Volume 59, Issue 2

Abstract: The purpose of this study was to investigate how well a polytetrafluoroethylene graft interposition works in limited situations to avoid the use of prosthetic venous access grafts or installing a permanent dialysis catheter. A retrospective examination of clinical data from a single institution was undertaken on a case series from January 2018 to September 2019. We included in our study 28 polytetrafluoroethylene interpositions, done using a mean prosthetic length of 3.5 cm and diameters of 5 and 6 mm. The patency at 24 months was 71.43%, higher than the literature percentages. We found that these interventions were successful and long-lasting, and the technique we used has a minimal risk of thrombosis, infection, or bleeding.

Abstract: Electromagnetic compatibility issues and those generated by these radiations are a major concern for electrical and electronic products, mainly in the fields of communications, information technology, transportation, security and medical services. The paper presents the way to obtain nanostructured paint/plastic/nanopowder paint systems with electromagnetic shielding properties, as well as their characterization by FTIR analysis, DSC and dielectric tests. These systems have Electro-magnetic Interference (EMI)/Electromagnetic Compatibility (EMC) and Electrostatic Discharge (ESD) applications in the manufacture of enclosures for various electronic devices and for the automotive industry. At the laboratory level, 4 non-additive experimental models (EM) coded M1-M4 and 16 additive experimental models coded M5-M20 were obtained. Revolutionary to these materials is the fact that inside they are insulating and, on the outside, they behave like a shield. The results obtained from the dielectric tests performed on the 16 additive systems showed that the samples with a maximum percentage (20 %) of metal nanopowders show the highest values of electrical conductivity. Of the two nanopowders used, that of Fe from samples M11, M12, M19 and M20 which induces the composite higher conductivities than Al nanopowders. The ATR/FTIR spectra of the two paint samples analyzed showed that they were almost identical, suggesting that the paints tested had the same basic chemical structure. DSC analysis showed that pigment paint (V2) has low thermal oxidation stability and lower decomposition temperatures than pigment-free paint (V1), therefore, V2 is less stable under usage conditions, under the influence of normal environmental factors (temperature, humidity, natural or artificial light, etc.) compared to V1.

Abstract: In this paper some mechanical characteristics of a composite made from a hybrid resin and reinforced with corn cob powder are presented. The hybrid resin was made with a combination between the natural dammar resin combined with a small percentage of acrylic one. The synthetic resin was inserted in order to increase the polymerization process which was produced in about 24 h. In the fist part of the investigation, from the compression test, some mechanical characteristics are determined, such as: breaking strength or maximum force obtained at breaking. Then, by using the SEM analysis and EDS spectrometry, some samples with 50% dammar and 60% dammar were investigated. The last hybrid resin test was Shore D hardness and it was found out that the hardness decreases with the increase of dammar percentage. In the last part of the study, some composites by using the poposed hybrid resin reinforced with corn cob powder were manufactured. It has been found out that the proposed composite reinforced with corn cob powder has increased compression mechanical properties compared other composites that have the same reinforcement.

Abstract: The PPR pipes are more and more used in different industrial applications, due to their multiple advantages compared with the conventional metallic pipes. The experimental study presented in this article, was conducted in two directions, analyzing the behavior of welded PPR pipes and also the behaviour of unwelded PPR pipes exposed to different aggressive environments. In the second investigation, the PPR pipes were immersed in different chemically active environments as gasoline, sodium hypochlorite (NaClO), water + sodium hypochlorite (NaClO)-20% NaClO volume concentration, for a period of 3 weeks (21 days), in order to reveal the influence on the mechanical properties of the PPR pipes. The examination was made by using both visual inspection and tensile and bending tests. The investigations made have led to the conclusion that the presence of sodium hypochlorite do not affect the mechanical properties of PPR pipes, unlike the gasoline which significantly decrease the yield stress value. For the welded PPR pipes it was found that they failed at pressures of about 180 bar. Although the optimal welding parameters, recommended by the manufacturer, were modified (maintenance time), the only sample that failed in the welded joint was the one with the most acute misalignment and the shortest welding time. However, the sample withstood high pressures, reaching about 55% of the burst pressures obtained for welded pipes with the recommended welding parameters. The need to conduct such studies derived from the fact that most of the information regarding the behavior of PPR pipes is provided by the manufacturers and there is insufficient information in the scientific literature.

Abstract: Boswellia seratta (BS) is the best herbal medicine to treat Rheumatoid Arthritis (RA), due to its anti-inflammatory and anti-arthritic activity. Delivering BS through an oral drug delivery system has been in effective, because of its enzymatic degradation within the Gastro-Intestinal (GI) tract. In this paper, we develop a gastro retentive approach for delivering BS to avoid high hepatic first pass metabolism and optimized buccal patch based on the drug delivery characteristics. There are seven different formulated buccal films of BS that were prepared by the solvent casting method, using mucoadhesive polymers, Poly Vinyl Alcohol (PVA), and Sodium Carboxy Methyl Cellulose (SCMC). These with drug formulation can be represented as PCB. The prepared films were evaluated by various physicochemical properties and characterization studies. Results obtained from physico-chemical properties, in-vitro and ex-vivo studies among all seven patches, PCB5 shows better drug-releasing characteristics. This was further confirmed by FT-IR and XRD characterization studies. Also, the data was statistically analysed using Analysis of Variance (ANOVA).

Abstract: Novel block biocopolymers were made by copolymerizing the prepared polylactide-dipenta-erythritol macromonomer with two different monomers, N-hydroxyethyl acrylamide (HEAA) and N,N-dimethylamino ethyl methacrylate (DMAEMA), with an activator generated by atom transfer radical polymerization (ATRP), to have a different duplicating unit of 10, 25, 50, and 100. ATRP employs a copper(I) bromide (CuBr) catalyst system with N, N, N′, N′′, N′′-pentamethyl diethylenetriamine (PMDETA). Different spectroscopic and analytical methods used for characterization of the prepared biocopolymers, such as FT-IR, 1H NMR, 13C NMR, and GPC, showed that they had narrow dispersity with controllable molecular weight and were accompanied by nanostructures as examined by SEM technique on all biocopolymers, confirming the correctness of the expected structures of biocopolymers. The shape and size of the produced polymeric nanoparticles were determined using a scanning electron microscope (SEM), and they were developed using the Image-J application.

Abstract: The timber industry takes an important place in our modern life, and there has been an increased interest in it for a long time, especially in industrially developed countries. The concerns of the environmental organization regarding the plant wealth preservation have caused scientific trends to search for sources or industries that can achieve acceptable alternatives to natural wood. The materials in this article are related to industrial timber manufacturing of greenhouse wood waste, low density polyethylene and non-standard joinery waste. Moreover, panel samples made from the above materials were briefly subjected to tests as well as tested by fresh and salt water absorption.The density calculation results for all samples have shown the possibility of obtaining a wide range of wooden planks from the lightest to the heaviest ones, depending on the type of filler used. Additionally, the conducted research has shown the possibility of producing artificial wood panels made from the studied materials with good quality and fully satisfactory physical and mechanical properties.

Abstract: Every day, the need for composite materials grows. The physical and chemical characteristics of the constituent materials inside the hybrid composite impact the final structure. The rate at which these individual properties are sustained varies, but it has an impact on the final properties of hybrid composites. Sporting goods and lightweight orthopaedic components are made from hybrid composites. Glass fibre epoxy and sawdust are utilised to construct hybrid composites in this study, using glass fibre to epoxy resin ratios of (60:40, 60:39, 60:38, 60:37).The current research involves the creation of hybrid composites and their study for flexural and tensile strength under various load conditions. Applying resin and hardener, as well as inserting reinforcement, is repeated in the hand-layup manufacturing process to improve characteristics and create a laminate form. They improve fatigue and fracture resistance while providing dimensional stability and weight savings.

Abstract: The purpose of the present research was to assess the effect of three different fresh detox juices on the color stability of the resin composite with three different adhesive systems. Disc-shaped resin composite specimens were prepared. Composite discs were randomly divided into 3 subgroups according to the adhesive system (Adper EasyOne, BondForce, Clearfil QuickBond), adhesive system was applied to the upper surfaces of the composite discs according to the manufacturer`s instructions. The first color measurements were made with a spectrophotometer after the composite discs were kept in water for 24 hours. Samples in each group were divided into 4 subgroups according to the immersion solution (n=10; brands, water). The samples, which were kept in respective detox juices, were kept for 10 minutes twice a day, at other times they were kept in distilled water. Second color measurements were performed 30 days later. Data were analyzed with two-way ANOVA and Tukey HSD tests. According to the two-way analysis of variance, the adhesive system does not affect the color change significantly (p=0.773), but the detox juices has a significant effect on the color change (p=0.01). Fresh detox juices may adversely affect the color stability of adhesive systems, regardless of their color, but this effect may not be expected to be clinically observable.

Abstract: Research on crack propagation for fiber reinforced composites containing flame retardant is rare. The micro-cracks propagation is a reason for delamination and debonding failure of fiber reinforced composites. To study the crack propagation of continuous glass fiber reinforced epoxy resin laminates that contained ammonium polyphosphate flame retardant (GFRP-APP), the quasi-static single-edge tensile loading (SETL) experiments for the end-notched GFRP-APP specimens were carried out by MTS universal electronic testing machine. The crack propagation of the end-notched 90° GFRP-APP specimen includes two types, both of which belong to opening type (mode I). Namely, one type is mode I multi-cracks propagation without preexisting crack, and the other is mode I fiber bridge propagation with preexisting crack. The intralaminar fracture toughness along fiber direction of GFRP-APP is approximately 8.4 N/mm, which is calculated by area method. The opening displacement-tensile force curves can be divided into three stages for 90° GFRP-APP specimen without crack, i.e., crack gestation, crack birth and crack propagation. However, the 90° GFRP-APP specimen with crack not contains the crack birth stage. Additionally, the microscopic morphology for the fracture face of pure epoxy resin and GFRP-APP, and the phase analysis for GFRP-APP were performed by scanning electron microscope (SEM), X-ray diffraction (XRD) and energy dispersive spectrometer (EDS). As a conclusion, the pores and interfaces in materials were the guiding factors of micro-crack propagation, and the ammonium polyphosphate flame retardant particle contributed extra interfaces.

Abstract: At the moment, the tendency in the composites field, is to use natural resins and fibers to obtain „environmental friendly” materials, that are compostable and biodegradable. In this paper there is an experimental study of the depletion capacity of the vibration from the composite beams, using the hardener made of cotton, flax, hemp, silk textile and the three types of the Dammar hybrid resin matrix. The damping factor and the eigenfrequency of the vibrations was determined experimentally for these bars. Based on the acquired results, the dynamic elasticity modulus and the loss factor were calculated, for each composite material studied.

Abstract: Highlighting the properties of polymer composites is a complex process given their great diversity and the wide range in which their characteristics could vary. An Artificial Neural Network model for predicting tensile strength was designed using LabVIEW software. The proposed model was developed for randomly reinforced polymeric composite materials with 30%, 40% and 50% fiber-glass. Volume fraction of glass fibre has represented the independent variable for this study. The dependence of the tensile strength on the volume fraction was investigated and highlighted by modelling using neural networks. The designed Artificial Neural Network behaves as a computational system that process data input into a desired output using a network of functions composed of layers. The training process was developed with different Artificial Neural Network architectures with two hidden layers to produce the best prediction results. For each hidden layer the number of neurons was varied be-tween 3 to 50.

Abstract: The present paper analyses the possibility of using the digital image correlation technique to study the mechanical behavior of small scale components. A microscope is supplemented to the equipment for magnification, together with a miniature tensile testing machine. Several samples with already studied stress concentrators were analyzed. For comparison purposes, a finite element model of the geometry, with appropriate loading conditions, is created and the strain field is compared, in orderv to be validated to the experimental one. Results show that an accurate reading can be made by using this technique. Furthermore, crack initiation and its propagation path can be determined, by the appearance of high strains in the region.

Abstract: The search for green composite for sound-absorbing material has increased a significant interest. In this study, polystyrene (PS) composite foam filled with primary sludge and boiler ash from pulp mill was produced. The product was characterized using analytical techniques such as FTIR, XRD, SEM, TGA, and DSC, while the mechanical properties and sound-absorbing coefficient were analyzed regarding ASTM D 2240 and ASTM E-1050-98, respectively. The results showed that the sludge has 1β crystalline polymorph cellulose from the pulp. The chemical reaction can be seen by the chemical bond formed during the mixing process. The peak expansion occurred at 1600.44 cm-1 indicating the presence of a C=C functional group of maleic anhydride with polymer and filler. SEM images showed that the filler was distributed and dispersed into the polymer matrix and no agglomeration was produced. The sound-absorbing composites had complied ISO 11654:1997 regarding the sound absorption coefficient rating level on materials for rooms with sound absorption classes D and C with the value of α 0.328-0.793.

Abstract: This study was geared to analyze the preparation methods of pullulan acetate-based nanoparticles loaded with 5-fluorouracil, as well as the potential of pullulan as a biopolymer matrix for obtaining nanoparticles applied in the delivery of anticancer drugs (5-FU). Various methods were used to produce pullulan acetate-based nanoparticles loaded with 5-FU, including nanoprecipitation, modified nanoprecipitation, and double emulsion. Pullulan was previously chemically modified with acetic anhydride, dimethylformamide and pyridine, and yielded pullulan acetate. Pullulan was made using the Aureobasidium pullulans strain through a fermentation procedure. UV-Vis Spectro-photometric and dynamic light scattering (DLS) methods were used to assess entrapment effectiveness, size, and polydispersity index (PDI) of pullulan acetate-based nanoparticles loaded with 5-FU. Based on the properties of the nanoparticles obtained, the optimum preparation method was chosen. The maximum entrapment efficiency was found in pullulan acetate nanoparticles loaded with 5-FU generated by a double emulsion method. The mean hydrodynamic size and PDI of all nanoparticles were adequate. The best formulation showed faster 5-FU release profile in acid phosphate-buffered saline (pH 5) than in phosphate-buffered saline pH 7.4. According to the findings, pullulan derivatives have a great potential for producing nanoparticles that might be used to deliver anticancer medicines.

Abstract: Intended to draw a frame of the impact of plastics usage and the role of the circular economy, this paper relied on specific literature, data from different studies, case studies, reports and databases existing on the research area. Being produced at low costs and used in a wide range of fields, plastics has been confirmed as one of the most impactful inventions for human. Recently, during the pandemic years, plastics has gotten multiple usages, such as keeping a hygienic sanitary environment facing the critical situations, with a highly increased role in the fight against the SARS-COVID-19 crisis. It is also well known that plastics presents risks arising from its production flow, linked to a huge degree of massive pollution with high impact on the environment. Plastic waste exposed to the environment generated problems and it is of huge concern for all forms of life. As plastics products are present all around the world, there is an increasing statement to one-use plastics in the environment. Thus, it is urge to take actions for managing this situation as appropriate, to protect the environment and reduce the consumption of plastics, which can be achieved by developing and sustain the circular economy, as a new research field to explore. Through this paper we intended to emphasize the importance that, both theoretical contribution and practical measures, have on the production, the use and recycling of plastics and on the circular economy.

Abstract: The recycling and high-valued added reuse of automotive plastics have elicited global attention as the number of end-of-life vehicles increase. In the paper, the two-stage high-voltage electrostatic separation is used to explore the sorting of passenger vehicle plastic mixtures of PP, ABS and PVC. The purities of PP, ABS and PVC are all higher than 97%, and the recovery rates are 55%, 93%, and 48%, respectively. Taking PP plastic as an example, the mechanical properties of the recycled materials and the different ratios of recycled and new material mixtures are studied. Results show that the passenger car bumpers reproduced with a 7:3 ratio of new and recycled materials can satisfy the performance requirements. The finding provides a reference for the high additional value reuse of other automotive plastics.

Abstract: Purpose was to determine the viscoelastic properties of three root canal sealers as a function of temperature, time and frequency using dynamic oscillatory measurements. Methods: Measurements were performed on the dynamic oscillatory rheometer set to temperatures: 25°C, 35°C, 40°C and 65°C. Stress sweep and frequency sweep tests were used in order to determine storage moduli G’, loss moduli G’’ and complex viscosity η*. Results Higher values of storage compared to loss moduli indicate the more pronounced solid-like behavior of tested materials. EndoREZ showed the highest values of G’ and G’’ moduli at all temperatures. With temperature increase the G’ and G’’ moduli of Sealapex and EndoREZ increased while the moduli of AH Plus decreased. With frequency increase all materials showed viscosity decrease exhibiting non-Newtonion, shear-thinning behavior. With temperature increase AH Plus demonstrated viscosity decrease, while the viscosity of Sealapex and EndoREZ increased. Clinical significance: All tested materials were temperature, time and frequency dependent and this dependency varied between them. The obtained results may be used to predict the rheological behavior of root canal sealers in different temperature conditions, thus helping as to estimate optimal handling characteristics for specific clinical applications.

Abstract: Atherosclerosis can affect the blood vessels in any region of the body and the stenosis (narrowing) can be located on an artery that vascularize important organs, such as the brain, abdominal organs or limbs. The endovascular surgery is a modern approach to vascular pathology through minimally invasive techniques (puncture, minimally vascular approach) and it represents an enrichment of the arsenal of surgical techniques and brings considerable improvements in post-operative and long-term outcomes The use of polymer drug-coating balloons is an attractive alternative because they can offer the promise of an improved patency compared to the simple balloons and a reduction in the need for stents. The aims of this study were to describe the polymer materials and to compare the medical endpoints obtained in angiosome-targeted infrapopliteal angioplasty using a simple balloon with two layers, based on polyethylene, and respectively a drug-coated balloon that contains a multiblock copolymer from polyethylene, poly(cylohexylethylene), polyisoprene and poly(1,3-butadiene) covered by Paclitaxel. The balloons were characterized by differential scanning calorimetry, stress-strain and puncture tests in order to describe their physical and mechanical characteristics. On the other hand, 51 patients with critical limb ischemia were treated with different balloon angioplasty and they were monitored for 12 months after the intervention; the following parameters have been evaluated: diabetes, hypertension, renal insufficiency, hemodialysis, stroke, dyslipidemia, heart disease, heart failure, body mass index, number of angiosomes, creatinine, and wound healing, leg salvage and amputation-free survival at 1, 2, 3, 6, 9, 12 months. Significant associations were found in the case of anterior-tibial-artery and posterior-tibial-artery angioplasy and the age, hypertension and renal insufficiency. On the other hand, the results indicate that the drug deposition on the surface of the balloons lead to improved values for the observed medical endpoints. In conclusion, this study reveals that angiosome-based infrapopliteal angioplasty with drug-coated balloons can be associated with better wound healing and leg salvage.

Abstract: The goal of this research is to show that epoxy resin (ER) / coir fiber mats (CFM) hybrid composite laminates with nano-silica particle (NP) reinforcement improve mechanical characteristics and water absorption. Lately, it has been employed in automotive, aerospace, and structural industries where coir fiber-reinforced polymers are safe for ecologically friendly composite applications. The Compression - Hand layup technique is used to make the epoxy composites reinforced with natural coir fibres and nano-silica particles in various weight fractions (5, 10, 15, 20 and 25% by weight). Mechanical parameters such as tensile, flexural, compressive, impact strength, thermal conductivity and also water absorption of composites are evaluated in this study. Scanning electron microscopy is also used to analyze the surface morphology of cracked surfaces (SEM). Hybrid nanosilica-coir fiber mat reinforced epoxy resin has decreased water absorption (percent) suggesting better mechanical qualities. Furthermore, the hybrid epoxy-containing 20% nano-silica coir mat improves all the said mechanical properties.

Abstract: The study aims to investigate the influence of TiO2 nanoparticles on the permeation and retention properties of polymeric membranes used in wastewater nanofiltration systems from the medical sector. The research is focused on the influence of the TiO2 nanoparticles concentration on the membrane properties. Additives in general determine enhanced membrane properties like permeation and retention capacity. Hydrophobicityhowever, is decreasing due to the nanoparticles affinity for water and this have an important effect on the permeation properties, at the same time with the decrease in surface roughness, with an important influence on the fouling effect. Membranes with four different concentrations of TiO2 nanoparticles were studied, from 0 to 2% nanoparticles. Results showed that small percent of nanoparticles have an important impact on the permeation properties of the membranes, finding that at 2% nanoparticles the permeation decreases due to the nanoparticles aggregations which are blocking the pores.