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In this article, some advantages and disadvantages of the incorporation method of azobenzene moieties in several polymer matrices (polymethacrylate, poly(styrene-alt-maleimide), poly(oxazoline-co-methacrylate), poly(methacrylate-co-methacryloxypropyl trimethoxy-silane)) are highlighted. Their physical properties (molecular weights, glass transition temperatures, chromophore load, solubility, and solvatochromism) are discussed with regard to their macromolecular architecture. Solvent effect on the UV-Vis absorption spectra of azo-polymers was investigated using Reichardt’s solvent polarity scale and Kamlet-Taft multiparameter equation. Kamlet-Taft equation revealed that hydrogen bond acceptor properties and dipolarity/polarizability of the solvent have a significant contribution upon the solvatochromic behaviour of azopolymers. Keywords: azobenzene, side-chain polymers, solvatochromism, Kamlet-Taft equation

A series of six new experimental light-curing dental composites based on two Bis-GMA-type oligomers, quartz and nano-fluorohydroxyapatite (nano-FHAP), in different ratios, were prepared. The paper refers to the characterization of organic and inorganic phases from the uncured composite pastes and determination of the properties of the light-cured composite materials. Differential scanning calorimetry was used to measure the heat of polymerization of the monomer mixtures. Investigation of nano-FHAP was made by transmission electron microscopy TEMBF, HRTEM and X-ray diffraction. The mechanical strengths, water sorption and solubility were determined. We came to the conclusion that for the same monomer mixture, the water sorption and solubility values increased with the content of nano-FHAP in the composite material, but there remained in the limits of ISO 4049/2000 for the compositions comprising up to 50% nano-FHAP in the filler. The highest mechanical strengths were obtained in the case of composites containing 75% quartz in the filler. Keywords: dental nanocomposites, extent of polymerization, mechanical properties, water sorption, solubility

Fibre Reinforced Polymers (FRP) confinements on square and rectangular sections behave differently from confined circular sections. Confining inward pressure over the entire circular section is uniform, whereas in non-circular sections confining pressure development is inconsistent. As a result, these sections could be divided into the distinct properly and partially confined areas. Presence of these partially confined regions would much reduce influence of FRP confinements to increase concrete’s peak strength and ultimate strain. To evaluate confinement effectiveness, effect of mentioned areas must be taken into account precisely. This paper describes a theoretical model adapted to seismic strengthening and retrofit of the square section RC columns confined with advanced composite materials. The model is the author’s earlier proposed one calibrated with cautious survey on the existing test data. This model takes into account geometrical parameters of the column shape such as overlapping length and corner rounding radius; furthermore both concrete and FRP confinement mechanical properties. Finally it proposes a new shape factor for the square sections which plays a major role in effectiveness evaluation of FRP confinement. Keywords: Fibre Reinforced Polymers, square section, Reinforced Concrete columns, strengthening

Lignin, a natural renewable material, was incorporated in a series of polydimethylsiloxane/silica composites. Besides the effect as bulk filler, the presence of lignin determines the change of some properties among them being surface properties that were evaluated by contact angle and water sorption measurements. The contact angles were determined in static regime by using the sessile drop technique. Dynamic water vapour sorption was applied to register the sorption/desorption isotherms and kinetic curves. The sorption type and maximum vapour sorption capacity were evaluated based on these data. The results were correlated with the composition of the prepared materials. Keywords: surface properties; siloxanes; composites; lignin

Organic biopolymers are a source of raw material for agriculture, whereas the composition of protein wastes provides sufficient elements to improve the composition and remediation of degraded soils and plants by exploiting elements, such as nitrogen, calcium, magnesium, sodium, potassium etc. From processing one tone of raw hide, 75% is discarded, of which 50% could be further used as organic fertilizer. Protein biopolymers were obtained by means of an innovative enzymatic procedure for waste processing. In combination with polyacrylamide, acrylic, maleic, cellulose, starch etc. are used in the agricultural field. We characterize the protein biopolymers by specific morpho-structural analysis methods (UV-Vis, IR spectroscopy, thermal analyses, X-ray diffraction, microscopy).The novelty of this work is the biochemical combination process of synthetic polymers with organic biopolymers from tanneries with viable and interesting applications in agriculture. Keywords: biopolymer, protein wastes, tannery, soil, structural analysis

Functionalized dental implants represent an advanced approaching in implantology, aiming to improve the biointegration and the long-term success of surgical procedures. In this article are reported the synthesis of hydroxyapatite (HA) and Poly(methyl methacrylate) (PMMA) thin films on metallic substrates – used as dental implant-type structures – by pulsed laser deposition (PLD) method. Plasma and plume evolution of ablated HA and PMMA species was registered through optical analyze by fast CCD camera. Numerical simulation performed using a simple hydrodynamic model properly reproduce this type of plasma behaviour. SEM-EDAX measurements were performed assessing the apatitic-type structure of the prepared films along with their satisfactory mechanical adhesion. Keywords: synthetic polymer, pulsed laser deposition, hydrodynamic model

The use of the acrylic resins in the dental technique was a very important gain for the manufacturing and treatment of dentures and during the years new materials and technologies have appeared on the market, promising a better quality. Full-denture casting currently represents a technological alternative. The casting system we tested usually uses reversible hydrocolloids for investing wax patterns, and has certain advantages. Thermoplastic materials are used more and more widely in the technology of complete or removable partial dentures due to their superior qualities. Thermoplastic resins are suitable for manufacturing a wide range of removable partial dentures without metallic structure, in optimal conditions of biocompatibility, by injection. Our aim is to compare thermopolimerysable acrylic resins, manufactured using the classic technology with cast full dentures and injected thermoplastic resins. Keywords: thermopolimerisable acrylic resin, thermoplastic resin, molding-injection devices, casting, full dentures

The polysiloxane networks have been prepared by means of hydrosilylation reaction of poly(dimethyl, hydrogen-methyl)siloxanes (HlPDMS) containing Si–H groups and siloxane copolymers named VlPDMS and VcPDMS containing Si-CH=CH2 functional groups. The structure of the siloxane copolymers was determined from 1H-NMR and FT-IR spectra analyse and the characterization of the siloxane copolymers was performed by gel permeation chromatography (GPC), viscosity and determination of the content of functional groups. The mechanical properties of the newly obtained networks were determined by physico-mechanical measurements, dynamic mechanical analysis (DMA), and differential scanning calorimetry (DSC). Keywords: polysiloxane, hydrosilylation crosslinking, polymer networks

A series of thermotropic liquid crystalline phosphorus-containing copolyesters was prepared by polycondensation reaction starting from various ratios of 2-(6-oxido-6H-dibenz[c,e][1,2]oxaphosphorin-6-yl)-1,4-benzene diol, 1, terephthaloyl bis-(4-oxybenzoyl-chloride), 2, and, 1,12-dodecanediol, 3. The molar ratio of aromatic bisphenol to aliphatic diol was varied in order to generate copolyesters with tailored physico-chemical properties. The chemical structure of the synthesized polymers has been confirmed by Fourier transform infrared and 1H NMR spectroscopy. The phase transitions of the phosphorus-containing copolyesters have been investigated by differential scanning calorimetry, polarizing optical microscopy and X-ray diffraction measurements, structure–properties relationships being established and discussed. Keywords: phosphaphenanthrene; phase transitions; structure-property relations

The objective of the present study was to check the debonding strength in four types of orthodontic adhesives frequently purchased at present in our country: Ortho-Loc, Transbond XT, Tranasbond Self Etching Primer and Grengloo. For this study forty patients with integral maxillary arches and minor dental-maxillary abnormalities were selected and further randomly divided into four groups (one for each adhesive), each group being bonded with Resolve® Classic Bracket-type metal brackets. After one month, during which the brackets were subjecte to the action of oral factors, they were debonded using the force measurement FK model of the SAUTER device. There were no signficant differences between the four types of adhesives, nevertheless, the highest values were obtained for Transbond XT. All four types of adhesives were within the clinically acceptable interval being able to be safely used by clinicians. Key words: orthodontic adhesives, brackets, self-etching, debonding strengths