Volume 43, Issue 4

Abstract: Plasticulture is a system of growingcrops in a way so that a significant benefit is derived from using plastic polymers. We have obtained a threeyer polymeric foil with photoselective additives in order to modificate the microclimate. This foil was subjected to an experiment by covering high tunnels with tobacco culture. We have reported about optical and mechanical properties of this foil, before and after the experiment and the influence on tobacco culture. Keywords: plasticulture, polymeric foil, co-extraction, multilayer film, solar radiation

Abstract: The present work investigates the possibility to control the alcoholysis reaction in order to obtain various sorts of polyvinyl alcohol with a predetermined degree of alcoholysis and high block copolymer character. On this purpose, two methods are suggested: quantitative determination of methyl acetate (resulted as a by product of the alcoholysis reaction) existing at a certain time in the system, and termination of the alcoholysis reaction according to a predetermined calibration curve. Keywords: Polyvinyl alcohol, polyvinyl acetate

Abstract: The paper presents the international trends in the use of PEHD pipes considering losses in the distribution pipeline. It also presents elements imposed by the quality assurance conditions, from the PEHD welded pipes execution point of view, of welding technology homologation according to PT ISCIR CR 21-1999, of verification and certification of welders who make such welded joints according to EN 13067 Keywords: PEHD, distribution pipes, welded joints

Abstract: The high values of the penetration and of the ring and ball softening point of the distillation road bitumen are determined by the absence from its composition of the high molecular weight fraction, solved in this medium. The effect of the modification of the distillation bitumen with additives designed for decreasing the penetration, on all the bitumen properties is presented. The low density polyethylene determines a drastic diminishing of the distillation road bitumen penetration and an important increasing of its softening point. This polymer is very well dispersed in the bitumen matrix, where it is possible to be solved. Keywords: distillation bitumen, polymer modified bitumen

Abstract: Formaldehyde resins containing resin acid derivatives in their structure were synthesized. The insertion of resin acid derivatives into molecular chains was carried out to improve the cohesive strength of pressure sensitive adhesives. IR, 1H-NMR spectroscopy and other methods were used to characterize the monomers and polymers. The presence of the hydrophenanthrene moieties in the chemical structure of these polymers confer them, high solubility in common organic solvents, high adhesiveness, hydrophobicity and water resistance. The presence of formaldehyde resins with hydrophenanthrene moieties (up to 10 wt-% referred to the adhesive composition) into pressure sensitive formulation offer them high increase of cohesive strength without affecting the adhesive strength. Keywords: formaldehyde resins, hydrophenanthrene moieties

Abstract: The paper presents definitions of the main kind of mesogenic groups recognized by IUPAC. For a better understanding of the terms, for every type of mesogen, we attached a structure or picture. Keywords: liquid crystals, mesogenic group

Abstract: This work presents the study of the pyrolysis process of polysilane preceramic precursors. This study stated that the yield in ceramic material is influenced by the heating rate and depends on the chemical structure and polydipersity index of the polysilane. Therefore, the yield in ceramic material is improved when the polymeric precursor has a high content in thermal unstable groups, a narrow molecular weight distribution and a low content in linear and cyclic oligomers. Keywords: thermal behaviour; polysilane precursor; ceramic material

Abstract: In situ via anionic ring¡Vopening polymerization of epsilon¡Vcaprolactam in the presence of bronze microparticles was promoted as a route for the synthesis of nylon 6/bronze composites by rotational molding. The process was performed at 160 oC well below the melting temperature of the nylon 6 (Tm~225 oC) and initiated/activated with ethyl magnesium bromide/N,N¡¦¡Visophthaloyl¡Vbis¡Vepsilon¡Vcaprolactam system. The experimental data demonstrated that the physical and mechanical properties of polyamide 6/bronze composites depend on the filler concentration. Keywords: anionic polymerization; epsilon¡Vcaprolactam; polyamide 6/bronze composites, rotational molding

Abstract: Some organosilicone monomers with -CHO functional groups were synthesized by a condensation reaction between the methyl- or phenyl-chlorosilanes and an aromatic aldehyde. The products were characterized by IR and 1H-NMR spectroscopy, elemental analyses, melting points. Keywords: chlorosilanes, organosilane, aromatic aldehydes, functional groups

Abstract: The paper defines the notion of charge space whose study is very important for the improvement of the characteristics of the polymeric electroinsulated materials. The latest nondistructive methods used for the determination of ions improvement are described, insisting on the information obtained in polymers by using them. The interfacial phenomena in the mica-epoxide-novolac compound are studied, used as isolation for copper bars in alternative current generators, focussing on the variation of the electrical characteristics of the material with temperature and frequency. Keywords: charge space, electrical characteristics, temperature, frequency

Abstract: This paper presents some considerations about influences of the milling process on the quality of plastic materials in the process of recycling. There are presented the advantage and disadvantage of the use of the proposed milling system, economic and serial implications. Special part is destined on the technologies processes, granulometric analyze and equipment. Keywords: plastics recycling, raw materials, milling, granulometric analysis, quality, optimization, environment

Abstract: This paper proposes a genuine mathematical pattern for the study of the unsteady phenomena that characterize the working out of polyethilene and steel repartition pipeline from the natural gas distribution networks. The calculation programme elaborated on the basis of the mathematical model allows to determine the period of the two steady regimes between which the unsteady movement takes place. Keywords: pipeline, natural gas, network, unsteady movement

Abstract: This paper presents a study of the reactivity for some acrylates and methacrylates with two double bonds: diethylene glycol diacrylate (DEGDA), tetraethylene glycol diacrylate (TTEGDA), dipropylene glycol diacrylate (DPGDA), tripropylene glycol diacrylate (TPGDA), ethylene glycol dimethacrylate (EGDMA), triethylene glycol dimethacrylate (TEGDMA). The reactivity was studied by photopolymerization (Du Pont de Nemours 930 DPC) and thermal polymerisation (DSC 204 Netzsch). The used initiators are Lucirin TPO and Irgacure 1700 (3%w for photopolymerization) and benzoyl peroxide (POB 1 and 3% w for thermal polymerization). Correlations between monomers structure and theirs reactivity were established. Keywords: activation energy, diethylene glycol diacrylate, tetraethylene glycol diacrylate, dipropylene glycol diacrylate, tripropylene glycol diacrylate, ethylene glycol dimethacrylate, triethylene glycol dimethacrylate, DSC, DPC

Abstract: 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

Abstract: 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

Abstract: 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

Abstract: 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

Abstract: 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

Abstract: 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