Volume 59, Issue 4

Abstract: The study establishes a theoretical evaluation trough several models concerning the dielectric properties of some new eco-composites made of a cellulosic derivative matrix – hydroxypropyl methylcellulose (HPMC) – in which distinct sorts of fillers (ceramic, metallic and bio-derived) were introduced. The investigation describes the impact of the filler addition on the dielectric constant, the dielectric breakdown, and finally how these two factors are contributing to the electric energy density of purposed eco-composites. After incorporation of the reinforcement agents, the dielectric constant significantly increases comparatively with the matrix, as a function of the type of filler used. Moreover, by assessing of the dielectric breakdown, it is observed that with the increase of filler quantity, this parameter slightly decreases for all samples. The data concerning the electric energy density reveal that, by filler insertion in the HPMC matrix, an improvement occurs, especially for the barium titanate system owing to its large dielectric constant. These data are promising for design of new eco-composites having improved dielectric features as demanded for green energy storage devices. Since the materials have biodegradable and biocompatible character, they also have importance in bio-related applications.

Abstract: The industrial grade hollow beads were divided into three particle sizes of 40 mesh, 60 mesh and 80 mesh and added into the epoxy resin material matrix to prepare porous foam composites. The quasi-static compression experiments were performed on porous foam composites at room temperature, and the stress-strain curves of quasi-static compression processes were analyzed separately for different particle sizes. According to the characteristics of the compression curve of porous foam materials, the representative characteristic parameters of each stage are extracted separately. The fracture characteristics of the microscopic samples of the compressed material specimens were observed by electron microscopy, and the deformation patterns of the composite materials were analyzed. And combined with SEM pictures to analyze the form of microbead crushing and matrix pore collapse mode, according to which the particle size suitable for this matrix is 60 mesh and the mass fraction of microbeads is 10%.

Abstract: Polyethylene (PE) materials have been widely used in industrial and living fields such as natural gas pipelines, drainage pipes, sewage pipes. Punch test is an interesting tool for studying the mechanical properties of materials. However, the deformation behavior involved in punch test is complicated, it is, therefore, essential to investigate the influence of punch test conditions on the mechanical properties of PE materials. Punch tests have been carried out on PE specimens with different punching speed (0.01, 0.1, 1, 10 and 100mm/min) and different punch head diameters (4, 6, 8 and 10mm). The experimental results show that the maximum load from the load-displacement curve increases with the increase of the punch head diameter under the same punch speed. When the punch speed is slow, the force-displacement curve of PE specimens contains four typical stages, namely, elastic stage, yield stage, strain softening stage and strain hardening stage. However, the PE specimen breaks before reaching the strain hardening stage when the punch speed is fast. Similarly, the maximum load increases with the increase of punch speed when the same punch head diameters are used. Furthermore, a three-dimensional finite element (FE) model of PE specimens subjected to punch load has been established to further analyze the deformation and failure behavior. A good agreement between the simulation results and the punch test data is achieved.

Abstract: To analyze the implant overdentures components as following: morphology and composition aspects of several small diameter systems, evaluating both the implant and the retention system (1); biomechanical characteristics of some of the polymers used for manufacturing the overdenture base (2). An experimental in vitro study was carried out through optic microscopy to analyze the metallic structure of dental implants components and anchor systems. The marketed products analyzed were mini1SKY (Bredent) and 3M ESPE MDI Mini dental implant (3M ESPE). A Zeiss microscope with Kohler illumination was used. Samples from polymeric materials commonly used for overdenture based (i.e. Duracryl and Superacryl) were analyzed by 3 point bending test by Tira device. In the case of the mini1SKY system (Bredent), the dental implant has the typical structure of marketed pure titanium that went through thermomechanical processing, resulting in a higher rate of granulation, and the matrix has a completely different structure, as it is a monophasic structure specific to materials that crystalize in the cubic system of the stainless steels. In the case of the 3M ESPE MDI system, the implant and the matrix have a similar microstructure, specific to a Ti-6Al-4V beta alloy annealed with an extremely fine rate of granulation. Duracryl and Superacryl samples fractured variable (frequently close to the midline) and were similar in regard to the value of breaking force. Knowledge of the materials of the components of implant overdenture guide their selection from the point of view of biocompatibility, resistance and ensuring denture retention.

Abstract: In this present research work, Poly(azomethine), ZnO, TiO2, poly(azomethine)/TiO2 and poly(azomethine)/ZnOnanocomposites were synthesized. Prepared nanocompositewas characterized by FourierTransform-Infrared spectroscopy, UV-Visiblespectroscopy, PowderX-raydiffraction, band gap, EDAX and SEM. The Photocatalytic activity of the samples was evaluated for the degradation of MethylorangeandAlizarin red S under natural sunlight. The effects of dye concentration were studies for the decolorization of MethylorangeandAlizarin red S. The degradationefficiency,reactionkinetics and isotherm studies revealed that the Polyazomethine /ZnO(PNZ) and poly(azomethine)/TiO2(PNT) nano-composites have shown excellent photocatalytic activity than PAZ, ZnO and TiO2.At optimum dye concentrations of 10ppm Methyl orange and Alizarin Red S shows maximum degradation efficiency was 87% and 86% usingPNZ and PNT nanocomposites asaphotocatalysts at 5 h contact time. FT-IR, UV-Visible spectroscopy, SEM and EDAX were used to describe the samples after the photocatalytic investigation. To examine the effect of decolorisation of dyes using synthesized photocatalysts Pseudo first order kinetic, pseudosecond order model, Langmuir, Freundlichisothermsstudieswere carriedout and also followed by intra-particle diffusion model, whereas diffusion is not only the rate-controlling step. The results show that the degradation capacity decreases with an increase in solution temperature from303 K to 333 K. The thermodynamics parameters were evaluated.

Abstract: Nowadays, research is focused on using bio-degradable natural fibre-based composites for secondary structural members. The present study aims to investigate the effect of fiber loading and surface treatment on the mechanical, vibrational, and viscoelastic properties of short, randomly oriented Abelmoschus Esculentus fiber-reinforced epoxy composites. The composite was fabricated by reinforcing various weight percentages of Abelmoschus Esculentus in epoxy resin by hand lay-up method and tested for tensile, flexural, and impact tests as per ASTM standards. Further, the fibres are treated with alkali to evaluate their effect on the mechanical properties of composites. The analysis indicated that fiber loading had a significant impact on the mechanical properties of the composite, with the maximum tensile strength of 27.8 MPa being obtained at a fiber loading of 20 volume %. The surface treatment of the fiber with 2% NaOH solution increased the tensile strength by 34%. All composite specimens were subjected to vibration analysis. The results showed that composite reinforced with 20% fibre loading provided superior mechanical and damping qualities. Dynamic Mechanical Analysis revealed that the Storage Modulus (E’) improved with the addition of Abelmoschus Esculentus fiiber.

Abstract: The purpose of this paper was to obtain new hybrid composite materials (HCM) with applications in electromagnetic shielding and their characterization using new methods. The paper presents 6 experimental models (EM) of new hybrid composite materials (HCM) with applications in the electromagnetic shielding and their characterization using new methods. EMs were obtained by extrusion and melt injection, with different ratios of HDPE/hybrid NiFe2O4/Ag mixture concentrations: 100/0 - I0; 97/3 - I1; 95/5 - I2; 93/7 - I3; 90/10 - I4 and 80/20 - I5. The characterizations performed within this work are imposed and correlated with the operating conditions of these materials. Thus, we studied the behavior of polymer composite materials with hybrid fillers, under the action of different degradation factors such as ionizing radiation, UV radiation and moisture. Following the tests performed, the experimental model I5, composite with maximum ferrite concentration, i.e. 20 %, was chosen as the optimal variant. It was aimed to identify the degree of degradation of the developed composite materials, as a function of the variation of tan δ with frequency, at different aging/ conditioning cycles. The originality element of the paper consisted in determining the life time remaining of the HCM until the moment it needs to be replaced, by an original method protected of by an invention patent.

Abstract: SiO2 nanoparticle were used in aPolyphenylsulfone (PPSU) matrix to obtain nanofiltration membranes used in the pharmaceutical sector to remove pollutants from the water processes. In this study was investigated the influence of SiO2 nanoparticles on the PPSU membranes performance at different concentration of polymer and at six different concentrations of SiO2. Adding SiO2 like additive in the PPSU membrane matrix, the permeability increases due to the higher porosity. Increasing the polymer concentration, the pores are smaller and the permeation properties are decreasing. The affinity for water of membrane surface is higher when nanoparticles are added in the polymer matrix. Adding 0.3 wt.% SiO2 the permeation properties are increasing with more than 10% in comparison with membranes without nanoparticles.

Abstract: The search for nanofillers in polymer industries to improve composite material properties for several purposes has increased significant interest. In this study, dioctyl phthalate-plasticized polyvinyl chloride (PVC) reinforced either with sepiolite or MgO was produced in which the characteristic of composite sepiolite/MgO-filled was compared. Sepiolite and MgO were added into PVC matrices with 5, 10, and 20 phr concentrations. The product was characterized using analytical techniques such as SEM, TGA, DSC, and the mechanical properties regarding ASTM D 638 Type IV. The tensile strength of the composite increased with the presence of sepiolite and MgO. The highest result showed at the concentration of 5 phr. However, the elongation at the break of the composite decreased with the addition of MgO. The morphology analysis showed that PVC-filled sepiolite had a rough surface with a sharp fracture, but no sharp fracture was found in the PVC-filled MgO. At a concentration of 5 phr, both sepiolite and MgO increased the thermal properties of PVC with a residue of PVC control, PVC-Sepiolite, and PVC-MgO at 14.74%, 19.34%, and 26.33% respectively.

Abstract: Plastic parts in retired passenger vehicles are derived from non-renewable oil resources, and recycling them can conserve energy and reduce the burden on the environment. Effective separation is the premise of recycling vehicle plastics, and electrostatic separation is a clean and efficient method of plastic separation. On the basis of a self-developed, two-stage electrostatic separation equipment, this study investigated the high-voltage electrostatic separation of polyamide (PA), polyethylene (PE), and polypropylene (PP) mixtures. First, the single-factor experiment method was used to explore the influence of voltage, electrode spacing, and electrode inclination angle on the separation results. Second, the response surface methodology was employed to comprehensively analyze the effects of voltage, electrode spacing, and electrode inclination angle on the recovery rates of the three particles and their interactions. The optimum parameters for the secondary electrostatic separation of the three particles were determined to be 44 kV voltage, 156 mm electrode spacing, and 10° electrode inclination. Experimental verification showed that after the two-stage, electrostatic separation device was optimized through the response surface methodology, the purity of the PA particles reached 98.56%, and the recovery rate reached 96%. The purity of the PP particles reached 81.93%, and the recovery rate was 87.5%. Meanwhile, the purity of the PE particles reached 86.11%, and the recovery rate was 73%. This research provides a reference for the multi-stage, high-voltage, electrostatic separation of various automotive plastic particles.

Abstract: Chitosan is a natural biopolymer, being a cationic polysaccharide, which is generally obtained by deacetylation of chitin. Aminophosphorylated chitosan is of interest due to the presence of its multiple functional groups of aminophosphonate type that can serve as chelating sites and their interesting biological and chemical properties. This paper presents the achievement of antibacterial adsorbent based on modified chitosan with aminphosphonic groups and Zn(II) ions. The new aminophosphonic adsorbent supported on chitosan was modified by impregnation with Zn(II) ions using the hydrothermal reaction. It was prepared from the natural biopolymer of chitosan type. The obtained product was characterized by different techniques: FTIR, SEM / EDX, XPS and thermogravimetric analysis. This research aimed to test modified chitosan against the strains (Staphylococcus aureus and Pseudomonas aeruginosa). In order to highlight the effect of the presence of Zn(II) ions, both the chitosan functionalized with aminophosphonic groups and impregnated with Zn(II) ions (code: ChitPZn) and the chitosan functionalized with aminophosphonic groups (code: ChitP) were tested. It was found that Zn(II) ions impregnation on chitosan functionalized with aminophosphonic groups increases the antibacterial effect in both St. aureus as well as at Ps. aeruginosa.

Abstract: Polyurethanes are widely used in different industries, as insulators, coating or adhesive agents. Several of their medical applications include various implants, artificial heart valves, surgical instruments or catheters. The versatility and biocompatibility of these polymer products lead to their application as drug or genetic material delivery systems. We aim to evaluate different parameters that affect the encapsulation efficiency of polyurethanes, using a computational approach, in order to improve the transmembrane transfer and the bioavailability of an active agent loaded inside a drug delivery system. 2D structures of different etheric- and esteric-PU macromolecular chains were modeled in ChemBioDraw, while molecular structures of the three active agents (Deoxyribonucleic acid, Guanidine,1`-[(methylethanediylidene)dinitrilo]di-, mixt. with Calf Thymus DNA, and 2`-Deoxycytidine-5`-phosphonic acid) were imported from PubChem database. Open software such as Open Babel and PyRx were used to convert files and to analyze the binding affinity based on the predicted dissociation constants. Structural parameters of the tested compounds were calculated in HyperChem 8.0. The polymer chains showed very large values for van der Waals potentials, refractivity and polarizability compared to the active agents. Even if there were no major differences in terms of binding affinities between the tested assemblies, the best orientation ligand-macromolecule was the 2`-Deoxycytidine-5`-phosphonic acid encapsulated inside LDI and PEG-based polyurethane carrier. On the other hand, the values of Root Mean Square Deviation have identified that the best geometric fit to be the Deoxyribonucleic acid encapsulated inside IPDI and PCL-based polyurethane macromolecule. The assemblies between genetic materials and polyurethane drug delivery systems are not experimentally known and this study could orientate towards new potential therapies. These results indicate that there is no significant change in the values of the docking parameters with different PU synthesis precursors; however, a good compatibility between LDI and PEG-based chain and 2`-Deoxycytidine-5`-phosphonic acid was identified. Further studies are needed to evaluate the in vitro and in vivo utility of this finding.

Abstract: This paper presents preliminary results and discussion on two aramid fabrics in order to establish their stab resistance when used as panels with different numbers of layers. Twaron fabrics SRM509 and CT736CMP, were arranged in 16 and 20 layers and in a combination of them (10 layers SRM509 and 10 layers CT736CMP). Samples of 130 mm x 130 mm were cut from the fabrics, weighed and measured for thickness. All tests were done for an impact energy of 24 J (the resulting impact velocity being 3 m/s). The blade had the geometry recommended in the standard Stab Resistance of Personal Body Armor NIJ Standard–0115.00 as P1. The conclusion of this analysis is that the better behavior to stab is obtained for panels that have higher gradients in time, for all four characteristics here discussed: force, displacement, absorbed energy and velocity. When using hybrid panels, the results could intermediate those of the components, this solution could be recommended for reasons as price, weight.

Abstract: The torus or toroidal surfaces are geometries that can be easily found in various industrial applications, from containers, devices, cartwheels, design objects and even machine parts, being also a geometric primitive often used in solid constructive geometry. For a better understanding of the torus–type surface mechanical behavior, this paper aims to study the toroidal geometry manufactured from ABS material by using the FDM 3D printing method and subjecting each sample to compression tests to identify the influence of the sample filling percentage in the case of triangular pattern.

Abstract: In this study, Ethylene-vinyl acetate (EVA) based composites filament, with four different volume fraction of the nano-sized carbon black particles (NCB) were produced by melt mixing using a single extruder. The morphology of the EVA/NCB was studied using SEM, where a 3-D network of the NCB was presented. Thermal gravity analysis (TGA) measurement was utilized, denoting the degradation temperature of EVA, and presetting the actual volume fraction of NCB in the composites. Mechanical properties, e.g. elongation at break, tensile strength of the EVA/NCB filament was studied. Most importantly, the strain sensoring behavior of the EVA/NCB was investigated ultilizing a tensile testing machine coupled with a pico-ammeter. The gauge factor for various strain range, as well as the relative change of the resistance during the cyclic measurement of the NCB/EVA composites was calculated. Moreover, the measured data were fitted using some mathematical modellings, which reveals the potential of the strain sensoring behavior of the NCB/EVA composites in this study. Overall, this study introduces a durable NCB/EVA composites using as strain sensor oriented to industrial large-scale production, and the proposed modelling provides an effective evaluation method on its strain sensoring behavior.

Abstract: In this study, a selective flexible flow path system was developed so that two types (4 cavities) of different shapes, sizes, and weights could be produced simultaneously or individually according for a production plan.The selective flexible flow path system is a method of exchanging sprue parts manufactured in a branched or one-way direction. This method reduces mold costs and provides production flexibility because only the desired cavities can be filled with resin in a multi-cavity mold. Since parts with different shapes and weights are produced simultaneously or separately, it is most important to maintain a uniform filling balance between each cavity. To optimize of filling balance, the optimum value of control factors was derived using the Taguchi technique (DOE) to improve the filling balance. In addition, molds were manufactured under the optimal conditions after checking the filling balance through a CAE analysis. As a result, the flow balance ratio of each product was confirmed to be within 0.6%, and the precision of the product was guaranteed to be within 1%. In this study, it was confirmed once again that the improvement of the filling balance of the family mold had a great influence on the production.