Volume 44, Issue 3

Abstract: Polymeric nanoparticles are widely used as drug carriers in order to achieve the targeting of drug to the ill tissue. N-vinyl-2-pyrrolidone and itaconic anhydride were copolymerized and the alternating copolymer was then grafted with PEG of different molecular weight, to form amphiphilic copolymers. The grafted copolymers have been used to prepare polycaprolactone nanoparticles. The PCL has been chosen as it can mimic the hydrophobic drugs. Several emulsions were stabilized and characterized by SLS. The synthesized copolymers proved to be effective in stabilizing nanoparticles. The mean diameter of nanoparticles was stable in time, over 12 weeks. Keywords: Polycaprolactone nanoparticles, amphiphilic surfactants, radical polymerization

Abstract: Composite materials fatigue is a process which causes early failure or damage of variable loading subjected structure. Prediction of life period of composite materials uses different deterioration models. Quantifying of interlaminar stress and delamination can be underlined on load capacity of stratified composite materials subjected to fatigue. Keywords: composite materials, fatigue, interlaminar stress, delamination, load capacity

Abstract: In this paper the static traction behavior of two types of talcum polyethylene, having the same friction coefficient but different modulus of elasticity and different tensile strengths, individually used and assembled with bolt, is studied. The behavior evaluation is done on the force-displacement curves and on the mechanical characteristics basis, specific to the materials (tensile strength, elongation, Young modulus), emphasizing the tension concentrator effect. Keywords: polymers, static loading, assemblies, mechanical characteristics

Abstract: Impact damage in structures made of composite materials is a major concern since such damage can be introduced during the life of the structure, and its mechanical properties can be dramatically reduced as a result. Many efforts have been made in order to predict the damage and residual properties after impact. In the present paper a previously verified model is used in order to evaluate the residual tensile strength of woven fabric laminated composites. The model takes into account the number of plies; the impact energy and the stacking sequence. The effect of the thickness on the residual tensile strength as well as on the impact energy threshold was also examined. The predicted values seem to be a very good approximation of the experimental results. Keywords: Laminate, reinforcement, impact device, residual stiffness, uniaxial tension

Abstract: This paper comprises the results of an experimental study about cyclotrimerisation using the 4,4’- biphenylmetan diisocyanats in order to obtain isocyanurat oligomers with practical importance as isocyanic component in varnishes, paints, adhesives, etc. The kinetic study was focussed on the influences of various catalysts and water (as component in the solvent) on the reaction mechanism and on physico-chemical properties of the final obtained product. The way to stop the cyclotrimerisation reaction was discussed. Keywords: isocyanic oligomers, cyclotrimerisation, 4,4’-biphenylmethan diisocyanat, reticulation agent

Abstract: The studies were concerned on the releasing of nystatin from polyurethane urea (PUU) microporous membrane at different pH values at room temperature. The whole ATR-FTIR spectrum of PUU-nystatin is shifted to smaller wave numbers compared to control PUU which indicates the increasing of structurated degree of PUU-nystatin. The stress-strain curves are sustained by the ATR-FTIR results demonstrating the structurating effects of a polar bioactive nystatin materialized through an increasing of the initial modulus. The nystatin delivery in watery solution has a strong reaction to pH. At pH 3, in the first 170 minutes, the nystatin is released in proportion of 38% whereafter drug release is approximately constant in time. Key words: polyurethane urea, nystatin, release

Abstract: Aromatic polyimides containing side azobenzene groups has been synthesized by low-temperature solution polycondensation of certain aromatic dianhydrides with aromatic diamines containing preformed side azobenzene groups followed by chemical imidization at 100 °C în the presence of pyridine and acetic anhydride. The glass transition temperature of these polyimides is in the range of 185-230°C and the average weight molecular weight is in the range of 16000-129000. Keywords: polyimides, side azobenzene groups, glass transition

Abstract: The paper presents the modalities employed in the achievement of peptide chains and our contributions regarding the introduction of peptide moieties in the macromolecular structure. Keywords: organic synthesis, peptide, biomacromolecules

Abstract: Developed in last decade, the shape memory polymers have been gaining widespread attention for new product innovation. They are lightweight, have high strain/shape recovery ability, easy to process and required properties can be tailored for variety of different applications. Polyurethane elastomers (PUs) based on polyether diols and aliphatic diisocyanates can be used as passive isolation bearings in railway applications. In the present study poly(1,4-butane) diols (Terathane) and 1,6-hexamethylene diisocyanate (HDI) have been used in polyurethanes, using glycerin, 1,4-butane diol or 1,6 hexane diol as chain extenders. Effect of varying the concentrations of diisocyanates and structure and amount of chain extenders on polyurethane elastomers has been discussed with reference to mechanical properties. IR and thermal analysis techniques (TGA) were used for characterization. Keywords: polyurethane elastomers, chain extenders, mechanical properties, railway isolation

Abstract: This paper discusses the reaction mechanism and kinetic study of linear unsaturated polyesters, based on polycondensation reaction of maleic anhydride with different glycols (ethylene glycol, diethylene glycol and neopentyl glycol) utilized for the fabrication of polyurethanes. This polyester-diols with relatively high molecular weight (1000-1500) were characterized by IR, H-NMR, GPC, end groups analysis, as well as by the double bond content determination. Keywords: unsaturated polyester, reaction mechanism, kinetic study

Abstract: For more than 30 years, ultra-high-molecular-weight polyethylene (UHMWPE) has been used as a bearing material in total-joint-replacement prostheses. Such orthopaedic implants usually comprise a metal (typically a cobalt-chromium alloy) or ceramic component that articulates against a UHMWPE component in vivo use. It has been well established that the longevity of such implants depends on the wear performance of the UHMWPE components [1, 2]. The presence of particulate wear debris of UHMWPE that is generated due to the sliding of UHMWPE components against the metal or ceramic counter-face has been linked to complications such as tissue inflammation, bone loss (or osteolysis), and implant loosening. Osteolysis resulting from wear of UHMWPE is recognized as the leading problem in orthopaedic surgery today. Because de wear volume influence the mechanical performances of a prosthetic device in this paper is studied the variation of the wear volume depending on the number of cycle motion and the time. Keywords: polyethylene, prosthesis, cross-linked, wear

Abstract: The study presents rheological behaviour of some solution mixtures from poly(vinyl alcohol) (PVA) and starch in water, with addition of glycerol as plasticizer and urea (nitrogen source for microorganisms). These solutions were used to obtained biodegradable films. The effect of temperature and concentration on the rheological behaviour of poly(vinyl alcohol) and starch solutions in water, was studied in the temperature range of 20-60 0C and concentration 10-20 % at different gravimetrical ratio PVA/starch (3.00, 1.66, 1.00, 0.60, 0.33). The rheological behaviour was studied to gradient of shear rate which varied between 3 and 1310 s-1. From experimental data it was established that concentrated solutions of PVA/starch blends exhibit a non-newtonian rheological behaviour of pseudoplastic type. The flow activation energies versus temperature are situated in range of 11.86-49.92 kJ/mol, while against the concentration between 1.61-4.54 kJ/mol. The consistency index increased with decrease of temperature and recording great values in the concentrated solutions case. The solutions with PVA/starch subunitar gravimetrical ratio have great values of consistency index, to compare those with supraunitar ratio. This fact shows that the starch is the polymer which confers solutions a great viscosity, but low temperatures determines even their jellification. Keywords: biodegradable materials, rheological behaviour, poly(vinyl alcohol), starch

Abstract: A series of phosphorous-containing copolyesters was prepared by polycondensation of 2-(6-oxido-6H-dibenzo[c,e][1,2]oxaphosphorin-6-yl)1,4-benzenediol, 1, or of an equimolecular amount of 1 and different aliphatic diols 2, such as: ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,6-hexanediol and 1,12-dodecanediol with an aromatic diacid chloride containing two preformed ester groups 3, namely terephthaloyl-bis-(4-oxybenzoyl-chloride). The copolyesters exhibited good thermal stability having the decomposition temperature above 360°C and char yield at 700°C in the range of 8.4-41%. The glass transition temperature was in the range of 83-160°C. The polymers exhibited thermotropic liquid crystalline behaviour. Keywords: polyesters, phosphorus-containing polymers, solution polycondensation, thermal properties

Abstract: Some methods for the preparation of cellulose microfibrils and polymer composites with such microfibrils are presented in this paper. Morphological aspects of microfibrils and their dispersion in the polymer matrix are characterized using SEM and optical microscopy. Cellulose microfibrils show a clear reinforcing effect of the polymer matrix as pointed out by mechanical characterization. Keywords: polymer composites, cellulose microfibrils, mechanical properties

Abstract: The paper presents the kinetic characteristics in non-isothermal conditions obtained by degradation in argon of some aromatics copolyethers with semi rigid and flexible spacer and by comparing the results obtained for the homopolyethers corresponding to the bisphenols and spacer used. Copolyethers were synthesised by phase transfer catalysis method in liquid/liquid system. Oxetanic, diethyl etheric or hexamethilenic spacers have been used. 4,4’-dihidroxy azobenzene and 4,4’ dihidroxy biphenyl were used as bisphenol. Thermogravimetric analysis and derivative thermogravimetric analysis were applied. The kinetic characteristics suggest the complexity of the thermal degradation mechanism up to 1000°C. The degradation rate is depending on the chemical structure of the main chain. Compensation equations are proposed. Keywords: kinetic characteristics, aromatic copolyethers, thermal degradation

Abstract: The topochemistry of the process of suspension alkoholysis of vinyl polyacetate has been studied. It was thus demonstrated that the alkoholysis occurs in three stages: the first takes place in the homogeneous phase, the second in the gel phase, and in the third sineresis takes place a process that leads to forming a numerous pores within the polyvinyl alkohol pearls fact demonstrated by SEM. This study made possible to propose a mechanism, through which the pores are formed as well as the dependence of pearl porosity on the concentration of initial vinyl polyacetate solutions subjected to alkoholysis. Keywords: alkoholysis, polyvinylacetate, polyvinylalcohol

Abstract: In this paper, a comparative study was conducted on the behaviour of three types of thermoplastic materials during the injection molding of a complex part using the Moldflow software. The numerical simulation is based on the Hele-Shaw flow model for the inelastic non-Newtonian fluids under non-isothermal conditions. Based on the numerical results accurate prediction of weld lines and air traps were carried out. Keywords: injection molding, plastic materials, air trap, weld line

Abstract: The radial, branched, styrene-butadiene block-copolymers with different polybutadiene block microstructures have been synthesized via anionic two stages sequential polymerization of monomers in solution, followed by the coupling reaction with SiCl4. This synthesis route involves the polymerization of styrene first, and after that polystyril-lithium was modified with variable amounts of tetrahydrofurane before introducing the butadiene, in order to obtain the middle polybutadiene block with different microstructure. The paper shows the effect of the polybutadiene block microstructure on the HDPE blending modification. The HDPE modification is meant to improve the mechanical properties, especially impact resistance.

Abstract: Synthesis of pyridine groups grafted on copolymers is described. The method is applied, extended and optimised for gel-type styrene-divinylbenzene copolymers (S-DVB) with 5% and 7% degree of crosslinking. Keywords: 2-amino-pyridine pendant groups, styrene-divinylbenzene copolymers