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This work is devoted to the preparation and characterization of some polystyrene/multiwall carbon nanotubes (PS/MCNT) systems. The dispersion of the reinforcement agent within the PS medium was done via sonication and the resulting nanocomposites containing 0-40 wt% MCNTs were achieved by solution blending procedure. Shear flow and viscoelastic properties were tested by means of rheology, revealing some changes in the sample microstructure. Dispersion curves of the matrix and low filled nanocomposite were registered at variable temperatures. The theoretical refractive index and corresponding dielectric constant at optical frequencies were analyzed as a function of the system composition. Heat transport in the reinforced materials was examined by computer modeling, which enabled calculation of thermal conductivity. Electrical transport features were assessed using a theoretical approach relying on the physical properties of each phase. The surface adhesion of the samples with various materials was determined to check the suitability for applications in technical or bio-related fields.

In the presented study, the load induced long-term behavior of a biocomposite material is analyzed. The studied material is a unidirectional flax fiber reinforced epoxy resin, material, whose quasi-static mechanical properties can compare with those of glass fiber composites. Samples with a fiber direction of 0° were subjected to two types of multi-level creep-recovery tests, one with a varying creep duration, and the other with a varying creep stress, with the purpose of discriminating the viscoplastic and viscoelastic behavior of the composite. Results show a significant viscous response in time, dependent on both creep duration and creep stress, up to 20% of the elastic one. Sample damage is absent, leading to the conclusion that the viscoplastic response is caused by the permanent reorganization of the fiber’s internal structure.

This aim of this paper is to perform a study on the way the material of the fittings that can be welded through eletrofusion on polyethylene pipes withstands. The process is observed by means of the thermal and fast cameras. Also we intend to analyze the way the assembly consisting of the polyethylene fitting and pipe behaves during welding. The stresses caused by the welding process are observed, as well as the concurrent welding of the tapping tee and the branch saddle tee.

Heat cured polymethylmethacrylate (PMMA) has been used as denture bases since 1937. PMMA is a vinyl polymer, made by free radical vinyl polymerization from the monomer methyl methacrylate [1]. After the success of using as prosthetic material in the mouth, PMMA began to be used in other areas, for example in facial prosthetics, for facial epitheses. The facial epitheses are exposed permanently to ambiental changes (temperature, air currents, humidity). Secondary, for a better esthetic effect, in facial epitheses PMMA often contain variables quantities of natural fibers (cotton, wool). Our study has analyzed how a PMMA facial epithesis reacts to temperature changes during heat exposure in the summer, especially depending on the amount of fiber it contains, considering that the biological interface between the prosthesis and facial tissues is sensitive to heat [2].

Nowadays, the investigation of both classic and new materials for blast mitigation applications is a subject intensively approached in the scientific literature. Due to their mechanical behavior, the polyurethane foams are materials with high potential for this type of applications. Within the current paper a EUROPLASTIC® polyurethane foam grade mixed with fly ash ceramic micro powder was experimentally investigated. Using a single stage gas gun, the dynamic response of polyurethane/fly ash ceramic foam was thoroughly evaluated in terms of specific stress vs volumetric strain curves response and dissipated kinetic energy, also.

The paper presents the structural and dimensional differences of rectangular shape samples manufactured by selective laser sintering (SLS) according to three process sinterization energies. In this study we determine the geometrical and structural characteristics of biocompatible PA2200 polyamide manufactured at a low energy density E1, and intermediate value E2 and a high energy density E3. Relaying on these results, four custom-made medical parts have been built using biocompatible polyamide PA2200 powder, in order to evaluate their performances.

Cranioplasty is a surgical procedure that is used to correct any defect in skull bones after a previous decompresive craniectomy, usually made for traumatic brain injuries, with ischemic or hemorragic nature, or after a tumor removal. A composite for modeling on a defect in skull bones was prepared by crosslinking poly(methyl methacrylate) in the presence of barium sulfate. The crosslinking rate of methyl polymethacrylate in the presence of the benzoyl peroxide initiator, the N, N-dimethyl-β-toluidine polymerization accelerator and the hydroquinone polymerization inhibitor allows modeling according to the location and size of the defect. Thus, the concentration of composite precursor components was optimal for this purpose. The TGA diagram shows the almost total consumption of methyl methacrylate and butyl methacrylate monomers in the crosslinking process of methyl polymethacrylate with the formation of the composite. This technical study demonstrate the efficacy of this treatment, as well as to show all the possible scenarios in such procedures.

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.