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Polymer composites from polypropylene (PP) and treated and untreated hemp fibers (HF) were prepared using a twin screw extruder and separated feeding ports. Both treated and untreated HF show reinforcing effect in PP composites but the treatments applied to HF accentuate this effect. An increase with 78 % of tensile strength and with 61 % of Young’s modulus was obtained with untreated fibers and double tensile strength and modulus when using treated HF. Aminosilane treatment of HF was the most efficient, leading to simultaneous improvement of tensile properties and impact strength of PP composites. Keywords: hemp fibers, mechanical properties, twin screw extruder, polymer composites

The bonding materials used in orthodontics must resist to masticatory and active orthodontic forces. The aim of this study is to evaluate and compare the tensile bond strength of three orthodontic bonding procedures: acid etching and chemically cured macrofilled composite (Evicrol, SpofaDental, Jièin, Cehia), glass ionomer cement Ketac Cem (3M ESPE AG, Seefeld, Germany) and self-etching primer with light cure adhesive bond material (Transbond Plus Self Etching Primer + Transbond Plus Color Changer Adhesive, 3M Unitek, Monrovia, California). Moreover, after removing the brackets, the Adhesive Remnant Index (ARI) has also been measured. For this purpose 30 recently extracted human premolars were used, grouped randomly in three groups, 10 teeth for each tested material. After bonding the brackets, these were torn off from the teeth surfaces with a tensile testing machine (Instron 1195). The ultimate tensile strenght (UTS) and the ARI has been measured. Our conclusion was that glass ionomer cement fails first to the tractioning forces, while light cured composite has proven to resist best to streching and traction. Although light-cured composite has failed to lower forces than the chemically cured one, the frequency of ARI score 3 has been the highest, which means that its adhesion is the best. Key words: tensile bond strength, bonding material, adhesive remnant index

The paper presents our results with polymethylmethacrylate cement augmentation osteosynthesis around the knee joint and to discuss the advantages and complications encountered. We presented the benefits and limitations of cement augmented fixation constructs around the knee because of the lack of such studies that focus on this particular anatomical location. We consider that the cases described can contribute to a greater understanding when searching for solutions targeted on the knee defects. In conclusion, we find polymethylmethacrylate cement augmentation of implants to provide excellent fixation around the knee both for tumoral resections as well as for managing complex trauma cases. Keywords: polymethylmethacrylate spacers, osteosynthesis, knee joint

The purpose of this paper is a radiological evaluation of the prosthetic polyethylene component wear in time (years), a quantification of this wear depending on the different types of prostheses and a correlation between the degree of wear and the radiological signs of deterioration of the periprosthetic bone structures, resulting in mobilization of the prosthetic components (loosening). Keywords: polyethylene, hip prosthesis, particle disease, loosening

This paper presents the study of sorption kinetics and thermodynamic equilibrium of chloroform and methanol sorption in thin polyvinyl acetate (PVAc) films. Experiments were conducted on a laboratory set-up using a pressure-decay technique. The obtained data were compared with other literature data obtained using other experimental method and are in good agreement. Comparison between the actual experimental and other literature data obtained using different investigation techniques are in good agreement. Keywords: polymer films, solvent sorption, pressure-decay technique

In this paper are presented structural parameters that influenced the metachromatic phenomenon induced by two maleic acid copolymers in form of sodium salts, as anionic partners. One is hydrophilic, namely the copolymer sodium maleate-vinyl acetate, (NaM-VA), and the other is a hydrophobic one, namely sodium maleate-styrene copolymer (NaM-S). The cationic dye was Methylene Blue. The correlations between UV-Vis spectrum data and those of spectral remission are also discussed. Keywords: maleic acid copolymers, Methylene Blue, metachromasy, Melana fiber, spectral remission, K/S values

Asphalt nanocomposites were prepared by mixing nanoparticles of calcium carbonate with a solution of bitumen in xylene in the presence of a solution of polymer in xylene. Calcium carbonate nanoparticles were obtained by wet milling and their characterization was performed by dynamic light scattering (DLS). The polymers used were either polyacrylate type and polystyrene homopolymers or copolymer of polyacrylate-polystyrene type synthesized by solution process. Asphalt nanocomposites prepared were characterized by dynamic mechanical analysis (DMA). The results indicate a close behaviour of nanocomposite based on polyacrylate and polystyrene homopolymers and polyacrylate-polystyrene copolymer. Keywords: asphalt nanocomposites, calcium carbonate, dynamic mechanical analysis

The objective of our study was to assess the “in vivo” wear of cross linked polyethylene in contact with different materials surfaces. Thus, we compared the polyethylene acetabular cups wear when they function in a couple with ceramicized metal heads (zirconium oxide) with those in a couple with cobalt chromium metal heads, in total hip arthroplasties. The polyethylene wear was quantified by digital measurements on standardised digital front and lateral view X-rays and the differences were statistically analysed. Keywords: ceramicized metal, polyethylene, hip prosthesis

Thin films of polyamide 6 (with various concentrations) were deposited by spin-coating method (at various rotation speeds) and surface morphology of these films was analyzed by scanning electron microscopy. Following this analysis it was revealed that deposited film thickness depends on solution density, its viscosity, rotation speed and rotation time. In the context of multi-scale type theories, a theoretical model which explains our experimental results is established. Keywords: spin-coating, polyamide, thin film, multi-scale theory

Nowadays, the growing environmental awareness throughout the world has triggered a paradigm shift towards designing environmentally friendly materials. The interest in cellulose fibers as reinforcement agents in composite materials with polymer matrices has increased dramatically in the last decades, the main reasons associated with this upsurge being their renewable and ubiquitous character, good mechanical properties, low density, low cost and recyclability. Focus on dielectric spectroscopy technique, the article makes a comparison between the dielectric properties of transformer board and composite materials obtained by mixing recycled polyethylene with wood powder or lignin in different percentages. Keywords: recycled polyethylene, transformer board, dielectric spectroscopy analysis