Browse Articles

The expresion of the twin screw extruder flow rate was established in correlation with the filling degree and pressure variation along the screw. Starting from the twin screw extruder flow rate expression, the pressure evolution and the maximum pressure in the melting area have been calculated. Keywords: twin-screw extruder, flow rate, crew

This paper contains the results of an experimental research regarding the synthesis of some types of thermoplastic polyurethane based on 1,6-hexanedyol polyadipate (PAH), 1,4-buthanedyol and ethyleneglycol polyadipate (PABE) and ethyleneglycol polyadipate (PAE) and pure 4,4’-diphenyl-methane-diisocyanate (pure MDI). The thermoplastic polyurethanes were physically and mechanically characterized by observing the characteristics variation mode after the synthesis and also after their processing by dissolution and squeeze for the obtaining of marks with preordained properties. Keywords: polyester, di-isocianate, thermoplastic polyuretane, physical-mechanical properties

Based on the evaluation of the position occupied by silicones in biomaterials field in general, and in hydrolytically degradable materials in particular, some original results obtained in this direction are presented. Keywords: biomaterials, silicone, siloxane-organic copolymers, hydrolytic degradability

Atom transfer radical polymerization (ATRP) is one of the most versatile controlled/living radical polymerization (CLRP) method for the production of well-defined materials. As a consequence, ATRP has been employed for the synthesis of a large variety of materials, e. g. end-functional oligomers (telechelics, macromonomers), copolymers (statistical, gradient, block, graft, brush, star), hyperbrached polymers, organic - inorganic hybrids (organic - inorganic block and graft copolymers, polymer - layered silicate nanocomposites and polymer - grafted nanoparticles and flat surfaces), etc. The present paper briefly reviews these ATRP applications, in completion to the previous article dealing with ATRP fundamentals [1]. Keywords: atom transfer radical polymerization, block copolymers, graft copolymers, end-functional oligomers, organic-inorganic hybrids

The expresion of the twin-scren extruder flow rate was established in correlation with the filling degree and pressure variation along the screw. The authors used the hypothesis of the single-screw extruder flow analysis and the relation of the single-screw extruder flow rate. This relation has been corrected by correcting the hypothesis used in the single-screw extruder flow rate relation. Starting from the twin-screw extruder flow rate expression, the pressure evolution and the maximum pressure in the melting area have been calculated. Keywords: twin-scren extruder, flow rate, screw

This paper presents some background aspects of the applications of polymers in the area of the screening of stationary, quasistationary and nonstationary electric and magnetic fields on the Black Sea coast. Some solutions for the electromagnetic depollution involving polymers are proposed. Keywords: polymer, electromagnetic pollution, electromagnetic field polymeric materials, dielectric polymers

Mathematical modeling of resin flow into the cavity of the mold is a very complex problem due to the porous medium realized by reinforced material. The paper is presented the start evolution and the velocity of the flow for the polyester resin thermosetting in the molding process of the composite plate through „Resin Transfer Molding” (R.T.M.) procedure. Considering an elementary volume dV, the following were determined: friction forces in porous medium, elementary mechanical work dL, and power P in injection process. At the end, the equation of the fluid flow rate u(x,y,z) was established and graphical represented using MATHCAD program. Resin flow modeling and simulation allows the optimum choice of the injection point in the case of complex parts. The validation of a theoretical model was established by the experimental tests. Keywords: resin, composite, friction, flow, fluid

The secondary rheodynamic quantities in case of strain(e)-controlled relaxation processes, including the storage, loss, and absolute compliances as well as the corresponding loss factor, are considered from the standpoint of frequency dependence. The exact relationships providing different e - characteristic frequencies related to maximum and inflection points are obtained for the (1,1) standard linear viscoelastic model, the results being illustrated in natural, semi-logarithmic, logarithmic and double-logarithmic coordinate representations. Keywords: exact relationships, rheodynamic relaxation, linear viscoelasticity, polymer systems

The paper presented aspects relats to the thermoforming simulation with T-SIM and the crash simulation with LS-DYNA, of a polymeric energy absorber called SafetyPlastic®. SafetyPlastic® is an energy absorbing technology that offers a performance, cost, and mass competitive energy management solution. It is characterized by a connected plurality of structural recesses of various shape that repeatedly give resistance, and then buckle when impacted. By considering the strain rate dependence of the polymer, a good correlation of the associated finite element analysis with the experiment was obtained enabling the model to be used in automotive industry for the simulation in both head and side impact, FMVSS 201u and FMVSS 214 respectively, tests. Keywords: polymeric energy absorber, finite element model, buckling, strain rate sensitive

Polyurethane elastomers (PEs) based on polyether diols and polyester diols can be used as passive isolation bearings in building applications. In the present study polyetherdiol, polyesterdiol, aromatic diisocyanate have been used in polyurethanes, using glycerine, ethylene glycol as chain extenders. The optimization of the synthesis of polyurethanes was studied based upon a design matrix with 9 experiments and a forward stepwise regression procedure was employed to achieve a statistically significant regression equation. These empirical equations were used to construct contour plots, facilitating comparisons of synergistic/antagonistic effects among the mixed polymers. The contour plots show that the maximum of the force and elongation at break appears at a maximum of the polyester in the reaction compound. The interaction between the experimental evaluation of algorithm behavior and the theoretical analysis of algorithm performance plays an important role in our research. The satisfactory performance of polyurethanes indicates the feasibility of applying the results found in this study for the fabrication of polyurethanes. Keywords: polyurethane elastomers; optimization; mechanical properties; passive isolation