Browse Articles

This paper describes the kinetic evolution, in solution, of N-phenylmaleimide - vinyl acetate alternating copolymerization. The rate of consumption for the equimolar composition of the two monomers is described by the empirical equation: Valt=k . [M]1.70[I]0,49. There were formulated hypotheses to explain those dependences. The copolymers obtained were analysed by SEC. It was proved the structure of the alternate copolymer and the fact that high molecular products results . Keywords: N-phenylmaleimide, vinyl acetate, alternate copolymerization, alternate copolymer

Thermoplastics are widely used for engineering application and customer goods. One of the application area is automotive industry. The passengers’ compartment is an example of using high quality materials and advanced design solution in order to achieve aesthetic interiors and performance when safety is the issue. The impact of the passenger’s head with the cockpit module is studied by experimental and numerical simulation. Material models are studied in order to obtain good results and to validate the numerical model for further investigation. Keywords: thermoplastics, material characterization, impact, experiment, numerical simulation

In this paper, a methodology to evaluate the dynamic fracture toughness of polymethyl methacrylate (PMMA) is presented. The proposed methodology is based on a hybrid-numerical formulation and requires the evaluation of the dynamic stress intensity factor along the experimentally measured dynamic crack fronts, and the three-parameter Weibull stress model for brittle fracture. The apparent fracture toughness master curves are determined for Double Cantilever Beam (DCB) specimens of PMMA with different thickness. Keywords: dynamic fracture toughness, polymethyl methacrylate, Weibull master curve

The paper presents two methods for similarity measurement of plastic textured images, and also for identification and localization of defective region in textured images. In order to have less sensitive statistic features regarding to rotated image, we introduce the notion of average co-occurrence matrix. With the purpose of algorithm validation, the images are divided into four equivalent regions. For the proper region similarity measurement, a decision theoretic method is used. In the fractal approach, we consider a new fractal dimension derived from box-counting algorithm, named effective fractal dimension, with an increasing efficiency for texture classification. Two experimental studies, one for statistical features and one for fractal type features, in a plastic simulated wood case, validate the algorithms. The algorithms are implemented in Visual C++ and Matlab. They allow the simultaneously display of both the investigated region, and the Euclidian distance between this and a reference image. The results confirm the fact that the distances between the regions without defect are relatively small, and the distance between a region with defect and a region without defect is relatively large. Also, the results show that features extracted from average co-occurrence matrix and the effective fractal dimension have a good discriminating power. Keywords: texture similarity, statistic features, fractal dimension, plastic simulated wood, defect detection

This paper presents the effects of high energy irradiation on polyvinylchloride samples, some of them containing filler (1 and 5 % mica). The generation of dipoles as oxygenated radiolysis products modifies electrical behavior of polymer matrix. The presence of mica influences the rate of oxidation by decreasing the progress in the accumulation of oxygenated products. The values of volume resistivity, dielectric constant and loss factors are consequently changed as the mica content differs due to the adsorbent action of filler. Keywords: PVC, mica, irradiation, volume resitivity, dielectric constant, loss factors

The three new polyanionic polymer conjugates were synthesized by the chemical bonding of some N-mustard derivatives of di-(b-chloroethyl)-amine and tri-(b-chloroethyl)-amine with poly(maleic anhydride-alt-vinyl acetate). The chemical structure of the compounds obtained was verified by FTIR, H1-NMR and elemental analysis. Keywords: poly(maleic anhydride-alt-vinyl acetate) conjugates, alkylating agents

The paper investigates the influence of rubber elastic properties on modal behaviour of truck tyres. Hyperelastic models and numerical values of coefficients in these models used for defining rubber hyperelastic behaviour are presented. The choice of the appropriate hyperelastic model to be introduced in the tyre finite element model is motivated. The main characteristics of the finite element model of a radial truck tyre are presented. A series of modal analyses is performed, in which elastic properties of tread rubber are modified in a wide range. Finally, the influence of tread rubber elasticity characteristic values on natural frequencies and mode shapes of truck tyres is analysed. Keywords: tyre, hyperelasticity, modal behaviour, finite element model

In this paper is presented an analytical model, which makes the similitude between the DTMM theory of composite multilayer bars and the FSDT theory used in the study of composite bars and plates in a dynamic regime. The authors proposed a numerical application of the model, for two different bars made from glass-epoxy reinforced composite. The experimental validation of theoretical results was made on a composite bar as a component of a quadrilateral mechanism, whereon the leading element describes a rotation motion with the constant angular speed. Keywords: composite materials, vibrations, movement in a plane

The behaviour of some microstructured polymers obtained in dynamic conditions using a mixture (1:1) of EPDM (ethylene-propylene-dien monomer) rubber and high-density polyethylene (in the presence of sulphur as reticulating agent) was studied. The experiments consisted in determination of swelling by maintaining the polymeric composite materials in three organic solvents (benzene, p-xylene, carbon tetrachloride) and also in recording their IR spectra. The results are useful for selection of operating conditions during preparation and for choosing the appropriate utilization of polymeric products. Keywords: microstructural polymer, EPDM (ethylene-propylene-dien monomer) rubber, polyethylene, swelling, IR spectroscopy

The paper deals with the shrinkage and warpage phenomenon briefly presenting the most important influence factors and their interaction involved in dimensional changes of injected plastic parts. The predictable tolerances, design strategy and the main required action are debated for one final purpose: maximum and yet realistic accuracy of dimensional precision, in a cheapest, easy manufacturability and easy operating injection tool. Finally, there are presented some useful considerations for minimizing the effect of shrinkage and warpage in dimensional variance of injected plastic parts. Keywords: injection moulding, tolerance, shrinkage, warpage