium sulfate by-products were Na₂SO₄.     

Superabsorbent polymer composites: does clay always improve properties?

Clay is frequently incorporated to many materials including superabsorbent polymers (SAPs) to improve their properties. Superior properties have been reported for the SAP composite (SAPC) materials comparing to their clay-free counterparts. However, study of the effect of clay on some of very important requirements of superabsorbents, particularly the residual monomer (RM), has been unnoticed in the academic literature. Here, we report preparation of a series of SAPCs via a conventional solution polymerization of partially neutralized acrylic acid in the presence of common MMT clay (Na-montmorillonite). The products were characterized by FTIR spectroscopy, differential scanning calorimetry, thermogravimetric, thermomechanical, and rheometrical analyses. The RM content of the samples was determined by high performance liquid chromatography. It was found that the clay had unfavorable effects on the crosslinking polymerization process. This fact was observed as declining mechanical strength of the SAPCs in both dried and swollen states, increased swelling capacity, decreased gel fraction, and increased RM content. For instance, RM of clay-free sample was 740 ppm which was continuously increased with level of the clay incorporated. It surprisingly reached to ~34,000 ppm at clay content of 12%. The undesirable function of clay was attributed to inactivation and barrier effects of clay incorporated to the polymerization medium. These unwanted effects were more pronounced at high clay content. However, overall thermostability of SAPCs was improved comparing to the non-composite counterpart. It was concluded that such conventionally prepared SAPCs, in spite of the previously reported claims, could not be suitable candidates for hygienic applications, particularly those prepared with high clay percentages.     

Sense of Immersion in Computer Games Using Single and Stereoscopic Augmented Reality

As a novel interaction and presentation technology, Augmented Reality (AR) has been widely used in education, tourism, entertainment, psychology, and many other applications. In the game industry, this revolutionary technology has introduced a new form of interaction between players and the gaming environment. In this article, we aim to find if exploiting AR in computer games can enhance the sense of immersion, and consequently, satisfying the players. To this end, a mobile game called Ladybug is implemented using three different techniques including the regular virtual reality (VR) camera, single AR camera, and stereoscopic AR camera. The results of a comprehensive user study on these techniques showed that the single AR camera and stereoscopic AR camera can result in more sense of immersion in players in comparison to the VR camera. However, the hypothesis that the stereoscopic AR results in more sense of presence in comparison to the single AR camera is rejected. On the other hand, our findings show that the AR stereoscopic camera can lead to a better emotional involvement and enjoyment in comparison to the single AR camera and VR camera.     

Novel approach to highly porous superabsorbent hydrogels: synergistic effect of porogens on porosity and swelling rate

A novel practical strategy for preparing highly porous superabsorbent hydrogels (HPSHs) was invented. HPSHs were quantitatively prepared through an optimized rapid convenient solution polymerization of partially neutralized acrylic acid in the presence of a crosslinking agent under normal atmospheric conditions. Acetone and sodium bicarbonate were used as porosity generators (porogens) during the polymerization process to create highly porous structures. Time and sequence of addition of the porogens, as well as the gelation time of the polymerization, were recognized to affect the efficiency of the porogens. Sodium bicarbonate produced the more porous hydrogels with a higher rate of swelling. In comparison with a hydrogel prepared under porogen‐free conditions (control), acetone and sodium bicarbonate enhanced the swelling rate as high as 43–55% and 111–131% of the control, respectively. When both the porogens were used consecutively in the process, a remarkable synergistic effect was observed in the swelling rate of the products. Nearly all the two‐porogen processes resulted in foamy products from the polymerization system. With the single‐porogen systems, however, the foam formation stage was observed only in a part of the total process time. The apparent volume of the as‐synthesized foamy products prepared from the two‐porogen system was more than that of the single‐porogen systems by up to fourfolds. Morphological studies using scanning electron microscopy (SEM) showed that the two‐porogen systems created highly porous structures. The density of all the HPSHs synthesized was about 1.5 g cm^?3 and no distinct differences were observed in their equilibrium swelling. These superabsorbent hydrogels exhibited a very high rate of swelling, so that their swelling time was measured to be less than one minute. Copyright © 2003 Society of Chemical Industry     

Electromagnetic THz Radiation Modeling by DPSM

THz or T-ray imaging and spectroscopy are becoming increasingly popular nondestructive evaluation techniques for damage detection and characterization of materials. In order to understand the interaction between the T-ray electromagnetic waves and dielectric media a reliable model of electromagnetic wave propagation through dielectric materials must be developed. A recently developed semi-analytical method called the distributed point source method (DPSM) is extended to model electromagnetic wave propagation in THz range. Since T-ray signals generated by emitters or sources are close to Gaussian beams, the DPSM modeling is carried out for Gaussian beams generated by finite sized emitters. The DPSM generated results are compared with the analytical and experimental results. T-ray propagation in layered structures in absence of any anomaly and the interaction between the Gaussian beam and the spherical scatterer are also investigated.     

Minimization of residual monomer content of superabsorbent hydrogels via alteration of initiating system

Production of superabsorbent polymer hydrogels with minimized residual monomer content is an essential prerequisite particularly in their related hygienic, pharmaceutical, and food packaging products. Effect of two thermodissociating initiators and an innovative two‐step initiation approach on the residual monomer content of acrylic acid‐based SAP was preliminarily investigated. Ammonium persulfate (APS) and 4,4′‐azobis(4‐cyanopentanoic acid) (ACPA) were used as water‐soluble initiators for the aqueous solution polymerization. FTIR spectroscopy was used for the structural characterization. It was found that APS was more effective than ACPA, and residual monomer was determined in the range of 2200–3000 and 8900–16,600 ppm for APS‐ and ACPA‐initiated polymerization products, respectively. Residual monomer resulted from APS/tetramethyl ethylenediamine (TMEDA) initiation system was measured to be about 4500 ± 117 ppm for one step initiation. However, a two‐step initiation strategy using the APS‐TMEDA was exposed to be a very effective method to decrease residual monomer to 212 ± 6 ppm. The variation of the hydrogel properties (i.e., gel content, swelling capacity, and the residual monomer content) versus the initiator system and concentration was discussed based on the basic literature and supported by some rheological evidences obtained from rheoanalysis of water‐swollen samples. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

An investigation into novel multifunctional cross-linkers effect on microgel prepared by precipitation polymerization

Novel microgels composed of acrylaic acid and multifunctional cross-linkers, acrylate/methacrylate cross-linkers, were synthesized via thermal initiated free radical precipitation polymerization in organic solvents. The effect of cross-linker functionality on the properties of microgels was investigated. Results showed both the solvent absorbency and apparent viscosity depend on the network structure, the cross-linker functionality and number of hydrophobic groups. Gel content indicated more reactivity of acrylate than methacrylate cross-linkers. A linear relation exists between elastic modulus (G′) and functionality (f). Also the results suggested an equation that confirmed a direct relationship between glass transition temperature (T_g) and (f). The rotational and apparent viscosity results supported the thickening properties of the microgels. Based on the observations, it is concluded that trifunctional AC cross-linker (TMPTA) choose as an improvement of thickening properties over another cross-linkers.     

Advances in non-hygienic applications of superabsorbent hydrogel materials

Superabsorbent polymers (SAPs) are organic materials with lightly crosslinked three-dimensional structure possessing high to very high swelling capacity in aqueous media. These are in fact the most commercially successful members of the hydrogel family. The SAP production for personal care products (baby diapers and feminine incontinence products) accounts for about 80% of the overall hydrogel production. Research during the past 30 years, although not affected the commercial status of SAPs, has led to more and more understanding of superabsorbent structures, their properties, and potential uses. Beyond the hygienic use, the SAPs have found very wide applications from the agricultural formulations to pharmaceutical dosage forms. Since hygiene applications of SAPs are very well established and well reviewed, this article reviews and highlights the SAP applications in other sectors, such as in agriculture, pharmaceutics, separation technology, fibers/textiles, water-swelling rubbers, soft actuators/valves, electrical and construction.