Browse Articles

The paper presents the optimisation using genetic algorithms of some characteristics of the composite reinforced with plain weave fabric regarding the type of the polimers used as matrix and the type of the fibres, approaching a new geometric model of the woven structure which takes in consideration the fabric counts, different crimps in the warp and fill directions, the size of the gap between yarns of the two systems, the compactness of the yarns in the chosen structure. Keywords: composites, genetic algorithms, woven composites

Rubber is often used as a vibration insulator for technical systems. Its behavior is linear until a deformation of at least 15%, by over this limit the behavior becomes non-linear. This means that the dynamic rigidity and implicitly the elasticity module change its value during the element is stressed under dynamic regime. The authors have developed a method to find out this parameters by processing data obtained by measurements with the Wigner-Ville Distribution. Keywords: rubber, mechanical properties, time-frequency representations

This paper studies the bidimensional pulses generation in organic materials and technical polymers starting from a practical test functions basis, having as purpose their viscoelastic behaviour analysis. A heuristic algorithm for generating the test function using MATLAB procedures is presented. Keywords: viscoelastic behaviour, test functios, polymer

The authors present a way of manufacturing composite materials for building use by adding value to a waste resulted in an oil refinery. The said waste is the spent caustic proceeding from the Fluid Catalytic C racking units. The manufacturing process implies: 1.The recovery of the organic content from the spent caustic 2.Transforming the organic phase into resin 3.Impregnating natural fibres with resin in order to obtain fibre reinforced materials .The possible materials to obtain are: boards and hydro-insulating materials for plumbing. The work was oriented towards the building material (boards). The paper presents: the chemical characterization of the waste (the spent caustic), the organic compounds recovery process, and the resin synthesis, the manufacture of the composite material by moulding and the results of the mechanical tests. Keywords: recycling, waste management, composite material

In this study there were investigated some mixtures obtained from epoxy resins and polyaminobismaleimides. The preparation, working conditions and their characterization by IR, softening points and thermogravimetric analysis are also given. Keywords: epoxy resin, polyaminobismaleimide, thermal behaviour

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

Thermal stability of low density polyethylene stabilized with different diamine compounds: N-phenyl-1-naphtyl-amine, N-cyclohexyl-N’-phenyl-p-phenylen-diamine, N-(1,3-dimethyl-butyl)-N’-phenyl-p-phenylen-diamine and N, N’-di-(1,4-dimethylpentyl)-p-phenylen-diamine was investigated by chemiluminescence method. Kinetic parameters depicting the progress in thermal degradation at various temperatures, concentrations and irradiation doses were calculated. Energetic considerations on thermal stability induced by diamine presence are commented and antirad effect of this kind of compounds is emphasized. Keywords: low density polyethylene, diamine compounds

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

Two macromolecular products, of polyethyleneimine and of polyamineamide type, were synthesized by the polycondensation of triethylenetetramine with 1,2 dichloroethane with adipic acid and e-caprolactam, respectively. The secondary amine groups of the two polymers were substituted with specific agents, e.g. the reaction product between triethylamine and epichlorohydrin and/or 1,2 dichloroetane, in order to produce their cationization. The intermediates and the polymers were characterized by FTIR spectroscopy, elemental analysis, solution viscometry and polyelectrolyte titration. Some properties of the synthesized polymers such as molecular weight, charge density, inability to crosslink, recommended them as retention or drainage agents in the papermaking, or as purification agents in the waste water treatment. Keywords: polyetyleneimine, polymineamide, retention aid, flocculation, polyelectrolyte titration

The aim of this study is to calculate the kinetic parameters for thermal cracking of waste PET in presence of radical donors. The thermal decomposition of PET is carried out at different temperatures (693-773 K), high pressure and by using heavy paraffinic hydrocarbons as radical donors. A simple first order kinetic model was proposed for thermal cracking and kinetic parameters (A and E) were calculated. Radical donors assure a high degree of waste PET decomposition in valuable products as gas fraction, gasoline and middle distillate. The coke is very spongious and a small quantity of undecomposed PET is blocked inside of the cavities. Keywords: Thermal, cracking, waste, PET, radical donors