Browse Articles

This paper presents the synthesis of complex nanostructures of the Fe3O4-n[SiO1.5g-(CH2)3(NH2)](NH2)nd-(GL)ne type [Fe3O4 = magnetic core; n[SiO1.5g-(CH2)3(NH2)] = coated layer; (NH2)nd,-NH2= surface and deep amino groups which play an important role in biochemical interfacing; (GL)ne= exterior superficial glutaraldehyde layer]. These nanostructures have several interesting physical and chemical characteristics, such as: biochemical fixing without destructing the microorganisms on the Fe3O4-n[SiO1.5g-(CH2)3(NH2)](NH2)nd-(GL)ne surface and the ability to differentiate the microorganisms in magnetic field, according to the mass and volume. In order to obtain superior biochemical fixing performances we have analysed and determined the chemical and physical distributional mechanisms of (NH2)nd, -NH2 groups on the surface and in the depth of the above-mentioned nanostructure. For this purpose we have deduced the control equations according to the synthesis parameters, which triggers the growth of the silicone polymer layer and the distribution of the amino groups in its structure. Keywords: Magnetite, coated nanoparticle, biochemical fixing, crosslinking molecules

This paper presents the influence of processing temperature on the mechanical-physical properties of thermoplastic polyurethanes (TPU) used at injection moulding of performance sport products. The test-pieces were moulded at the following real injection temperatures : 200°C, 210°C, 220°C, 230°C and 240°C. It was determined that the in-mould pressure decreased with increasing of the processing temperature. Also the following thermal analysis were performed : Thermogravimetry (TG), Differential Scanning Calorimetry (DSC) and Dynamic-Mechanical Analysis (DMA). It was established that the processing temperature has a significant influence on the thermal stability and on the glass transition temperature of polymer while the flow temperature is slightly influenced by the processing temperature. Keywords: thermoplastic polyurethane (TPU), injection moulding, Thermogravimetry (TG), Differential Scanning Calorimetry (DSC) , Dynamic-Mechanical Analysis (DMA)

This paper presents a study of the reactivity new carbosiloxane cyclic structures in anionic ring opening polymerization reactions in the presence of catalyst potassium siloxanolate. For this purpose, 2,2,5,5-tetramethyl-3,4-diphenyl-1-oxa-2,5-disilacyclo-pentane, 2,2,5,5-tetramethyl-3,3-diphenyl-1,4-dioxa-2,5-disilacyclopentane, 2,2,7,7-tetra-methyl-3,3,6,6-tetraphenyl-1-oxa-2,7-disilacycloheptane and bis-[1,4-bis-(dimethylsiloxanyl)-dihydronaphthalene] were used. The evolution of the polymerization reaction was observed through measurements of the reaction mixture inherent viscosity at various temperatures. The obtained results were processed in order to obtain the influence of the chemical structures on the processes conditions of development and kinetic parameters related to the transformation of the cycles to linear compounds. Keywords: cyclocarbosiloxanes, siloxanes, anionic polymerization, ring opening polymerization, organo-silicon compounds

The more reliable values of the crystallization temperature were obtained from the non – isothermal DSC thermograms recorded at low cooling rate. The crystallization time was evaluated from the isothermal DSC thermogrames recorded at those temperatures at which the crystallization occurs. PP nucleated with Irgastab NA 21, has crystalline phase that contains the smallest spherulites, as compared to those nucleated with Irgastab NA 04 and Irgaclear DM. The incorporation of the nucleating / clarifying agents into the polymer matrix is homogeneous only if the melt processing conditions were well defined for each of them. A dependence on the molecular weight of the nucleated PP morphology was observed. The spherulite size decreases with the increase of the molecular weight. Keywords: crystalization, nucleation, polypropylene, nucleating agent, spherulite

This article presents the experimental results regarding the glucose influence on poly (vinyl alcohol) (PVA) films. The results of infrared spectroscopy (FTIR), atomic force microscopy (AFM) and X-ray diffraction (XRD) measurements revealed the surface and structural changes induced by increasing the glucose concentration. Keywords: PVA, AFM, XRD, FTIR

In this paper the 3D simulation model of typical porous polymer is presented. Porosity growth was caused by numerical handling of a spatial pores network. Although the algorithm has a good accuracy it is noticed that the final average pore sizes for simulated polymer networks are larger than the desired pore size. Keywords: polymer network, porosity, tissue engineering

Mixing and processing characteristics, mechanical properties and thermal characteristics of dimethyl vinyl silicone/poly(tetrafluoroethylene)(MVQ/PTFE) blends were investigated. With the rise Poly(tetrafluoroethylene) (PTFE) portion in blends, the values of both torque and total torque of blend materials decrease. In MVQ/PTFE blends, PTFE act as inactive filler and some mechanical properties decreases in blends compared to component polymers with the increases portion of plastic in blend compositions. The heterogenity of MVQ/PTFE blends was determined by thermomechanical analysis-dilatometry. Silicone (MVQ) and PTFE show separate Tgs, which indicate that they are not compatible. Thermogravimetric analysis of these blends, show that with increased portion of PTFE in blends, the TGA characteristics Tbeg and T5% is moved at higher temperature, which mean increased of thermal blend stability. Keywords: blends, dilatometry, TGA

This paper is focused on the main static and dynamic characteristics in case of rubber elements designated to damp the vibrations transmitted to the surrounding buildings by means of the railway. Thus, the experimental methods performed on a stand having harmonic excitation in case of actual loading under dynamic regime both stationary and transient attaining the resonance point are presented. Based on this, the system dynamic parameters such as: dynamic rigidity, critical damping fraction, dissipation coefficient (hysteresis) can be determined. Aiming this the free damped vibration method and the controlled excitation method with monotone increasing variation for the excitation frequency have been used. In this way can comparatively be determined both the rigidity and the damping dynamic characteristics of the rubber for various manufacturing receipts taking into account the chemical composition as well as the manufacturing process. Finally, the paper presents experimental results obtained by our research institute ICECON Bucharest in cooperation with University “Dunãrea de Jos” of Galaþi during the works carried out for the tram rails in Bucharest, Romania. Keywords: elastomer, rigidity, damping, vibration, structural noise, antivibrating insulation

Using the linearity of the term we will deduce a new formula for the calculus of the fracture strength for composites with randomly dispersed fibres. This formula will depend on the reinforcement volume fraction. Using the mean values for longitudinal and/or transversal modulus, with respect to the rotated reference system, we will obtain an original relation for the calculation of the elasticity modulus for composite plates with a randomly dispersed reinforcement. We preferred to write this relation in a similar manner to the one used for the failure strength, using the linearity related to . Experimental determinations were made for three sets of samples obtained from composite plates with various mass fractions of reinforcement, confirming thus the theoretical results obtained by the authors. Keywords: composite materials, fracture strength, longitudinal/transverse modulus

One major disadvantage of polymeric composites is their low electrical conductivity. This is a trail-and-error study regarding PMC’s conductivity modification by filling the polymer matrix with various powders. Clay, CNT and Ferrites were used as fillers, Epoxy Epiphen RE 4020 with Epiphen DE 4020 as hardener was used as matrix and simple type fabric of alternate kevlar and carbon untwisted tows was used as reinforcement. The mechanical properties of a PMC are improved by using reinforcements so it is naturally to ask what is happening when a reinforced composite is formed with filled polymer matrix. Plate samples were formed and their electrical conductivity was evaluated. The filler’s concentration was considered and information was used in order to form the reinforced composite with the highest conductivity. Keywords: CNT, Ferrite, Clay, Epoxy, Fiber Fabric Reinforcement