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This study aims to reveal the consequence of thickness reinforcement on Fiber Laminates (Polyester Resin, Glass Fiber, Aluminum, and Bentonite) and to see if it can enhance the mechanical properties and resistance of laminates. Glass fiber reinforced polymer composites have recently been used in automotive, aerospace, and structural applications where they will be safe for the application`s unique shape. Hand layup was used to fabricate three different combinations, including Aluminium /Glass fiber reinforced polyester composites (A/GFRP), Bentonite/Glass fiber reinforced polyester composites (B/GFRP), and Aluminium&Bentonie/Glass fiber reinforced polyester composites (AB/GFRP). Results revealed that AB/GFRP had better tensile strength, flexural strength, and hardness than GFRP and A/GFRP. Under normal atmospheric conditions and after exposure to boiling water, hybrid Aluminium&Bentonite and glass fiber-reinforced nanocomposites have improved mechanical properties than other hybrid composites. After exposure to temperature, the flexural strength, tensile strength and stiffness of AB/GFRP Composites are 40 % higher than A/GFRP and 17.44% higher than B/GFRP Composites.

The electrical properties of conductive carbon black (CB) nanoparticles (0.1wt percent) doped thin films made of poly(ethylene oxide) (PEO) filled with varying amounts of the electrolyte potassium alum salt and doped with conductive carbon black (CB) nanoparticles (0.1wt percent) have been investigated. The dependence of the activation energy of the composites on frequency, temperature, and filler content was studied using the AC impedance technique. The current research looked at how activation energy changed with frequency (200-1000 kHz) and temperature (30-55oC) for composites with varied potassium alum salt concentrations: 0, 2, 4, 8, 12, and 16 wt. percent. The activation energy (Ea) values measured exhibited frequency, temperature, and filler content relationships. According to polarization processes, the activation energy of the produced sheets decreases with the potassium alum salt content in the composite and decreases with the temperature. With increasing frequency, the activation energy of the produced thin films decreases.

Results obtained from the characterization of three water samples (one representing the effluent of a municipal treatment plant and the two others representing surface water from the Jiu River/Romania, upstream and downstream of the effluent discharge point) are presented in this study in terms of microplastic content. The water samples were processed by successively passing them through a series of filters with the following dimensions: 5 mm, 0.5 mm (500 im), 0.1 mm (100 im) and then through some microfiltration membranes (MF) type EZ-Pak Membrane Filters (Merk-Millipore) made of a mixture of cellulose esters, with an average pore diameter of 0.45µm. In order to highlight the microplastics in the water samples, their analysis was performed as well as the solid material retained on the microfiltration membranes, by scanning electron microscopy (SEM) using a SEM Quanta FEG 250/Thermo Fischer Scientific. The results obtained highlighted the existence of microplastics in all the analyzed samples, in the known forms presented in the specialized literature: irregular planes, fibers and spheres. Their dimensions are variable, ranging between 3.2 µm and 119.5 µm for irregular plane microplastics and between 3 µm and 15 µm for spherical microplastics. The dimensions of microplastics in the form of fibers are also in the range of tens of µm and cannot be established exactly because in most cases they appear in the form of conglomerates. The treatment plant’s microplastic effluents content led to the modification of the physical-chemical indicators of the water in their natural receptor. Thus, the content of organic matter and total suspended matter in the downstream water compared to the effluent discharge point is higher than in the upstream water. The analysis of microplastics by SEM allows only their highlighting and their geometry, being a first step in the study of the pollution induced by such materials.

Ophthalmic treatments using contact lenses are now used by more and more specialists around the world. Improving contact lens (CL) materials is a condition that is constantly evolving. Contact lens materials are usually composed of polymer hydrogel or silicone hydrogel. The materials used for night contact lenses are gas permeable and they gradual flatten the center of the cornea which decreases the progression of myopia or myopic astigmatism. The aim of this study is to identify, in correlation with the chemical interactions between structural components of contact lenses and their biocompatibility with the surface layer and microtopography of the cornea or sclera, different incidents that occur in patients who have used rigid gas permeable contact lenses. The study was performed on a group of 10 patients who had a follow-up period between 4 and 6 years, who presented regularly for eye examinations. The following clinical parameters were analyzed: ocular refraction before and after wearing night contact lenses, types of contact lens materials, appearance of corneal topography, biomicroscopic examination of the anterior segment of the eye, keratometry, ocular comfort, as well as other incidents regarding this type of lenses. Difficulties caused by wearing contact lenses at night arose due to poor hygiene and maintenance in two cases or due to interruption of lens wear in one case.

Ureteral catheters, commonly known as double j stents according to their specific shape, are largely used worldwide with good results to assure proper renal drainage and to overpass ureteral obstacles successfully. This study deals with the aging behavior of polyurethane-based urinary catheters, explanted at different time intervals: 22 days, 29 days, three months, and eight months respectively. TGA (Thermogravimetric analyses) tests showed significant differences in the thermal behavior of polyurethane-based material, especially at eight months, where a higher thermostability was noticed. Also, the DSC (Differential Scanning Calorimetry) curves presented different shapes for the samples of polyurethane-based urinary catheters after three months and eight months. FTIR (Fourier-Transform Infrared Spectrometry) spectra gave a detailed picture of the chemical trans-formation which has occurred within the material at eight months. All the analyses gave an overview of the aging process of polyurethane-based urinary catheters and showed insights into the chemical/ physical transformations that the polymeric material suffers from prolonged usage.

In this study, a new organic nucleating agent N, N`-bis(stearic acid)-1,4-dicarboxybenzene dihydrazide (PASH) to improve crystallization behavior of poly(L-lactic acid) (PLLA) along with the effect of PASH on melting behavior, thermal stability of PASH-nucleated PLLA was holistically reported. The melt-crystallization process illustrated that PASH as an effective heterogeneous nucleating agent could boost PLLA’s crystallization rate, but increasing PASH concentration and cooling rate conversely inhibited melt-crystallization process of PLLA in this study. With respect to melt-crystallization process, a larger amount of PASH leaded to a shift of cold-crystallization peak to lower temperature level. Isothermal crystallization revealed, in comparison to pure PLLA, that the half time of overall crystallization of PLLA/PASH was significantly decreased with PLLA containing 3 wt% PASH having the minimum t1/2= 67.3 s at 105ºC. The different melting behaviors of PLLA/PASH under different conditions were attributed to the nucleating effect of PASH within PLLA. In particular, the melting behavior at a heating rate of 10°C/min after isothermal crystallization depended primarily on the crystallization temperature. Whereas, the impact of crystallization time on melting behavior was negligible. Nonetheless, the melting behavior was influenced by the heating rate after non-isothermal crystallization. The thermal stability of PLLA was detrimental with the addition of PASH owing to a typical drop in onset thermal decomposition temperature.

Sustainable materials made from recycled materials are an alternative to traditional materials (synthetic ones) and present a lower environmental impact. Due to the fact that natural fibers were successfully used to produce environmentally friendly sound adsorbing materials, biocomposites made from recycled polypropylene (PPR), feathers flour (FF) with / without compatibilizers (C) were obtained and characterized from the point of view of their acoustical behavior. Obtained materials were characterized also from the morphological and compositional point of view by scanning electron microscopy and thermal gravimetric analysis. All tested samples presented sound adsorption properties but the best results were obtained for the biocomposites with FF content of 10%-20%.

Architectured structures, particularly auxetic materials, have demonstrated encouraging applications in energy absorption as they facilitate the customization of their structural response. Specific geometries of unit cells can thus be tailored for particular needs due to recent progress in additive manufacturing techniques. This paper experimentally studies how the grading of the cell unit angle of an auxetic core in a sandwich panel affects its energy absorbing capability and structural response. 3D printed sandwich panels with uniform and graded auxetic cellular core were tested under quasistatic compression. The results show that sandwich panels with graded core exhibit much better energy absorption capabilities with higher plateau stress and densification strain. This indicates that, by appropriately controlling its geometry, auxetic structures can show further potential as core in sandwich panels for energy absorption applications.

The shape memory effect, as the most important ability of shape memory polymers, is a working property and provides the design ability to shape memory polymer features. Shrinkage and warpage are important parameters to control the dimensional accuracy of permanent and temporary shapes of an injection moulded shape memory polyurethane (SMPU) part. In this study, the effects of injection moulding parameters on the shrinkage and warpage of the permanent shape of moulded SMPU parts were experimentally investigated. The parameters of injection pressure, melt temperature, mould temperature, packing pressure, packing time, and cooling time, were chosen as the injection moulding control factors. Taguchi’s L27 orthogonal array design table was used with six injection moulding parameters and their three levels. The results showed that the part has different shrinkage ratios in three main directions, namely, the flow direction, perpendicular to the flow direction, and the direction through the thickness. The results of the analysis of variance showed that the cooling time is the most influential parameter on both the shrinkage (except in thickness) and warpage. The shrinkage in the flow direction as well as in perpendicular to the flow direction decreased with increasing the cooling time. Warpage also decreased with increasing the cooling time. Injection pressure and melt temperature were found to be effective on shrinkage in thickness. Effects of mould temperature, packing pressure, and packing time were found to be limited. A statistically significant relationship has been noticed among shrinkage, warpage, and residual stresses during the study.

The aim of the paper consisted in the development of an injection mold for plastic horn cover parts in commercial vehicles. Three mold types were designed in anticipation of the structure and quality of molds, and injection molding numerical analyses were conducted for the three types of molds. One mold type was selected in consideration of the resin flow patterns inside the mold, surface quality, and final deflection amount of the horn cover. To perform optimal injection molding using the selected mold, optimization of injection molding parameters was performed using the Taguchi method, one of the designs of experiment (DOE) and ANOVA methods. As a result, it was confirmed that the deflection amount of the molding under optimal molding parameters decreased by about 34.3% compared to the deflection amount before optimization of the molding parameters. Based on these encouraging results, the previously selected mold type was actually manufactured. The horn cover was molded using the obtained optimal injection molding parameters to the manufactured mold. To verify the precision of the molded horn cover, the deflection amount of the molding was measured with a 3D scanner. The deflection amount of the horn cover was estimated to be about 11% to 43% larger for each measurement position than the deflection amounts in the analysis results. The manufactured mold was revised to solve the problem that the deflection amount of the actual molding is larger than the deflection amount predicted by injection molding analysis. The dimensions and surface quality of the horn cover with a revised mold were satisfactory.