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Cellulose composites with maleic anhydride – dicyclopentadiene copolymer matrix were obtained by “in situ” free-radical polymerization. The syntheses were carried out in two different solvents: toluene and dioxane, aiming at determining their influence upon both the polymerization process and properties of the resulting materials. The composite materials obtained were characterized both structurally by FT-IR, XRD and SEM, and from the thermal behavior point of view by TGA-DSC-MS analyses. Keywords: cellulose composites, maleic anhydride – dicyclopentadiene copolymer, in situ polymerization

Among the methods used nowadays for studying the microscopic properties of polymers, proteins, membranes and other bio-materials is the molecular dynamics. One of the widely used software in molecular dynamics is Gromacs developed at the University of Groningen. From a computational perspective, molecular dynamics requires large computational power and an increased storage capacity. Different physical models were recently defined for trying to reduce the complexity and to make more efficient the computational it molecular models. In this paper we present the Gromacs implementation of a new multiscaling MD model with a space dependent multiscaling parameter and we discuss efficiency measurements. Keywords: polymers, molecular dynamics, Gromacs, multiscaling modeling

A rheological study was performed in order to appreciate the compatibility of the expanded polystyrene beads with the concrete matrix. In order to prepare homogeneous dispersions of the expanded polystyrene (EPS) in the cement paste, the EPS beads were first surface pre-treated with carboxymethylcellulose (CMC), intending to achieve the compatibility between the hydrophilic concrete matrix and the hydrophobic polystyrene beads. In this study, the mass fractions of aggregates, cement and water were maintained constantly for all the probes and it was checked the influence of two parameters: the EPS mass fraction and the CMC concentration. The study was performed with EPS mass fractions between 0.0028 – 0.0041 and with CMC – water solutions having concentrations between 0.5% - 2% (mass). The results showed that CMC can achieve the compatibility between concrete and EPS and that within a 2% CMC solution an important amount of EPS beads can be incorporated. Keywords: lightweight concrete, expanded polystyrene, concrete rheology

Functionalized organogelators derived from 1,3;2,4-bis-O-benzylidene-D-sorbitol with methoxy and carbonylaminoethyl methacrylate moieties were prepared, characterized and their gelation ability was evaluated in order to be utilized as additives for dental materials obtained by photopolymerization of several dimethacrylate (DMA) monomers. Keywords: 1,3:2,4-bis-O-(p-methoxybenzylidene)-D-sorbitol, 1,3:2,4-bis-O-benzylidene-5,6-bis-carbonylamino -ethyl methacrylate-D-sorbitol, isocyanatoethyl methacrylate

Development of CAx for numerical simulation of injection molding and mold design have opened new possibilities of product analysis during the design process of plastic production. This development contributes to higher quality performance as well as to lower cost of production. The paper deals with the design of plastic products with state-of-the-art integrated CAD/CAE software for mold design. The possibility of solving problems in mold construction appeared by integrated CAx universal system with unique applications (CAE/II module) for mold parameters verification, mold calculation and selection and final mold modeling (CAD/II module). Thus, the specializated CAD/CAE system for automated mold design is successfully created. Keywords: plastic injection molding, mold design, CAD, CAE

The internal friction phenomenon in metallic and polymeric shape memory materials is analyzed. The experimental results permit validation of a theoretical model which describes qualitatively the temperature dependence of the internal friction for the investigated materials. Moreover, theoretical model accepts not only evaluations of different states of material (solid state structural transformations as martensite – austenite) but also materials very different as nature (metallic or plastic). Keywords: shape memory polymers, damping capacity, internal friction, martensitic transformation

For the modeling and usual analysis of mechanical structures it is considered that the whole structure and its components accomplish one of the fundamental conditions of strength of materials – the condition of continuity and homogeneity. This paper presents some modeling techniques useful for the optimization of the numerical models in order to improve the structural response for impact applications. As some parts have to be damaged a material model capable of material failure must be used. The differences between the results obtained using a model without failure and a model with failure compared to the experiments were discussed. The second procedure is regarding the random distribution of the thickness properties of the elements for a selected area within the user specified tolerance. Procedures implemented in custom written code and the algorithms presented for the random distribution were presented. Keyword: material homogeneity, material model, random thickness, numerical simulation

The radiation stability of low density polyethylene in the presence of several additives as antioxidants (two derivatives from rosin, two commercial stabilizers, Irganox 1076 and Irganox 1081 and elementary selenium) was carried out by oxygen uptake method. The values of oxidation induction times of stabilised PEjd were discussed. A stabilisation mechanism concerning derivatives of rosin was reported. The antioxidant efficiency of studied compounds was compared to propose a reliable alternative to commercial antioxidants for the radiation sterilisation of PEjd. Keywords: LDPE, oxygen uptake, gamma irradiation.

This study focuses on possible applications of polystyrene in the medical field. Nonwoven fiber mats were produced through electrospinning, using limonene or, as control, the conventionally used ethyl acetate. Subsequently, different types of dilutions were tested. Electrospinning (ES) was performed with different parameters to study the effect upon the fibrous materials resulted, in view of obtaining structures with high porosity and a specific desired morphology. Thin fibers were obtained using both solvents, with fibers average diameter of 1.98-2.58 mm for limonene and 8.87-13.81 mm for ethyl acetate. The obtained various materials are a result of the different solvent densities, surface tensions and polymer concentrations. Best quality fibers, when using limonene, were obtained for 35 % polystyrene, while when using ethyl acetate the high quality fibers were obtained for 60 % polystyrene in solution. The mats morphology and structure were compared and analyzed through optical microscopy, scanning electron microscopy and Fourier Transform Infrared Spectroscopy. This study proposes the fabrication of nonwoven fibrous mats from polystyrene using a natural, economical, biocompatible and environmentally friendly solvent that can successfully replace the common and toxic solvents in medical applications involving wound dressing or tissue reconstruction. Keywords: electrospinning, limonene, polystyrene, ethyl acetate, wound dressings

Radiation-induced polymerization can produce a wide variety of water-soluble polyelectrolytes which are used to increase the performance of the waste water treatment. The main goal of this study was to investigate the influence of the radiation dose (D), initiator concentration [I], sodium chloride concentration, total monomer concentration [TMC] and monomer ratio (R) on the physical and chemical properties of the acrylamide – acrylic acid based polyelectrolites, obtained by copolymerization in accelerated electron beam fields. In accordance with the established purposes, the polyelectrolyte must have high conversion coefficient (CC > 95%), low residual monomer content (Mr < 0.01), high intrinsic viscosity (hintr > 7 dL/g), low linearity coefficient (kH < 0.4) and a very good solubility in water. The experiments were performed using a linear accelerator facility (ALIN-10, built in NILPRP Accelerators Laboratory, Bucharest) of 6.23 MeV at irradiation doses between 0.9 kGy and 1.8 kGy at room temperature and ambient pressure. The best results were obtained at 1.5 kGy. Keywords: acrylamide, acrylic acid, ionizing radiation, polyelectrolytes