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The present paper was focused on studying the influence of shelf life of an epoxy matrix on the mechanical properties of glass fibre reinforced composites. For the study, two types of the same epoxy system were used, one during its shelf life and one out of its shelf life. The reinforcement used consisted in E-glass fibre fabric. Mechanical investigations were realized in order to compare the materials in terms of loss of mechanical strength and elastic properties. Therefore, three mechanical tests were performed: tensile tests, in-plane shear and open-hole tensile tests. The results showed that the shelf life affects the mechanical properties of the polymeric composite. A decrease of 24% in tensile strength was recorded along with a 28% decrease of the in-plane shear strength and 55% of open-hole tensile strength for the composite manufactured with the out of shelf life epoxy system compared with the other composite. An overall reduction of mechanical strength and elastic properties of the composite material was observed, primarily due to polymeric matrix degradation, which after long periods it could be prone to brittleness and susceptible to delamination and fracture. The thermogravimetric analysis showed that thermal induced changes are happening at a higher speed in the out of shelf life composite, a lower mass loss being registered for new epoxy composite.

In order to improve thermal behavior and dimensional strability of polylactic acid (PLA) designed both for 3D and 4D printing technology-fused deposition modeling (FDM) using a scalable procedure, the polymer was melt compounded with additives which control the morphology by crystallization and/or reinforcing. Using the formulations which provide polylactic acid (PLA) improved thermo-mechanical properties and desired dimensional stability, the new materials were shaped, on a laboratory line, as filaments for printing technology. The selected compounds were than scaled up on a 50 kg/h compounding line into granules which prove to have good shapability as filaments for printing technology (1.85 +/- 0.05 mm diameter, required ovality, good appearance and smooth surface) and performed properly at 3D printing. The obtained results proved that functional properties of PLA can be improved by various methods so that, depending on the reached performances, the new material can be converted through printing technology into items for performance applications. The novelty of the article is related to the fact that it identifies a modifying solution for controlling the morphology of a type of PLA designed for 3D printing that already has an advanced crystallinity.

Wastewater containing Cu (II) ions has become a huge environmental problem worldwide because ingestion of copper ions affects the human body leading to epigastric pain, nausea, vomiting, diarrhea and even death. The researches for new methods of treatment of wastewater polluted with heavy metals more efficient than the conventional ones led us to study Fe3O4 and his corresponding hybrid Fe3O4 –PVP as potential adsorbent nanomaterials for the removal of copper ions from industrial wastewater. First, the two nanomaterials were synthesized by precipitation method and characterized by XRD, FTIR and TEM analyses. Then, the two obtained nanomaterials were tested within the process of copper ions removal from wastewater and factors influencing the process including pH and contact time were investigated. The maximum wastewater treatment capacity reached up to 97 % under the optimal condition using Fe3O4 and 70% for Fe3O4 –PVP.

Graphene is a microstructure of graphite that has enormous properties and is also one of the carbon allotropes. There are several metals with low strength. The properties of these metals can be increased by coating the graphene. The primary goal of the work is to create composite graphene that exhibits the optimised properties and characteristics that meet the requirements of the industries. The properties of graphene when coated with other metals are studied and their applications in different industrial fields are analysed through several tests and experiments. Research-based on graphene coatings and composites is studied and the properties are adapted.

Recently, 3D-printed polymeric materials have been successfully replacing the usual ones especially used in sliding systems like couplings. Among the polymeric materials, Acrylonitrile Butadiene Styrene (ABS) and Poly Lactic Acid (PLA) can be the competitive materials in such application after 3D-printing. In this study, 3D printing was used to produce samples from ABS and PLA via fused deposition modelling (FDM) technology. Then friction behavior of 3D-printed samples was investigated depending on printing orientation of the samples. Ultra High Molecular Polyethylene Weight (UHMWPE), as a well-known industrial polymer, was also used for comparing the friction behavior of 3D-printed ABS and PLA polymers. Friction tests were conducted using a pin-on-plate type tribometer according to ASTM G133 under different applied loads and sliding speeds at room temperature. It was found that printing orientation of all ABS and PLA samples has a considerable effect on their friction behavior. Transverse direction (T.D) of the 3D-printed samples shows higher coefficient of friction (COF) values than the longitudinal direction under all applied loads and sliding speeds. On the other hand, COF values obtained in both 3D-printed samples increase as the load and speed increase regardless of the printing direction. When both 3D-printed materials are compared, PLA samples exhibit lower COF values than ABS samples in both printing directions and under all loads and speeds. However, the UHMWPE sample produced with traditional method shows much lower COF values and stable change in friction behavior under all conditions compared to 3D-printed PLA and ABS samples.

Due to the continuous decrease in the level of oil resource, nowadays researchers from all fields are concerned with the creation of new bio plastics with special properties. The present work presents a series of such properties, which become achievable when reinforcing organic fibre materials obtained by reactive extrusion of thermoplastic Polyurethan (TPU) with Polylactid-Acid (PLA) in a twin-screw extruder and covalently linked into PLA-TPU-Blends, through the innovative `one-step process` technology, using the IMC Krauss Maffei injection moulding compounder, at the IKT University of Stuttgart. The elongation at break of PLA-TPU-Blends and the impact strength could be increased without significant reduction of strength and stiffness. A balanced relation between improved impact strength and reduced stiffness can be achieved by varying of the blend components. By using the partially biobased Polyurethane and natural fibres, a biobased content of more than 90% could be achieved. More and more advanced technologies allow the manufacture of components with reinforcements made of glass fibres, natural or carbon fibres obtained from polypropylene or Lignin. Due to their low specific weight compared to glass, carbon fibres are preferred for lightweight structures in the automotive or aeronautics industries. Green Carbon fibres, made in innovative ways from acrylonitrile resulting in the production of Bio-Diesel from algae, can successfully replace the conventional carbon fibres of Polypropylene, having identical properties. Fibre reinforcement aims to improve mechanical strength and impact resistance and increases the dimensional stability under heat of the composite. This feasibility study shows a method to realize fibre-reinforced materials using Green Carbon fibres with remarkable stability and rigidity similar or better than aluminum and steel for lightweight constructions.

In this work, the corrosion resistance of hybrid coatings obtained from plastic materials was evaluated and compared with the corrosion resistance of Zn coatings. Zinc and hybrid coatings were obtained by electrodeposition from zinc sulphate electrolyte. For obtained hybrid coatings it was used as disperse phase two type of plastic materials: phenol-formaldehyde resin and epoxy resin. Polarization was used to measure the corrosion rate and behaviour of zinc and hybrid coatings in 3.5% NaCl solution. Tafel curves show that the including particles of plastic materials in zinc matrix disturbs the cathodic reactions and reduces anodic reaction leading to decrease of corrosion current and increase the corrosion resistance of hybrid coatings obtained at the same electrodeposition parameters as zinc coatings. Smallest values of corrosion rate were evaluated for hybrid coatings obtained with phenol-formaldehyde resin as disperse phase that indicates a good corrosion resistance in 3.5% NaCl solution.

The current study was proposed in order to obtain, to characterize by usually physico-chemical methods and to assess in vitro, the potential cytotoxic effect of polyurethane microstructures loaded with epigallocatechin gallate (PU_MS) on human pharyngeal carcinoma cells (Detroit 562) and squamous cell carcinoma (SCC-4). The results showed that polyurethane microstructures obtained are stable and have dimensions that make them biocompatible with the biological environment. The cytotoxicity of test samples is dependent on concentration and 72 hours after stimulation at the highest concentration tested the viability of tumor cells was below 50%, the decrease being much more pronounced in the case of squamous cell carcinoma. The novel nanostructures loaded with epigallocatechin gallate induced an augmented cytotoxic effect, suggesting that this drug carriers are suitable to enhance the antitumor effect of epigallocatechin gallate.

The main aim of the present in-vitro study is to assess the effect of daily consumable drinks on the aesthetics of the dental composite resin materials. Sixty-four microhybrid and nanohybrid direct composite resin (3M™ Filtek™ Z350 XT Universal Restorative, Filtek™ Bulk Fill Flowable Restorative, USA) block samples were made with a dimension of 15mm X 2mm and are allocated into four groups. Each sample was immersed in test media such as Arabic coffee, black tea, orange-juice and distilled water as control group at room temperature for 15 days (n = 16). The color stability and microhardness measurements were taken at pre-immersion and after two weeks of immersion in test media. These parameters were assessed by electro spectrophotometerusing the CIE (Commission Internationale de l´Eclairage) system and Vickers microhardness indenter respectively. Each group was immersed in its test media for the complete duration of the study. On completion of 15 days, the samples were blot dried out with absorbent paper and microhardness dimensions and color stability measures were performed. The collected data was subjected to statistical analysis to formulate the results. Significant discoloration was observed with the Arabic coffee, black tea and orange-juice compared with control group. The Arabic coffee caused most significant discoloration followed by black tea and orange-juice. Although the highest values of microhardness was noted in the Arabic coffee followed by black tea and orange juice, whereas the lowest values were noted in the control. The color stability and microhardness of the composite resin restorations is affected by the everyday drinks that are consumed, from some more than others. Some of the everyday drinks affect the color stability and microhardness of the composite resin restorations more than the others.

The paper presents a theoretical study for the cooling of polymer samples in an injection molding process. The study is applied for neat polylactic acid (PLA), PlA-talc and PLA-starch composite samples representing specimens for mechanical tests reported in literature. A one dimensional model was developed for the heat transport through the thickness of the sample from the polymer to the cooling agent: air in natural convection and water flowing through cooling channels. The heat of solidification of molten polymer was also considered. The model was solved in the frame of Matlab software. The results obtained consist in the evaluation of the final time required to reaches a temperature of about 60°C in the core of the specimen and the evaluation of the temperature profile along the cooling process. When using cooling air in natural convection the temperature profile shows insignificant space variation, but the duration of cooling is about 6 min. The use of cooling water proved to be more efficient in terms of cooling time is about 15-25s, while the temperature gradient in the thickness of the specimen is quite significant at any moment of time.