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In this article we obtained the characteristic curves for polyester and epoxy resins used in the process of making composites, and determined their elastic and resistance properties as well as the characteristic curves on two directions for the epoxy and polyester resin composites, reinforced with woven polypropylene. We established the flow strain and two coefficients from the calculus relation for the plastic potential. We determined the equation of nonlinear dependency between strain and deformation in the plastic field using a fourth degree polynomial relation which indicates the specific elongation and resistance to fracture. Keywords: composite materials, polypropylene fabric, plastic field

The polymers with special properties represent the starting point in order to obtain a wide range of new materials used in various fields of activity. Poly (methyl methacrylate) (PMMA), a transparent thermoplastic material, is an attractive polymer because of it’s unique properties, in comparison with other polymers, such as: high mechanical strength, special optic properties, and durability. The incorporation of silicate layers (for example, clay, minerals) in the polymer microstructure in order to improve the mechanical, thermal and interface properties has become one of the interesting of the researchers nowadays. Thus, depending on the working conditions and the interactions between the clay layers and the polymer system, a series of composites with different morphology, for instance, agglomerated, intercalated and exfoliated, has become accessible. In order to promote solutions for improving PMMA properties and to have a better general view on the action of oxide nanoparticles, we chose to analyze the structure and mechanical properties of some methacrylic composites with TiO2, Al2O3, and PMMA fillers. Keywords: nanocomposites, mechanical properties, poly(methyl methacrylate), SEM

The paper presents a modern method to optimize welding procedures for PE 100 polyethylene pipelines using computer-assisted design of experiments. The design of experiments method RSD (Response Surface Design) was applied for optimizing the heated tool butt-welding of PE 100 type polyethylene pipes meant for pressure pipelines. Experimental researches made on 110mm diameter pipes had in view the mathematical modelling of the welding process, so that, on the basis of a number of 32 welding technological versions made, the optimum welding procedure was established, a procedure that met all the imposed conditions. Keywords: Optimizing, heated tool welding, polyethylene PE 100

Flow through tubular runners presented is a very important flow type encountered in polymer processing, especially during injection mold filling. The filling pattern developed during the mold filling plays a decisive role on the final part quality, thus, in this paper we have investigated the filling pattern and the volumetric flow rate during the filling of a tubular runner for three different materials. The melt is treated as an incompressible, non-Newtonian the Ostwald-de Waele model with a power-law relationship between the shear stress and the shear rate. Keywords: runner, injection molding, flow front, polymer melt

The paper aims to present a theoretical-experimental approach of a particular class of composite materials known as multiphase composites in order to retrieve its effective dynamic moduli and identify the major influencing factors on these variations. Supplementary, will be presented a two step homogenization concept based on the well known theoretical predictions from the micromechanics of composite materials approaches, the Mori-Tanaka that applies to the particle reinforced composites and Halpin-Tsai that applies to the random fibre composites. The theoretical values were compared with the experimental data, the later being retrieved during a two heating cycles with temperature ranging from -300C to 1600/2000C, in air, at a frequency of 1 Hz, using a DMA 242 C device, from Netzsch, Germany. The samples were manufactured using a self-developed technology. The samples were ceramics (Al2O3) and metal (Fe) reinforced particles embedded in small volume fraction along with random E-glass fibres (65%) into a polymeric matrix material. Keywords: composites, multiphase, polymer, dynamic modulus, testing

The replacement of glass fibers polymer composites with those containing polymers and cellulose fibers, friendly for environment and human health has gained a special importance in recent years. The paper presents some mechanical and thermal characteristics of composites of neat polypropylene and jute fibers from technological wastes, treated and untreated. The use of waste fibers in polypropylene led to a significant increase of the elastic modulus and tensile strength which highlights the reinforcing effect of the waste fibers, the effect being more important in case of jute fibers treated with aminosilane. Keywords: polypropylene, composites, jute, mechanical properties

Nanoxide based composites are suitable materials for advanced medical application. Fe3O4, CoFe2O4 and MnO2 nanoparticles, synthesized by different soft chemistry routes (precipitation in the presence of soft template and solution combustion) were coated by a biocompatible polymer, sodium alginate. The oxides and corresponding composites were structural and morphological characterized. The saturation magnetization for Fe3O4-based composite is 10.1 emu·g-1, resulting magnetic domains of 5.2 nm that suggests a superparamagnetic property. Radical scavenging capability of the composites was investigated by two different methods, Trolox Equivalent Antioxidant Capacity (TEAC) and peroxide-chronoamperometry. Keywords: ferrites, MnO2 , oxide-based composites, biopolymer matrix, radical scavenger

Thin films, in the range of tens of micrometers thickness, have been prepared by casting onto glass plates the N-methyl-2-pyrrolidone solutions of two poly(ether imide)s containing isopropylidene or hexafluoroisopropylidene groups. The polymers have been synthesized by solution polycondensation reaction of 4,4’-(1,3-phenylenedioxy)dianiline, with 2,2-bis[(3,4-dicarboxyphenoxy)phenyl]propane dianhydride or 1,1,1,3,3,3-hexafluoro-2,2-bis[(3,4-dicarboxyphenoxy)phenyl]propane dianhydride. The dynamic mechanical analysis and dielectric spectroscopy were employed to study thermal and electrical behaviour of polymer films. Keywords: poly(ether-imide)s, thin films, dynamic mechanical analysis, dielectric spectroscopy

The paper focuses on rheokinetic investigations on matrix of a new composite material. A simple, yet effective, experimental method has been employed to measure several parameters that can help, by resin’ viscosity measurements, in finding resin kinetic hardening parameters. As it is shown by one of our papers [1.3,4] CFRAl (Carbon Fibers Reinforced Aluminum) is a new hybrid composite under development . It has unique and promising properties, with foreseeable excellent results in applications requiring a reliable, yet light, reinforcement material that can also withstand powerful thermal shocks. Keywords: rheokinetic model, composite material, carbon fibers, bullet-proof material

Polysulfone based membranes with controlled porosity pore density, size and orientation were synthesized. The predicted pore characteristics are obtained by adding magnetite (nano or micro) particles into the polysulfone gel and the pores obtained by applying different magnetic fields. The pore density, size and orientation can be designed based on the magnetite particle concentration, on the magnetite particles size and respectively based on the angle between membrane surface and magnetite field. The pore density, size and orientation of the membranes were analyzed by SEM. FTIR was used to investigate the membrane composition and to prove the possibility of removing the magnetite particles by acidic dissolution or by extended membrane exposure to the magnetic field. The complex thermal analysis was used to characterize the thermal behaviour of the synthesized membranes. Keywords: polysulfone membranes, pore characteristics, predicted porosity and separation ability, scanning electron microscopy