Browse Articles

Ultra-high molecular weight polyethylene generally cannot be processed by injection moulding because of its high viscosity. In this paper, the formability of GUR-UHMW-polyethylene is numerically investigated during the injection moulding in an acetabulat cup. A number of numerical simulation tests have been performed on different acetabular cups to select the most appropriate process parameters and to optimize the injection moulding process. The numerical analysis demonstrates that the GUR-UHMW- polyethylene can be processed by injection moulding. Keywords: injection moulding, finite element analysis, UHMW-PE

Composite materials fatigue is a process which causes early failure or damage of variable loading subjected structure. Prediction of life period of composite materials uses different deterioration models. Quantifying of interlaminar stress and delamination can be underlined on load capacity of stratified composite materials subjected to fatigue. Keywords: composite materials, fatigue, interlaminar stress, delamination, load capacity

In this paper the static traction behavior of two types of talcum polyethylene, having the same friction coefficient but different modulus of elasticity and different tensile strengths, individually used and assembled with bolt, is studied. The behavior evaluation is done on the force-displacement curves and on the mechanical characteristics basis, specific to the materials (tensile strength, elongation, Young modulus), emphasizing the tension concentrator effect. Keywords: polymers, static loading, assemblies, mechanical characteristics

Impact damage in structures made of composite materials is a major concern since such damage can be introduced during the life of the structure, and its mechanical properties can be dramatically reduced as a result. Many efforts have been made in order to predict the damage and residual properties after impact. In the present paper a previously verified model is used in order to evaluate the residual tensile strength of woven fabric laminated composites. The model takes into account the number of plies; the impact energy and the stacking sequence. The effect of the thickness on the residual tensile strength as well as on the impact energy threshold was also examined. The predicted values seem to be a very good approximation of the experimental results. Keywords: Laminate, reinforcement, impact device, residual stiffness, uniaxial tension

Polyphenols have antioxidant character due the presence of several phenol functional groups. In human health, they are thought to be useful in combating oxidative stress, a syndrome causative of neurodegenerative and cardiovascular diseases. The main source of polyphenol antioxidants is nutritional, since they are found in most vegetables and fruits. We used tannic acid as polyphenol model. The polyphenols are encapsulated in chitosan matrices because chitosan is a natural bioactive material and it is pursued to release the polyphenols only in a certain medium. In this paper, the obtaining strategy of chitosan nanostructurate membranes with tannic acid, as Controlled Delivery System, is presented. Keywords: chitosan, cationic surfactant, tannic acid, morphological analysis

The thermal decomposition behaviour of some phosphorus-containing polyesters and a polyesterimide was studied using thermogravimetric analysis in air at several heating rates between 5°C/min and 20°C/min. The results of this study, realized for polyesters with phosphorus linkage as pendant group, were compared with the behavior of some polyesters having the same backbone structure, with phosphorous in the main chain, respectively without phosphorous. A kinetic model of the reaction order was also proposed for thermal degradation of studied polymers by using Vyazovkin method. Keywords: phosphorus-containing polymers, thermal degradation, flame retardant properties

Aromatic hydrocarbons especially 1,2 benzanthracene and perylene were effective in suppression of carbonyl and hydroperoxide formation upon irradiation, while carbon structures (carbon black and graphite) seems to produce increased radiation degradability, as it was shown by IR data. Pyrene and perylene induced increased stability to thermal oxidation subsequent to irradiation. The radiation induced formation of some hydroxyl groups grafted on degraded polynuclear structure has been supposed to explain the observed increased stability. Several changes in IR absorption bands observed with these irradiated hydrocarbons support this hypothesis. Keywords: chemiluminescence, aromatic compounds, degradation, polyethylene

In the generation of new materials replaceing the metals, taking into account their characteristics and future perspectives, one should pay a special attention to the composite materials, which were named consolidated plastic materials, just a short time ago. This paper emphasizes that the quality of the drilling tools and the geometry of their active part, the dimensional precision and of geometric form and also the quality of the surfaces processed by drilling, depend especially on the nature of the composite material and of the reinforcing fibers. Keywords: composite material, drilling, machining, wear

In this study the polymer transport dynamics in a 2D lattice model is investigated. The dependence of the polymer escape time through a nanometer pore on the stiffness and the monomers number of the polymer is demonstrated. We have also proved the major effect of superimposed electric field on the polymer translocation. Keywords: 2D lattice model, Langevin equation, nanopore, transport phenomena, translocation time

The paper deals with the synthesis and characterization as polymer processing aids, i.e. as plasticizers and/or lubricants, of some mixed (unsymmetrical) diesters of adipic acid by using aliphatic alcohols of variable length, such as C4, C6, C2-6, izo C10 and izo C13, along with complex aliphatic-aromatic alcohols, like 2-phenoxyethanol, 2-[(o-sec-butyl)phenoxy]ethanol and 2-[(p-nonyl)phenoxy]ethanol, respectively. The diesters derivatives obtained this way showed plasticizing and/or lubricating properties. The variation of such properties was studied by varying the polar / unpolar ratio within each structure of the considered product. Interesting correlations were recorded and the theoretical premises were fully proved. Keywords: unsymmetrical adipic diesters, plasticizers, lubricants, phenoxy-ethanols