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The article presents and discusses experimental data regarding synthesis and characterization of epoxy resins modified with glycols of different molecular weight, synthesized in a 2: 1 molar ratio resin / glycol. The synthesis of epoxy resins modified with glycols was examined by using the spectrophotometer (FT-IR methods) against analytical (chemical) methods, by determining the content of the epoxy groups in time. Furthermore, in order to determine the influence of the glycol nature on the characteristics of the resulted resins, they were cured by using an aromatic polyamine hardener such as 4.4’-diaminodiphenylmetane (DDM), and the resulted epoxy resins were characterized by using both conventional mechanical analyses and the dynamic mechanical analyses (DMA). From the DMA determinations we noticed that resin flexibility increases in the same time with the polieteric chain length. Keywords: epoxy resin, glycol, glass transition, dynamical properties, mechanical properties

Optical coherence tomography is a new noninvasive investigation method with various applications in dentistry and orthodontics respectively. The intra-oral OCT investigation opens a totally new perspective on the investigation of orthodontic bonding. Polymeric orthodontic brackets (Damon Clear) were bonded on the teeth of the upper arch of a patient following the manufacturer instructions with a light-curing orthodontic adhesive (Blugloo). After bonding the teeth were examined by spectral OCT in order to examine the interface formed by the enamel, orthodontic resin and the bracket. Several images were obtained. Intra-oral OCT is a method of great potential and real benefits in elaborating a prognosis on the clinical durability of bonded polymeric brackets. Keywords: spectral optical coherence tomography, orthodontic bonding, orthodontic adhesives, polymeric brackets

The fundamental assumptions of the traditional deterministic linear models are those of continuous and differentiability of physical quantities involved in drug release processes. However, these assumptions are in reality contrary to the evidence given by the complexity of the drug release process. Thus, we will consider that, at mesoscopic scale, the drug release mechanisms are based on the assumption that the drug particle movements take place on continuous, but non-differentiable curves (fractal curves), for which a Weibull type equation results. In this approach, analyzing some experimental data, information on the drug release mechanism and system complexity are obtained. Keywords: fractal, drug release mechanism, polymers microparticles, mesoscopic scale

Flavonoids pigments exert a broad range of biological activities in both plants and animals. Natural polyphenols mainly occur as glycosilated molecules, usualy with a b-linked sugar. In this paper are cited several methods and techiques uses in flavonoid analysis. Chromatographic methods are usually cited techniques for quantifying flavonoids. HPLC methods utilizing UV detection system are commonly employed, as the conjugated p-systems of flavonoids afford good UV absorbtion. IR spectroscopy is useful to determine the functional groups attached to the basic structure of the flavonoid molecule and this is of value in the later interpretation of NMR scans. In order to determine that the isolated compounds are flavonoid pigments, the UV spectra (with and without adding the specific agents) are compared with literature data.

Aromatic diamines are antidegradants with outstanding capability in protection against oxidative and ozone destruction of elastomers and elastomer-based compounds. Their performances are dependent, among others, on their solubility in elastomer matrix and on migration rate to the matrix surface. In an attempt to control solubility and migration of amine antidegradants, the influence of some special additives (fatty amines, fatty amides, ethoxilated phenols) has been investigated and migration characteristics like diffusion coefficient, migration rate and specific migration are presented and discussed. The obtained data correlate in a semi-quantitative manner with main physical characteristics of vulcanizates in circumstances of thermo-oxidative and ozone degradation.

A new set of molecularly imprinted polymers (MIPs), based on acrylonitrile: methacrylic acid (AN:MAA) matrix, selective for diosgenin, was synthesized and characterized. The target molecule, diosgenin, is an important anticancer and antileukemia bioactive compound. The phase inversion method, an emerging and insufficient studied preparation method, was used to prepare 0.5 mm spherical MIPs. Three copolymers of acrylonitrile with methacrylic acid were synthesized by radical copolymerization: AN:MAA 90:10, 80:20 and 70:30 and used for diosgenin imprinting. The imprinted materials were analysed by elemental analysis (EA), attenuated total reflectance infrared spectroscopy (ATR FT-IR), RAMAN spectroscopy, size exclusion chromatography (SEC), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and batch rebinding tests. The affinity for the template, expressed as the imprinting factor IF, decreases in the order MIP-AN:MAA-80:20 ] MIP-AN:MAA-90:10 ] MIP-AN:MAA-70:30, meaning that -COOH functional groups have an important role in the imprinting process. Too much methacrylic groups, however, do not exhibit the highest affinity, maybe due to the steric obstruction of methyl groups and to a less stability of the structure by decreasing the AN ratio. Keywords: molecular imprinting, diosgenin, phase inversion, acrylic copolymers, MIPs

This paper presents a usage method of wood waste as sawdust resulting from sawing processes, by achieving hybrid composite materials consisting of epoxy resin reinforced with flax weave fabrics and wood particles. Mechanical characteristics obtained from tensile testing of the material on both directions of the natural fibres weave fabric used as reinforcement are also presented here. New lignocellulosic composite has application to automotive interior components industry, furniture with complex shapes, etc. Keywords: wood sawdust, hybrid composite, weave fabrics, natural fibres, tensile tests, automotive applications

We deduced the equation of motion for free vibrations using Mohr-Maxwell method, considering that the bar is requested to bending by the inertial forces and by the damping forces. We experimentally obtained the dynamic response for sandwich bars with polypropylene honeycomb core, which have the exterior layers made of epoxy resin reinforced with steel fabric. In addition, we determined the damping coefficients per unit mass and per unit length of the bar, for bar with core thicknesses equal to 10, 15 , 20 mm; width of 40 and 60 mm, and the free length of embedded bar equal to 200, 250, 300 and 350 mm. For each type of bar studied, we determined the relationships of exponential type for the calculus damping coefficients (mentioned above), according to the free length of the embedded bar. Keywords: sandwich beam, damping factor, polypropylene honeycomb, free vibrations

The purpose of this paper is to show the possibility of finding the location and to describe internal discontinuities in plates made of plastic materials using non-destructive evaluation methods. Their effect on the mechanical behaviour is also evaluated by means of numerical calculus. The technique of computer tomography („CT”) is used as a non-destructive evaluation method whereas the numerical calculus is realized by the finite element method. Keywords: computer tomography, discontinuity, finite element analysis

The paper refers to the new approach in bone grafting: biomaterials. Many artificial bone substitute materials are currently available for use in orthopaedic trauma surgery. The selection of these materials is more and more difficult as many bone substitute products are now available for use and this method led to a new approach, although the autologus bone grafting still represents the “gold standard” in bone reconstruction surgery. Keywords: bone grafting, biomaterials, reconstruction, fracture