Browse Articles

In order to evaluate the possibility of reuse of some mixed waste from plastic and paper, composite samples of both HDPE and PP basis were made with different filler contents of crushed postage envelope waste. From the morphostructural characterization (SEM images) of the samples obtained it was observed that the HDPE and PP samples had had a homogeneous single-phase structure in contrast to the composite samples with filler from mixed plastic and paper waste. The latter, have a biphasic heterogeneous structure in which the cellulose particles are uniformly distributed. Determinations performed through the dielectric spectroscopy technique indicated that the cellulose content of the composite samples leads to a systematic increase of the dielectric losses (up to about 40% for the HDPE samples, respectively about 30% for the samples with PP), the increases being in direct correlation with the cellulose content of the composite.Mechanical determinations have shown that the average values of tensile strength recorded on the achieved samples, systematically decrease at the increase in the chips content of the samples - decreases up to 10% at an addition up to 15% chips from the waste are explained by the substantially lower mechanical strength of waste paper than that of the HDPE, respective PP.

The present paper describe the production and characterization of novel collagen films containing propolis encapsulated in chitosan nanoparticles, for biomedical applications such as cutaneous wound healing. Structural and morphological details were investigated by ATR FTIR spectroscopy, SEM and nanoindentation measurements, revealing the collagen fibers aligned in a quasi-parallel distribution, which might be favorable for biomedical applications. Moreover, the vibrational marker bands of propolis were well preserved in the final polymeric mixture, indicating the stability of bioactive compounds upon the encapsulation procedure. The antibacterial effect depends on the nanoparticles concentration in collagen film, the effect being more evident with respect to E. coli than S. aureus. The antioxidant capacity monitored by CUPRAC assay, indicated a synergic effect of chitosan nanoparticles matrix and propolis extract, incorporated in collagen films.

Soil pollution with plastics represents a great threat to plants, animals, but especially to humans, as a very small quantity of the plastic which is discarded daily is recycled or incinerated in waste facilities, much of it reaching landfills where their decomposition lasts up to 1000 years and during this time the toxic substances penetrate the soil and the water. If, initially, the pollution with plastics has been identified and recognized in the aquatic environment, recent studies show that plastics residues exist in huge quantities in the soil. The present study focuses on the analysis of factors that pollute soil, so the various studies that have been carried out claim that soil pollution with plastic is much higher and increases in an aggressive manner, being estimated to be 4 to 23 times higher than water pollution with plastics, and the accumulation of microplastics in the soil has a negative impact on soil biota. Thus, once the plastic material accumulates in the soil, it is assimilated to organic matter and the mineral substitutes of the soil and persists for several hundred years.

In the recent years, the electric vehicles have drawn great attention worldwide as a feasible solution for clean transportation. The charging infrastructure for electric vehicles is expanding throughout the world, encouraged by large investments from the automotive industry, to reduce carbon emissions. The purpose of this paper is to design the shell of an electrical vehicle charger by using polymeric composite materials. The manufacturing technology is proposed and the analysis of the product behaviour during the wind action in extreme conditions is presented. The paper includes studies and research regarding the design, the manufacturing and the simulation for the action of wind upon the product’s walls. The simulations are performed for the actual used material (ordinary sheet steel) and for the proposed composite material in order to compare the results. The composite material seems to be an adequate solution for the electric charger shell.

The damages and casualties inflicted by mine and IED attacks in security challenging areas generated a strong and quick response from nations all over the world. As a part of this response several national and private research facilities increased their efforts in identifying and implementing new ways or technologies to enable blast wave mitigation. The current paper aim to investigate the opportunity of using polyurea coated steel plates as a possible new blast mitigation approach, as suggested by several investigators. In order to objectively conclude about the ability of polyurea coated plates to sustain locally blast loads several experimental tests were performed according to STANAG 4569 demands for a 1/6 scaled plate structure. In order to numerically validate the experimental results several Autodyn simulations were set-up. The numerical and experimental results exibits a fair correlation, both pointing towards a dismiss of the idea of using polyurea coated steel plates as structural and cost effective blast mitigation approach.

Designing a sample to be made by FDM 3D printing is a fundamental problem in further studies related to such printed structures as material properties vary depending on filament orientation and G-code particularities. Samples designed to simulate wall structures inside 3D printed parts have been tested to allow separate evaluation of key components in such parts. Results show a very long plastic region in filaments without imperfections. As filament strands break steps of similar values appear in the reaction force measured by the machine.

The aim of our study was to determine the wear resistance of vacuum-formed retainers (VFRs) made out of polyethylene terephthalate glycol (PETG), from four different manufacturers (Essix, Leone, Erkodent, Bio-Art), under high load forces (600 N), for 10000 cycles. Forty thermoplastic sheets were divided in four groups, each group consisting of a set of ten sheets from each manufacturer, thermoformed on two matching study models with an ideal occlusion. The Instron 8874 equipment was used to simulate the accelerated wear of VFR surfaces. The surfaces of the VFRs were visually inspected using a KEYENCE VHX-600 digital microscope, but this proved difficult because of the surface shine. 3D models were generated using a GOM industrial laser surface scanner. Several wear areas were identified, having various degrees of roughness, with no evident tear points or perforations. One-way ANOVA analysis showed no statistically significant differences in net mass loss between the four groups.

The high global production of electric and electronic equipment increases in the same manner the amount of the waste that needs to be recycled. Special attention is given to the plastics recycling from the waste in addition to the metals recovery that brings economic advantages. Considering that the plastic amount contains about 80% polystyrene polymers, the paper presents a recycling study of this fraction as reinforcing agent for a styrene-butadiene block copolymer. In order to reduce the melt viscosity, some of the composites were extended with paraffin-naphthenic “heavy white oil”. The blends were characterized by mechanical testing, thermal and dynamo-mechanical analysis. Based on the resulted properties, it can be concluded that the extended and reinforced composites can be used as material for shoe soles.

New nanogels (NGs) with tailored properties were obtained using a mini-emulsion technique, from poly(ethylene glycol) diacrylate (PEGDA) self-crosslinking macromers of various molecular weight. By modifying synthesis parameters (hydrophilic-lipophilic balance, emulsifier and the ratio of organic-aqueous medium), optimum recipes of NGs were selected. Therefore, the molecular weight distribution and the functionalization degree of the PEGDA2000 macromer were assessed by Gel Permeation Chromatography (GPC) and Nuclear Magnetic Resonance (NMR), respectively. Furthermore, the PEGDA-NGs were investigated by Dynamic Light Scattering (DLS) and Transmission Electron Microscopy (TEM) for size distributions and morphology. DLS and TEM results confirm that these new PEGDA-NGs hold potential for biomedical applications.

The hypercaloric diet leads to obesity which is a risk factor for developing many systemic diseases such as diabetes, cardiovascular diseases and cancer. The purpose of our study was to observe the antioxidants effects of entrapped alfa-tocopherol (vitamin E) and lutein in Poly Lactic-CO-Glycolic acid (PLGA) in Wistar rats that received 3 weeks hypercaloric diet. Hepatic and splenic lysates have been used to detect changes in total antioxidant capacity (TAC) and advanced oxidative protein products (AOPP). The AOPP liver levels were statistically decreased in the case of rats groups that received a daily dose of PLGA-lutein or PLGA-vitamin E versus the control group. The AOPP level was decreased but statistically insignificant in Wistar rats spleen who received a daily dose of PLGA-lutein. At hepatic level, TAC was statistically increased in rats groups that received a daily dose of vitamin E or lutein. An increased statistical level of TAC was observed in the spleen cell lysing in Wistar rats who received the daily dose of PLGA-vitamin E. Entrapment of vitamin E and lutein in PLGA structure has diminished the effects of hypercaloric diet and can be considered a attractive and promising approach to enhance the bioavailability and activity of poorly water soluble compounds.